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Sample records for all-conjugated diblock copolymers

  1. Optoelectronic properties and charge transfer in donor-acceptor all-conjugated diblock copolymers.

    SciTech Connect

    Botiz, I.; Schaller, R. D.; Verduzco, R.; Darling, S. B.

    2011-05-12

    All-conjugated block copolymers, which can self-assemble into well-ordered morphologies, provide exciting opportunities to rationally design and control the nanoscale organization of electron-donor and electron-acceptor moieties in optoelectronic active layers. Here we report on the steady-state and time-resolved optical characterization of block copolymer films and solutions containing poly(3-hexylthiophene) as the donor block and poly(9,9-dioctylfluorene) with and without copolymerization with benzothiadiazole as the acceptor block. Transient absorption measurements suggest rapid charge transfer occurs in both systems, with higher efficiency observed in the latter composition. These results indicate that this class of materials has promise in preparing highly ordered bulk heterojunction all-polymer organic photovoltaic devices.

  2. Face-on and Edge-on Orientation Transition and Self-epitaxial Crystallization of All-conjugated Diblock Copolymer

    NASA Astrophysics Data System (ADS)

    Yang, Hua; Han, Yanchun

    The orientation transition and self-epitaxial crystallization of all-conjugated diblock copolymers poly(p-phenylene)-block-(3-hexylthiophene) (PPP- b-P3HT, BmTn) were systematically investigated by in-situ temperature-resolved two-dimensional grazing incidence X-ray diffraction (2D GIXD) in step-by-step heating and cooling process. B39T18 was selected, the results of 2D GIXD showed that the PPP block crystal adopted a face-on orientation while the crystallization of P3HT block was hindered in as-casted films. Three different molecular orientations transition were obtained in self-epitaxial crystallization circles. First, P3HT crystallize with edge-on during the heating process and induced the PPP blocks crystallized with edge-on during the cooling process. Then, the as-casted film was heated in the melting temperature region of PPP blocks and isothermally crystallized. The partial melting of PPP blocks promoted the P3HT blocks crystallize in a face-on due to the steric limitation effect, PPP blocks crystallized with a face-on via the self-epitaxy during cooling. Furthermore, the face-on transformed to thermodynamically stable edge-on in the melt annealing process. The financial support from the National Basic Research Program of China (973 Program, 2012CB821500) is gratefully acknowledged.

  3. Hyperviscous diblock copolymer vesicles

    NASA Astrophysics Data System (ADS)

    Dimova, R.; Seifert, U.; Pouligny, B.; Förster, S.; Döbereiner, H.-G.

    2002-03-01

    Giant vesicles prepared from the diblock copolymer polybutadien-b-polyethyleneoxide (PB-PEO) exhibit a shear surface viscosity, which is about 500 times higher than those found in common phospholipid bilayers. Our result constitutes the first direct measurement of the shear surface viscosity of such polymersomes. At the same time, we measure bending and stretching elastic constants, which fall in the range of values typical for lipid membranes. Pulling out a tether from an immobilized polymersome and following its relaxation back to the vesicle body provides an estimate of the viscous coupling between the two monolayers composing the polymer membrane. The detected intermonolayer friction is about an order of magnitude higher than the characteristic one for phospholipid membranes. Polymersomes are tough vesicles with a high lysis tension. This, together with their robust rheological properties, makes them interesting candidates for a number of technological applications.

  4. Phase behaviors of cyclic diblock copolymers.

    PubMed

    Zhang, Guojie; Fan, Zhongyong; Yang, Yuliang; Qiu, Feng

    2011-11-01

    A spectral method of self-consistent field theory has been applied to AB cyclic block copolymers. Phase behaviors of cyclic diblock copolymers, such as order-disorder transition, order-order transition, and domain spacing size, have been studied, showing good consistency with previous experimental and theoretical results. Compared to linear diblocks, cyclic diblocks are harder to phase separate due to the topological constraint of the ring structure. A direct disorder-to-cylinder transition window is observed in the phase diagram, which is significantly different from the mean field phase diagram of linear diblock copolymers. The domain spacing size ratio between cyclic and linear diblock copolymers is typically close to 0.707, indicating in segregation that the cyclic polymer can be considered to be made up of linear diblocks with half of the original chain length. PMID:22070321

  5. Morphologies of poly(cyclohexadiene) diblock copolymers

    SciTech Connect

    Kumar, Rajeev; Mays, Jimmy; Sides, Scott; Goswami, Monojoy; Sumpter, Bobby G; Hong, Kunlun; Avgeropoulos, Apostolos; Russell, Thomas P; Gido, Samuel; Tsoukatos, Thodoris; Beyer, Fredrick

    2012-01-01

    Concerted experimental and theoretical investigations have been carried out to understand the micro-phase separation in diblock copolymer melts containing poly (1,3-cyclohexadiene), PCHD, as one of the constituents. In particular, we have studied diblock copolymer melts containing polystyrene (PS), polybutadiene (PB), and polyisoprene (PI) as the second block. We have systematically varied the ratio of 1,2- /1,4-microstructures of poly (1,3-cyclohexadiene) to tune the conformational asymmetry between the two blocks and characterized the effects of these changes on the morphologies using transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). Our experimental investigations reveal that the melts of PCHD-b-PB, PCHD-b-PS and PCHD-b-PI containing nearly equal fractions of each component and high percentage of 1,4-microstructures in the PCHD block form cylindrical rather than lamellar morphologies as expected in symmetric diblock copolymers. In contrast, the morphologies of PCHD-b-PB, PCHD-b-PS and PCHD-b-PI containing PCHD block with higher 1,2-microstructure are found to be disordered at 110 C. The change in the morphological behavior is in good agreement with our numerical calculations using the random phase approximation and self-consistent field theory for conformationally asymmetric diblock copolymer melts. Also, the effects of composition fluctuations are studied by extending the Brazovskii-Leibler-Fredrickson-Helfand (J. Chem. Phys. 87, 697 (1987)) theory to conformationally asymmetric diblock copolymer melts. These results allow the understanding of the underlying self-assembly process that highlights the importance of the conformational asymmetry in tuning the morphologies in block copolymers.

  6. Crystallization in Ordered Polydisperse Polyolefin Diblock Copolymers

    SciTech Connect

    Li, Sheng; Register, Richard A.; Landes, Brian G.; Hustad, Phillip D.; Weinhold, Jeffrey D.

    2010-12-07

    The morphologies of polydisperse ethylene-octene diblock copolymers, synthesized via a novel coordinative chain transfer polymerization process, are examined using two-dimensional synchrotron small-angle and wide-angle X-ray scattering on flow-aligned specimens. The diblock copolymers comprise one amorphous block with high 1-octene content and one semicrystalline block with relatively low 1-octene content, and each block ideally exhibits the most-probable distribution. Near-symmetric diblocks with a sufficiently large octene differential between the amorphous and semicrystalline blocks show well-ordered lamellar domain structures with long periods exceeding 100 nm. Orientation of these domain structures persists through multiple melting/recrystallization cycles, reflecting a robust structure which self-assembles in the melt. The domain spacings are nearly 3-fold larger than those in near-monodisperse polyethylene block copolymers of similar molecular weights. Although the well-ordered lamellar domain structure established in the melt is preserved in the solid state, the crystallites are isotropic in orientation. These materials display crystallization kinetics consistent with a spreading growth habit, indicating that the lamellae do not confine or template the growing crystals. The exceptionally large domain spacings and isotropic crystal growth are attributed to interblock mixing resulting from the large polydispersity; short hard blocks dissolved in the soft-block-rich domains swell the domain spacing in the melt and allow hard block crystallization to proceed across the lamellar domain interfaces.

  7. Molecular origin of photovoltaic performance in donor-block-acceptor all-conjugated block copolymers

    DOE PAGES

    Smith, Kendall A.; Lin, Yen -Hao; Mok, Jorge W.; Yager, Kevin G.; Strzalka, Joseph; Nie, Wanyi; Mohite, Aditya D.; Verduzco, Rafael

    2015-11-03

    All-conjugated block copolymers may be an effective route to self-assembled photovoltaic devices, but we lack basic information on the relationship between molecular characteristics and photovoltaic performance. Here, we synthesize a library of poly(3-hexylthiophene) (P3HT) block poly((9,9-dialkylfluorene)-2,7-diyl-alt-[4,7-bis(alkylthiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (PFTBT) donor-block-acceptor all-conjugated block copolymers and carry out a comprehensive study of processing conditions, crystallinity, domain sizes, and side-chain structure on photovoltaic device performance. We find that all block copolymers studied exhibit an out-of-plane crystal orientation after deposition, and on thermal annealing at high temperatures the crystal orientation flips to an in-plane orientation. By varying processing conditions on polymer photovoltaic devices, we show thatmore » the crystal orientation has only a modest effect (15-20%) on photovoltaic performance. The addition of side-chains to the PFTBT block is found to decrease photovoltaic power conversion efficiencies by at least an order of magnitude. Through grazing-incidence X-ray measurements we find that the addition of side-chains to the PFTBT acceptor block results in weak segregation and small (< 10 nm) block copolymer self-assembled donor and acceptor domains. This work is the most comprehensive to date on all-conjugated block copolymer systems and suggests that photovoltaic performance of block copolymers depends strongly on the miscibility of donor and acceptor blocks, which impacts donor and acceptor domain sizes and purity. Lastly, strategies for improving the device performance of block copolymer photovoltaics should seek to increase segregation between donor and acceptor polymer domains.« less

  8. On the birefringence of multilayered symmetric diblock copolymer films

    SciTech Connect

    Kim, J.; Chin, I.; Smith, B.A.; Russell, T.P. ); Mays, J.W. . Dept. of Chemistry)

    1993-09-27

    The chain extension at lamellar interfaces was studied in thin films of symmetric diblock copolymers on gold substrates. The first copolymer consisted of blocks of polystyrene (PS) and poly(2-vinylpyridine) (P2VP), denoted P(S-b-2VP). The second was a diblock copolymer of PS and poly(methyl methacrylate) (PMMA), denoted P(S-b-MMA), on a gold substrate. Using attenuated total reflectance spectroscopy, the refractive indices parallel, n[sub [parallel

  9. Complexation Between Cationic Diblock Copolymers and Plasmid DNA

    NASA Astrophysics Data System (ADS)

    Jung, Seyoung; Reineke, Theresa; Lodge, Timothy

    Deoxyribonucleic acids (DNA), as polyanions, can spontaneously bind with polycations to form polyelectrolyte complexes. When the polycation is a diblock copolymer with one cationic block and one uncharged hydrophilic block, the polyelectrolyte complexes formed with plasmid DNA (pDNA) are often colloidally stable, and show great promise in the field of polymeric gene therapy. While the resulting properties (size, stability, and toxicity to biological systems) of the complexes have been studied for numerous cationic diblocks, the fundamentals of the pDNA-diblock binding process have not been extensively investigated. Herein, we report how the cationic block content of a diblock influences the pDNA-diblock interactions. pDNA with 7164 base pairs and poly(2-deoxy-2-methacrylamido glucopyranose)-block-poly(N-(2-aminoethyl) methacrylamide) (PMAG-b-PAEMA) are used as the model pDNA and cationic diblock, respectively. To vary the cationic block content, two PMAG-b-PAEMA copolymers with similar PMAG block lengths but distinct PAEMA block lengths and a PAEMA homopolymer are utilized. We show that the enthalpy change from pDNA-diblock interactions is dependent on the cationic diblock composition, and is closely associated with both the binding strength and the pDNA tertiary structure.

  10. Molecular Exchange in Ordered Diblock Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Choi, Soo-Hyung; Lodge, Timothy; Bates, Frank

    2011-03-01

    Previously, molecular exchange between spherical micelles in dilute solution (1 vol% polymer) was investigated using time-resolved small-angle neutron scattering (TR-SANS). As the concentration of spherical micelles formed by the diblock copolymers increases, the micelles begin to overlap and eventually pack onto body-centered cubic (BCC) lattice. In this study, concentrated, ordered micelles (15 vol% polymers) prepared by dispersing isotopically labeled poly(styrene- b -ethylene-alt-propylene) in an isotopic squalane mixture was investigated to understand the micellar concentration dependence of the molecular exchange. Perfectly random mixing of isotopically labeled micelles on the BCC lattice was confirmed by SANS patterns where the interparticle contribution vanishes, resulting in an intensity that directly relates to the exchange kinetics. The measured molecular exchange process for the concentrated, ordered system is qualitatively consistent with the previous observations, but the rate is more than an order of magnitude slower than that for the dilute, disordered system. Infineum(IPrime), MRSEC(NSF), NIST.

  11. Comparison of complex coacervate core micelles from two diblock copolymers or a single diblock copolymer with a polyelectrolyte.

    PubMed

    Hofs, Bas; Voets, Ilja K; de Keizer, Arie; Cohen Stuart, Martien A

    2006-09-28

    With light scattering titrations, we show that complex coacervate core micelles (C3Ms) form from a diblock copolymer with a polyelectrolyte block and either an oppositely charged polyelectrolyte, a diblock copolymer with an oppositely charged polyelectrolyte or a mixture of the two. The effect of added salt and pH on both types of C3Ms is investigated. The hydrodynamic radius of mixed C3Ms can be controlled by varying the percentage of oppositely charged polyelectrolyte or diblock copolymer. A simple core-shell model is used to interpret the results from light scattering, giving the same trends as the experiments for both the hydrodynamic radii and the relative scattering intensities. Temperature has only a small effect on the C3Ms. Isothermal titration calorimetry shows that the complexation is mainly driven by Coulombic attraction and by the entropy gain due to counterion release.

  12. Relaxation processes in a lower disorder order transition diblock copolymer

    SciTech Connect

    Sanz, Alejandro; Ezquerra, Tiberio A.; Nogales, Aurora

    2015-02-14

    The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition T{sub ODT}, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.

  13. Relaxation processes in a lower disorder order transition diblock copolymer.

    PubMed

    Sanz, Alejandro; Ezquerra, Tiberio A; Hernández, Rebeca; Sprung, Michael; Nogales, Aurora

    2015-02-14

    The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition TODT, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system. PMID:25681940

  14. Molecular origin of photovoltaic performance in donor-block-acceptor all-conjugated block copolymers

    SciTech Connect

    Smith, Kendall A.; Lin, Yen -Hao; Mok, Jorge W.; Yager, Kevin G.; Strzalka, Joseph; Nie, Wanyi; Mohite, Aditya D.; Verduzco, Rafael

    2015-11-03

    All-conjugated block copolymers may be an effective route to self-assembled photovoltaic devices, but we lack basic information on the relationship between molecular characteristics and photovoltaic performance. Here, we synthesize a library of poly(3-hexylthiophene) (P3HT) block poly((9,9-dialkylfluorene)-2,7-diyl-alt-[4,7-bis(alkylthiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (PFTBT) donor-block-acceptor all-conjugated block copolymers and carry out a comprehensive study of processing conditions, crystallinity, domain sizes, and side-chain structure on photovoltaic device performance. We find that all block copolymers studied exhibit an out-of-plane crystal orientation after deposition, and on thermal annealing at high temperatures the crystal orientation flips to an in-plane orientation. By varying processing conditions on polymer photovoltaic devices, we show that the crystal orientation has only a modest effect (15-20%) on photovoltaic performance. The addition of side-chains to the PFTBT block is found to decrease photovoltaic power conversion efficiencies by at least an order of magnitude. Through grazing-incidence X-ray measurements we find that the addition of side-chains to the PFTBT acceptor block results in weak segregation and small (< 10 nm) block copolymer self-assembled donor and acceptor domains. This work is the most comprehensive to date on all-conjugated block copolymer systems and suggests that photovoltaic performance of block copolymers depends strongly on the miscibility of donor and acceptor blocks, which impacts donor and acceptor domain sizes and purity. Lastly, strategies for improving the device performance of block copolymer photovoltaics should seek to increase segregation between donor and acceptor polymer domains.

  15. Self-assembly of cyclic rod-coil diblock copolymers.

    PubMed

    He, Linli; Chen, Zenglei; Zhang, Ruifen; Zhang, Linxi; Jiang, Zhouting

    2013-03-01

    The phase behavior of cyclic rod-coil diblock copolymer melts is investigated by the dissipative particle dynamics simulation. In order to understand the effect of chain topological architecture better, we also study the linear rod-coil system. The comparison of the calculated phase diagrams between the two rod-coil copolymers reveals that the order-disorder transition point (χN)ODT for cyclic rod-coil diblock copolymers is always higher than that of equivalent linear rod-coil diblocks. In addition, the phase diagram for cyclic system is more "symmetrical," due to the topological constraint. Moreover, there are significant differences in the self-assembled overall morphologies and the local molecular arrangements. For example, frod = 0.5, both lamellar structures are formed while rod packing is different greatly in cyclic and linear cases. The lamellae with rods arranged coplanarly into bilayers occurs in cyclic rod-coil diblocks, while the lamellar structure with rods arranged end by end into interdigitated bilayers appears in linear counterpart. In both the lamellar phases, the domain size ratio of cyclic to linear diblocks is ranged from 0.63 to 0.70. This is attributed to that the cyclic architecture with the additional junction increases the contacts between incompatible blocks and prevents the coil chains from expanding as much as the linear cases. As frod = 0.7, the hexagonally packed cylinder is observed for cyclic rod-coil diblocks, while liquid-crystalline smectic A lamellar phase is formed in linear system. As a result, the cyclization of a linear rod-coil block copolymer can induce remarkable differences in the self-assembly behavior and also diversify its physical properties and applications greatly. PMID:23485326

  16. Phase Behavior of All-Hydrocarbon ``Diblock-Random'' Copolymers

    NASA Astrophysics Data System (ADS)

    Beckingham, Bryan; Register, Richard

    2013-03-01

    ``Block-random'' copolymers (AxB1-x) -(AyB1-y) , where each of the two blocks is a random copolymer of monomers A and B, present a convenient and useful variation on the typical block copolymer architecture, as the interblock interactions and physical properties can be tuned continuously through the random block's composition. The ability to tune the effective interaction parameter between the blocks continuously, allows for the order-disorder transition temperature (TODT) to be tuned independently of molecular weight using only two monomers. This flexibility makes block-random copolymers a versatile platform for the exploration of polymer phase behavior and structure-property relationships. Here, we present the phase behavior of hydrogenated derivatives of various lamellae-forming diblock-random copolymers where one block is a styrene/isoprene (S rI) random copolymer. Using small-angle x-ray scattering, we investigate a series of isoprene hydrogenated hI-S rhI with varying styrene content, determine order-disorder transition temperatures and compare the observed phase behavior to that of more typical S-hI block copolymers via mean-field theory. Additionally, diblock-random copolymers, 50 wt. % styrene in the S rI block, are synthesized with polyisoprene, polybutadiene or polystyrene blocks and we examine the phase behavior of both their hydrogenated derivatives, prepared with catalysts which either leave the S units intact or saturate them to vinylcyclohexane.

  17. Nanostructured diblock copolymer films with embedded magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Xia, Xin; Metwalli, Ezzeldin; Ruderer, Matthias A.; Körstgens, Volker; Busch, Peter; Böni, Peter; Müller-Buschbaum, Peter

    2011-06-01

    Nanostructured diblock copolymer films with embedded magnetic nanoparticles are prepared by solution casting. The diblock copolymer polystyrene-block-polymethylmethacrylate with a fully deuterated polystyrene block of a weight ratio of 0.22 is used as a structure-directing matrix. Maghemite nanoparticles (γ-Fe2O3) are coated with polystyrene and thus have a selective affinity to the minority block of the diblock copolymer. The hybrid film morphology is investigated as a function of nanoparticle concentration. The surface structure is probed with atomic force microscopy and scanning electron microscopy. The inner film structure and the structure at the polymer-substrate interface are detected with grazing incidence small angle neutron scattering (GISANS). Irrespective of the nanoparticle concentration a well developed micro-phase separation structure is present. From the Bragg peaks observed in the GISANS data a linear nanoparticle concentration dependence of the inter-domain spacing of the micro-phase separation structure is determined. The superparamagnetic and blocking behavior can be explained with a generalized Stoner-Wohlfarth-Néel theory which includes either an elastic torque being exerted on the nanoparticles by the field or a broad distribution of anisotropy constants.

  18. Synthesis of amphiphilic diblock copolymer for surface modification of Ethylene-Norbornene Copolymers

    NASA Astrophysics Data System (ADS)

    Levinsen, Simon; Svendsen, Winnie Edith; Horsewell, Andy; Almdal, Kristoffer

    2014-03-01

    The aim of this work is to produce polymer modifiers in order to develop hydrophilic polymeric surfaces for use in microfluidics. The use of hydrophilic polymers in microfluidics will have many advantages e.g. preventing protein absorbance. Here we present an amphiphilic diblock copolymer consisting of a bulk material compatible block and a hydrophilic block. To utilize the possibility of incorporating diblock copolymers into ethylene-norbornene copolymers, we have in this work developed a model poly(ethylene-1-butene) polymer compatible with the commercial available ethylene-norbornene copolymer TOPAS. Through matching of the radius of gyration for the model polymer and TOPAS the miscibility was achieved. The poly(ethylene-1-butene) polymer was synthesized from a hydrogenated anionic polymerized polybutadiene polymer. As hydrophilic block poly(ethylene oxide) was subsequently added also with anionic polymerization. Recent miscibility results between the model polymer and TOPAS will be presented, as well ongoing efforts to study the hydrophilic surface.

  19. In-Plane Ordering in Diblock Copolymer Brushes.

    NASA Astrophysics Data System (ADS)

    Akgun, Bulent; Ugur, Gokce; Brittain, William J.; Foster, Mark D.; Li, Xuefa; Wang, Jin

    2007-03-01

    Internal and surface structures of polystyrene-b-polyacrylate and polyacrylate-b-polystyrene diblock copolymer brushes have been studied using grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM). Each asymmetric, as-deposited diblock brush that contains a poly(methyl acrylate) (PMA) block shows an in-plane structure with a spacing comparable to the PMA layer thickness. The correlation length of the in-plane ordering is about the nearest neighbor distance and grows with annealing at 180^o C. After a brush is treated with a solvent selective for the bottom block, Bragg rods appear in the GISAXS pattern. The lateral spacing corresponding to the Bragg rods is on the order of the brush total thickness. This lateral correlation is also detected by power spectral density analysis of AFM images of the samples' surfaces. The Bragg rods disappear upon heating to 80^o C.

  20. Gyroid nickel nanostructures from diblock copolymer supramolecules.

    PubMed

    Vukovic, Ivana; Punzhin, Sergey; Voet, Vincent S D; Vukovic, Zorica; de Hosson, Jeff Th M; ten Brinke, Gerrit; Loos, Katja

    2014-01-01

    Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology. PMID:24797367

  1. Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

    PubMed Central

    Vukovic, Ivana; Punzhin, Sergey; Voet, Vincent S. D.; Vukovic, Zorica; de Hosson, Jeff Th. M.; ten Brinke, Gerrit; Loos, Katja

    2014-01-01

    Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology. PMID:24797367

  2. Simulating the morphology and mechanical properties of filled diblock copolymers.

    PubMed

    Buxton, Gavin A; Balazs, Anna C

    2003-03-01

    We couple a morphological study of a mixture of diblock copolymers and spherical nanoparticles with a micromechanical simulation to determine how the spatial distribution of the particles affects the mechanical behavior of the composite. The morphological studies are conducted through a hybrid technique, which combines a Cahn-Hilliard (CH) theory for the diblocks and a Brownian dynamics (BD) for the particles. Through these "CH-BD" calculations, we obtain the late-stage morphology of the diblock-particle mixtures. The output of this CH-BD model serves as the input to the lattice spring model (LSM), which consists of a three-dimensional network of springs. In particular, the location of the different phases is mapped onto the LSM lattice and the appropriate force constants are assigned to the LSM bonds. A stress is applied to the LSM lattice, and we calculate the local strain fields and overall elastic response of the material. We find that the confinement of nanoparticles within a given domain of a bicontinous diblock mesophase causes the particles to percolate and form essentially a rigid backbone throughout the material. This continuous distribution of fillers significantly increases the reinforcement efficiency of the nanoparticles and dramatically increases the Young's modulus of the material. By integrating the morphological and mechanical models, we can isolate how modifications in physical characteristics of the particles and diblocks affect both the structure of the mixture and the macroscopic behavior of the composite. Thus, we can establish how choices made in the components affect the ultimate performance of the material.

  3. Morphology of diblock copolymers under confinement

    NASA Astrophysics Data System (ADS)

    Ackerman, David; Ganapathysubramanian, Baskar

    The structure adopted by polymer chains is of particular intrest for materials design. In particular, a great deal of effort has been made to study diblock polymers due to the importance they have in industrial applications. The bulk structure of most systems has been the most widely studied. However, when under the effect of confinement, the polymer chains are forced to adopt structures differing from the familiar bulk phases. As many applications utilize polymers in sizes and shapes that lead to these non bulk structures, the confinement effects are important. A commonly used tool for computationally determining structures is the continuum self consistant field theory (SCFT). We discuss our highly scalable parallel framework for SCFT using real space methods (finite element) that is especially well suited to modelling complex geometries. This framework is capable of modeling both Gaussian and worm like chains. We illustate the use of the software framework in determining structures under varying degrees of confinement. We detail the method used and present selected results from a systematic study of confinement using arbitrary structures.

  4. Charged Diblock Copolymers at Interfaces: Micelle Dissociation Upon Compression

    SciTech Connect

    Checco, A.; Theodoly, O.; Muller, P.

    2010-05-20

    We use grazing incidence X-ray scattering to study the surface micellization of charged amphiphilic diblock copolymers poly(styrene-block-acrylic acid) at the air-water interface. Scattering interference peaks are consistent with the formation of hexagonally packed micelles. The remarkable increase of inter-micelle distance upon compression is explained by a dissociation of micelles into a brush. Hence, surface micelles reorganize, whereas micelles of the same copolymers in solutions are 'frozen'. We show indeed that the energetic cost of unimer extraction from micelles is much lower for surface than for solution. Finally, a model combining electrostatic interactions and micelle/brush equilibrium explains surface pressure vs. area without free parameters. keywords - soft matter, liquids and polymers, biological physics, chemical physics and physical chemistry.

  5. Charged Diblock Copolymers at Interfaces: Micelle Dissociation Upon Compression

    SciTech Connect

    Theodoly, O.; Checco, A; Muller, P

    2010-01-01

    We use grazing incidence X-ray scattering to study the surface micellization of charged amphiphilic diblock copolymers poly(styrene-block-acrylic acid) at the air-water interface. Scattering interference peaks are consistent with the formation of hexagonally packed micelles. The remarkable increase of inter-micelle distance upon compression is explained by a dissociation of micelles into a brush. Hence, surface micelles reorganize, whereas micelles of the same copolymers in solutions are 'frozen'. We show indeed that the energetic cost of unimer extraction from micelles is much lower for surface than for solution. Finally, a model combining electrostatic interactions and micelle/brush equilibrium explains surface pressure vs. area without free parameters.

  6. Molecular Interaction Control in Diblock Copolymer Blends and Multiblock Copolymers with Opposite Phase Behaviors

    NASA Astrophysics Data System (ADS)

    Cho, Junhan

    2014-03-01

    Here we show how to control molecular interactions via mixing AB and AC diblock copolymers, where one copolymer exhibits upper order-disorder transition and the other does lower disorder-order transition. Linear ABC triblock copolymers possessing both barotropic and baroplastic pairs are also taken into account. A recently developed random-phase approximation (RPA) theory and the self-consistent field theory (SCFT) for general compressible mixtures are used to analyze stability criteria and morphologies for the given systems. It is demonstrated that the copolymer systems can yield a variety of phase behaviors in their temperature and pressure dependence upon proper mixing conditions and compositions, which is caused by the delicate force fields generated in the systems. We acknowledge the financial support from National Research Foundation of Korea and Center for Photofunctional Energy Materials.

  7. Topography of neutron scattering from diblock copolymer film

    SciTech Connect

    Cai, Z.; Russell, T.P.

    1994-10-01

    The surface structure of a multilayered film of symmetric perdeuterated diblock copolymers of polystyrene and polymethylmethacrylate, denoted P(d-S-b-d-MMA), was investigated by neutron scattering at grazing incidence. The film surfaces were covered by islands or holes of uniform height with a lateral size of several micrometers. With the angle of incidence fixed, the off-specular neutron scattering was measured as function of scattering angle and neutron wavelength. The off-specular scattering intensity shows ridges at constant q{sub z}, the momentum transfer along the surface normal. The scattering arises from the surface domains. It was found that the off-specular ridges developed from minima in the oscillations in the specular profile corresponding to domain height. The characteristic of the off-specular scattering, which is different from that of the off-specular scattering due to the conformal roughness in a multilayered film, is interpreted in terms of the correlations of the surface domains.

  8. Elastic torsion effects in magnetic nanoparticle diblock-copolymer structures.

    PubMed

    Schulz, L; Schirmacher, W; Omran, A; Shah, V R; Böni, P; Petry, W; Müller-Buschbaum, P

    2010-09-01

    Magnetic properties of thin composite films, consisting of non-interacting polystyrene-coated γ-Fe(2)O(3) (maghemite) nanoparticles embedded into polystyrene-block-polyisoprene P(S-b-I) diblock-copolymer films are investigated. Different particle concentrations, ranging from 0.7 to 43 wt%, have been used. The magnetization measured as a function of external field and temperature shows typical features of anisotropic superparamagnets including a hysteresis at low temperatures and blocking phenomena. However, the data cannot be reconciled with the unmodified Stoner-Wohlfarth-Néel theory. Applying an appropriate generalization we find evidence for either an elastic torque being exerted on the nanoparticles by the field or a broad distribution of anisotropy constants.

  9. From multi-responsive tri- and diblock copolymers to diblock-copolymer-decorated gold nanoparticles: the effect of architecture on micellization behaviors in aqueous solutions.

    PubMed

    Song, Lichun; Sun, Hui; Chen, Xiaolu; Han, Xia; Liu, Honglai

    2015-06-28

    This work reports on the aqueous stimuli-responsive behaviors of an ABA triblock copolymer, a BAB triblock copolymer, an AB diblock copolymer and citrate-based gold nanoparticles decorated with AB diblock copolymers (where A is the pH- and thermo-responsive poly[N,N-(dimethylamino)ethyl methacrylate] (PDMAEMA) and B is the thermo-responsive poly[2-(2-methoxyethoxy)ethyl methacrylate] (PMEO2MA)). The symmetric triblock polymers were synthesized via sequential atom transfer radical polymerization (ATRP) using a disulfide-functionalized initiator. Subsequently, the thiol-ended diblock copolymers were facilely obtained by reducing these triblock copolymers and were grafted onto gold nanoparticle (AuNP) surfaces via ligand exchange to yield stimuli-sensitive gold nanoparticles (Au@AB and Au@BA). The ABA and BAB triblock copolymers exhibited two-step thermo-induced aggregation behavior in water at a pH near the isoelectric point (IEP), which resulted in the formation of micelles after the first lower critical solution temperature (LCST) and large aggregates consisting of clustered micelles above the second LCST transition. The significant difference between the micelle sizes of the ABA and BAB copolymers, such that the micelle size of the BAB copolymer was smaller than that of the ABA copolymer although both had a similar unit composition, suggests a distinction between the micelle structures. The "branch" and "flower-like" micelles that are formed in the ABA and BAB aqueous solutions, respectively, ultimately governed the phase transition behaviors. The AB diblock copolymer exhibited similar micellization behavior and a micelle size roughly similar to that of the ABA triblock copolymer, although the chain length of the AB copolymer is only half that of the ABA copolymer. Both Au@PDMAEMA-PMEO2MA and Au@PMEO2MA-PDMAEMA showed similar dual LCST behaviors and pH-responsive behaviors in aqueous solutions without the addition of salt. A significant difference was observed

  10. Clear antismudge unimolecular coatings of diblock copolymers on glass plates.

    PubMed

    Macoretta, Danielle; Rabnawaz, Muhammad; Grozea, Claudia M; Liu, Guojun; Wang, Yu; Crumblehulme, Alison; Wyer, Martin

    2014-12-10

    Two poly[3-(triisopropyloxysilyl)propyl methacrylate]-block-poly[2-(perfluorooctyl)ethyl methacrylate] (PIPSMA-b-PFOEMA) samples and one poly(perfluoropropylene oxide)-block-poly-[3-(triisopropyloxysilyl)propyl methacrylate] (PFPO-b-PIPSMA) sample were synthesized, characterized, and used to coat glass plates. These coatings were formed by evaporating a dilute polymer solution containing HCl, which catalyzed PIPSMA's sol-gel chemistry. Polymer usage was minimized by targeting at diblock copolymer unimolecular (brush) layers that consisted of a sol-gelled grafted PIPSMA layer and an oil- and water-repellant fluorinated surface layer. Investigated is the effect of varying the catalyst amount, polymer amount, as well as block copolymer type and composition on the structure, morphology, and oil- and water-repellency of the coatings. Under optimized conditions, the prepared coatings were optically clear and resistant to writing by a permanent marker. The marker's trace was the faintest on PFPO-b-PIPSMA coatings. In addition, the PFPO-b-PIPSMA coatings were far more wear-resistant than the PIPSMA-b-PFOEMA coatings. PMID:25399630

  11. Clear antismudge unimolecular coatings of diblock copolymers on glass plates.

    PubMed

    Macoretta, Danielle; Rabnawaz, Muhammad; Grozea, Claudia M; Liu, Guojun; Wang, Yu; Crumblehulme, Alison; Wyer, Martin

    2014-12-10

    Two poly[3-(triisopropyloxysilyl)propyl methacrylate]-block-poly[2-(perfluorooctyl)ethyl methacrylate] (PIPSMA-b-PFOEMA) samples and one poly(perfluoropropylene oxide)-block-poly-[3-(triisopropyloxysilyl)propyl methacrylate] (PFPO-b-PIPSMA) sample were synthesized, characterized, and used to coat glass plates. These coatings were formed by evaporating a dilute polymer solution containing HCl, which catalyzed PIPSMA's sol-gel chemistry. Polymer usage was minimized by targeting at diblock copolymer unimolecular (brush) layers that consisted of a sol-gelled grafted PIPSMA layer and an oil- and water-repellant fluorinated surface layer. Investigated is the effect of varying the catalyst amount, polymer amount, as well as block copolymer type and composition on the structure, morphology, and oil- and water-repellency of the coatings. Under optimized conditions, the prepared coatings were optically clear and resistant to writing by a permanent marker. The marker's trace was the faintest on PFPO-b-PIPSMA coatings. In addition, the PFPO-b-PIPSMA coatings were far more wear-resistant than the PIPSMA-b-PFOEMA coatings.

  12. Dodecagonal Quasicrystal Phase in a Diblock Copolymer Melt

    NASA Astrophysics Data System (ADS)

    Bates, Frank; Gillard, Timothy; Lee, Sangwoo

    Recent experiments with low molecular weight asymmetric poly(isoprene- b-lactide) (PI-PLA) diblock copolymers have established an equilibrium Frank-Kasper σ-phase at compositions between 18 and 22 percent by volume PLA, which transforms to a BCC phase followed by disordering with increasing temperature. This presentation will describe synchrotron small-angle x-ray scattering and dynamic mechanical spectroscopy experiments conducted following rapid temperature quenches from the disordered state to temperatures associated with the σ-phase. We document the development of a long-lived dodecagonal quasicrystalline (DQC) phase that transforms with time into the associated quasicrystal approximate σ-phase at a rate that is highly temperature dependent. Remarkably, the DQC does not form from either the σ-phase or BCC state. These finding will be discussed in the context of an apparent spontaneous structural transition that occurs when the disordered melt is supercooled below a threshold temperature coincident with the BCC to σ-phase order-order transition temperature. Support provided by the National Science Foundation (1104368).

  13. Non-Newtonian Behavior of Diblock and Triblock Copolymer Solutions

    NASA Astrophysics Data System (ADS)

    Watanabe, Hiroshi

    2006-03-01

    Non-Newtonian flow behavior was examined for butadiene-styrene (BS) diblock and BSB triblock copolymers dissolved in a S-selective solvent, dibutyl phthalate (DBP). Spherical domains of the non-solvated B blocks were arranged on a bcc lattice in both solutions at equilibrium, as revealed from SANS. The solutions exhibited significant thinning under steady flow, which was well correlated with the disruption of the bcc lattice detected with SANS. The lattice disruption was most prominent at a shear rate comparable to the frequency of B/S concentration fluctuation. For the BS/DBP solution, the recovery of the lattice structure after cessation of flow was the slowest for the most heavily disrupted lattice, as naturally expected. In contrast, for the BSB/DBP solution, the recovery rate was insensitive to the magnitude of lattice disruption. This peculiar behavior of the BSB solution suggests that the rate-determining step of the recovery in this solution is the transient B/S mixing required for reformation of the S bridges connecting the B domains.

  14. Microphase separation in thin films of lamellar forming polydisperse di-block copolymers

    SciTech Connect

    Kumar, Rajeev; Lokitz, Bradley S.; Sides, Scott W.; Chen, Jihua; Heller, William T.; Ankner, John F.; Browning, James F.; Kilbey, II, S. Michael; Sumpter, Bobby G.

    2015-02-03

    Despite the ubiquity of polydispersity in chain lengths of di-block copolymers, its effects on microphase separation in thin films have eluded a clear understanding. In this paper, we have studied effects of polydispersity on the microphase separation in thin films of lamellar forming di-block copolymers using self-consistent field theory (SCFT) and neutron reflectivity experiments. Di-block copolymers containing a polydisperse block of poly(glycidylmethacrylate) (PGMA) connected to a near-monodisperse block poly(2-vinyl-4,4-dimethyl-d6 azlactone) (PVDMA-d6) are considered in this work. Effects of chain length polydispersity, film thickness, substrate–monomer and monomer–monomer interactions on the microphase segregation are studied using SCFT. The theoretical study reveals that in comparison to a film created with monodisperse di-block copolymers, an increase in polydispersity tends to decrease the number of lamellar strata that can be packed in a film of given thickness. This is a direct consequence of an increase in lamellar domain spacing with an increase in polydispersity index. Furthermore, it is shown that polydispersity induces conformational asymmetry and an increase in the polydispersity index leads to an increase in the effective Kuhn segment length of the polydisperse blocks. It is shown that the conformational asymmetry effects, which are entropic in origin and of increasing importance as film thickness decreases, drive the polydisperse blocks to the middle of the films despite favorable substrate interactions. These predictions are verified by results from neutron reflectivity experiments on thin films made from moderately polydisperse PGMA-PVDMA-d6 di-block copolymer deposited on silicon substrates. In conclusion, results from SCFT are used to predict neutron reflectivity profiles, providing a facile and robust route to obtain useful physical insights into the structure of polydisperse diblock copolymers at

  15. Microphase separation in thin films of lamellar forming polydisperse di-block copolymers

    DOE PAGES

    Kumar, Rajeev; Lokitz, Bradley S.; Sides, Scott W.; Chen, Jihua; Heller, William T.; Ankner, John F.; Browning, James F.; Kilbey, II, S. Michael; Sumpter, Bobby G.

    2015-02-03

    Despite the ubiquity of polydispersity in chain lengths of di-block copolymers, its effects on microphase separation in thin films have eluded a clear understanding. In this paper, we have studied effects of polydispersity on the microphase separation in thin films of lamellar forming di-block copolymers using self-consistent field theory (SCFT) and neutron reflectivity experiments. Di-block copolymers containing a polydisperse block of poly(glycidylmethacrylate) (PGMA) connected to a near-monodisperse block poly(2-vinyl-4,4-dimethyl-d6 azlactone) (PVDMA-d6) are considered in this work. Effects of chain length polydispersity, film thickness, substrate–monomer and monomer–monomer interactions on the microphase segregation are studied using SCFT. The theoretical study reveals thatmore » in comparison to a film created with monodisperse di-block copolymers, an increase in polydispersity tends to decrease the number of lamellar strata that can be packed in a film of given thickness. This is a direct consequence of an increase in lamellar domain spacing with an increase in polydispersity index. Furthermore, it is shown that polydispersity induces conformational asymmetry and an increase in the polydispersity index leads to an increase in the effective Kuhn segment length of the polydisperse blocks. It is shown that the conformational asymmetry effects, which are entropic in origin and of increasing importance as film thickness decreases, drive the polydisperse blocks to the middle of the films despite favorable substrate interactions. These predictions are verified by results from neutron reflectivity experiments on thin films made from moderately polydisperse PGMA-PVDMA-d6 di-block copolymer deposited on silicon substrates. In conclusion, results from SCFT are used to predict neutron reflectivity profiles, providing a facile and robust route to obtain useful physical insights into the structure of polydisperse diblock copolymers at interfaces.« less

  16. “Smart” Diblock Copolymers as Templates for Magnetic-Core Gold-Shell Nanoparticle Synthesis

    SciTech Connect

    Nash, Michael A.; Lai, James J.; Hoffman, Allan S.; Yager, Paul; Stayton, Partick S.

    2010-01-13

    We report a new strategy for synthesizing temperature-responsive γ-Fe2O3-core/Au-shell nanoparticles (Au-mNPs) from diblock copolymer micelles. The amphiphilic diblock copolymer chains were synthesized using reversible addition-fragmentation chain-transfer (RAFT) with a thermally responsive “smart” poly(N-isopropylacrylamide) (pNIPAAm) block and an amine-containing poly(N,N-dimethylaminoethylacrylamide) (DMAEAm) block that acted as a reducing agent during gold shell formation. The Au-mNPs reversibly aggregated upon heating the solution above the transition temperature of pNIPAAm, resulting in a red-shifted localized surface plasmon resonance.

  17. Biocompatible Polysiloxane-Containing Diblock Copolymer PEO-b-PγMPS for Coating Magnetic Nanoparticles

    PubMed Central

    Chen, Hongwei; Wu, Xinying; Duan, Hongwei; Wang, Y. Andrew; Wang, Liya; Zhang, Minming; Mao, Hui

    2009-01-01

    We report a biocompatible polysiloxane containing amphiphilic diblock copolymer, poly(ethylene oxide)-block-poly(γ-methacryloxypropyltrimethoxysilane) (PEO-b-PγMPS), for coating and stabilizing nanoparticles for biomedical applications. Such amphiphilic diblock copolymer which comprises both a hydrophobic segment with “surface anchoring moiety” (silane group) and a hydrophilic segment with PEO (Mn=5000 g/mol) was obtained by the reversible addition fragmentation chain transfer (RAFT) polymerization using the PEO macromolecular chain transfer agent. When used for coating paramagnetic iron oxide nanoparticles (IONPs), copolymers were mixed with hydrophobic oleic acid coated core size uniformed IONPs (D=13 nm) in co-solvent tetrahydrofuran. After being aged over a period of time, resulting monodispersed IONPs can be transferred into aqueous medium. With proper PγMPS block length (Mn=10,000 g/mol), polysiloxane containing diblock copolymers formed a thin layer of coating (~3 nm) around monocrystalline nanoparticles as measured by transmission electron microscopy (TEM). Magnetic resonance imaging (MRI) experiments showed excellent T2 weighted contrast effect from coated IONPs with a transverse relaxivity r2=98.6 mM−1s−1 (at 1.5 Tesla). Such thin coating layer has little effect on the relaxivity when compared to that of IONPs coated with conventional amphiphilic copolymer. Polysiloxane containing diblock copolymer coated IONPs are stable without aggregation or binding to proteins in serum when incubated for 24 h in culture medium containing 10% serum. Furthermore, much lower level of intracellular uptake by macrophage cells was observed with polysiloxane containing diblock copolymers coated IONPs, suggesting the reduction of non-specific cell uptakes and antibiofouling effect. PMID:20161520

  18. Synthesis and Characterization of Fluorescently Labeled Diblock Copolymers for Location-Specific Measurements of The Glass Transition Temperature

    NASA Astrophysics Data System (ADS)

    Christie, Dane; Register, Richard; Priestley, Rodney

    Interfaces play a determinant role in the size dependence of the glass transition temperature (Tg) of polymers confined to nanometric length scales. Interfaces are intrinsic in diblock copolymers, which, depending on their molecular weight and composition, are periodically nanostructured in the bulk. As a result diblock copolymers are model systems for characterizing the effect of interfaces on Tg in bulk nanostructured materials. Investigating the effect of intrinsic interfaces on Tg in diblock copolymers has remained unexplored due to their small periodic length scale. By selectively incorporating trace amounts of a fluorescent probe into a diblock copolymer, Tg can be characterized relative to the diblock copolymer's intrinsic interface using fluorescence spectroscopy. Here, pyrene is selectively incorporated into the poly(methyl methacrylate) (PMMA) block of lamellar forming diblock copolymers of poly(butyl- b-methyl methacrylate) (PBMA-PMMA). Preliminary results show a correlation of Tg as measured by fluorescence with the onset of Tg as measured by calorimetry in labeled homopolymers of PMMA. This result is consistent with previous characterizations of Tg using fluorescence spectroscopy. In selectively labeled diblock copolymers Tg is found to vary systematically depending on the distance of the probe from the PBMA-PMMA interface. We acknowledge funding from the Princeton Center for Complex Materials, a MRSEC supported by NSF Grant DMR 1420541.

  19. Template-Free Bottom-Up Method for Fabricating Diblock Copolymer Patchy Particles.

    PubMed

    Ye, Xianggui; Li, Zhan-Wei; Sun, Zhao-Yan; Khomami, Bamin

    2016-05-24

    Patchy particles are one of most important building blocks for hierarchical structures because of the discrete patches on their surface. We have demonstrated a convenient, simple, and scalable bottom-up method for fabricating diblock copolymer patchy particles through both experiments and dissipative particle dynamics (DPD) simulations. The experimental method simply involves reducing the solvent quality of the diblock copolymer solution by the slow addition of a nonsolvent. Specifically, the fabrication of diblock copolymer patchy particles begins with a crew-cut soft-core micelle, where the micelle core is significantly swelled by the solvent. With water addition at an extremely slow rate, the crew-cut soft-core micelles first form a larger crew-cut micelle. With further water addition, the corona-forming blocks of the crew-cut micelles begin to aggregate and eventually form well-defined patches. Both experiments and DPD simulations indicate that the number of patches has a very strong dependence on the diblock copolymer composition-the particle has more patches on the surface with a lower volume fraction of patch-forming blocks. Furthermore, particles with more patches have a greater ability to assemble, and particles with fewer patches have a greater ability to merge once assembled. PMID:27109249

  20. Biocompatibility of poly(epsilon-caprolactone)/poly(ethylene glycol) diblock copolymers with nanophase separation.

    PubMed

    Hsu, Shan-Hui; Tang, Cheng-Ming; Lin, Chu-Chieh

    2004-11-01

    In this study, we prepared diblock copolymers of poly(epsilon-caprolactone) (PCL) and poly(ethylene glycol) (PEG) by aluminum alkoxide catalysts. The biological responses to the spin cast surface of different PCL/PEG diblock copolymers were investigated in vitro. Our results showed that surface hydrophilicity improved with the increased PEG segments in diblock copolymers and that bacteria adhesion was inhibited by increased PEG contents. PCL-PEG 23:77 showed nanotopography on the surface. The number of adhered endothelial cells, platelets and monocytes on diblock copolymer surfaces was inhibited in PCL-PEG 77:23 and enhanced in PCL-PEG 23:77. Nevertheless, the platelet and monocyte activation on PCL-PEG 23:77 was reduced. PCL-PEG 23:77 had better cellular response as well as lower degree of platelet and monocyte activation. The current study was the first one to demonstrate that surface nanotopography could influence not only cell adhesion and growth but also platelet and monocyte activation.

  1. Template-Free Bottom-Up Method for Fabricating Diblock Copolymer Patchy Particles.

    PubMed

    Ye, Xianggui; Li, Zhan-Wei; Sun, Zhao-Yan; Khomami, Bamin

    2016-05-24

    Patchy particles are one of most important building blocks for hierarchical structures because of the discrete patches on their surface. We have demonstrated a convenient, simple, and scalable bottom-up method for fabricating diblock copolymer patchy particles through both experiments and dissipative particle dynamics (DPD) simulations. The experimental method simply involves reducing the solvent quality of the diblock copolymer solution by the slow addition of a nonsolvent. Specifically, the fabrication of diblock copolymer patchy particles begins with a crew-cut soft-core micelle, where the micelle core is significantly swelled by the solvent. With water addition at an extremely slow rate, the crew-cut soft-core micelles first form a larger crew-cut micelle. With further water addition, the corona-forming blocks of the crew-cut micelles begin to aggregate and eventually form well-defined patches. Both experiments and DPD simulations indicate that the number of patches has a very strong dependence on the diblock copolymer composition-the particle has more patches on the surface with a lower volume fraction of patch-forming blocks. Furthermore, particles with more patches have a greater ability to assemble, and particles with fewer patches have a greater ability to merge once assembled.

  2. Formation of Frank-Kasper σ-phase from polydisperse diblock copolymers

    NASA Astrophysics Data System (ADS)

    Liu, Meijiao; Li, Weihua; Shi, An-Chang

    Recent experimental and theoretical studies have revealed a number of complex spherical phases including the complex Frank-Kasper σ-phase, which consists of 30 spheres in a unit cell. It is desirable to understand the mechanisms for the formation of the complex spherical phases such as the A15-phase and the Frank-Kasper σ-phase in block copolymers. Based on the observation that the A15-phase and the Frank-Kasper σ-phase are composed of spherical domains with different sizes, we hypothesize that polydispersity of the block copolymers could be used to obtain these complex phases. We tested this hypothesis by carrying out self-consistent field theory for polydisperse AB diblock copolymers. Specially we studied the relative stability of various spherical phases, including the fcc, bcc, A15 and Frank_Kasper σ-phase, in binary blends composed of AB block copolymers different lengths of the A-blocks. Our results revealed that the Frank-Kasper σ-phase could be stabilized by tailoring the length ratio as well as the compositions of the two diblock copolymers. The distribution of the diblocks in the system indicates that copolymer segregation is the origin of the formation of spherical domains with different sizes.

  3. Self-oscillating AB diblock copolymer developed by post modification strategy

    SciTech Connect

    Ueki, Takeshi E-mail: ryo@cross.t.u-tokyo.ac.jp; Onoda, Michika; Tamate, Ryota; Yoshida, Ryo E-mail: ryo@cross.t.u-tokyo.ac.jp; Shibayama, Mitsuhiro

    2015-06-15

    We prepared AB diblock copolymer composed of hydrophilic poly(ethylene oxide) segment and self-oscillating polymer segment. In the latter segment, ruthenium tris(2,2′-bipyridine) (Ru(bpy){sub 3}), a catalyst of the Belousov-Zhabotinsky reaction, is introduced into the polymer architecture based on N-isopropylacrylamide (NIPAAm). The Ru(bpy){sub 3} was introduced into the polymer segment by two methods; (i) direct random copolymerization (DP) of NIPAAm and Ru(bpy){sub 3} vinyl monomer and (ii) post modification (PM) of Ru(bpy){sub 3} with random copolymer of NIPAAm and N-3-aminopropylmethacrylamide. For both the diblock copolymers, a bistable temperature region (the temperature range; ΔT{sub m}), where the block copolymer self-assembles into micelle at reduced Ru(bpy){sub 3}{sup 2+} state whereas it breaks-up into individual polymer chain at oxidized Ru(bpy){sub 3}{sup 3+} state, monotonically extends as the composition of the Ru(bpy){sub 3} increases. The ΔT{sub m} of the block copolymer prepared by PM is larger than that by DP. The difference in ΔT{sub m} is rationalized from the statistical analysis of the arrangement of the Ru(bpy){sub 3} moiety along the self-oscillating segments. By using the PM method, the well-defined AB diblock copolymer having ΔT{sub m} (ca. 25 °C) large enough to cause stable self-oscillation can be prepared. The periodic structural transition of the diblock copolymer in a dilute solution ([Polymer] = 0.1 wt. %) is closely investigated in terms of the time-resolved dynamic light scattering technique at constant temperature in the bistable region. A macroscopic viscosity oscillation of a concentrated polymer solution (15 wt. %) coupled with the periodic microphase separation is also demonstrated.

  4. Kinetically Controlled Nanostructure Formation in Self-Assembled Globular Protein-Polymer Diblock Copolymers

    PubMed Central

    Thomas, Carla S.; Xu, Liza; Olsen, Bradley D.

    2014-01-01

    Aqueous processing of globular protein-polymer diblock copolymers into solid-state materials and subsequent solvent annealing enables kinetic and thermodynamic control of nanostructure formation to produce block copolymer morphologies that maintain a high degree of protein fold and function. Using model diblock copolymers composed of mCherry-b-poly(N-isopropylacrylamide), orthogonal control over solubility of the protein block through changes in pH and the polymer block through changes in temperature is demonstrated during casting and solvent annealing. Hexagonal cylinders, perforated lamellae, lamellae, or hexagonal and disordered micellar phases are observed depending upon the coil fraction of the block copolymer and the kinetic pathway used for self-assembly. Good solvents for the polymer block produce ordered structures reminiscent of coil-coil diblock copolymers, while an unfavorable solvent results in kinetically trapped micellar structures. Decreasing solvent quality for the protein improves long-range ordering, suggesting that the strength of protein interactions influences nanostructure formation. Subsequent solvent annealing results in evolution of the nanostructures, with the best ordering and the highest protein function observed when annealing in a good solvent for both blocks. While protein secondary structure was found to be almost entirely preserved for all processing pathways, UV-vis spectroscopy of solid-state films indicates that using a good solvent for the protein block enables up to 70% of the protein to be retained in its functional form. PMID:22924842

  5. Kinetically controlled nanostructure formation in self-assembled globular protein-polymer diblock copolymers.

    PubMed

    Thomas, Carla S; Xu, Liza; Olsen, Bradley D

    2012-09-10

    Aqueous processing of globular protein-polymer diblock copolymers into solid-state materials and subsequent solvent annealing enables kinetic and thermodynamic control of nanostructure formation to produce block copolymer morphologies that maintain a high degree of protein fold and function. When model diblock copolymers composed of mCherry-b-poly(N-isopropylacrylamide) are used, orthogonal control over solubility of the protein block through changes in pH and the polymer block through changes in temperature is demonstrated during casting and solvent annealing. Hexagonal cylinders, perforated lamellae, lamellae, or hexagonal and disordered micellar phases are observed, depending on the coil fraction of the block copolymer and the kinetic pathway used for self-assembly. Good solvents for the polymer block produce ordered structures reminiscent of coil-coil diblock copolymers, while an unfavorable solvent results in kinetically trapped micellar structures. Decreasing solvent quality for the protein improves long-range ordering, suggesting that the strength of protein interactions influences nanostructure formation. Subsequent solvent annealing results in evolution of the nanostructures, with the best ordering and the highest protein function observed when annealing in a good solvent for both blocks. While protein secondary structure was found to be almost entirely preserved for all processing pathways, UV-vis spectroscopy of solid-state films indicates that using a good solvent for the protein block enables up to 70% of the protein to be retained in its functional form. PMID:22924842

  6. Cross-Linked Conjugated Polymer Fibrils: Robust Nanowires from Functional Polythiophene Diblock Copolymers

    SciTech Connect

    Hammer, Brenton A. G.; Bokel, Felicia A.; Hayward, Ryan C.; Emrick, Todd

    2011-09-27

    A series of poly(3-hexyl thiophene) (P3HT)-based diblock copolymers were prepared and examined in solution for their assembly into fibrils, and post-assembly cross-linking into robust nanowire structures. P3HT-b-poly(3-methanol thiophene) (P3MT), and P3HT-b-poly(3-aminopropyloxymethyl thiophene) (P3AmT) diblock copolymers were synthesized using Grignard metathesis (GRIM) polymerization. Fibrils formed from solution assembly of these copolymers are thus decorated with hydroxyl and amine functionality, and cross-linking is achieved by reaction of diisocyanates with the hydroxyl and amine groups. A variety of cross-linked structures, characterized by transmission electron microscopy (TEM), were produced by this method, including dense fibrillar sheets, fibril bundles, or predominately individual fibrils, depending on the chosen reaction conditions. In solution, the cross-linked fibrils maintained their characteristic vibronic structure in solvents that would normally disrupt (dissolve) the structures.

  7. Complex macrophase-separated nanostructure induced by microphase separation in binary blends of lamellar diblock copolymer thin films.

    PubMed

    Zhang, Jianqi; Posselt, Dorthe; Smilgies, Detlef-M; Perlich, Jan; Kyriakos, Konstantinos; Jaksch, Sebastian; Papadakis, Christine M

    2014-09-01

    The nanostructures of thin films spin-coated from binary blends of compositionally symmetric polystyrene-b-polybutadiene (PS-b-PB) diblock copolymer having different molar masses are investigated by means of atomic force microscopy (AFM) and grazing-incidence small-angle X-ray scattering (GISAXS) after spin-coating and after subsequent solvent vapor annealing (SVA). In thin films of the pure diblock copolymers having high or low molar mass, the lamellae are perpendicular or parallel to the substrate, respectively. The as-prepared binary blend thin films feature mainly perpendicular lamellae in a one-phase state, indicating that the higher molar mass diblock copolymer dominates the lamellar orientation. The lamellar thickness decreases linearly with increasing volume fraction of the low molar mass diblock copolymer. After SVA, well-defined macrophase-separated nanostructures appear, which feature parallel lamellae near the film surface and perpendicular ones in the bulk. PMID:25159458

  8. Investigation of Universal Behavior in Symmetric Diblock Copolymer Melts

    NASA Astrophysics Data System (ADS)

    Medapuram, Pavani

    Coarse-grained theories of dense polymer liquids such as block copolymer melts predict a universal dependence of equilibrium properties on a few dimensionless parameters. For symmetric diblock copolymer melts, such theories predict a universal dependence on only chieN and N¯, where chie is an effective interaction parameter, N is the degree of polymerization, and N¯ is a measure of overlap. This thesis focuses on testing the universal behavior hypothesis by comparing results for various properties obtained from different coarse-grained simulation models to each other. Specifically, results from pairs of simulations of different models that have been designed to have matched values of N¯ are compared over a range of values of chiN. The use of vastly different simulation models allows us to cover a vast range of chi eN ≃ 200 - 8000 that includes most of the experimentally relevant range. Properties studied here include collective and single-chain correlations in the disordered phase, block and chain radii of gyration in the disordered phase, the value of chieN at the order-disorder transition (ODT), the free energy per chain, the latent heat of transition, the layer spacing, the composition profile, and compression modulus in the ordered phase. All results strongly support the universal scaling hypothesis, even for rather short chains, confirming that it is indeed possible to give an accurate universal description of simulation models that differ in many details. The underlying universality becomes apparent, however, only if data are analyzed using an adequate estimate of chie, which we obtained by fitting the structure factor S( q) in the disordered state to predictions of the recently developed renormalized one-loop (ROL) theory. The ROL theory is shown to provide an excellent description of the dependence of S(q on chain length and thermodynamic conditions for all models, even for very short chains, if we allow for the existence of a nonlinear dependence of

  9. Strong stretching theory for diblock copolymers in thin films under application of electric fields.

    PubMed

    Harrach, Michael F; Heckmann, Marianne; Drossel, Barbara

    2012-07-28

    We investigate the microphases of asymmetric AB diblock copolymers confined to thin films in the strong segregation limit under the application of electric fields. We evaluate the free energy of a given set of possible phases and present phase diagrams for diblock copolymers with a cylindrical bulk phase in dependence of the film thickness and the attraction between the confining walls and the A or B monomers. This is done for different field strengths and volume fractions. We find that with increasing field strength structures show a preference for alignment with the field. The alignment is stronger when the permittivity of the minority monomer is larger than that of the majority monomer. Depending on the strength of the wall potential and the film thickness, the walls can become completely wetted by the minority monomer. PMID:22852656

  10. Highly ordered nanoporous films from supramolecular diblock copolymers with hydrogen-bonding junctions.

    PubMed

    Montarnal, Damien; Delbosc, Nicolas; Chamignon, Cécile; Virolleaud, Marie-Alice; Luo, Yingdong; Hawker, Craig J; Drockenmuller, Eric; Bernard, Julien

    2015-09-14

    We designed efficient precursors that combine complementary associative groups with exceptional binding affinities and thiocarbonylthio moieties enabling precise RAFT polymerization. Well defined PS and PMMA supramolecular polymers with molecular weights up to 30 kg mol(-1) are synthesized and shown to form highly stable supramolecular diblock copolymers (BCPs) when mixed, in non-polar solvents or in the bulk. Hierarchical self-assembly of such supramolecular BCPs by thermal annealing affords morphologies with excellent lateral order, comparable to features expected from covalent diblock copolymer analogues. Simple washing of the resulting materials with protic solvents disrupts the supramolecular association and selectively dissolves one polymer, affording a straightforward process for preparing well-ordered nanoporous materials without resorting to crosslinking or invasive chemical degradations. PMID:26234749

  11. Synergistic effects of ion pairs on the dielectric properties of diblock copolymer melts.

    PubMed

    Nakamura, Issei

    2014-12-28

    We study the solvation of ion pairs in diblock copolymer melts. Our theory accounts for the size of the ions, the permanent dipole moment and the molecular polarizability of the monomers, the Kuhn length, the compressibility of the liquid mixtures, and the degrees of polymerization. We demonstrate that the electrostatic field near an ion pair causes marked, synergistic effects on the volume fractions of the two blocks and hence the dielectric function. In particular, we illustrate the oscillatory behavior of the dielectric function near an ion pair and the disparity of the dielectric functions between like and unlike charges. These results depend significantly on the chain length and Kuhn length of the diblock copolymers on the nanometer scale.

  12. Self-assembly of diblock copolymer confined in an array-structure space

    NASA Astrophysics Data System (ADS)

    He, Xuehao; Zou, Zhixiang; Kan, Di; Liang, Haojun

    2015-03-01

    The combination of top-down and bottom-up technologies is an effective method to create the novel nanostructures with long range order in the field of advanced materials manufacture. In this work, we employed a polymeric self-consistent field theory to investigate the pattern formation of diblock copolymer in a 2D confinement system designed by filling pillar arrays with various 2D shapes such as squares, rectangles, and triangles. Our simulation shows that in such confinement system, the microphase structure of diblock copolymer strongly depends on the pitch, shape, size, and rotation of the pillar as well as the surface field of confinement. The array structures can not only induce the formation of new phase patterns but also control the location and orientation of pattern structures. Finally, several methods to tune the commensuration and frustration of array-structure confinement are proposed and examined.

  13. Self-assembly of diblock copolymer confined in an array-structure space

    SciTech Connect

    He, Xuehao E-mail: hjliang@ustc.edu.cn; Zou, Zhixiang; Kan, Di; Liang, Haojun E-mail: hjliang@ustc.edu.cn

    2015-03-14

    The combination of top-down and bottom-up technologies is an effective method to create the novel nanostructures with long range order in the field of advanced materials manufacture. In this work, we employed a polymeric self-consistent field theory to investigate the pattern formation of diblock copolymer in a 2D confinement system designed by filling pillar arrays with various 2D shapes such as squares, rectangles, and triangles. Our simulation shows that in such confinement system, the microphase structure of diblock copolymer strongly depends on the pitch, shape, size, and rotation of the pillar as well as the surface field of confinement. The array structures can not only induce the formation of new phase patterns but also control the location and orientation of pattern structures. Finally, several methods to tune the commensuration and frustration of array-structure confinement are proposed and examined.

  14. Strain rate effects on symmetric diblock copolymer liquid bridges: order-induced stability of polymer fibres.

    PubMed

    Peters, Robert D; Dalnoki-Veress, Kari

    2014-10-01

    Optical microscopy is used to study the effect of lamellar order on the evolution of polymer-melt bridges. Measurements are performed on symmetric diblock copolymers and linear homopolymers in the melt state. Diblock copolymer bridges measured in the disordered phase are shown to exhibit the same strain rate response as their homopolymer counterparts: shear thinning at low strain rates and shear thickening at high strain rates. However, when measured in the ordered phase, copolymer-melt bridges demonstrate an increased effective viscosity due to the lamellar order and a shear thinning response over the entire range of strain rates probed. The increased viscosity demonstrates an enhanced stability in lamellae forming diblock liquid bridges, presumed to be caused by the isotropic orientational order of lamellar domains that provide energy barriers to flow within the bridge. The shear thinning can be understood as an alignment of lamellae along the axis of the bridge due to flow, facilitating unimpeded diffusion of polymer out of the liquid bridge along lamellar boundaries.

  15. Morphologies of charged diblock copolymers simulated with a neutral coarse-grained model.

    PubMed

    Pantano, Diego A; Klein, Michael L; Discher, Dennis E; Moore, Preston B

    2011-04-28

    We present the results of coarse grained molecular dynamics simulation using a charge free model that is able to capture different regions of the morphological phase diagram of charged diblock copolymers. Specifically, we were able to reproduce many phases of the poly(acrylic acid)-(1,4)-polybutadiene (PAA-PBA) diblock copolymer, Ca(2+) and water systems as a function of pH and calcium concentration with short-range LJ type potentials. The morphologies observed range from bilayers to cylinders to spherical micelles. Such polyanionic/cationic amphiphiles in water typically present multiple challenges for molecular simulations, particularly due to the many charge interactions that are long ranged and computationally costly. Further, it is precisely these interactions that are thought to modulate large amphiphile assemblies of interest such as lipid rafts. However, our model is able to reproduce different morphologies due to pH and with or without the addition of Ca(2+) as well as the lateral phase segregation and the domain registration observed in neutral and charged diblock copolymer mixtures. The results suggest that the overall effect of charges is a local structural rearrangement that renormalizes the steric repulsion between the headgroups. This simple model, which is devoid of charges, is able to reproduce the complex phase diagram and can be used to investigate collective phenomena in these charged systems such as domain formation and registration or colocalization of lipid rafts across bilayer leaflets.

  16. Galactose-functionalized cationic polycarbonate diblock copolymer for targeted gene delivery to hepatocytes.

    PubMed

    Ong, Zhan Yuin; Yang, Chuan; Gao, Shu Jun; Ke, Xi-Yu; Hedrick, James L; Yan Yang, Yi

    2013-11-01

    To mediate selective gene delivery to hepatocytes via the asialoglycoprotein receptors (ASGP-Rs), we designed and synthesized well-defined and narrowly dispersed galactose- and glucose-functionalized cationic polycarbonate diblock copolymers (designated as Gal-APC and Glu-APC, respectively) using organocatalytic ring-opening polymerization of functionalized carbonate monomers, with a subsequent quaternization step using bis-tertiary amines to confer quaternary and tertiary amines for DNA binding and endosomal buffering, respectively. The sugar-functionalized diblock copolymers effectively bound and condensed DNA to form positively charged nanoparticles (<100 nm in diameter and ≈30 mV zeta-potential) that were stable under high physiological salt conditions. In comparison to the control Glu-APC/DNA complexes, Gal-APC/DNA complexes mediated significantly higher gene expression in ASGP-R positive HepG2 cells with no significant difference observed in ASGP-R negative HeLa cells. The co-incubation of Gal-APC/DNA complexes with a natural ASGP-R ligand effectively led to a decrease in gene expression, hence providing evidence for the ASGP-R mediated endocytosis of the polyplexes. Importantly, the Gal-APC/DNA complexes induced minimal cytotoxicities in HepG2 cells at the N/P ratios tested. Taken together, the galactose-functionalized cationic polycarbonate diblock copolymer has potential for use as a non-viral gene vector for the targeted delivery of therapeutic genes to hepatocytes in the treatment of liver diseases.

  17. Novel synthesis of cellulose-based diblock copolymer of poly(hydroxyethyl methacrylate) by mechanochemical reaction.

    PubMed

    Ohura, Takeshi; Tsutaki, Yusaku; Sakaguchi, Masato

    2014-01-01

    The mechanical fracture of polymer produces polymeric free radical chain-ends, by which liner block copolymers have been synthesized. A diblock copolymer of microcrystalline cellulose (MCC) and poly 2-hydroxyethyl methacrylate (pHEMA) was produced by the mechanochemical polymerization under vacuum and room temperature. The fraction of pHEMA in MCC-block-pHEMA produced by the mechanochemical polymerization increased up to 21 mol% with increasing fracture time (~6 h). Then, the tacticities of HEMA sequences in MCC-block-pHEMA varied according to the reaction time. In the process of mechanochemical polymerization, cellulose could play the role of a radical polymerization initiator capable of controlling stereoregularity.

  18. Influence of chain rigidity on the phase behavior of wormlike diblock copolymers.

    PubMed

    Jiang, Ying; Chen, Jeff Z Y

    2013-03-29

    We utilize the wormlike chain model in the framework of the self-consistent field theory to investigate the influence of chain rigidity on the phase diagram of AB diblock copolymers in the full three-dimensional space. We develop an efficient numerical scheme that can be used to calculate the physical properties of ordered microstructures self-assembled from semiflexible block copolymers. The calculation describes the entire physical picture of the phase diagram, crossing from the flexible over to rodlike polymer behavior. PMID:23581386

  19. Self-assembly of 21-arm star-like diblock copolymer in bulk and under cylindrical confinement.

    PubMed

    Xu, Yuci; Li, Weihua; Qiu, Feng; Lin, Zhiqun

    2014-06-21

    Phase behaviors of a 21-arm star-like diblock copolymer in bulk and under confinement were explored by using the pseudo-spectral method of a self-consistent mean field theory. An asymmetrical phase diagram in bulk was constructed by comparing the free energy of different structures. The gyroid phase was found to possess a large phase region when the inner block in the star-like diblock copolymer has a small volume fraction, suggesting the propensity to form the gyroid phase under this condition. Combined with the early experimental work, a scaling law correlating the period of lamellae D(multiarms) formed from multi-arm star-like block copolymers with the number of arms f was identified, that is, D(multiarms) = D/f(1/2), where D is the period of a linear diblock copolymer with the same degree of polymerization N as a star-like diblock copolymer. The scaling law was also substantiated by the scaling theory. The bridging fraction of the lamellae formed in a star-like diblock copolymer was nearly 100%, which is advantageous for improving its mechanical properties. Some interesting two-dimensional and three-dimensional morphologies were yielded under the cylindrical confinement, where a 3D double helix was found to be the most stable structure. PMID:24830862

  20. Structure of poly(styrene-b-ethylene-alt-propylene) diblock copolymer micelles in squalane.

    PubMed

    Choi, Soo-Hyung; Bates, Frank S; Lodge, Timothy P

    2009-10-22

    The temperature dependence of the micellar structures formed by poly(styrene-b-ethylene-alt-propylene) (SEP) diblock copolymers in squalane, a highly selective solvent for the PEP blocks, has been studied using dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). Four SEP diblock copolymers were prepared by sequential anionic polymerization of styrene and isoprene, followed by hydrogenation of the isoprene blocks, to yield SEP(17-73), SEP(26-66), SEP(36-69), and SEP(42-60), where the numbers indicate block molecular weights in kDa. All four polymers formed well-defined spherical micelles. In dilute solution, DLS provided the temperature-dependent mean hydrodynamic radius, R(h), and its distribution, while detailed fitting of the SAXS profiles gave the core radius, R(c), the equivalent hard sphere radius, R(hs), and an estimate of the aggregation number, N(agg). In general, the micelles became smaller as the critical micelle temperature (CMT) was approached, which was well above the glass transition of the core block. As concentration increased the micelles packed onto body centered cubic lattices for all four copolymers, which underwent order-disorder transitions upon heating near the dilute solution CMTs. The results are discussed in terms of current understanding of block copolymer solution self-assembly, and particular attention is paid to the issue of equilibration, given the high glass transition temperature of the core block.

  1. Phase Behavior of Weakly Ordered Diblock Copolymers in the High Molecular Weight Limit

    NASA Astrophysics Data System (ADS)

    Patel, Amish; Balsara, Nitash

    2004-03-01

    Poly(tert-butylstyrene-block-polydiene) (TBS-D) diblock copolymers with molecular weights ranging from 10 kg/mol to 500 kg/mol have been synthesized. The dienes studied thus far are 1-4 polyisoprene and 1-2 polybutadiene. The Flory-Huggins interaction parameters (kii) between TBS and D chains are negative at room temperature. Thus, the mean field theory of polymer blends predicts that TBS-D diblock copolymers must be disordered, regardless of their molecular weight. With increasing temperature, kii increases, and we thus expect the formation of ordered phases. The nature of these transitions can be also predicted by mean-field theory. We are conducting small-angle X-ray scattering and optical birefringence experiments on the TBS-D block copolymers to test the applicability of the mean-field theory. This enables a test of the mean-field theory of block copolymers over an unprecedented range of molecular weights. The results of these tests will be presented at the meeting.

  2. Structure of Poly(styrene-b-ethylene-alt-propylene) Diblock Copolymer Micelles in Squalane

    SciTech Connect

    Choi, Soo-Hyung; Bates, Frank S.; Lodge, Timothy P.

    2009-11-04

    The temperature dependence of the micellar structures formed by poly(styrene-b-ethylene-alt-propylene) (SEP) diblock copolymers in squalane, a highly selective solvent for the PEP blocks, has been studied using dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). Four SEP diblock copolymers were prepared by sequential anionic polymerization of styrene and isoprene, followed by hydrogenation of the isoprene blocks, to yield SEP(17-73), SEP(26-66), SEP(36-69), and SEP(42-60), where the numbers indicate block molecular weights in kDa. All four polymers formed well-defined spherical micelles. In dilute solution, DLS provided the temperature-dependent mean hydrodynamic radius, R{sub h}, and its distribution, while detailed fitting of the SAXS profiles gave the core radius, R{sub c}, the equivalent hard sphere radius, R{sub hs}, and an estimate of the aggregation number, N{sub agg}. In general, the micelles became smaller as the critical micelle temperature (CMT) was approached, which was well above the glass transition of the core block. As concentration increased the micelles packed onto body centered cubic lattices for all four copolymers, which underwent order-disorder transitions upon heating near the dilute solution CMTs. The results are discussed in terms of current understanding of block copolymer solution self-assembly, and particular attention is paid to the issue of equilibration, given the high glass transition temperature of the core block.

  3. Donor/acceptor morphology control for efficient and stable photovoltaic cells by using semiconducting diblock copolymers

    NASA Astrophysics Data System (ADS)

    Tajima, Keisuke; Miyanishi, Shoji; Zhang, Yue; Hashimoto, Kazuhito

    2012-09-01

    Poly(3-alkylthiophene)-based diblock copolymers with controllable block lengths were synthesized by combining Grignard metathesis (GRIM) method, Ni-catalyzed quasi-living polymerization and a subsequent azide-alkyne click reaction to introduce a fullerene functionality into the side chains of one of the blocks. The fullerene-attached copolymers had good solubility (> 30 g L-1 in chlorobenzene) with high molecular weights (Mn > 20000). The diblock copolymer films showed the formation of clear nanostructures with the size of 20 nm in AFM phase image driven by the crystallization of poly(3-hexylthiophene) block and aggregation of the fullerene groups. The photovoltaic device based on the copolymers showed a power conversion efficiency of 2.5% with a much higher fill factor of 0.63 compared with the single component devices previously reported. These results indicate that the rational material designs enable to construct the donor-acceptor nanostructure suitable for the photovoltaic application without relying on the mixing of the materials.

  4. Micelle Formation of Diblock Copolymers in Thin Film Homopolymers and Homopolymer Blends

    NASA Astrophysics Data System (ADS)

    Chen, Chelsea; Green, Peter

    2010-03-01

    A-b-B diblock copolymers, at very small concentrations, form micelles in a melt of homopolymer chains of type A or B. In the bulk, the critical micelle concentration, φcmc, is a function of the symmetry of the copolymer chain and exhibits a strong dependence on χN, where χ is the interaction parameter and N is the degree of polymerization of the copolymer. We examined micelle formation in thin film mixtures of: (1) polystyrene-b-poly(2-vinylpyridine) (PS-b-PVP)/polystyrene (PS); (2) PS-b-PVP/ blend of PS and tetramethyl bisphenol-A polycarbonate (TMPC); and (3) polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA)/PS. The critical micelle concentration is found to be orders of magnitude larger than the bulk; it is a strong function of film thickness, the substrate/chain segment interactions and the interactions between the different polymeric segments in the system.

  5. Controllable stacked disk morphologies of charged diblock copolymers

    SciTech Connect

    Goswami, Monojoy; Sumpter, Bobby G; Mays, Jimmy

    2010-01-01

    Monte Carlo simulations are used to demonstrate the controlled stacking of charged block copolymer disk morphologies that can be obtained under certain thermodynamic conditions. We examine a partially charged block copolymer where 75% of the blocks are neutral and 25% of the blocks are charged. The presence of strong electrostatic interactions promotes charge agglomeration thereby changing morphologies in these systems. This study relates different thermodynamic quantities for which disk-like stackings can be obtained. The long-range order can be sustained even if hydrophobicity is increased albeit with lower dimensional structures. Our simulation results agree very well with recent experiments and are consistent with theoretical observations of counterion adsorption on flexible polyelectrolytes.

  6. Supramolecular self-assembly of conjugated diblock copolymers.

    SciTech Connect

    Wang, H.; You, W.; Jiang, P.; Yu, L.; Wang, H. H.; Univ. of Chicago

    2004-02-20

    This paper describes the synthesis and characterization of a novel series of copolymers with different lengths of oligo(phenylene vinylene) (OPV) as the rod block, and poly(propylene oxide) as the coil block. Detailed characterization by means of transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle neutron scattering (SANS) revealed the strong tendency of these copolymers to self-assemble into cylindrical micelles in solution and as-casted films on a nanometer scale. These micelles have a cylindrical OPV core surrounded by a poly(propylene glycol) (PPG) corona and readily align with each other to form parallel packed structures when mica is used as the substrate. A packing model has been proposed for these cylindrical micelles.

  7. Mechanical characterization of diblock copolymer ``armored'' emulsion droplets

    NASA Astrophysics Data System (ADS)

    Rozairo, Damith; Croll, Andrew

    2013-03-01

    There has been an increased interest in block copolymer vesicles due to a plethora of possible application ranging from targeted drug delivery to cosmetically active agents. In this regard, understanding the physics of the block copolymer vesicle and its morphology is critical to the rational development of these technologies. As a step towards more complex vesicle structures, we describe experiments in which we carefully examine the interface and morphology of polystyrene-b-polyethyleneoxide (PS-PEO) emulsion drops. In our study, PS-PEO acts as a surfactant and at the toluene-water interface creates a monolayer, inhibiting drop recombination and minimizing interfacial energies. Our experiments are conducted in a water cell where the buoyant force is exploited to push drops against a thin sheet of mica. The shape of the drops is measured using an upright confocal microscope and compared with a Bashforth-Adams model in order to examine the mechanical response to the buoyant force. We observe unique dynamics as the drops buckle at short timescales trapping a small pocket of fluid which slowly drains away. Furthermore, the influence of polymer concentration, changes in pH and block copolymer architecture on the morphology and dynamics of the droplets is examined.

  8. Shear induced order in SEP diblock copolymer micelles: multiple BCC slip systems

    NASA Astrophysics Data System (ADS)

    Torija, Maria A.; Choi, Soohyung; Bates, Frank S.; Lodge, Timothy P.

    2010-03-01

    Poly(styrene-b-ethylene-alt-propylene) (SEP) diblock copolymers are solvated by squalane leading to glassy poly(styrene) domains dispersed in a viscoelastic medium. For diblocks containing less than about 50% by weight poly(styrene) and at SEP concentrations greater than 6 w. % these mixtures self-assemble into glassy spherical microdomains that order on a body centered cubic (BCC) lattice. We have investigated how polycrystalline configurations respond to large amplitude oscillatory shear as a function of shear rate, strain amplitude and block copolymer composition. Structure was characterized by small-angle X-ray scattering measurements while simultaneously deforming the mixtures with an in-situ rheometer. All three slip systems associated with plastic deformation in BCC metals110<111>,211<111>,321<111>, were identified with the x-ray beam oriented perpendicular to the shear plane. Higher shear rates and larger strain amplitudes produced more slip within the 211<111> system. These results represent one of the most comprehensive assessments of BCC structure in solvated copolymers and will be discussed within the context of the associated linear viscoelastic behavior.

  9. Adsorption and aqueous lubricating properties of charged and neutral amphiphilic diblock copolymers at a compliant, hydrophobic interface.

    PubMed

    Røn, Troels; Javakhishvili, Irakli; Jankova, Katja; Hvilsted, Søren; Lee, Seunghwan

    2013-06-25

    We have investigated the adsorption and lubricating properties of neutral and charged amphiphilic diblock copolymers at a hydrophobic polydimethylsiloxane (PDMS) interface in an aqueous environment. The diblock copolymers consist of a hydrophilic block of either neutral poly(ethylene glycol) (PEG) or negatively charged poly(acrylic acid) (PAA) and of a hydrophobic block of polystyrene (PS) or poly(2-methoxyethyl acrylate) (PMEA), thus generating PEG-b-X or PAA-b-X, where X block is either PS or PMEA. The molecular weight ratios were roughly 1:1 with each block ca. 5 kDa. Comparing the neutral PEG and charged PAA buoyant blocks with all other conditions identical, the former showed superior adsorption onto nonpolar, hydrophobic PDMS surfaces from a neutral aqueous solution. PEG-based copolymers showed substantial adsorption for both PS and PMEA as the anchoring block, whereas PAA-based copolymers showed effective adsorption only when PMEA was employed as the anchoring block. For PAA-b-PS, the poor adsorption properties are chiefly attributed to micellization due to the high interfacial tension between the PS core and water. The poor lubricating properties of PAA-b-PS diblock copolymer for a PDMS-PDMS sliding contact was well correlated with the poor adsorption properties. PAA-b-PMEA copolymers, despite their sizable amount of adsorbed mass, showed insignificant lubricating effects. When the charges of the PAA-b-PMEA diblock copolymers were screened by either adding NaCl to the aqueous solution or by lowering the pH, both the adsorption and lubricity improved. We ascribe the poor adsorption and inferior aqueous lubricating properties of the PAA-based diblock copolymers compared to their PEG-based counterparts mainly to the electrostatic repulsion between charged PAA blocks, hindering the facile formation of the lubricating layer under cyclic tribological stress at the sliding PDMS-PDMS interface. PMID:23725290

  10. Multiple patterns of diblock copolymer confined in irregular geometries with soft surface

    NASA Astrophysics Data System (ADS)

    Li, Ying; Sun, Min-Na; Zhang, Jin-Jun; Pan, Jun-Xing; Guo, Yu-Qi; Wang, Bao-Feng; Wu, Hai-Shun

    2015-12-01

    The different confinement shapes can induce the formation of various interesting and novel morphologies, which might inspire potential applications of materials. In this paper, we study the directed self-assembly of diblock copolymer confined in irregular geometries with a soft surface by using self-consistent field theory. Two types of confinement geometries are considered, namely, one is the concave pore with one groove and the other is the concave pore with two grooves. We obtain more novel and different structures which could not be produced in other two-dimensional (2D) confinements. Comparing these new structures with those obtained in regular square confinement, we find that the range of ordered lamellae is enlarged and the range of disordered structure is narrowed down under the concave pore confinement. We also compare the different structures obtained under the two types of confinement geometries, the results show that the effect of confinement would increase, which might induce the diblock copolymer to form novel structures. We construct the phase diagram as a function of the fraction of B block and the ratio of h/L of the groove. The simulation reveals that the wetting effect of brushes and the shape of confinement geometries play important roles in determining the morphologies of the system. Our results improve the applications in the directed self-assembly of diblock copolymer for fabricating the irregular structures. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20121404110004), the Research Foundation for Excellent Talents of Shanxi Provincial Department of Human Resources and Social Security, China, and the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province, China.

  11. Nanopatterned Protein Films Directed by Ionic Complexation with Water-Soluble Diblock Copolymers

    PubMed Central

    Kim, Bokyung; Lam, Christopher N.; Olsen, Bradley D.

    2014-01-01

    The use of ionic interactions to direct both protein templating and block copolymer self-assembly into nanopatterned films with only aqueous processing conditions is demonstrated using block copolymers containing both thermally responsive and pH responsive blocks. Controlled reversible addition-fragmentation chain-transfer (RAFT) polymerization is employed to synthesize poly(N-isopropylacrylamide-b-2-(dimethylamino)ethyl acrylate) (PNIPAM-b-PDMAEA) diblock copolymers. The pH-dependent ionic complexation between the fluorescent protein, mCherry, and the ionic PDMAEA block is established using dynamic light scattering (DLS) and UV-Vis spectroscopy. DLS shows that the size of the resulting coacervate micelles depends strongly on pH, while UV-Vis spectroscopy shows a correlation between the protein’s absorption maximum and the ionic microenvironment. Zeta potential measurements clearly indicate the ionic nature of the complex-forming interactions. Spin casting was used to prepare nanostructured films from the protein-block copolymer coacervates. After film formation, the lower critical solution temperature (LCST) of the PNIPAM blocks allows the nanomaterial to be effectively immobilized in aqueous environments at physiological temperatures, enabling potential use as a controlled protein release material or polymer matrix for protein immobilization. At pH 9.2 and 7.8, the release rates are at least 10 times faster than that at pH 6.4 due to weaker interaction between protein and PNIPAM-b-PDMAEA (PND) diblock copolymer. Due to the ionic environment in which protein is confined, the majority of the protein (80%) remains active, independent of pH, even after having been dehydrated in vacuum and confined in the films. PMID:24904186

  12. Nanopatterned Protein Films Directed by Ionic Complexation with Water-Soluble Diblock Copolymers.

    PubMed

    Kim, Bokyung; Lam, Christopher N; Olsen, Bradley D

    2012-06-12

    The use of ionic interactions to direct both protein templating and block copolymer self-assembly into nanopatterned films with only aqueous processing conditions is demonstrated using block copolymers containing both thermally responsive and pH responsive blocks. Controlled reversible addition-fragmentation chain-transfer (RAFT) polymerization is employed to synthesize poly(N-isopropylacrylamide-b-2-(dimethylamino)ethyl acrylate) (PNIPAM-b-PDMAEA) diblock copolymers. The pH-dependent ionic complexation between the fluorescent protein, mCherry, and the ionic PDMAEA block is established using dynamic light scattering (DLS) and UV-Vis spectroscopy. DLS shows that the size of the resulting coacervate micelles depends strongly on pH, while UV-Vis spectroscopy shows a correlation between the protein's absorption maximum and the ionic microenvironment. Zeta potential measurements clearly indicate the ionic nature of the complex-forming interactions. Spin casting was used to prepare nanostructured films from the protein-block copolymer coacervates. After film formation, the lower critical solution temperature (LCST) of the PNIPAM blocks allows the nanomaterial to be effectively immobilized in aqueous environments at physiological temperatures, enabling potential use as a controlled protein release material or polymer matrix for protein immobilization. At pH 9.2 and 7.8, the release rates are at least 10 times faster than that at pH 6.4 due to weaker interaction between protein and PNIPAM-b-PDMAEA (PND) diblock copolymer. Due to the ionic environment in which protein is confined, the majority of the protein (80%) remains active, independent of pH, even after having been dehydrated in vacuum and confined in the films. PMID:24904186

  13. Polymerization-Induced Self-Assembly of Galactose-Functionalized Biocompatible Diblock Copolymers for Intracellular Delivery

    PubMed Central

    2013-01-01

    Recent advances in polymer science are enabling substantial progress in nanobiotechnology, particularly in the design of new tools for enhanced understanding of cell biology and for smart drug delivery formulations. Herein, a range of novel galactosylated diblock copolymer nano-objects is prepared directly in concentrated aqueous solution via reversible addition–fragmentation chain transfer polymerization using polymerization-induced self-assembly. The resulting nanospheres, worm-like micelles, or vesicles interact in vitro with galectins as judged by a turbidity assay. In addition, galactosylated vesicles are highly biocompatible and allow intracellular delivery of an encapsulated molecular cargo. PMID:23941545

  14. Influence of polydispersity on the isotropic-nematic boundary in melt of semiflexible diblock copolymer

    NASA Astrophysics Data System (ADS)

    Aliev, M. A.

    2015-12-01

    The analytical expressions have been obtained to describe the dependence of spinodal curve at which isotropic state of polydisperse melt of semiflexible diblock copolymer becomes unstable with respect to formation of nematic state on the polydispersity indices of the blocks, parameters of anisotropic interactions, and flexibility of blocks. The flexibility of blocks is taken into account within discrete worm-like chain model, lengths of blocks are assumed to be distributed by the Schulz-Zimm distribution. It is shown that increase of degree of polydispersity of blocks yields the increase of nematic spinodal temperature.

  15. Fluctuation effects and the stability of the Fddd network phase in diblock copolymer melts.

    PubMed

    Miao, Bing; Wickham, Robert A

    2008-02-01

    We examine the effect of composition fluctuations on the stability of the orthorhombic Fddd network phase in the diblock copolymer melt phase diagram within the self-consistent Hartree approximation to the Landau-Brazovskii theory. For weak fluctuations, the Fddd structure is an equilibrium phase; however, stronger fluctuations render this phase metastable. These results suggest a reinterpretation of a recent experiment beyond mean-field theory. Fluctuations may also explain why an equilibrium Fddd phase is not generally observed in analogous self-assembling systems. PMID:18266460

  16. Ordered phases of diblock copolymers in selective solvent

    NASA Astrophysics Data System (ADS)

    Grason, Gregory M.

    2007-03-01

    The authors propose a mean-field model to explore the equilibrium coupling between micelle aggregation and lattice choice in neutral copolymer and selective solvent mixtures. They find both thermotropic and lyotropic transitions from face-centered cubic to body-centered cubic ordered phases of spherical micelles, in agreement with experimental observations of these systems over a broad range of conditions. The stability of the nonclosed packed phase can be attributed to two physical mechanisms: the large entropy of lattice phonons near crystal melting and the preference of the intermicelle repulsions for the body-centered cubic structure when the lattice becomes sufficiently dense at higher solution concentrations. Both mechanisms are controlled by the decrease of micelle aggregation and subsequent increase of lattice density as solvent selectivity is reduced. These results shed new light on the relationship between micelle structure—"crewcut" or "hairy"—and long-range order in micelle solutions.

  17. Liquid-liquid interfaces of semifluorinated alkane diblock copolymers with water, alkanes, and perfluorinated alkanes.

    SciTech Connect

    Perahia, Dvora, Dr.; Pierce, Flint; Tsige, Mesfin; Grest, Gary Stephen, Dr.

    2008-08-01

    The liquid-liquid interface between semifluorinated alkane diblock copolymers of the form F3C(CF2)n-1-(CH2)m-1CH3 and water, protonated alkanes, and perfluorinated alkanes are studied by fully atomistic molecular dynamics simulations. A modified version of the OPLS-AA (Optimized Parameter for Liquid Simulation All-Atom) force field of Jorgensen et al. has been used to study the interfacial behavior of semifluorinated diblocks. Aqueous interfaces are found to be sharp, with correspondingly large values of the interfacial tension. Due to the reduced hydrophobicity of the protonated block compared to the fluorinated block, hydrogen enhancement is observed at the interface. Water dipoles in the interfacial region are found to be oriented nearly parallel to the liquid-liquid interface. A number of protonated alkanes and perfluorinated alkanes are found to be mutually miscible with the semifluorinated diblocks. For these liquids, interdiffusion follows the expected Fickian behavior, and concentration-dependent diffusivities are determined.

  18. Spotted Polymersomes and Striped Worms - a theoretical analysis of lateral segregation of diblock copolymers

    NASA Astrophysics Data System (ADS)

    Ellenbroek, Wouter G.; Christian, David A.; Tian, Aiwei; Liu, Andrea J.; Baumgart, Tobias; Discher, Dennis E.

    2008-03-01

    Lipids and amphiphilic block copolymers are both known to assemble into vesicle and worm-like micelle morphologies, but only mixtures of lipids in vesicles have been directly seen to phase separate into meso-scale lateral domains. Here we show direct visualization of meso-scale spots in tough polymersomes and micron-length stripes in stable worms that result from strong lateral segregation of polyanionic and neutral diblock copolymers. We present a model for understanding the crucial role of calcium ions on segregation behavior, which incorporates counterion condensation and ``crosslinking'' (ion bridging). We find a tendency towards segregation near the isoelectric point as a result of competition among counterion entropy, repulsion due to the net charge, and attraction due to crosslinking. These results portend new classes of robust membranes and cylinders that exhibit lateral patterns at the meso-scale.

  19. Quantifying Fluctuation Effects on the Order-Disorder Transition of Symmetric Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Zong, Jing; Wang

    2012-02-01

    How fluctuations change the order-disorder transition (ODT) of symmetric diblock copolymers is a classic yet unsolved problem in polymer physics.ootnotetextL. Leibler, Macromolecules, 13, 1602 (1980); G. H. Fredrickson and E. Helfand, J. Chem. Phys., 87, 697 (1987). Here we unambiguously quantify the fluctuation effects by direct comparisons between fast off-lattice Monte Carlo (FOMC) simulationsootnotetextQ. Wang and Y. Yin, J. Chem. Phys., 130, 104903 (2009). and mean-field theory using exactly the same model system (Hamiltonian), thus without any parameter-fitting. The symmetric diblock copolymers are modeled as discrete Gaussian chains with soft, finite-range repulsions as commonly used in dissipative-particle dynamics simulations. The effects of chain discretization and finite-range interactions on ODT are properly accounted for in our mean-field theory.ootnotetextQ. Wang, J. Chem. Phys., 129, 054904 (2008); 131, 234903 (2009). Our FOMC simulations are performed in a canonical ensemble with variable box lengths to eliminate the adverse effects of fixed box sizes on ODT.ootnotetextQ. Wang et al., J. Chem. Phys., 112, 450 (2000). Furthermore, with a new order parameter for the lamellar phase, we use replica exchange and multiple histogram reweighting to accurately locate ODT in our simulations.

  20. A Small-Angle Scattering Study of the Bulk Structure of a Symmetric Diblock Copolymer System

    NASA Astrophysics Data System (ADS)

    Papadakis, Christine M.; Almdal, Kristoffer; Mortensen, Kell; Posselt, Dorthe

    1997-12-01

    The bulk structure of a homologous series of symmetric polystyrene-polybutadiene (SB) diblock copolymers is investigated using small-angle X-ray and neutron scattering (SANS). The study focuses on the lamellar thickness, the lamellar correlation length and the concentration profile as a function of the chain length and the preparation method applied. The characteristic length, D, scales with the chain length, N, in the whole range studied, but with a clear change in scaling exponent near χ N = 29, in accordance with theoretical predictions of a crossover from an Intermediate-Segregation Regime (ISR) to the Strong-Segregation Limit (SSL). In the ISR (χ N simeq 5-29), D is found to scale like D propto N^{0.83} and in the SSL (χ N > 29) like D propto N^{0.61} . The temperature dependence of the SANS spectra is studied for a low molar mass sample in an interval around the order-disorder transition temperature (TODT). The peak position is found to vary more strongly with temperature than expected for Gaussian chains. Only a weak discontinuity of the peak position at TODT is observed. In summary, the phase behavior of symmetric SB diblock copolymers in the bulk spans three regimes: the Gaussian regime in the region χ N < 5, the ISR for 5 < χ N < 29 and the SSL for χ N > 29.

  1. Microphase separation patterns in diblock copolymers on curved surfaces using a nonlocal Cahn-Hilliard equation.

    PubMed

    Jeong, Darae; Kim, Junseok

    2015-11-01

    We investigate microphase separation patterns on curved surfaces in three-dimensional space by numerically solving a nonlocal Cahn-Hilliard equation for diblock copolymers. In our model, a curved surface is implicitly represented as the zero level set of a signed distance function. We employ a discrete narrow band grid that neighbors the curved surface. Using the closest point method, we apply a pseudo-Neumann boundary at the boundary of the computational domain. The boundary treatment allows us to replace the Laplace-Beltrami operator by the standard Laplacian operator. In particular, we can apply standard finite difference schemes in order to approximate the nonlocal Cahn-Hilliard equation in the discrete narrow band domain. We employ a type of unconditionally stable scheme, which was introduced by Eyre, and use the Jacobi iterative to solve the resulting implicit discrete system of equations. In addition, we use the minimum number of grid points for the discrete narrow band domain. Therefore, the algorithm is simple and fast. Numerous computational experiments are provided to study microphase separation patterns for diblock copolymers on curved surfaces in three-dimensional space. PMID:26577816

  2. Structure and phase behaviour of diblock copolymer monolayers investigated by means of Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Słyk, Edyta; Rżysko, Wojciech; Bryk, Paweł

    2015-10-01

    We use grand canonical Monte Carlo simulation paired with multiple histogram reweighting, hyperparallel tempering and finite size scaling to investigate the structure and phase behaviour of monolayers of diblock copolymers. The chain molecules are arranged on the square lattice and we consider both fully flexible and rod-coil polymer models. In contrast to the majority of previous studies we assume that the interactions between the segments belonging to one of the two subunits are weaker than the remaining segment-segment interactions. We find that when the diblock copolymer is fully flexible, this choice of the interactions leads to a suppression of the ordered phase, and the phase behaviour is analogous to that of the fully flexible homopolymer model. However, when one of the subunits is rigid, we observe the formation of a novel hairpin chessboard ordered structure with fully stretched chains bent in the middle. The topology of the phase diagram depends on the chain length. For shorter chains the global phase diagram features a critical point and a triple point. For longer chains the gas—disordered liquid phase transition is suppressed and only the order-disorder transition remains stable. The resulting phase diagram is of the swan neck type.

  3. Structure and phase behaviour of diblock copolymer monolayers investigated by means of Monte Carlo simulation.

    PubMed

    Słyk, Edyta; Rżysko, Wojciech; Bryk, Paweł

    2015-10-21

    We use grand canonical Monte Carlo simulation paired with multiple histogram reweighting, hyperparallel tempering and finite size scaling to investigate the structure and phase behaviour of monolayers of diblock copolymers. The chain molecules are arranged on the square lattice and we consider both fully flexible and rod-coil polymer models. In contrast to the majority of previous studies we assume that the interactions between the segments belonging to one of the two subunits are weaker than the remaining segment-segment interactions. We find that when the diblock copolymer is fully flexible, this choice of the interactions leads to a suppression of the ordered phase, and the phase behaviour is analogous to that of the fully flexible homopolymer model. However, when one of the subunits is rigid, we observe the formation of a novel hairpin chessboard ordered structure with fully stretched chains bent in the middle. The topology of the phase diagram depends on the chain length. For shorter chains the global phase diagram features a critical point and a triple point. For longer chains the gas-disordered liquid phase transition is suppressed and only the order-disorder transition remains stable. The resulting phase diagram is of the swan neck type. PMID:26414501

  4. Congruent Lamellar-to-Disorder Phase Transitions in Diblock Copolymer-Homopolymer Ternary Blends

    NASA Astrophysics Data System (ADS)

    Hickey, Robert; Gillard, Timothy; Irwin, Matthew; Lodge, Timothy; Bates, Frank

    Symmetric ternary blends of AB diblock copolymers and the corresponding A and B homopolymers are predicted to be characterized by a multicritical Lifshitz point within mean-field theory. Previous studies have shown that fluctuations destroy the predicted Lifshitz point and lead to a bicontinuous microemulsion (B μE) channel, which separates the lamellar and 2-phase regions in the ternary phase prism. Here, we establish the existence of a line of congruent first-order lamellar-to-disorder transitions when appropriate amounts of poly(cyclohexylethylene) (C) and poly(ethylene) (E) homopolymers are mixed with the corresponding symmetric CE diblock copolymer. We present complimentary optical transmission, small-angle X-ray scattering, transmission electron microscopy (TEM), and rheological results obtained using two experimental protocols: (1) fixing the CE volume fraction and varying the C/E ratio, and (2) setting the C/E ratio at the condition of congruency and varying CE volume fraction from 0 to 1. These results establish a quantitative and facile method for identifying the detailed phase behavior in the vicinity of the B μE, and provide fresh insight into the nature of such mixtures near the nominal Lifshitz conditions. Surprisingly, well-ordered lamellae are revealed by TEM at compositions within 1% of the B μE channel, suggesting a remarkably close approach to the predicted, mean-field unbinding transition. Moreover, the width of the B μE narrows to about 1% under congruent conditions.

  5. Direct synthesis of inverse hexagonally ordered diblock copolymer/polyoxometalate nanocomposite films.

    PubMed

    Lunkenbein, Thomas; Kamperman, Marleen; Li, Zihui; Bojer, Carina; Drechsler, Markus; Förster, Stephan; Wiesner, Ulrich; Müller, Axel H E; Breu, Josef

    2012-08-01

    Nanostructured inverse hexagonal polyoxometalate composite films were cast directly from solution using poly(butadiene-block-2-(dimethylamino)ethyl methacrylate) (PB-b-PDMAEMA) diblock copolymers as structure directing agents for phosphomolybdic acid (H(3)[PMo(12)O(40)], H(3)PMo). H(3)PMo units are selectively incorporated into the PDMAEMA domains due to electrostatic interactions between protonated PDMAEMA and PMo(3-) anions. Long solvophilic PB chains stabilized the PDMAEMA/H(3)PMo aggregates in solution and reliably prevented macrophase separation. The choice of solvent is crucial. It appears that all three components, both blocks of the diblock copolymer as well as H(3)PMo, have to be soluble in the same solvent which turned out to be tetrahydrofuran, THF. Evaporation induced self-assembly resulted in highly ordered inverse hexagonal nanocomposite films as observed from transmission electron microscopy and small-angle X-ray scattering. This one-pot synthesis may represent a generally applicable strategy for integrating polyoxometalates into functional architectures and devices. PMID:22757978

  6. Stable gene transfection mediated by polysulfobetaine/PDMAEMA diblock copolymer in salted medium.

    PubMed

    Dai, Fengying; Liu, Yuan; Wang, Wei; Liu, Wenguang

    2013-01-01

    Cationic polyplexes would aggregate immediately after intravenous injection due to the plasma proteins and high ionic strength. A cationic polyplexes with long-term and salt stability was very important for a systemic gene therapy. In this research, a polysulfobetaine-b-polycation diblock copolymer composed of cationic block of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and zwtterionic block of poly(propylsulfonate dimethylammonium ethylmethacrylate) (PSPE) was conveniently synthesized by atom transfer radical polymerization method to obtain a cationic polymers with long-term and salt stability. The results of agarose gel electrophoresis and transmission electron microscope indicated that copolymerization of PSPE did not compromise the DNA condensation ability of PDMAEMA, meanwhile exhibiting lower cytotoxicity. The effect of salt on the absorbance and particle size of PDMAEMA100/DNA and PDMAEMA100-PSPEy/DNA complexes was investigated, which showed that PSPE block could increase the resistance of polyplexes against salt-induced aggregation owing to the antielectrolyte effect. In comparison with PDMAEMA homopolymer, PDMAEMA100-PSPEy retained more stable gene transfection in a certain range of salt concentration. The expression of red fluorescence protein (RFP) was evaluated by small animal in vivo fluorescence imaging system and the results showed that the expression of RFP was much higher in the mice injected with PDMAEMA100-PSPE20/pDNA-RFP than with PDMAEMA/pDNA-RFP. Both in vitro and in vivo results suggested that PDMAEMA-PSPE diblock copolymer may be potentially used as a vector for systemic gene therapy. PMID:23565651

  7. Tissue anti-adhesion potential of ibuprofen-loaded PLLA-PEG diblock copolymer films.

    PubMed

    Lee, Jin Ho; Go, Ae Kyung; Oh, Se Heang; Lee, Ka Eul; Yuk, Soon Hong

    2005-02-01

    This study was designed to evaluate the effect of polyethylene glycol (PEG) and nonsteroidal anti-inflammatory drug (ibuprofen) on the prevention of postsurgical tissue adhesion. For this, poly(L-lactic acid) (PLLA)-PEG diblock copolymers were synthesized by ring opening polymerization of L-lactide and methoxy polyethylene glycol (Mw 5000) of different compositions. The synthesized copolymers were characterized by gel permeation chromatography and 1H-nuclear magnetic resonance spectroscopy. PLLA-PEG copolymer films were prepared by solvent casting. The prepared copolymer films were more flexible and hydrophilic than the control PLLA film, as investigated by the measurements of glass transition temperature, water absorption content, and water contact angle. The drug release behavior from the ibuprofen (10 wt%)-loaded copolymer films was examined by high performance liquid chromatography. It was observed that the drug was released gradually up to about 40% of total loading amount after 20 days, depending on PEG composition; more drug release from the films with higher PEG compositions. In vitro cell adhesions on the copolymer films with/without drug were compared by the culture of NIH/3T3 mouse embryo fibroblasts on the surfaces. For in vivo evaluation of tissue anti-adhesion potential, the copolymer films with/without drug were implanted between the cecum and peritoneal wall defects of rats and their tissue adhesion extents were compared. It was observed that the ibuprofen-containing PLLA-PEG films with high PEG composition (particularly PLLA113-PEG113 film with PEG composition, 50 mol%) were very effective in preventing cell or tissue adhesion on the film surfaces, probably owing to the synergistic effects of highly mobile, hydrophilic PEG and anti-inflammatory drug, ibuprofen.

  8. Poly(trimethylene carbonate)/Poly(malic acid) Amphiphilic Diblock Copolymers as Biocompatible Nanoparticles.

    PubMed

    Barouti, Ghislaine; Khalil, Ali; Orione, Clement; Jarnouen, Kathleen; Cammas-Marion, Sandrine; Loyer, Pascal; Guillaume, Sophie M

    2016-02-18

    Amphiphilic polycarbonate-poly(hydroxyalkanoate) diblock copolymers, namely, poly(trimethylene carbonate) (PTMC)-b-poly(β-malic acid) (PMLA), are reported for the first time. The synthetic strategy relies on commercially available catalysts and initiator. The controlled ring-opening polymerization (ROP) of trimethylene carbonate (TMC) catalyzed by the organic guanidine base 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), associated with iPrOH as an initiator, provided iPrO-PTMC-OH, which served as a macroinitiator in the controlled ROP of benzyl β-malolactonate (MLABe) catalyzed by the neodymium triflate salt (Nd(OTf)3). The resulting hydrophobic iPrO-PTMC-b-PMLABe-OH copolymers were then hydrogenolyzed into the parent iPrO-PTMC-b-PMLA-OH copolymers. A range of well-defined copolymers, featuring different sizes of segments (Mn,NMR up to 9300 g mol(-1) ; ÐM =1.28-1.40), were thus isolated in gram quantities, as evidenced by NMR spectroscopy, size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry, and contact angle analyses. Subsequently, PTMC-b-PMLA copolymers with different hydrophilic weight fractions (11-75 %) self-assembled in phosphate-buffered saline upon nanoprecipitation into well-defined nano-objects with Dh =61-176 nm, a polydispersity index <0.25, and a negative surface charge, as characterized by dynamic light scattering and zeta-potential analyses. In addition, these nanoparticles demonstrated no significant effect on cell viability at low concentrations, and a very low cytotoxicity at high concentrations only for PTMC-b-PMLA copolymers exhibiting hydrophilic fractions over 47 %, thus illustrating the potential of these copolymers as promising nanoparticles.

  9. An inorganic-organic diblock copolymer photoresist for direct mesoporous SiCN ceramic patterns via photolithography.

    PubMed

    Nguyen, Chi Thanh; Hoang, Phan Huy; Perumal, Jayakumar; Kim, Dong-Pyo

    2011-03-28

    A high resolution negative-tone-type of inorganic-organic diblock copolymer photoresist was synthesized as a novel precursor for simple and direct fabrication of SiCN ceramic mesoporous patterns with ordered nanoscale pores by using a "top-down" photolithographic technique and the subsequent sacrificial processes of a "bottom-up" self-assembled nanostructure.

  10. Lyotropic Phase Behavior of Polybutadiene-Poly(ethylene oxide) Diblock Copolymers in Ionic Liquids

    SciTech Connect

    Simone, Peter M.; Lodge, Timothy P.

    2008-08-26

    The lyotropic phase behavior of three poly(1,2-butadiene-b-ethylene oxide) diblock copolymers (PB-PEO) with different monomer volume fractions has been studied in two different ionic liquids, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMI][PF{sub 6}]), across the complete concentration range. The ordered microstructures present in the solutions were characterized via small-angle X-ray scattering (SAXS). The phase diagrams for the PB-PEO/ionic liquid solutions include regions corresponding to the classical copolymer microstructures: body-centered-cubic lattices of spheres, hexagonally ordered cylinders, and lamellae. Additionally, the phase diagrams also include wide regions of coexisting microstructures and regions apparently corresponding to a disordered network microstructure. The phase behavior of the PB-PEO copolymers in both ionic liquids was comparable to their previously reported aqueous solution behavior. The temperature dependence of the phase diagrams was very modest, indicative of a highly segregated system. The level of solvent selectivity was also investigated via cryogenic transmission electron microscopy (cryo-TEM) on dilute solutions. On the basis of the morphology of the dilute solution copolymer aggregate structures in the ionic liquid solvents, and on the structural length scales of the concentrated solutions, it was concluded that for PB-PEO [BMI][PF{sub 6}] behaves as a more selective solvent than [EMI][TFSI].

  11. Solid-State Structure and Crystallization in Double-Crystalline Diblock Copolymers of Linear Polyethylene and Hydrogenated Polynorbornene

    SciTech Connect

    Li, Sheng; Myers, Sasha B.; Register, Richard A.

    2012-10-10

    Double-crystalline diblock copolymers of linear polyethylene (LPE) and hydrogenated polynorbornene (hPN) are synthesized, and their crystallization behavior and morphology are examined using small-angle (SAXS) and wide-angle X-ray scattering (WAXS). In symmetric hPN/LPE diblocks with molecular weights above 50 kg/mol, the hPN block has previously been shown to crystallize first and set the solid-state microstructure. Two-dimensional WAXS on hand-drawn fiber specimens reveals that the LPE crystals formed in confinement stack orthogonally to the hPN crystals. By adjusting total molecular weight, the order of block crystallization may be reversed, even while holding the block length ratio fixed. At a diblock molecular weight of 20 kg/mol, simultaneous time-resolved SAXS/WAXS reveals that the LPE block crystallizes first, even when LPE is the minority component, and restricts hPN to crystallize between the LPE lamellae. The relative orientation of the LPE and hPN crystals in the lower molecular weight diblocks is examined by modeling changes in the SAXS primary peak intensity on cooling two diblocks through the hPN crystal-crystal transition, where hPN densifies as it adopts a rotationally ordered crystal structure. Only a perpendicular stacking of hPN and LPE crystals consistently yields the large reduction in primary SAXS peak intensity observed for both diblocks. Thus, even though the templating block switches from hPN to LPE as the diblock molecular weight is reduced, the orthogonal stacking motif is retained for both high- and low-molecular-weight copolymers.

  12. Protonation-induced microphase separation in thin films of a polyelectrolyte-hydrophilic diblock copolymer

    NASA Astrophysics Data System (ADS)

    Stewart-Sloan, Charlotte; Olsen, Bradley

    2014-03-01

    Materials with easily and controllably tuneable morphologies are of interest for many applications where the relevant properties depend upon the microstructure. Here, we present a novel double hydrophilic diblock copolymer whose solid state morphology is responsive to protonation. It contains one block which is neutral and hydrophilic at all values of pH, poly(oligoethylene glycol methyl ether methacrylate) (POEGMA), and one block which is neutral and hydrophobic above its pKa but positively charged and hydrophilic when protonated, poly(2-vinylpyridine) (P2 VP). This material is disordered when cast from acid-free solutions but displays increasing segregation between the two blocks with increasing protonation of the pyridine groups. The protonation-induced microphase separation is shown to be due to ionomer-like effects and not to the selective solubilzation of ions in one of the blocks. Order-disorder transitions occur between 1:0.28 and 1:0.55 pyridine group:acid content for thin films of a 50kg/mol POEGMA-30kg/mol P2VP diblock and between 1:0.8 and 1:0.9 pyridine group:acid content for thin films of a 43kg/mol POEGMA-13kg/mol P2VP diblock. The latter also displays an order-order transition between spheres and in-plane cylinders between 1:1 and 1:1.1 pyridine group:acid loading. These films can be annealed in aqueous as well as polar organic solvents, allowing for both traditional polymer processing and environmentally friendly water-based casting and annealing.

  13. Coil fraction-dependent phase behaviour of a model globular protein–polymer diblock copolymer

    SciTech Connect

    Thomas, Carla S.; Olsen, Bradley D.

    2014-01-01

    The self-assembly of the model globular protein–polymer block copolymer mCherry-b-poly(N-isopropyl acrylamide) is explored across a range of polymer coil fractions from 0.21 to 0.82 to produce a phase diagram for these materials as a function of molecular composition. Overall, four types of morphologies were observed: hexagonally packed cylinders, perforated lamellae, lamellae, and disordered nanostructures. Across all coil fractions and morphologies, a lyotropic re-entrant order–disorder transition in water was observed, with disordered structures below 30 wt% and above 70 wt% and well-ordered morphologies at intermediate concentrations. Solid state samples prepared by solvent evaporation show moderately ordered structures similar to those observed in 60 wt% solutions, suggesting that bulk structures result from kinetic trapping of morphologies which appear at lower concentrations. While highly ordered cylindrical nanostructures are observed around a bioconjugate polymer volume fraction of 0.3 and well-ordered lamellae are seen near a volume fraction of 0.6, materials at lower or higher coil fractions become increasingly disordered. Notable differences between the phase behaviour of globular protein–polymer block copolymers and coil–coil diblock copolymers include the lack of spherical nanostructures at either high or low polymer coil fractions as well as shifted phase boundaries between morphologies which result in an asymmetric phase diagram.

  14. Self-assembled diblock copolymer thin films for the analysis of bacteria-surface interactions

    NASA Astrophysics Data System (ADS)

    Li, Shuyan; Komaromy, Andras; Boysen, Reinhard I.; Nicolau, Dan V.; Hearn, Milton T. W.

    2008-12-01

    Self-assembling polymers have recently attracted significant scientific interest, since they spontaneously generate highly ordered structures with high resolution precision, and provide simple, parallel, and cost-effective processes for nanofabrication. Such systems can be achieved with block copolymers which, when produced as thin films, offer great potential as lithographic templates for the fabrication of photonic band-gap materials, ultrahigh-density nanodots or nanowire arrays, memory and capacitor devices, and nano-patterned substrates for biosensors. Although self-assembling block copolymers can form a variety of surface topographies at the nm scale, like spheres, cylinders, and lamellae, their structural steering through the annealing conditions has in many cases not been fully investigated. In the present investigation optimum production conditions for the preparation of nanostructures from poly(styrene)-block-poly(MMA) diblock copolymers have been established to enable the production of surfaces as thin films (<40 nm) on spin-coated silicon wafers either with parallel cylindrical structures or with vertical cylinders. The resulting self-assembling structures were then evaluated by atomic force microscopy. The obtained nanostructured polymers were then incubated with two microbial species, the gram negative E. coli and the gram positive S. aureus to assess their behaviour. The patterns of the thin film surfaces affected the bacterial attachment. Such self assembly processes can be used to create surfaces acting as bacterial attractants or repellents.

  15. Coil fraction-dependent phase behaviour of a model globular protein-polymer diblock copolymer.

    PubMed

    Thomas, Carla S; Olsen, Bradley D

    2014-05-01

    The self-assembly of the model globular protein-polymer block copolymer mCherry-b-poly(N-isopropyl acrylamide) is explored across a range of polymer coil fractions from 0.21 to 0.82 to produce a phase diagram for these materials as a function of molecular composition. Overall, four types of morphologies were observed: hexagonally packed cylinders, perforated lamellae, lamellae, and disordered nanostructures. Across all coil fractions and morphologies, a lyotropic re-entrant order-disorder transition in water was observed, with disordered structures below 30 wt% and above 70 wt% and well-ordered morphologies at intermediate concentrations. Solid state samples prepared by solvent evaporation show moderately ordered structures similar to those observed in 60 wt% solutions, suggesting that bulk structures result from kinetic trapping of morphologies which appear at lower concentrations. While highly ordered cylindrical nanostructures are observed around a bioconjugate polymer volume fraction of 0.3 and well-ordered lamellae are seen near a volume fraction of 0.6, materials at lower or higher coil fractions become increasingly disordered. Notable differences between the phase behaviour of globular protein-polymer block copolymers and coil-coil diblock copolymers include the lack of spherical nanostructures at either high or low polymer coil fractions as well as shifted phase boundaries between morphologies which result in an asymmetric phase diagram. PMID:24695642

  16. Bimetallic PdAg nanoparticle arrays from monolayer films of diblock copolymer micelles

    NASA Astrophysics Data System (ADS)

    Ehret, E.; Beyou, E.; Mamontov, G. V.; Bugrova, T. A.; Prakash, S.; Aouine, M.; Domenichini, B.; Cadete Santos Aires, F. J.

    2015-07-01

    The self-assembly technique provides a highly efficient route to generate well-ordered structures on a nanometer scale. In this paper, well-ordered arrays of PdAg alloy nanoparticles on flat substrates with narrow distributions of particle size (6-7 nm) and interparticle spacing (about 60 nm) were synthesized by the block copolymer micelle approach. A home-made PS-b-P4VP diblock copolymer was prepared to obtain a micellar structure in toluene. Pd and Ag salts were then successfully loaded in the micellar core of the PS-b-P4VP copolymer. A self-assembled monolayer of the loaded micelles was obtained by dipping the flat substrate in the solution. At this stage, the core of the micelles was still loaded with the metal precursor rather than with a metal. Physical and chemical reducing methods were used to reduce the metal salts embedded in the P4VP core into PdAg nanoparticles. HRTEM and EDX indicated that Pd-rich PdAg alloy nanoparticles were synthesized by chemical or physical reduction; UV-visible spectroscopy observations confirmed that metallic PdAg nanoparticles were quickly formed after chemical reduction; XPS measurements revealed that the PdAg alloy nanoparticles were in a metallic state after a short time of exposure to O2 plasma and after hydrazine reduction.

  17. Amphiphilic, cross-linkable diblock copolymers for multifunctionalized nanoparticles as biological probes

    NASA Astrophysics Data System (ADS)

    Schmidtke, Christian; Pöselt, Elmar; Ostermann, Johannes; Pietsch, Andrea; Kloust, Hauke; Tran, Huong; Schotten, Theo; Bastús, Neus G.; Eggers, Robin; Weller, Horst

    2013-07-01

    Nanoparticles (NPs) play an increasingly important role in biological labeling and imaging applications. However, preserving their useful properties in an aqueous biological environment remains challenging, even more as NPs therein have to be long-time stable, biocompatible and nontoxic. For in vivo applications, size control is crucial in order to route excretion pathways, e.g. renal clearance vs. hepato-biliary accumulation. Equally necessary, cellular and tissue specific targeting demands suitable linker chemistry for surface functionalization with affinity molecules, like peptides, proteins, carbohydrates and nucleotides. Herein, we report a three stage encapsulation process for NPs comprised of (1) a partial ligand exchange by a multidentate polyolefinic amine ligand, PI-N3, (2) micellar encapsulation with a precisely tuned amphiphilic diblock PI-b-PEG copolymer, in which the PI chains intercalate to the PI-N3 prepolymer and (3) radical cross-linking of the adjacent alkenyl bonds. As a result, water-soluble NPs were obtained, which virtually maintained their primal physical properties and were exceptionally stable in biological media. PEG-terminal functionalization of the diblock PI-b-PEG copolymer with numerous functional groups was mostly straightforward by chain termination of the living anionic polymerization (LAP) with the respective reagents. More complex affinity ligands, e.g. carbohydrates or biotin, were introduced in a two-step process, prior to micellar encapsulation. Advantageously, this pre-assembly approach opens up rapid access to precisely tuned multifunctional NPs, just by using mixtures of diverse functional PI-b-PEG polymers in a combinatorial manner. All constructs showed no toxicity from 0.001 to 1 μM (particle concentration) in standard WST and LDH assays on A549 cells, as well as only marginal unspecific cellular uptake, even in serum-free medium.Nanoparticles (NPs) play an increasingly important role in biological labeling and imaging

  18. Anisotropic Lithium Ion Conductivity in Single-Ion Diblock Copolymer Electrolyte Thin Films.

    PubMed

    Aissou, Karim; Mumtaz, Muhammad; Usluer, Özlem; Pécastaings, Gilles; Portale, Giuseppe; Fleury, Guillaume; Cloutet, Eric; Hadziioannou, Georges

    2016-02-01

    Well-defined single-ion diblock copolymers consisting of a Li-ion conductive poly(styrenesulfonyllithium(trifluoromethylsulfonyl)imide) (PSLiTFSI) block associated with a glassy polystyrene (PS) block have been synthesized via reversible addition fragmentation chain transfer polymerization. Conductivity anisotropy ratio up to 1000 has been achieved from PS-b-PSLiTFSI thin films by comparing Li-ion conductivities of out-of-plane (aligned) and in-plane (antialigned) cylinder morphologies at 40 °C. Blending of PS-b-PSLiTFSI thin films with poly(ethylene oxide) homopolymer (hPEO) enables a substantial improvement of Li-ion transport within aligned cylindrical domains, since hPEO, preferentially located in PSLiTFSI domains, is an excellent lithium-solvating material. Results are also compared with unblended and blended PSLiTFSI homopolymer (hPSLiTFSI) homologues, which reveals that ionic conductivity is improved when thin films are nanostructured.

  19. Phase diagram of rod-coil diblock copolymer melts by self-consistent field theory

    NASA Astrophysics Data System (ADS)

    Yan, Dadong; Tang, Jiuzhou; Jiang, Ying; Zhang, Xinghua; Chen, Jeff

    A unified phase diagram is presented for rod-coil diblock copolymer melts in the isotropic phase regime as a function of the asymmetric parameter. The study is based on free-energy calculation, which incorporates three-dimensional spatial variations of the volume fraction with angular dependence. The wormlike-chain model is used in a self-consistent field treatment. Body-centered cubic, A15, hexagonal, gyroid, and lamellar structures where the rod segments are packed inside the convex rod-coil interface are found stable. As the conformational asymmetric parameter increases, the A15 phase region expands and the gyroid phase region reduces. The stability of the structures is analyzed by concepts such as packing frustration, spinodal limit, and interfacial curvature.

  20. Surface Engineering of Cellulose Nanofiber by Adsorption of Diblock Copolymer Dispersant for Green Nanocomposite Materials.

    PubMed

    Sakakibara, Keita; Yano, Hiroyuki; Tsujii, Yoshinobu

    2016-09-21

    An effective approach for the dispersion of hydrophilic cellulose nanofiber (CNF) in hydrophobic high-density polyethylene (HDPE) is presented using adsorption of a diblock copolymer dispersant. The dispersant consists of both resin compatible poly(lauryl methacrylate) (PLMA) and cellulose interactive poly(2-hydroxyethyl methacrylate) blocks. The PLMA-adsorbed CNFs are characterized by FT-IR and contact angle measurement, revealing successful hydrophobization. X-ray CT imaging shows there are apparently less CNF aggregates in the nanocomposites if adding amount of the dispersant was enough. The good dispersion results in a high mechanical reinforcement, corresponding to 140% higher Young's modulus and 84% higher tensile strength than the neat HDPE. This approach is broadly applicable and allows for easy manufacturing process for strong and lightweight CNF-reinforced nanocomposite materials. PMID:27559606

  1. Crystallization in diblock copolymer thin films at different degrees of supercooling.

    PubMed

    Darko, C; Botiz, I; Reiter, G; Breiby, D W; Andreasen, J W; Roth, S V; Smilgies, D-M; Metwalli, E; Papadakis, C M

    2009-04-01

    The crystalline structures in thin films of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblock copolymers were studied in dependence on the degree of supercooling. Atomic force microscopy showed that the crystalline domains (lamellae) consist of grains, which are macroscopic at low and intermediate degrees of supercooling, but of submicrometer size for strong supercooling. Using grazing-incidence wide-angle x-ray scattering, we could determine the grain orientation distribution function which shows that the chain stems are perpendicular to the lamellae at low supercooling, but tilted at intermediate and strong supercooling. These results suggest that, at intermediate and strong supercooling, the crystalline PEO lamellae do not grow homogeneously, but by the formation of small crystallites at the growth front.

  2. Effects of polydispersity on the order-disorder transition of diblock copolymer melts

    NASA Astrophysics Data System (ADS)

    Beardsley, Tom; Matsen, Mark

    2009-03-01

    The effect of polydispersity on an AB diblock copolymer melt is investigated using lattice based Monte Carlo simulations with parallel tempering (PT) techniques. We consider melts where the B blocks are monodisperse and the A blocks are polydisperse with a Schultz-Zimm distribution. Expanding our previous work on polydisperse melts of symmetric composition, we now construct a polydisperse phase diagram, investigating the size of the domains and locations of the order-disorder (ODT) and order-order (OOT) transitions. The PT method has yielded a number of benefits over single-processor temperature scans, including: simulating a number of temperatures simultaneously, annealing out defects in the configurations more readily and capturing the distinctive spike in the heat capacity that occurs at the ODT, allowing the location of the transition to be determined more accurately than in previous studies. The results are compared to those of experiment and to the predictions of self-consistent field theory (SCFT).

  3. Phase Change Nanodot Arrays Fabricated Using a Self-Assembly Diblock Copolymer Approach

    SciTech Connect

    Zhang,Y.; Wong, H.; Raoux, S.; Cha, J.; Rettner, C.; Krupp, L.; Topuria, T.; Milliron, D.; Rice, P.; Jordan-Sweet, J.

    2007-01-01

    Self-assembling diblock copolymer, polystyrene-b-poly-4-vinylpyridine (PS-b-P4VP), was used as the template for fabricating phase change nanostructures. The high density GeSb nanodots were formed by etching into an amorphous GeSb thin film using silica hard mask which was patterned on top of polymer. The nanodot arrays are 15 nm in diameter with 30 nm spacing. This is smaller than most structures obtained by e-beam lithography. Time-resolved x-ray diffraction studies showed that the phase transition occurred at 235 {sup o}C, which is 5 {sup o}C lower than blanket GeSb film but higher than that of Ge{sub 2}Sb{sub 2}Te{sub 5} (150 {sup o}C). GeSb showed good temperature stability for fabrication of small memory devices.

  4. A Quantitative Study of Tethered Chains in Various Solution Conditions Using Langmuir Diblock Copolymer Monolayers

    SciTech Connect

    Kent, Michael S.

    1999-08-13

    This article summarizes our investigations of tethered chain systems using Langmuir monolayer of polydimethysiloxane-poly styrene (PDMS-PS) diblock copolymers on organic liquids. In this system, the PDMS block adsorbs to the air surface while the PS block dangles into the subphase liquid. The air surface can be made either repulsive or attractive for the tethered PS chain segments by choosing a subphase liquid which has a surface tension lower or greater than that of PS, respectively. The segment profile of the PS block is determined by neutron reflection as a function of the surface density, the molecular weights of the PS and PDMS blocks, and the solution conditions. We cover the range of reduced surface density (SIGMA) characteristic of the large body of data in the literature for systems of chains tethered onto solid surfaces from dilute solution in good or theta solvent conditions (SIGMA < 12). We emphasize quantitative comparisons with analytical profile forms and scaling predictions. We find that the strong-stretching limit invoked in analytical SCF and scaling theories is not valid over this Z range. On the other hand, over a large portion of this range (SIGMA < 5) tethered layers are well described by a renormalization group theory addressing weakly interacting or noninteracting chains. Simultaneous with the study of the profile form, the free energy of the chains is examined through the surface tension. A strong increase in the surface pressure is observed with increasing surface density which determines the maximum surface density which can be achieved. This apparently nonequilibrium effect is attributed to steric interactions and limited lateral interpenetration. This effect may explain several outstanding discrepancies regarding the adsorption of end-functionalized chains and diblock copolymers onto solid surfaces.

  5. Lyotropic Phase Behavior of Poly(ethylene oxide)-Poly(butadiene) Diblock Copolymers: Evolution of the Random Network Morphology

    SciTech Connect

    Jain, Sumeet; Dyrdahl, Mitchell H.E.; Gong, Xiaobo; Scriven, L.E.; Bates, Frank S.

    2008-10-24

    The phase behavior of poly(ethylene oxide)-poly(butadiene) (PEO-PB) diblock copolymers mixed with water was studied using small-angle X-ray scattering (SAXS), cryogenic scanning electron microscopy (cryo-SEM), cryogenic transmission electron microscopy (cryo-TEM), and dynamic mechanical spectroscopy. Two sets of diblocks were synthesized by adding different lengths of PEO to hydroxy terminated PB with degrees of polymerization N{sub PB} = 46 and 170. Two-component mixtures were investigated as a function of block composition and copolymer molecular weight, between 1 and 100 wt % polymer content. Melt phase behavior is consistent with established theory and known experimental behavior for diblock copolymers. Various lyotropic liquid crystalline structures, notably lamellae (L), hexagonally packed cylinders (H), and spheres (S) arranged on cubic (body-centered cubic, face-centered cubic) lattices, were documented as a function of water content. At the higher molecular weights (N{sub PB} = 170), a random network phase (N) was identified over a sizable portion of the phase portrait, located between hexagonally ordered cylinders and ordered lamellae. This new structure, along with branching of cylindrical micelles in the dilute limit, bear a striking similarity to experimentally observed and theoretically predicted phase behavior in certain ternary water/oil/surfactant systems. These findings demonstrate that block copolymer surfactants are characterized by at least four structural building blocks -- spheres, cylinders, bilayers, and branched cylinders -- above a threshold molecular weight.

  6. Sulfate-based anionic diblock copolymer nanoparticles for efficient occlusion within zinc oxide

    NASA Astrophysics Data System (ADS)

    Ning, Y.; Fielding, L. A.; Andrews, T. S.; Growney, D. J.; Armes, S. P.

    2015-04-01

    Occlusion of copolymer particles within inorganic crystalline hosts not only provides a model for understanding the crystallisation process, but also may offer a direct route for the preparation of novel nanocomposite materials with emergent properties. In the present paper, a series of new well-defined anionic diblock copolymer nanoparticles are synthesised by polymerisation-induced self-assembly (PISA) via reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerisation and then evaluated as crystal habit modifiers for the in situ formation of ZnO in aqueous solution. Systematic studies indicate that both the chemical nature (i.e. whether sulfate-based or carboxylate-based) and the mean degree of polymerisation (DP) of the anionic stabiliser block play vital roles in determining the crystal morphology. In particular, sulfate-functionalised nanoparticles are efficiently incorporated within the ZnO crystals whereas carboxylate-functionalised nanoparticles are excluded, thus anionic character is a necessary but not sufficient condition for successful occlusion. Moreover, the extent of nanoparticle occlusion within the ZnO phase can be as high as 23% by mass depending on the sulfate-based nanoparticle concentration. The optical properties, chemical composition and crystal structure of the resulting nanocomposite crystals are evaluated and an occlusion mechanism is proposed based on the observed evolution of the ZnO morphology in the presence of sulfate-based anionic nanoparticles. Finally, controlled deposition of a 5 nm gold sol onto porous ZnO particles (produced after calcination of the organic nanoparticles) significantly enhances the rate of photocatalytic decomposition of a model rhodamine B dye on exposure to a relatively weak UV source.Occlusion of copolymer particles within inorganic crystalline hosts not only provides a model for understanding the crystallisation process, but also may offer a direct route for the preparation of novel

  7. High-Performance Field-Effect Transistors Based on Polystyrene-b-Poly(3-hexylthiophene) Diblock Copolymers

    SciTech Connect

    Geohegan, David B; Sumpter, Bobby G; Hong, Kunlun; Xiao, Kai; Lavrik, Nickolay V; Yu, Xiang; Chen, Jihua

    2011-01-01

    Polystyrene-b-poly(3-hexylthiophene) (PS-b-P3HT) block copolymers with fixed PS block length have been synthesized by combined atom transfer radical polymerization (ATRP) and Grignard metathesis (GRIM) polymerization. The self-assembled structures of these diblock copolymer thin films based on PS-b-P3HT have been studied by TEM, SAED, GIXD, AFM, and additionally by first principles modeling and simulation. These block copolymers undergo microphase separation and form nanostructured spheres, lamellae, nanofibers, or nanoribbons in the films dictated by the molecular weight of the P3HT block. Within the diblock copolymer thin film, PS blocks segregate to form amorphous domains, and the covalently bonded conjugated P3HT blocks exist as highly ordered crystalline domains through intermolecular packing with their alkyl side chains aligned normal to the substrate while the thiophene rings align parallel to the substrate through stacking. The conjugated PS-b-P3HT block copolymers exhibited significant improvements in organic field-effect transistor (OFET) performance and environmental stability as compared to P3HT homopolymers, with up to a factor of 2 increase in measured mobility (0.08 cm2/(V 3 s)) for the P4 (85 wt % P3HT). Overall, this work demonstrates that the high degree of molecular order induced by block copolymer phase separation can improve the transport properties and stability of conjugating polymers, which are critical for high-performance OFETs and other organic electronics.

  8. Monte Carlo Study of Degenerate Behavior of AB Diblock Copolymer/Nanoparticle under Cylindrical Confinement.

    PubMed

    Wang, Yingying; Han, Yuanyuan; Cui, Jie; Jiang, Wei; Sun, Yingchun

    2016-08-23

    Degenerate behavior (i.e., forming different self-assembled structures for a given block copolymer (BCP) under the same confinement) commonly exists in various confined systems. Understanding degenerate behavior is crucial for precise control over the structures formed by self-assembly systems under confinement. In this study, the degenerate behavior of a self-assembled AB diblock copolymer/nanoparticle (NP) mixture in a cylindrical pore is studied using Monte Carlo simulation. We find that the degenerate behavior of such a mixture depends on the introduction of the NP. Under different pore sizes, four typical degenerate structures [i.e., single helices (S-helices), double helices (D-helices), parallel cylinders, and stacked toroids] can be obtained if the NP content is zero. However, when the NP content in the mixture is increased, it is found that the number of degenerate structures decreases, that is, only blocky structures can be obtained in the case of high NP content. Moreover, the probability of forming S-helices decreases, whereas the probability of forming D-helices increases with increase in the NP content. Analysis of the interactive enthalpy densities and the chain conformation of the systems indicates that entropy plays an important role in the degenerate structure formation. This study provides some new insights into the degenerate behavior of a BCP/NP mixture under confinement, which can offer a theoretical reference for further experiments. PMID:27459708

  9. Tuning phase structures of a symmetrical diblock copolymer with a patterned electric field.

    PubMed

    Kan, Di; He, Xuehao

    2016-05-11

    Electric fields can induce the orientation of the phase interfaces of block copolymers and provide a potential method to tune polymer phase structures for nanomaterial manufacture. In this work, we applied self-consistent field theory to study the self-assembly of a diblock copolymer confined between two parallel neutral substrates on which a set of electrodes was imposed to form a patterned electric field. The results showed that an alternatively distributed electric field can induce the formation of a parallel lamellar phase structure, which exists stably only in the system with selective substrates. The phase structure was proved to be sensitive to the characteristics of the electric field distribution, such as the strength of the electric field, the size and position of the electrodes, and the corresponding phase diagram was calculated in detail. The transition pathway of the phase structure from the perpendicular layered phase to the parallel layered phase was further analysed using the minimum energy path method. It is shown that the path and the active energy barrier of the phase transition depend on the electric field strength. Compound electric field patterns that can be designed to control the formation of novel and complex microphase structures were also examined. PMID:27102422

  10. Directed Self-Assembly of Diblock Copolymer Thin Films on Prepatterned Metal Nanoarrays.

    PubMed

    Chang, Tongxin; Huang, Haiying; He, Tianbai

    2016-01-01

    The sequential layer by layer self-assembly of block copolymer (BCP) nanopatterns is an effective approach to construct 3D nanostructures. Here large-scale highly ordered metal nano-arrays prepared from solvent annealed thin films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer are used to direct the assembly of the same BCP. The influence of initial loading concentration of metal precursor, the type of metal nanoparticle (gold, platinum, and silver), and the nanoparticle-substrate interaction on the directed assembly behavior of the upper BCP layer have been focused. It is found that the upper BCP film can be completely directed by the gold nanoarray with P2VP domain exclusively located between two adjacent gold nanowires or nanodots, which behaves the same way as on the platinum nanoarray. While the silver nanoarray can be destroyed during the upper BCP self-assembly with the silver nanoparticles assembled into the P2VP domain. Based on the discussions of the surface energy of nanoparticles and the interplay between nanoparticle-substrate interaction and nanoparticle-polymer interaction, it is concluded that the effect of immobilization of nanoparticles on the substrate, together with entropy effect to minimize the energetically unfavorable chain stretching contributes to the most effective alignment between each layer. PMID:26513110

  11. Structural development of gold and silver nanoparticles within hexagonally ordered spherical micellar diblock copolymer thin films.

    PubMed

    Chen, Chia-Min; Huang, Yi-Jiun; Wei, Kung-Hwa

    2014-06-01

    The spatial arrangement of metal nanoparticle (NP) arrays in block copolymers has many potential applications in OFET-type memory devices. In this study, we adopted a trapping approach in which we used a monolayer thin film of polystyrene-block-poly(4-vinylpyridine) (PS56k-b-P4VP8k)-a highly asymmetric diblock copolymer having a spherical micelle morphology-to incorporate various amounts of one-phase-synthesized dodecanethiol-passivated silver (DT-Ag) NPs and a fixed amount of ligand-exchanged pyridine-coated gold (Py-Au) NPs into the polystyrene (PS) and poly(4-vinylpyridine) (P4VP) blocks, respectively. We characterized the packing of these metal NPs in the two blocks of the nanostructured diblock copolymer using reciprocal-space synchrotron grazing incidence small-angle X-ray scattering (GISAXS) as well as atomic force microscopy (AFM) and transmission electron microscopy (TEM) in the real space. The packing of the Ag NPs in the PS block was dependent on their content, which we tuned by varying the concentrations in the composite solution at a constant rate of spin-coating. The two-dimensional hierarchical arrangement of Ag and Au NPs within the BCP thin films was enhanced after addition of the Py-Au NPs into the P4VP block and after spin-coating a thinner film from a low concentration solution (0.1 wt%), due to the DT-Ag NPs accumulating around the Py-Au/P4VP cores; this two-dimensional hierarchical arrangement decreased at a critical DT-Ag NP weight ratio (c) of 0.8 when incorporating the Py-Au NPs into the P4VP domains through spin-coating at higher solution concentration (0.5 wt%), where the DT-Ag NPs realigned by rotating 20° along the z axis in the real space, due to oversaturation of the DT-Ag NPs within the PS domains.

  12. Structural Evolution of Low-Molecular-Weight Poly(ethylene oxide)-block-polystyrene Diblock Copolymer Thin Film

    PubMed Central

    Huang, Xiaohua

    2013-01-01

    The structural evolution of low-molecular-weight poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer thin film with various initial film thicknesses on silicon substrate under thermal annealing was investigated by atomic force microscopy, optical microscopy, and contact angle measurement. At film thickness below half of the interlamellar spacing of the diblock copolymer (6.2 nm), the entire silicon is covered by a polymer brush with PEO blocks anchored on the Si substrate due to the substrate-induced effect. When the film is thicker than 6.2 nm, a dense polymer brush which is equal to half of an interlamellar layer was formed on the silicon, while the excess material dewet this layer to form droplets. The droplet surface was rich with PS block and the PEO block crystallized inside the bigger droplet to form spherulite. PMID:24302862

  13. Influence of composition fluctuations on the linear viscoelastic properties of symmetric diblock copolymers near the order-disorder transition

    SciTech Connect

    Hickey, Robert J.; Gillard, Timothy M.; Lodge, Timothy P.; Bates, Frank S.

    2015-08-28

    Rheological evidence of composition fluctuations in disordered diblock copolymers near the order disorder transition (ODT) has been documented in the literature over the past three decades, characterized by a failure of time–temperature superposition (tTS) to reduce linear dynamic mechanical spectroscopy (DMS) data in the terminal viscoelastic regime to a temperature-independent form. However, for some materials, most notably poly(styrene-b-isoprene) (PS–PI), no signature of these rheological features has been found. We present small-angle X-ray scattering (SAXS) results on symmetric poly(cyclohexylethylene-b-ethylene) (PCHE–PE) diblock copolymers that confirm the presence of fluctuations in the disordered state and DMS measurements that also show no sign of the features ascribed to composition fluctuations. Assessment of DMS results published on five different diblock copolymer systems leads us to conclude that the effects of composition fluctuations can be masked by highly asymmetric block dynamics, thereby resolving a long-standing disagreement in the literature and reinforcing the importance of mechanical contrast in understanding the dynamics of ordered and disordered block polymers.

  14. Worm-like micelles in water solutions of 1, 4 poly (1, 3-butadiene)-polyethylene oxide diblock copolymer.

    PubMed

    Arenas-Gómez, Brisa; Vinceković, Marko; Garza, Cristina; Castillo, Rolando

    2014-06-01

    The main purpose of this study is to determine for the first time the structure of the self-assembled aggregates in the system made of 1,4 poly(1,3-butadiene)-polyethylene oxide diblock copolymer (IUPAC name: poly(but-2-ene-1,4-diyl)-block-polyoxyethylene) and water, and the rheological behavior of the solution. The degree of polymerization of the polybutadiene and polyethylene oxide blocks is 37 and 45, respectively. The diblock copolymer concentration was limited to be ≤2.5 wt% to avoid phase separation. Small X-ray scattering revealed that the diblock copolymer self-assembles in worm-like micelles with a diameter of ∼ 12 nm. This system does not closely follow the rheological behavior of worm-like micelle solutions made of typical surfactants. The system steadily shear thins reaching very low viscosity values at large shear rates, however there are not shear-thickening peaks. In thixotropic loops, the micellar solution does not present hysteresis. The viscoelastic spectra do not follow the Maxwell model at low and intermediate frequencies. This uncommon behavior for a worm-like micellar system is explained by the slow dynamics of the self-assembly. The extremely high hydrophobicity of the polybutadiene block does not allow any micellar rearrangement. PMID:24965154

  15. Diblock copolymers of polystyrene-b-poly(1,3-cyclohexadiene) exhibiting unique three-phase microdomain morphologies

    DOE PAGES

    Misichronis, Konstantinos; Chen, Jihua; Kahk, Jong K.; Imel, Adam; Dadmun, Mark; Hong, Kunlun; Hadjichristidis, Nikos; Mays, Jimmy W.; Avgeropoulos, Apostolos

    2016-03-29

    Here, the synthesis and molecular characterization of a series of conformationally asymmetric polystyrene-block-poly(1,3-cyclohexadiene) (PS-b-PCHD) diblock copolymers (PCHD: ~90% 1,4 and ~10% 1,2), by sequential anionic copolymerization high vacuum techniques, is reported. A wide range of volume fractions (0.27 ≤ ΦPS ≤ 0.91) was studied by transmission electron microscopy and small-angle X-ray scattering in order to explore in detail the microphase separation behavior of these flexible/semiflexible diblock copolymers. Unusual morphologies, consisting of PCHD core(PCHD-1,4)–shell(PCHD-1,2) cylinders in PS matrix and three-phase (PS, PCHD-1,4, PCHD-1,2) four-layer lamellae, were observed suggesting that the chain stiffness of the PCHD block and the strong dependence ofmore » the interaction parameter χ on the PCHD microstructures are important factors for the formation of this unusual microphase separation behavior in PS-b-PCHD diblock copolymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1564–1572« less

  16. Self-Assembly of Novel Amphiphilic 21-Arm, Star-Like Coil-Rod Diblock Copolymers at Interfaces

    NASA Astrophysics Data System (ADS)

    Lin, Zhiqun; Zhao, Lei; Pang, Xinchang; Feng, Chaowei

    2012-02-01

    A series of novel amphiphilic 21-arm, star-like diblock copolymers, poly(acrylic acid)-b-poly(3-hexylthiophene) (PAA-b-P3HT) based on β-cyclodextrin (β-CD) with well defined molecular architectures and ratio of two chemically distinct blocks were prepared, for the first time, via a combination of quasi-living Grignard metathesis method (GRIM), click reaction, and atom transfer radical polymerization (ATRP). The star-like PAA-b-P3HT diblock copolymers consist of hydrophilic coil-like PAA cores and hydrophobic rod-like P3HT shells with narrow molecular weight distribution and controllable molecular weight of each block. Owing to the compact structure, the amphiphilic star-like PAA-b-P3HT formed a unimolecular micelle. Vesicles based on these novel amphiphilic star-like, coil-rod diblock copolymers were readily produced at the oil/water interface by crosslinking hydrophilic coil-like PAA cores with a bifunctional crosslinker, ethylenediamine. They also self-assembled into a nanotubular structure at the air/water interface.

  17. Micelles of a diblock copolymer of styrene and ethylene oxide in mixtures of 2,6-lutidine and water.

    PubMed

    Tuzar, Z; Kadlec, P; Stepánek, P; Kríz, J; Nallet, F; Noirez, L

    2008-12-16

    We studied the micelle formation of a diblock copolymer of styrene and ethylene oxide in mixtures of 2,6-dimethylpyridine (2,6-lutidine) and water. Micelles are formed in a broad solvent composition range with a volume fraction of water ranging from 0.05 to 0.85, where neither polystyrene nor polyethylene oxide homopolymers are soluble. The diffusion behavior of pure solvent mixtures and in solutions of copolymer micelles is reported. In LTD/water mixtures, two diffusive processes corresponding to self-difusion and two modes belonging to mutual diffusion and diffusion of solvent clusters have been found. In copolymer solutions, the mode of copolymer micelle diffusion replaces the mode of solvent cluster diffusion. Quasielastic light scattering, small-angle neutron scattering, and pulsed-field gradient NMR have been employed in our study.

  18. Structural development of gold and silver nanoparticles within hexagonally ordered spherical micellar diblock copolymer thin films

    NASA Astrophysics Data System (ADS)

    Chen, Chia-Min; Huang, Yi-Jiun; Wei, Kung-Hwa

    2014-05-01

    The spatial arrangement of metal nanoparticle (NP) arrays in block copolymers has many potential applications in OFET-type memory devices. In this study, we adopted a trapping approach in which we used a monolayer thin film of polystyrene-block-poly(4-vinylpyridine) (PS56k-b-P4VP8k)--a highly asymmetric diblock copolymer having a spherical micelle morphology--to incorporate various amounts of one-phase-synthesized dodecanethiol-passivated silver (DT-Ag) NPs and a fixed amount of ligand-exchanged pyridine-coated gold (Py-Au) NPs into the polystyrene (PS) and poly(4-vinylpyridine) (P4VP) blocks, respectively. We characterized the packing of these metal NPs in the two blocks of the nanostructured diblock copolymer using reciprocal-space synchrotron grazing incidence small-angle X-ray scattering (GISAXS) as well as atomic force microscopy (AFM) and transmission electron microscopy (TEM) in the real space. The packing of the Ag NPs in the PS block was dependent on their content, which we tuned by varying the concentrations in the composite solution at a constant rate of spin-coating. The two-dimensional hierarchical arrangement of Ag and Au NPs within the BCP thin films was enhanced after addition of the Py-Au NPs into the P4VP block and after spin-coating a thinner film from a low concentration solution (0.1 wt%), due to the DT-Ag NPs accumulating around the Py-Au/P4VP cores; this two-dimensional hierarchical arrangement decreased at a critical DT-Ag NP weight ratio (c) of 0.8 when incorporating the Py-Au NPs into the P4VP domains through spin-coating at higher solution concentration (0.5 wt%), where the DT-Ag NPs realigned by rotating 20° along the z axis in the real space, due to oversaturation of the DT-Ag NPs within the PS domains.The spatial arrangement of metal nanoparticle (NP) arrays in block copolymers has many potential applications in OFET-type memory devices. In this study, we adopted a trapping approach in which we used a monolayer thin film of

  19. Self-assembly of lamella-forming diblock copolymers confined in nanochannels: Effect of confinement geometry

    NASA Astrophysics Data System (ADS)

    Yu, Bin; Deng, Jian-Hua; Wang, Zheng; Li, Bao-Hui; Shi, An-Chang

    2015-04-01

    The self-assembly of symmetric diblock copolymers confined in the channels of variously shaped cross sections (regular triangles, squares, and ellipses) is investigated using a simulated annealing technique. In the bulk, the studied symmetric diblock copolymers form a lamellar structure with period LL. The geometry and surface property of the confining channels have a large effect on the self-assembled structures and the orientation of the lamellar structures. Stacked perpendicular lamellae with period LL are observed for neutral surfaces regardless of the channel shape and size, but each lamella is in the shape of the corresponding channel's cross section. In the case of triangle-shaped cross sections, stacked parallel lamellae are the majority morphologies for weakly selective surfaces, while morphologies including a triangular-prism-shaped B-cylinder and multiple tridentate lamellae are obtained for strongly selective surfaces. In the cases of square-shaped and ellipse-shaped cross sections, concentric lamellae are the signature morphology for strongly selective surfaces, whereas for weakly selective surfaces, stacked parallel lamellae, and several types of folding lamellae are obtained in the case of square-shaped cross sections, and stacked parallel lamellae are the majority morphologies in the case of ellipse-shaped cross sections when the length of the minor axis is commensurate with the bulk lamellar period. The mean-square end-to-end distance, the average contact number between different species and the surface concentration of the A-monomers are computed to elucidate the mechanisms of the formation of the different morphologies. It is found that the resulting morphology is a consequence of competition among the chain stretching, interfacial energy, and surface energy. Our results suggest that the self-assembled morphology and the orientation of lamellae can be manipulated by the shape, the size, and the surface property of the confining channels. Project

  20. How Do Spherical Diblock Copolymer Nanoparticles Grow during RAFT Alcoholic Dispersion Polymerization?

    PubMed Central

    2015-01-01

    A poly(2-(dimethylamino)ethyl methacrylate) (PDMA) chain transfer agent (CTA) is used for the reversible addition–fragmentation chain transfer (RAFT) alcoholic dispersion polymerization of benzyl methacrylate (BzMA) in ethanol at 70 °C. THF GPC analysis indicated a well-controlled polymerization with molecular weight increasing linearly with conversion. GPC traces also showed high blocking efficiency with no homopolymer contamination apparent and Mw/Mn values below 1.35 in all cases. 1H NMR studies confirmed greater than 98% BzMA conversion for a target PBzMA degree of polymerization (DP) of up to 600. The PBzMA block becomes insoluble as it grows, leading to the in situ formation of sterically stabilized diblock copolymer nanoparticles via polymerization-induced self-assembly (PISA). Fixing the mean DP of the PDMA stabilizer block at 94 units and systematically varying the DP of the PBzMA block enabled a series of spherical nanoparticles of tunable diameter to be obtained. These nanoparticles were characterized by TEM, DLS, MALLS, and SAXS, with mean diameters ranging from 35 to 100 nm. The latter technique was particularly informative: data fits to a spherical micelle model enabled calculation of the core diameter, surface area occupied per copolymer chain, and the mean aggregation number (Nagg). The scaling exponent derived from a double-logarithmic plot of core diameter vs PBzMA DP suggests that the conformation of the PBzMA chains is intermediate between the collapsed and fully extended state. This is in good agreement with 1H NMR studies, which suggest that only 5−13% of the BzMA residues of the core-forming chains are solvated. The Nagg values calculated from SAXS and MALLS are in good agreement and scale approximately linearly with PBzMA DP. This suggests that spherical micelles grow in size not only as a result of the increase in copolymer molecular weight during the PISA synthesis but also by exchange of individual copolymer chains between micelles

  1. Chemical modifications to vesicle forming diblock copolymers: Development of smart functional polymersome membranes

    NASA Astrophysics Data System (ADS)

    Katz, Joshua S.

    2011-07-01

    A major limitation to current treatment regimens for diseases is the inability to adequately deliver therapeutics. Many routes to encapsulation of these materials have been explored to improve biodistribution and better protect encapsulants from harsh biological conditions. One vehicle particularly attractive for encapsulation of such materials is the polymersome. While promising for translation to clinical use, there are still limitations in polymer chemistry and resulting polymersome behavior that will slow their adaptation. This thesis addresses several of these limitations. The first major limitation to polymersomes is lack of control over their release rate. Release is generally by simple diffusion, leading to a burst. To address this burst, Aim 1 proposes a route to stabilizing polymersome membranes through their polymerization. PCL-PEG copolymers were terminally acrylated and the acrylates polymerized in the membrane following vesicle assembly. Polymerization enhanced mechanical robustness of the membranes and reduced diffusion of encapsulated contents. To ultimately trigger release, Aim 2 presents a novel route to synthesizing diblock copolymers, enabling insertion of a functional group at the blocks' junction. To facilitate triggering of release, we inserted UV-cleavable 2-nitrophenylalanine. Polymersomes assembled from this polymer collapse upon exposure to light and molecules release. Demonstrating further utility of this synthetic route, fluorescent vesicles were prepared using fluorescent lysine as the joining molecule. These vesicles labeled dendritic cells, providing a novel route to cell labeling and tracking. The second limitation to vesicles promising for biomedical applications (made of PCL-PEG) is their solid membranes. Aim 3 demonstrates partial (or full) replacement of the PCL block with a caprolactone analogue, TOSUO, which is non-crystalline and assembles into soft, deformable vesicles. Increasing TOSUO content in the copolymer leads to

  2. From supramolecular polymersomes to stimuli-responsive nano-capsules based on poly(diene-b-peptide) diblock copolymers

    NASA Astrophysics Data System (ADS)

    Chécot, F.; Lecommandoux, S.; Klok, H.-A.; Gnanou, Y.

    2003-01-01

    This paper discusses the self-assembly of block copolymers into vesicular morphology. After a brief state of art of the field, a system based on an amphiphilic poly(butadiene)-b-poly(γ-L-glutamic acid) (PB-b-PGA) diblock copolymer in aqueous solution is discussed in detail. The aggregation behavior of this block copolymer has been investigated by means of fluorescence spectroscopy, dynamic (DLS) and static (SLS) light scattering as well as transmission electron microscopy (TEM). The diblock copolymer was found to form well-defined vesicles in water. The size of these so-called polymersomes or peptosomes could be reversibly manipulated as a function of both pH and ion strength. Depending on the pH of the aqueous solution, the hydrodynamic radii of these vesicles were found to vary from 100 nm to 150 nm. By cross-linking the 1,2-vinyl double bonds present in the polybutadiene block, the ability to transform a transient supramolecular self-organized aggregate into a permanent “shape-persistent stimuli-responsive nanoparticle” has been demonstrated.

  3. Sulfate-based anionic diblock copolymer nanoparticles for efficient occlusion within zinc oxide.

    PubMed

    Ning, Y; Fielding, L A; Andrews, T S; Growney, D J; Armes, S P

    2015-04-21

    Occlusion of copolymer particles within inorganic crystalline hosts not only provides a model for understanding the crystallisation process, but also may offer a direct route for the preparation of novel nanocomposite materials with emergent properties. In the present paper, a series of new well-defined anionic diblock copolymer nanoparticles are synthesised by polymerisation-induced self-assembly (PISA) via reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerisation and then evaluated as crystal habit modifiers for the in situ formation of ZnO in aqueous solution. Systematic studies indicate that both the chemical nature (i.e. whether sulfate-based or carboxylate-based) and the mean degree of polymerisation (DP) of the anionic stabiliser block play vital roles in determining the crystal morphology. In particular, sulfate-functionalised nanoparticles are efficiently incorporated within the ZnO crystals whereas carboxylate-functionalised nanoparticles are excluded, thus anionic character is a necessary but not sufficient condition for successful occlusion. Moreover, the extent of nanoparticle occlusion within the ZnO phase can be as high as 23% by mass depending on the sulfate-based nanoparticle concentration. The optical properties, chemical composition and crystal structure of the resulting nanocomposite crystals are evaluated and an occlusion mechanism is proposed based on the observed evolution of the ZnO morphology in the presence of sulfate-based anionic nanoparticles. Finally, controlled deposition of a 5 nm gold sol onto porous ZnO particles (produced after calcination of the organic nanoparticles) significantly enhances the rate of photocatalytic decomposition of a model rhodamine B dye on exposure to a relatively weak UV source.

  4. Effects of amphiphilic diblock copolymer on drug nanoparticle formation and stability

    PubMed Central

    Zhu, Zhengxi

    2013-01-01

    This study systematically compares the effects of amphiphilic diblock copolymer (di-BCP) on stabilizing hydrophobic drug nanoparticles formed by flash nanoprecipitation (FNP), and provides a guideline on choosing suitable di-BCPs. Four widely used di-BCPs, i.e., polystyrene-block-poly(ethylene glycol) (PS-b-PEG), polycaprolactone-block-poly(ethylene glycol) (PCL-b-PEG), polylactide-block-poly(ethylene glycol) (PLA-b-PEG), and poly(lactic-co-glycolic acid) (PLGA-b-PEG), and β-carotene as a model drug were used. The study showed that PLGA-b-PEG was the most suitable one, whose hydrophobic block was biodegradable and noncrystallizable as well as had relatively high glass transition temperature (Tg) and a right solubility parameter (δ). The molecular weight of PLGA block over the range from 5k to 15k showed an insignificant effect on controlling the particle size. Amorphous drug particles with a high drug loading of over 83 wt% can be achieved. Much remarkable evidence supported the nanoparticles with kinetically frozen and nonequilibrium packing structures of polymer chains rather than either the micelles or micellar nanoparticles with two well segregated polymer blocks. The thermodynamic effects of the drug and BCP on the particle stability, size and structures were discussed by using solubility parameters. PMID:24070569

  5. Disentangle Model Differences and Fluctuation Effects in DPD Simulations of Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Wang, David (Qiang); Sandhu, Paramvir; Jong, Jing; Yang, Delian

    2013-03-01

    In the widely used dissipative particle dynamics (DPD) simulations [Hoogerbrugge and Koelman, Europhys. Lett. 19, 155 (1992); Groot and Warren, J. Chem. Phys. 107, 4423 (1997)], polymers are commonly modeled as discrete Gaussian chains interacting with soft, finite-range repulsions. In the original DPD simulations of microphase separation of diblock copolymer melts by Groot and Madden [J. Chem. Phys. 108, 8713 (1998)], the simulation results were compared and found to be consistent with the phase diagram for the ``standard model'' of continuous Gaussian chains with Dirac ?-function interactions obtained from self-consistent field (SCF) calculations. Since SCF theory is a mean-field theory neglecting system fluctuations/correlations while DPD simulations fully incorporate such effects, the model differences are mixed with the fluctuation/correlation effects in their comparison. Here we report the SCF phase diagram for exactly the same model system as used in DPD simulations. Comparing our phase diagram with that for the standard model highlights the effects of chain discretization and finite-range interactions, while comparing our phase diagram with DPD simulation results reveal without any parameter-fitting the effects of fluctuations/correlations neglected in the SCF theory.

  6. Phase diagrams of diblock copolymers in electric fields: a self-consistent field theory study.

    PubMed

    Wu, Ji; Wang, Xianghong; Ji, Yongyun; He, Linli; Li, Shiben

    2016-04-21

    We investigated the phase diagrams of diblock copolymers in external electrostatic fields by using real-space self-consistent field theory. The lamella, cylinder, sphere, and ellipsoid structures were observed and analyzed by their segment distributions, which were arranged to two types of phase diagrams to examine the phase behavior in weak and strong electric fields. One type was constructed on the basis of Flory-Huggins interaction parameter and volume fraction. We identified an ellipsoid structure with a body-centered cuboid arrangement as a stable phase and discussed the shift of phase boundaries in the electric fields. The other type of phase diagrams was established on the basis of the dielectric constants of two blocks in the electric fields. We then determined the regions of ellipsoid phase in the phase diagrams to examine the influence of dielectric constants on the phase transition between ellipsoidal and hexagonally packed cylinder phases. A general agreement was obtained by comparing our results with those described in previous experimental and theoretical studies. PMID:27020849

  7. Water Diffusion Dependence on Amphiphilic Block Design in (Amphiphilic-Hydrophobic) Diblock Copolymer Membranes.

    PubMed

    Dorenbos, Gert

    2016-06-30

    Polyelectrolyte membranes (PEMs) are applied in polyelectrolyte fuel cells (PEFC). The proton conductive pathways within PEMs are provided by nanometer-sized water containing pores. Large-scale application of PEFC requires the production of low-cost membranes with high proton conductivity and therefore good connected pore networks. Pore network formation within four alternative model diblock (hydrophobic_amphiphilic) copolymers in the presence of water is studied by dissipative particle dynamics. Each hydrophobic block contains 50 consecutively connected hydrophobic (A) fragments, and amphiphilic blocks contain 40 hydrophobic A beads and 10 hydrophilic C beads. For one amphiphilic block the C beads are distributed uniformly along the backbone. For the other architectures C beads are located at the end of the side chains attached at regular intervals along the backbone. Water diffusion through the pores is modeled by Monte Carlo tracer diffusion through mapped morphologies. Diffusion is highest for the grafted architectures and increases with increase of length of the side chains. A consistent picture emerges in which diffusion strongly increases with the value of ⟨Nbond⟩ within the amphiphilic block, where ⟨Nbond⟩ is the average number of bonds between hydrophobic A beads and the nearest C bead. PMID:27266679

  8. Water Diffusion Dependence on Amphiphilic Block Design in (Amphiphilic-Hydrophobic) Diblock Copolymer Membranes.

    PubMed

    Dorenbos, Gert

    2016-06-30

    Polyelectrolyte membranes (PEMs) are applied in polyelectrolyte fuel cells (PEFC). The proton conductive pathways within PEMs are provided by nanometer-sized water containing pores. Large-scale application of PEFC requires the production of low-cost membranes with high proton conductivity and therefore good connected pore networks. Pore network formation within four alternative model diblock (hydrophobic_amphiphilic) copolymers in the presence of water is studied by dissipative particle dynamics. Each hydrophobic block contains 50 consecutively connected hydrophobic (A) fragments, and amphiphilic blocks contain 40 hydrophobic A beads and 10 hydrophilic C beads. For one amphiphilic block the C beads are distributed uniformly along the backbone. For the other architectures C beads are located at the end of the side chains attached at regular intervals along the backbone. Water diffusion through the pores is modeled by Monte Carlo tracer diffusion through mapped morphologies. Diffusion is highest for the grafted architectures and increases with increase of length of the side chains. A consistent picture emerges in which diffusion strongly increases with the value of ⟨Nbond⟩ within the amphiphilic block, where ⟨Nbond⟩ is the average number of bonds between hydrophobic A beads and the nearest C bead.

  9. Tethered Chains in Poor Solvent Conditions: An Experimental Study Involving Langmuir Diblock Copolymer Monolayers

    SciTech Connect

    Kent, M.S.; Lee, L.T.; Majewski, J.; Satija, S.; Smith, G.S.

    1998-10-13

    We have employed Langmuir monolayer of highly asymmetric polydimethylsiloxane- polystyrene (PDMS-PS) diblock copolymers on dioctyl phthalate (DOP) at temperatures ranging from 22 "C to -35 `C as a model system for tethered chains in poor solvent conditions. The thicknesses of the tethered PS layers extending into the DOP subphase, measured by neutron reflection, decrease with decreasing temperature (T) over this entire r~ge. However, the v~iation with T becomes weak below -20 "C. At the ]owest T, the layer thicknesses are contracted 55 % -75 `% of their values at the theta condition (T8 = 22 "C), but are still quite swollen compared to the fully collapsed, nonsolvent limit. The contraction of the layer with decreasing T is determined as a function of surface density and molecular weight. These data are compared to universal scaling forms. The PS segments are depleted from the air surface over the entire T range, the thickness of the depletion layer increasing slightly with decreasing T. The free energy of the surface layer is probed by surface tension measurements. Negative surface pressures are observed at low coverages for both PDMS-PS and PDMS monolayer, indicating metastability toward lateral phase separation. Evidence for a trruisition from a dispersed phase to a condensed phase with decreasing T was observed in the reflectivity at very low PDMS-PS coverage.

  10. Incorporating Diblock Copolymer Nanoparticles into Calcite Crystals: Do Anionic Carboxylate Groups Alone Ensure Efficient Occlusion?

    PubMed Central

    2016-01-01

    New spherical diblock copolymer nanoparticles were synthesized via RAFT aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA) at 70 °C and 20% w/w solids using either poly(carboxybetaine methacrylate) or poly(proline methacrylate) as the steric stabilizer block. Both of these stabilizers contain carboxylic acid groups, but poly(proline methacrylate) is anionic above pH 9.2, whereas poly(carboxybetaine methacrylate) has zwitterionic character at this pH. When calcite crystals are grown at an initial pH of 9.5 in the presence of these two types of nanoparticles, it is found that the anionic poly(proline methacrylate)-stabilized particles are occluded uniformly throughout the crystals (up to 6.8% by mass, 14.0% by volume). In contrast, the zwitterionic poly(carboxybetaine methacrylate)-stabilized particles show no signs of occlusion into calcite crystals grown under identical conditions. The presence of carboxylic acid groups alone therefore does not guarantee efficient occlusion: overall anionic character is an additional prerequisite. PMID:27042383

  11. Effect of mobile ions on the electric field needed to orient charged diblock copolymer thin films

    SciTech Connect

    Dehghan, Ashkan; Shi, An-Chang; Schick, M.

    2015-10-07

    We examine the behavior of lamellar phases of charged/neutral diblock copolymer thin films containing mobile ions in the presence of an external electric field. We employ self-consistent field theory and focus on the aligning effect of the electric field on the lamellae. Of particular interest are the effects of the mobile ions on the critical field, the value required to reorient the lamellae from the parallel configuration favored by the surface interaction to the perpendicular orientation favored by the field. We find that the critical field depends strongly on whether the neutral or charged species is favored by the substrates. In the case in which the neutral species is favored, the addition of charges decreases the critical electric field significantly. The effect is greater when the mobile ions are confined to the charged lamellae. In contrast, when the charged species is favored by the substrate, the addition of mobile ions stabilizes the parallel configuration and thus results in an increase in the critical electric field. The presence of ions in the system introduces a new mixed phase in addition to those reported previously.

  12. On the order-disorder transition of compressible diblock copolymer melts

    SciTech Connect

    Zong, Jing; Wang, Qiang

    2015-11-14

    We performed both the fast off-lattice Monte Carlo simulations of symmetric diblock copolymers (DBC) in an isothermal-isobaric ensemble and the self-consistent field calculations of asymmetric DBC to properly determine the order-disorder transition (ODT) of a model system of compressible DBC melts used in the literature when it is a first-order phase transition, and studied for the first time the co-existence of the two phases at ODT. We found that the co-existing region is quite small and decreases as the system becomes less compressible, which justifies the previous ODT results obtained by equating the Helmholtz free energy per chain of the two phases. We also found that for the most compressible system where there is no repulsion between the same type of segments, the self-consistent field theory predicts that ODT is a second-order phase transition even for asymmetric DBC melts due to its mean-field approximation.

  13. Morphology-Conductivity Relationship in Salt-containing Diblock Copolymer/Homopolymer Mixtures

    NASA Astrophysics Data System (ADS)

    Irwin, Matthew; Hickey, Robert

    2015-03-01

    In order to unravel how ion conductivity is affected by material morphology, a model system of polystyrene (PS), poly(ethylene oxide) (PEO), PS-block-PEO, and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) was fabricated and characterized. These pseudo-ternary polymer blends, in which the lithium salt associates nearly exclusively with the ethylene oxide, have the potential to form a variety of morphologies such as lamellae and the three-dimensionally interpenetrating bicontinuous microemulsion by simply changing blend composition. Similar to what has been observed in salt-containing diblock copolymers, both the order-disorder transition (ODT) temperature and the ODT temperature window of these blends increase sharply with salt loading. By modulating the relative volume fraction of the homopolymers in the blends, it was shown that, although less than order-of-magnitude changes in the domain spacing do not appreciably affect ion conductivity, some morphologies can result in significantly better conductivity than others. These results outline what factors matter most when designing polymer electrolytes for applications such as rechargeable lithium metal batteries and proton exchange membranes.

  14. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    An, Hyosung; Mike, Jared; Smith, Kendall A.; Swank, Lisa; Lin, Yen-Hao; L. Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie L.

    2015-09-01

    Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects.

  15. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    An, Hyosung; Mike, Jared; Smith, Kendall; Swank, Lisa; Lin, Yen-Hao; Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie

    Structural energy storage materials combining load-bearing mechanical properties and high energy storage performance are desired for applications in wearable devices or flexible displays. Vanadium pentoxide (V2O5) is a promising cathode material for possible use in flexible battery electrodes, but it remains limited by low Li+ diffusion coefficient and electronic conductivity, severe volumetric changes upon cycling, and limited mechanical flexibility. Here, we demonstrate a route to address these challenges by blending a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT- b-PEO), with V2O5 to form a mechanically flexible, electro-mechanically stable hybrid electrode. V2O5 layers were arranged parallel in brick-and-mortar-like fashion held together by the P3HT- b-PEO binder. This unique structure significantly enhances mechanical flexibility, toughness and cyclability without sacrificing capacity. Electrodes comprised of 10 wt% polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes.

  16. Tuning thermoresponsive behavior of diblock copolymers and their gold core hybrids. Part 2. How properties change depending on block attachment to gold nanoparticles.

    PubMed

    Chen, Ning; Xiang, Xu; Heiden, Patricia A

    2013-04-15

    Thermoresponsive diblock copolymers of di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo(ethylene glycol) methyl ether acrylate (OEGA) were synthesized by reversible addition-fragmentation chain transfer polymerization, allowing us to prepare diblocks with a thiol group at the desired chain end, and bond that block to a ~20 nm gold nanoparticle core. The cloud point and coil-globule transition window were measured by UV-vis spectroscopy. The gold core lowered the cloud point and narrowed the coil-globule transition window of all the diblock hybrids, but raised the cloud point of statistical copolymer hybrids that had similar cloud points. The extent of the change in the thermo-response properties of the hybrid diblock copolymers was more significant when the gold was bonded to the DEGMA block than the OEGA block. This block is less hydrophilic and sterically hindered than OEGA and may adsorb more effectively to the gold so that the hydration of the outer OEGA block is relatively unaffected by the Au core. This work indicates that diblock copolymers allow factors such as steric bulk and the effects on arrangement around a metal core to be effective tools for manipulating thermo-responsive properties that are not as significant with statistical copolymers.

  17. Small angle neutron scattering study of complex coacervate micelles and hydrogels formed from ionic diblock and triblock copolymers.

    PubMed

    Krogstad, Daniel V; Choi, Soo-Hyung; Lynd, Nathaniel A; Audus, Debra J; Perry, Sarah L; Gopez, Jeffrey D; Hawker, Craig J; Kramer, Edward J; Tirrell, Matthew V

    2014-11-13

    A complex coacervate is a fluid phase that results from the electrostatic interactions between two oppositely charged macromolecules. The nature of the coacervate core structure of hydrogels and micelles formed from complexation between pairs of diblock or triblock copolymers containing oppositely charged end-blocks as a function of polymer and salt concentration was investigated. Both ABA triblock copolymers of poly[(allyl glycidyl ether)-b-(ethylene oxide)-b-(allyl glycidyl ether)] and analogous poly[(allyl glycidyl ether)-b-(ethylene oxide)] diblock copolymers, which were synthesized to be nearly one-half of the symmetrical triblock copolymers, were studied. The poly(allyl glycidyl ether) blocks were functionalized with either guanidinium or sulfonate groups via postpolymerization modification. Mixing of oppositely charged block copolymers resulted in the formation of nanometer-scale coacervate domains. Small angle neutron scattering (SANS) experiments were used to investigate the size and spacing of the coacervate domains. The SANS patterns were fit using a previously vetted, detailed model consisting of polydisperse core-shell micelles with a randomly distributed sphere or body-centered cubic (BCC) structure factor. For increasing polymer concentration, the size of the coacervate domains remained constant while the spatial extent of the poly(ethylene oxide) (PEO) corona decreased. However, increasing salt concentration resulted in a decrease in both the coacervate domain size and the corona size due to a combination of the electrostatic interactions being screened and the shrinkage of the neutral PEO blocks. Additionally, for the triblock copolymers that formed BCC ordered domains, the water content in the coacervate domains was calculated to increase from approximately 16.8% to 27.5% as the polymer concentration decreased from 20 to 15 wt %.

  18. Short-range ordered photonic structures of lamellae-forming diblock copolymers for excitation-regulated fluorescence enhancement

    NASA Astrophysics Data System (ADS)

    Kim, Se Hee; Kim, Ki-Se; Char, Kookheon; Yoo, Seong Il; Sohn, Byeong-Hyeok

    2016-05-01

    Photonic crystals can be represented by periodic nanostructures with alternating refractive indices, which create artificial stop bands with the appearance of colors. In this regard, nanodomains of block copolymers and the corresponding structural colors have been intensively studied in the past. However, the practical application of photonic crystals of block copolymers has been limited to a large degree because of the presence of large defects and grain boundaries in the nanodomains of block copolymers. The present study focuses on the alternative opportunity of short-range ordered nanodomains of block copolymers for fluorescence enhancement, which also has a direct relevance to the development of fluorescence sensors or detectors. The enhancement mechanism was found to be interconnected with the excitation process rather than the alternation of the decay kinetics. In particular, we demonstrate that randomly oriented, but regular grains of lamellae of polystyrene-block-polyisoprene, PS-b-PI, diblock copolymers and their blend with PS homopolymers can behave as Bragg mirrors to induce multiple reflections of the excitation source inside the photonic structures. This process in turn significantly increases the effective absorption of the given fluorophores inside the polymeric photonic structures to amplify the fluorescence signal.Photonic crystals can be represented by periodic nanostructures with alternating refractive indices, which create artificial stop bands with the appearance of colors. In this regard, nanodomains of block copolymers and the corresponding structural colors have been intensively studied in the past. However, the practical application of photonic crystals of block copolymers has been limited to a large degree because of the presence of large defects and grain boundaries in the nanodomains of block copolymers. The present study focuses on the alternative opportunity of short-range ordered nanodomains of block copolymers for fluorescence

  19. The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes

    SciTech Connect

    Zhang, Bo; Edwards, Brian J.

    2015-06-07

    A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.

  20. The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes.

    PubMed

    Zhang, Bo; Edwards, Brian J

    2015-06-01

    A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.

  1. The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Edwards, Brian J.

    2015-06-01

    A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.

  2. Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions

    NASA Astrophysics Data System (ADS)

    Rymaruk, Matthew J.; Thompson, Kate L.; Derry, Matthew J.; Warren, Nicholas J.; Ratcliffe, Liam P. D.; Williams, Clive N.; Brown, Steven L.; Armes, Steven P.

    2016-07-01

    We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56-poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA-PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20-100 μm diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56-poly(benzyl methacrylate)300 [PGMA56-PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56-PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39-poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39-PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to substantial spectral

  3. Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions.

    PubMed

    Rymaruk, Matthew J; Thompson, Kate L; Derry, Matthew J; Warren, Nicholas J; Ratcliffe, Liam P D; Williams, Clive N; Brown, Steven L; Armes, Steven P

    2016-08-14

    We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56-poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA-PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20-100 μm diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56-poly(benzyl methacrylate)300 [PGMA56-PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56-PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39-poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39-PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to substantial spectral

  4. Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions.

    PubMed

    Rymaruk, Matthew J; Thompson, Kate L; Derry, Matthew J; Warren, Nicholas J; Ratcliffe, Liam P D; Williams, Clive N; Brown, Steven L; Armes, Steven P

    2016-08-14

    We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56-poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA-PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20-100 μm diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56-poly(benzyl methacrylate)300 [PGMA56-PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56-PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39-poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39-PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to substantial spectral

  5. Coexistence of ordered and disordered phases in a nearly symmetric diblock copolymer near an order-disorder transition point.

    PubMed

    Koga, T; Koga, T; Hashimoto, T

    1999-08-01

    We investigated the phase behavior near the order-disorder transition (ODT) temperature in a nearly symmetric diblock copolymer, using ultra-small-angle x-ray scattering method. In a narrow temperature range very close to the ODT temperature, we observed the scattering profiles that can be interpreted as a linear combination of the scattering from the disordered state and that from the ordered lamellar state. These profiles were stable during the observation time (50 h), revealing that the two-phase coexistence occurs at thermal equilibrium within this temperature range. PMID:11969941

  6. Diblock Copolymer Micelles and Supported Films with Noncovalently Incorporated Chromophores: A Modular Platform for Efficient Energy Transfer

    DOE PAGES

    Adams, Peter G.; Collins, Aaron M.; Sahin, Tuba; Subramanian, Vijaya; Urban, Volker S.; Vairaprakash, Pothiappan; Tian, Yongming; Evans, Deborah G.; Shreve, Andrew P.; Montaño, Gabriel A.

    2015-04-08

    Here we report generation of modular, artificial light-harvesting assemblies where an amphiphilic diblock copolymer, poly(ethylene oxide)-block-poly(butadiene), serves as the framework for noncovalent organization of BODIPY-based energy donor and bacteriochlorin-based energy acceptor chromophores. The assemblies are adaptive and form well-defined micelles in aqueous solution and high-quality monolayer and bilayer films on solid supports, with the latter showing greater than 90% energy transfer efficiency. Ultimately, this study lays the groundwork for further development of modular, polymer-based materials for light harvesting and other photonic applications.

  7. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    PubMed Central

    An, Hyosung; Mike, Jared; Smith, Kendall A.; Swank, Lisa; Lin, Yen-Hao; L. Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie L.

    2015-01-01

    Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects. PMID:26391053

  8. Porous Diblock Copolymer Thin Films in High-Performance Semiconductor Microelectronics

    SciTech Connect

    Black, C.T.

    2011-02-01

    The engine fueling more than 40 years of performance improvements in semiconductor integrated circuits (ICs) has been industry's ability to pattern circuit elements at ever-higher resolution and with ever-greater precision. Steady advances in photolithography - the process wherein ultraviolet light chemically changes a photosensitive polymer resist material in order to create a latent image - have resulted in scaling of minimum printed feature sizes from tens of microns during the 1980s to sub-50 nanometer transistor gate lengths in today's state-of-the-art ICs. The history of semiconductor technology scaling as well as future technology requirements is documented in the International Technology Roadmap for Semiconductors (ITRS). The progression of the semiconductor industry to the realm of nanometer-scale sizes has brought enormous challenges to device and circuit fabrication, rendering performance improvements by conventional scaling alone increasingly difficult. Most often this discussion is couched in terms of field effect transistor (FET) feature sizes such as the gate length or gate oxide thickness, however these challenges extend to many other aspects of the IC, including interconnect dimensions and pitch, device packing density, power consumption, and heat dissipation. The ITRS Technology Roadmap forecasts a difficult set of scientific and engineering challenges with no presently-known solutions. The primary focus of this chapter is the research performed at IBM on diblock copolymer films composed of polystyrene (PS) and poly(methyl-methacrylate) (PMMA) (PS-b-PMMA) with total molecular weights M{sub n} in the range of {approx}60K (g/mol) and polydispersities (PD) of {approx}1.1. These materials self assemble to form patterns having feature sizes in the range of 15-20nm. PS-b-PMMA was selected as a self-assembling patterning material due to its compatibility with the semiconductor microelectronics manufacturing infrastructure, as well as the significant body

  9. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    DOE PAGES

    An, Hyosung; Mike, Jared; Smith, Kendall A.; Swank, Lisa; Lin, Yen-Hao; L. Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie L.

    2015-09-22

    Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued togethermore » with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects.« less

  10. The impact of substrate interaction in directed self-assembly of symmetric diblock copolymer thin films

    NASA Astrophysics Data System (ADS)

    Seidel, Robert

    Block copolymers (BCP) are a class of materials that have attracted significant attention due to their ability to self-assemble into dense arrays of nanoscale features. These materials are being investigated for their use in applications such as nanolithography, but for commercial implementation require the ability to control or direct the self-assembly process. Chemoepitaxial directed self-assembly (DSA) is one avenue to achieving this control, where a BCP thin film self-assembles in the presence of precisely defined chemical boundary conditions. In such a process, the equilibrium structure of the BCP film and the kinetic pathways it evolves along to reach equilibrium are both a function of the thermodynamic landscape, which is in turn controlled by the chemical pattern. This thesis contributes to the significant body of work attempting to detail the relationship between chemical pattern parameters and the thermodynamics of assembly (both kinetic and equilibrium). We restrict our investigation to the assembly of lamellae-forming diblock copolymers on line/space chemical patterns that employ density multiplication, with a focus on developing technology for nanopatterning beyond the resolution limit of traditional lithography. In the first chapter we introduce the fundamental ideas of BCP DSA and develop the concepts of free energy balance that are crucial to framing the discussion in the following chapters. The second chapter explores using poly(methyl methacrylate) as a guide material and shows how the greater strength of guiding interaction for this system has the ability to guide complex, frustrated non-bulk morphologies. The third chapter develops a novel concept of using process conditions to generate so-called 'three-tone' chemical patterns with multiple guiding regions per patterned stripe. The fourth chapter looks at how guide stripe strength impacts and affects assembly kinetics, equilibrium structure, and process metrics such as line edge roughness (LER

  11. Short-range ordered photonic structures of lamellae-forming diblock copolymers for excitation-regulated fluorescence enhancement.

    PubMed

    Kim, Se Hee; Kim, Ki-Se; Char, Kookheon; Yoo, Seong Il; Sohn, Byeong-Hyeok

    2016-05-19

    Photonic crystals can be represented by periodic nanostructures with alternating refractive indices, which create artificial stop bands with the appearance of colors. In this regard, nanodomains of block copolymers and the corresponding structural colors have been intensively studied in the past. However, the practical application of photonic crystals of block copolymers has been limited to a large degree because of the presence of large defects and grain boundaries in the nanodomains of block copolymers. The present study focuses on the alternative opportunity of short-range ordered nanodomains of block copolymers for fluorescence enhancement, which also has a direct relevance to the development of fluorescence sensors or detectors. The enhancement mechanism was found to be interconnected with the excitation process rather than the alternation of the decay kinetics. In particular, we demonstrate that randomly oriented, but regular grains of lamellae of polystyrene-block-polyisoprene, PS-b-PI, diblock copolymers and their blend with PS homopolymers can behave as Bragg mirrors to induce multiple reflections of the excitation source inside the photonic structures. This process in turn significantly increases the effective absorption of the given fluorophores inside the polymeric photonic structures to amplify the fluorescence signal.

  12. Morphology and mechanical behavior of blends and diblock copolymers of 1,2 and 1,4 polybutadiene

    SciTech Connect

    Cohen, R.E.; Wilfong, D.E.

    1981-02-25

    The structure and mechanical properties of a series of polymer blends and block copolymers comprised of medium cis 1,4-polybutadiene and 99% 1,2-polybutadiene have been investigated. Thermal properties (DSC) were determined at two levels of radiation crosslinking and for various sample preparation procedures (solvent and thermal history). Dynamic mechanical spectra (3.5 Hz) were measured over temperature range from 180 to 310K. Transmission electron microscopy was also used for establishing the number phases and the domain size and geometry in the heterogeneous materials. Stress-strain curves were determined for the various samples as a function of crosslink density and casting solvent. Equilibrium swelling ratios were measured for each specimen at the same radiation dose in a good solvent. Swelling values were also obtained in a series of solvents for the parent homopolymers and for a diblock copolymer containing 45% 1,2 polybutadiene.

  13. Hierarchical Helical-Assembly of Conjugated Poly(3-hexylthiophene)- b-poly(3-triethylene glycol-thiophene) Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Lee, Eunji; Hammer, Brenton; Emrick, Todd; Hayward, Ryan C.

    2011-03-01

    One-dimensional crystalline fibrillar assemblies of poly(3-hexylthiophene) (P3HT)-based materials hold significant potential for fabrication of low-cost optoelectronic devices. We have studied the crystallization-driven assembly of a series of poly(3-hexylthiophene)-block-poly(3-triethylene glycol-thiophene) (P3HT- b -P3TEGT) diblock copolymers, which provide a large contrast in solubility due to the presence of non-polar (hexyl) and polar (TEG) side-chains. P3HT- b -P3TEGT diblock copolymers were found to form well-defined fibrillar structures in mixed solvents of chloroform and methanol, with lengths could be tuned easily by changing the solvent composition or relative block lengths. For polymers containing relatively short P3TEGT blocks, the resulting fibers show twisted ribbon-like structures. For appropriate block ratios, complexation of the TEG side chains to alkali metal cations drives formation of clearly defined single helical ribbons and superhelical structures.

  14. Solid-State Nanostructured Materials from Self-Assembly of a Globular Protein-Polymer Diblock Copolymer

    PubMed Central

    Thomas, Carla S.; Glassman, Matthew J.; Olsen, Bradley D.

    2014-01-01

    Self-assembly of three-dimensional solid-state nanostructures containing approximately 33% by weight globular protein is demonstrated using a globular protein-polymer diblock copolymer, providing a route to direct nanopatterning of proteins for use in bioelectronic and biocatalytic materials. A mutant red fluorescent protein, mCherryS131C, was prepared by incorporation of a unique cysteine residue and site-specifically conjugated to end-functionalized poly(N-isopropylacrylamide) through thiol-maleimide coupling to form a well-defined model protein-polymer block copolymer. The block copolymer was self-assembled into bulk nanostructures by solvent evaporation from concentrated solutions. Small-angle X-ray scattering and transmission electron microscopy illustrated the formation of highly disordered lamellae or hexagonally perforated lamellae depending upon the selectivity of the solvent during evaporation. Solvent annealing of bulk samples resulted in a transition towards lamellar nanostructures with mCherry packed in a bilayer configuration and a large improvement in long range ordering. Wide-angle X-ray scattering indicated that mCherry did not crystallize within the block copolymer nanodomains and that the β-sheet spacing was not affected by self-assembly. Circular dichroism showed no change in protein secondary structure after self-assembly, while UV-vis spectroscopy indicated approximately 35% of the chromophore remained optically active. PMID:21696135

  15. Self-consistent field theory and numerical scheme for calculating the phase diagram of wormlike diblock copolymers.

    PubMed

    Jiang, Ying; Chen, Jeff Z Y

    2013-10-01

    This paper concerns establishing a theoretical basis and numerical scheme for studying the phase behavior of AB diblock copolymers made of wormlike chains. The general idea of a self-consistent field theory is the combination of the mean-field approach together with a statistical weight that describes the configurational properties of a polymer chain. In recent years, this approach has been extensively used for structural prediction of block copolymers, based on the Gaussian-model description of a polymer chain. The wormlike-chain model has played an important role in the description of polymer systems, covering the semiflexible-to-rod crossover of the polymer properties and the highly stretching regime, which the Gaussian-chain model has difficulties to describe. Although the idea of developing a self-consistent field theory for wormlike chains could be traced back to early development in polymer physics, the solution of such a theory has been limited due to technical difficulties. In particular, a challenge has been to develop a numerical algorithm enabling the calculation of the phase diagram containing three-dimensional structures for wormlike AB diblock copolymers. This paper describes a computational algorithm that combines a number of numerical tricks, which can be used for such a calculation. A phase diagram covering major parameter areas was constructed for the wormlike-chain system and reported by us, where the ratio between the total length and the persistence length of a constituent polymer is suggested as another tuning parameter for the microphase-separated structures; all detailed technical issues are carefully addressed in the current paper. PMID:24229202

  16. Self-consistent field theory and numerical scheme for calculating the phase diagram of wormlike diblock copolymers

    NASA Astrophysics Data System (ADS)

    Jiang, Ying; Chen, Jeff Z. Y.

    2013-10-01

    This paper concerns establishing a theoretical basis and numerical scheme for studying the phase behavior of AB diblock copolymers made of wormlike chains. The general idea of a self-consistent field theory is the combination of the mean-field approach together with a statistical weight that describes the configurational properties of a polymer chain. In recent years, this approach has been extensively used for structural prediction of block copolymers, based on the Gaussian-model description of a polymer chain. The wormlike-chain model has played an important role in the description of polymer systems, covering the semiflexible-to-rod crossover of the polymer properties and the highly stretching regime, which the Gaussian-chain model has difficulties to describe. Although the idea of developing a self-consistent field theory for wormlike chains could be traced back to early development in polymer physics, the solution of such a theory has been limited due to technical difficulties. In particular, a challenge has been to develop a numerical algorithm enabling the calculation of the phase diagram containing three-dimensional structures for wormlike AB diblock copolymers. This paper describes a computational algorithm that combines a number of numerical tricks, which can be used for such a calculation. A phase diagram covering major parameter areas was constructed for the wormlike-chain system and reported by us, where the ratio between the total length and the persistence length of a constituent polymer is suggested as another tuning parameter for the microphase-separated structures; all detailed technical issues are carefully addressed in the current paper.

  17. Effect of PEG-PLLA diblock copolymer on macroporous PLLA scaffolds by thermally induced phase separation.

    PubMed

    Kim, Hyun Do; Bae, Eun Hee; Kwon, Ick Chan; Pal, Ravindra Ramsurat; Nam, Jae Do; Lee, Doo Sung

    2004-05-01

    A regular and highly interconnected macroporous poly(L-lactic acid) (PLLA) scaffold was fabricated from a PLLA-dioxane-water ternary system with added polyethylene glycol (PEG)-PLLA diblock using thermally induced phase separation (TIPS). The morphology of the scaffold was investigated in detail by controlling the following TIPS parameters: quenching temperature, aging time, polymer concentration, molecular structure, and diblock concentration. The phase diagram was assessed visually on the basis of the turbidity. The cloud-point curve shifted to higher temperatures with increasing PEG content in the additives (PEG-PLLA diblocks), due to a stronger interaction between PEG and water in solution. The addition of diblock series (0.5 wt% in solution) stabilized interconnections of pores at a later stage without segregation or sedimentation. The pore size of the scaffold could be easily controlled in the range 50-300 microm. A macroporous PLLA scaffold was used to study an MC3T3-E1 cell (an osteoblast-like cell) culture. The cells successfully proliferated in the PLLA scaffold in the presence of added PEG-PLLA diblock for 4 weeks.

  18. Synthesis and self-assembly of terpyridine end-capped poly(N-isopropylacrylamide)-block-poly(2-(dimethylamino)ethyl methacrylate) diblock copolymers.

    PubMed

    Brassinne, Jérémy; Poggi, Elio; Fustin, Charles-André; Gohy, Jean-François

    2015-04-01

    At the basis of smart self-assembled materials are lying small building blocks that can hierarchically assemble in response to stimuli, e.g., temperature or chemical species. In this context, the synthesis of terpyridine end-capped poly(2-(dimethylamino)ethyl methacrylate)-block-poly(N-isopropylacrylamide) diblock copolymers via controlled radical copolymerization is reported here. The self-assembly of those copolymers is investigated in dilute aqueous solutions while varying temperature or adding transition metal ions, respectively, leading to the formation of micellar nanostructures or metallosupramolecular triblock copolymers. PMID:25491079

  19. Phase Behavior and Ionic Conductivity of Concentrated Solutions of Polystyrene-Poly(ethylene oxide) Diblock Copolymers in an Ionic Liquid

    SciTech Connect

    Simone, Peter M.; Lodge, Timothy P.

    2010-03-16

    Concentrated solutions of poly(styrene-b-ethylene oxide) (PS-PEO) diblock copolymers were prepared using the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMI][TFSI] as the solvent. The self-assembled microstructures adopted by the copolymer solutions have been characterized using small-angle X-ray scattering. Lyotropic mesophase transitions were observed, with a progression from hexagonally packed cylinders of PEO, to lamellae, to hexagonally packed cylinders of PS upon increasing [EMI][TFSI] content. The change in lamellar domain spacing with ionic liquid concentration was found to be comparable to that reported for other block copolymers in strongly selective solvents. The ionic conductivity of the concentrated PS-PEO/[EMI][TFSI] solutions was measured via impedance spectroscopy, and ranged from 1 x 10{sup -7} to 1 x 10{sup -3} S/cm at temperatures from 25-100 C. Additionally, the ionic conductivity of the solutions was found to increase with both ionic liquid concentration and molecular weight of the PEO blocks. The ionic conductivity of PEO homopolymer/[EMI][TFSI] solutions was also measured in order to compare the conductivity of the PS-PEO solutions to the expected limit for a lamellar sample with randomly oriented microstructure grains.

  20. Novel Diblock Copolymer-Grafted Multiwalled Carbon Nanotubes via a combination of Living and Controlled/Living Surface Polymerizations

    SciTech Connect

    Priftis, Dimitrios; Sakellariou, Georgios; Mays, Jimmy; Hadjichristidis, Nikos

    2010-01-01

    Diels Alder cycloaddition reactions were used to functionalize multiwalled carbon nanotubes (MWNTs) with 1-benzocylcobutene-10-phenylethylene (BCB-PE) or 4-hydroxyethylbenzocyclobutene (BCB-EO). The covalent functionalization of the nanotubes with these initiator precursors was verified by FTIR and thermogravimetric analysis (TGA). After appropriate transformations/additions, the functionalized MWNTs were used for surface initiated anionic and ring opening polymerizations of ethylene oxide and e-caprolactone (e-CL), respectively. The OH-end groups were transformed to isopropylbromide groups by reaction with 2-bromoisobutyryl bromide, for subsequent atom transfer radical polymerization of styrene or 2-dimethylaminoethyl methacrylate to afford the final diblock copolymers. 1H NMR, differential scanning calorimetry (DSC), TGA, and transmission electron microscopy (TEM) were used for the characterization of the nanocomposite materials. TEM images showed the presence of a polymer layer around the MWNTs as well as the dissociation of MWNT bundles. Consequently, this general methodology, employing combinations of different polymerization techniques, increases the diversity of diblocks that can be grafted from MWNTs.

  1. Fluctuation Effects in AB/A/B Diblock Copolymer-Homopolymer Ternary Mixtures near the Lamellar-Disorder Transition

    NASA Astrophysics Data System (ADS)

    Gillard, Timothy; Hickey, Robert; Habersberger, Brian; Lodge, Timothy; Bates, Frank

    2015-03-01

    Fluctuations profoundly influence the phase behavior of block polymer-based soft materials. In ternary blends of an AB diblock copolymer with A- and B-type homopolymers, fluctuations destroy a mean-field predicted higher-order multicritical Lifshitz point and lead to the formation of the technologically important polymeric bicontinuous microemulsion phase (B μE). Here we report a fascinating change in character of the lamellar-to-disorder phase transition as the composition of homopolymer in the ternary blend is increased from zero (neat diblock) to the onset of the B μE channel. As the B μE channel is approached, the transition exhibits increasingly second-order character with the development of large-scale fluctuating smectic correlations in the disordered state near the transition. This change in character of the transition is documented with a combination of scattering, optical transmission, rheology, and TEM experiments in model blends of poly(cyclohexylethylene- b-ethylene) with the constituent homopolymers.

  2. Quantitative Control of Pore Size of Mesoporous Carbon Nanospheres through the Self-Assembly of Diblock Copolymer Micelles in Solution.

    PubMed

    Tian, Hao; Lin, Zhixing; Xu, Fugui; Zheng, Jingxu; Zhuang, Xiaodong; Mai, Yiyong; Feng, Xinliang

    2016-06-01

    This paper reports facile synthesis of nitrogen-doped mesoporous carbon nanospheres (MCNSs) with average diameters of around 300 nm and well-controlled pore sizes ranging from 8 to 38 nm, by employing polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblocks with different PS block lengths as the soft templates and dopamine as the carbon-rich precursor. For the first time, a linear equation is achieved for the quantitative control of the average pore size of MCNSs by simply adjusting a block length of diblock copolymer. The resultant MCNSs possess high surface areas of up to 450 m(2) g(-1) and nitrogen doping contents of up to ≈3 wt%. As electrode materials of supercapacitors, the MCNSs exhibit excellent electrochemical performance with high specific capacitances of up to 350 F g(-1) at 0.1 A g(-1) , superior rate capability, and cycling stability. Interestingly, the specific capacitance of the MCNSs reduces linearly with increasing pore size, whereas the normalized capacitance by specific surface area remains invariable. This represents a new spectrum of the relationship between electrochemical capacitance and pore size (>5 nm) for porous carbons, which makes a complement to the existing spectra focusing on pore diameters of <5 nm. PMID:27120340

  3. Ordered, microphase-separated, noncharged-charged diblock copolymers via the sequential ATRP of styrene and styrenic imidazolium monomers

    SciTech Connect

    Shi, ZX; Newell, BS; Bailey, TS; Gin, DL

    2014-12-15

    A series of imidazolium-based noncharged-charged diblock copolymers (1) was synthesized by the direct, sequential ATRP of styrene and styrenic imidazolium bis(trifluoromethyl)sulfonamide monomers with methyl, n-butyl, and n-decyl side-chains. Small-angle X-ray scattering studies on initial examples of 1 with a total of 50 repeat units and styrene:imidazolium-styrene repeat unit ratios of 25:25, 20:30, and 15:35 showed that their ability to form ordered nanostructures (i.e., sphere and cylinder phases) in their neat states depends on both the block ratio and the length of the alkyl side-chain on the imidazolium monomer. To our knowledge, the synthesis of imidazolium-based BCPs that form ordered, phase-separated nanostructures via direct ATRP of immiscible co-monomers is unprecedented. (C) 2014 Elsevier Ltd. All rights reserved.

  4. Mesosized Crystal-like Structure of Hexagonally Packed Hollow Hoops by Solution Self-Assembly of Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Zhang, Lifeng; Bartels, Carl; Yu, Yisong; Shen, Hongwei; Eisenberg, Adi

    1997-12-01

    Mesosize crystal-like aggregates with an internal structure of hexagonally packed hollow hoops (HHH) in a polystyrene matrix have been prepared in solution by self-assembly of asymmetric polystyrene-b-poly(acrylic acid) diblock copolymers. Most of the aggregates are cylindrical or in the shape of truncated cones. The external surface of the aggregates and the internal surface of the hollow hoops are lines with short poly(acrylic acid) chains. The hoop morphology is imposed because the end-capping energy of a rod on this size scale is more important than the curvature energy. A strong interdependence between the external shape and the internal structure in these mesosize particles is demonstrated.

  5. Self-Assembly of Charged Amphiphilic Diblock Copolymers with Insoluble Blocks of Decreasing Hydrophobicity: From Kinetically Frozen Colloids to Macrosurfactants

    SciTech Connect

    M Jacquin; P Muller; H Cottet; O Theodoly

    2011-12-31

    We have investigated the self-assembly properties in aqueous solution of amphiphilic diblock copolymers with insoluble blocks of different hydrophobicity and demonstrated that the condition to obtain dynamic micelles is to design samples with insoluble blocks of low enough hydrophobicity. We focus here on results with new water-soluble amphiphilic diblock copolymers poly(diethyleneglycol ethylether acrylate)-b-poly(acrylic acid), or PDEGA-b-PAA. The physical characteristics of PDEGA-b-PAA micelles at high ionization have been determined by small angle neutron scattering (SANS). We show that PDEGA-b-PAA samples form micelles at thermodynamic equilibrium. The critical micelle concentrations (CMCs) decrease strongly with ionic strength and temperature due to a solvent quality decrease for, respectively, the corona and the core. This behavior of reversible aggregation is remarkable as compared to the behavior of kinetically frozen aggregation that has been widely observed with samples of similar architecture and different hydrophobic blocks, for example, poly(styrene)-b-poly(acrylic acid), PS-b-PAA, and poly(butyl acrylate)-b-poly(acrylic acid), PBA-b-PAA. We have measured the interfacial tension between water and the homopolymers PDEGA and PBA at, respectively, 3 and 20 mN/m at room temperature, which permits one to estimate the energy cost to extract a unimer from a micelle. The results are consistent with a micelle association that is fast for PDEGA-b-PAA and kinetically frozen PBA-b-PAA. Hence, PDEGA-b-PAA samples form a new system of synthetic charged macrosurfactant with unique properties of fast dynamic association, tunable charge, and water solubility even at temperatures and NaCl concentrations as high as 65 C and 1 M.

  6. Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions

    NASA Astrophysics Data System (ADS)

    Rymaruk, Matthew J.; Thompson, Kate L.; Derry, Matthew J.; Warren, Nicholas J.; Ratcliffe, Liam P. D.; Williams, Clive N.; Brown, Steven L.; Armes, Steven P.

    2016-07-01

    We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56-poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA-PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20-100 μm diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56-poly(benzyl methacrylate)300 [PGMA56-PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56-PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39-poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39-PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to substantial spectral

  7. Thermodynamics of Polymer Adsorption onto Nanoporous Silica and its Application in the Large Scale Purification of Poly(styrene)-block-Poly(alkyl methacrylate) Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Abdulahad, Asem Irfan

    As a result of unavoidable inconsistencies in their synthesis via controlled radical polymerization techniques, block copolymers inherently have distributions in chemical composition and molecular weight in each block that can have significant impact on their viscoelastic properties as well as their ability to self-assemble into ordered phases. High performance liquid chromatography is routinely utilized for determining the average molecular weight distribution that exist in synthetic polymers and is becoming increasingly popular for the fractionation and purification of chemically diverse complex polymer materials such as diblock copolymers. However, the inability of HPLC fractionation to provide meaningful quantities of purified complex polymers makes this method extremely inefficient and limits the ability to characterize purified fractions further. Overall, this dissertation work can be digested in two distinct parts. In the first part, high performance liquid chromatography was used as a tool for studying the influential parameters affecting the critical adsorption point of poly(styrene) and poly(alkyl methacrylate) homopolymers. The understanding gained in the first portion was depended on for the development of large scale fractionation procedures. In the second part, a chemically diverse variety of poly(alkyl methacrylate)-block-poly(styrene) diblock copolymers synthesized by atom transfer radical polymerization and anionic polymerization were purified by large scale adsorption-based fractionation procedures that included chromatographic filtration and the sequential adsorption/desorption of bulk diblock copolymer materials. The impact of diblock copolymer purification is addressed by comparing the molecular weight distribution, chemical composition distribution, viscoelastic properties, and small-angle X-ray scattering profiles.

  8. Durability and performance of polystyrene- b -poly(vinylbenzyl trimethylammonium) diblock copolymer and equivalent blend anion exchange membranes

    SciTech Connect

    Vandiver, Melissa A.; Caire, Benjamin R.; Poskin, Zach; Li, Yifan; Seifert, Sönke; Knauss, Daniel M.; Herring, Andrew M.; Liberatore, Matthew W.

    2014-11-01

    Anion exchange membranes (AEM) are solid polymer electrolytes that facilitate ion transport in fuel cells. In this study, a polystyrene-b-poly(vinylbenzyl trimethylammonium) diblock copolymer was evaluated as potential AEM and compared with the equivalent homopolymer blend. The diblock had a 92% conversion of reactive sites with an IEC of 1.72 ± 0.05 mmol g-1, while the blend had a 43% conversion for an IEC of 0.80 ± 0.03 mmol g-1. At 50°C and 95% relative humidity, the chloride conductivity of the diblock was higher, 24–33 mS cm-1, compared with the blend, 1–6 mS cm-1. The diblock displayed phase separation on the length scale of 100 nm, while the blend displayed microphase separation (~10 μm). Mechanical characterization of films from 40 to 90 microns thick found that elasticity and elongation decreased with the addition of cations to the films. At humidified conditions, water acted as a plasticizer to increase film elasticity and elongation. While the polystyrene-based diblock displayed sufficient ionic conductivity, the films' mechanical properties require improvement, i.e., greater elasticity and strength, before use in fuel cells. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41596.

  9. Ellipsometric characterization of ethylene oxide-butylene oxide diblock copolymer adsorption at the air-water interface.

    PubMed

    Blomqvist, B Rippner; Benjamins, J-W; Nylander, T; Arnebrant, T

    2005-05-24

    Ellipsometry was used to determine the adsorbed layer thickness (d) and the surface excess (adsorbed amount, Gamma) of a nonionic diblock copolymer, E(106)B(16), of poly(ethylene oxide) (E) and poly(butylene oxide) (B) at the air-water interface. The results were obtained (i) by the conventional ellipsometric evaluation procedure using the change of both ellipsometric angles Psi and Delta and (ii) by using the change of Delta only and assuming values of the layer thickness. It was demonstrated that the calculated surface excesses from the different methods were in close agreement, independent of the evaluation procedure, with a plateau adsorption of about 2.5 mg/m(2) (400 A(2)/molecule). Furthermore, the amount of E(106)B(16) adsorbed at the air-water interface was found to be almost identical to that adsorbed from aqueous solution onto a hydrophobic solid surface. In addition, the possibility to use combined measurements with H(2)O or D(2)O as substrates to calculate values of d and Gamma was investigated and discussed. We also briefly discuss within which limits the Gibbs equation can be used to determine the surface excess of polydisperse block copolymers. PMID:15896051

  10. Preparation and solution behavior of a thermoresponsive diblock copolymer of poly(ethyl glycidyl ether) and poly(ethylene oxide).

    PubMed

    Ogura, Michihiro; Tokuda, Hiroyuki; Imabayashi, Shin-ichiro; Watanabe, Masayoshi

    2007-08-28

    A thermoresponsive diblock copolymer, poly(ethyl glycidyl ether)-block-poly(ethylene oxide) (PEGE-b-PEO), is synthesized by successive anionic ring-opening polymerization of ethyl glycidyl ether and ethylene oxide using 2-phenoxyethanol as a starting material, and its solution behavior is elucidated in water. In a dilute 1 wt % solution, the temperature-dependent alteration in the polymer hydrodynamic radius (RH) is measured in the temperature range between 5 and 45 degrees C by pulse-gradient spin-echo NMR and dynamic light scattering. The RH value increased with temperature in two steps, where the first step at 15 degrees C corresponds to the core-shell micelle formation and the second step at 40 degrees C corresponds to the aggregation of the core-shell micelles. The formation of the core-shell micelles is supported by the solubilization of a dye (1,6-diphenyl-1,3,5-hexatriene) in the hydrophobic core, which is recognized for a copolymer solution in the temperature range between 20 and 40 degrees C. In this temperature range, the core-shell micelles and the unimers coexist and the fraction of the former gradually increases with increasing temperature, suggesting equilibrium between the micelles and the unimers. In the concentrated regime (40 wt % solution), the solution forms a gel and the small-angle X-ray scattering measurements reveal the successive formation of hexagonal and lamellar liquid crystal phases with increasing temperature.

  11. Strongly segregated cubic microdomain morphology consistent with the double gyroid phase in high molecular weight diblock copolymers of polystyrene and poly(dimethylsiloxane)

    SciTech Connect

    Politakos, N.; Ntoukas, E; Avgeropoulos, A; Krikorian, V; Pate, B; Thomas, E; Hill, R

    2009-01-01

    We report the observation of a cubic phase consistent with the double gyroid structure in strongly segregated diblock copolymers of PS-b-PDMS over a volume fraction ({phi}{sub PDMS}) range of {approx}0.39 to 0.45. The samples have respective molecular weights of 127 kg/mol and 73 kg/mol and degree of segregation N{sub {chi}} equal to 187 and 106, respectively, at annealing temperature of 130 C. It is important to highlight that two out of the total four samples investigated, exhibited hexagonally close packed cylindrical domains of PDMS and alternating lamellae at {phi}{sub PDMS} = 0.39 and 0.45, respectively, indicating the possible narrow range of the DG morphology for the specific diblock copolymers.

  12. Terminal modification on mPEG-dendritic poly-(l)-lysine cationic diblock copolymer for efficient gene delivery.

    PubMed

    Sheng, Ruilong; Xia, Kejia; Chen, Jian; Xu, Yuhong; Cao, Amin

    2013-01-01

    The development of new non-viral gene vectors with the advantages of low cytotoxicity and high gene transfection efficiency is a recent trend in gene therapy. In this work, we developed a series of termini-modified mPEG-dendritic poly-(l)-lysine cationic diblock copolymers (mPEG5k-DPL4-CG) by coupling various cationic groups to the dendritic skeleton. Their molecular structures were characterized by (1)H NMR, and the buffering capacities were measured by acid titration. The plasmid DNA (pDNA) binding affinities of the mPEG5k-DPL4-CG copolymers were investigated by EB displacement and agarose gel retardation assay, and the average particle size and surface charge of the polyplexes were analyzed by dynamic light scattering. Cytotoxicity and in vitro gene transfection were evaluated in several cell lines in the presence and absence of serum by the luciferase expression assay. The results indicated that the low molecular weight polyethylenimine (PEI800) termini-modified copolymer, mPEG5k-DPL4-PEI800, possessed high pDNA binding affinity, low cytotoxicity, and high gene transfection capability which were maintained in the presence of serum (10% FBS). It is worth noting that the gene delivery efficiency of the dendritic poly-(l)-lysine gene vector was enhanced by termini modification of suitable cationic blocks. The low cytotoxicity and serum-resistance properties of mPEG5k-DPL4-PEI800 make it a potential long-circulating gene vector in gene therapy applications.

  13. One-pot glovebox-free synthesis, characterization, and self-assembly of novel amphiphilic poly(sarcosine-b-caprolactone) diblock copolymers.

    PubMed

    Cui, Saide; Wang, Xin; Li, Zhenjiang; Zhang, Qiguo; Wu, Wenzhuo; Liu, Jingjing; Wu, Hao; Chen, Cheng; Guo, Kai

    2014-11-01

    Novel amphiphilic polypeptoid-polyester diblock copolymers based on poly(sarcosine) (PSar) and poly(ε-caprolactone) (PCL) are synthesized by a one-pot glovebox-free approach. In this method, sarcosine N-carboxy anhydride (Sar-NCA) is firstly polymerized in the presence of benzylamine under N(2) flow, then the resulting poly(sarcosine) is used in situ as the macro-initiator for the ring-opening polymerization (ROP) of ε-caprolactone using tin(II) octanoate as a catalyst. The degree of poly-merization of each block is controlled by various feed ratios of monomer/initiator. The diblock copolymers with controlled molecular weight and narrow molecular weight distributions (Đ(M) < 1.2) are characterized by (1)H NMR, (13)C NMR, and size-exclusion chromatography. The self-assembly behavior of PSar-b-PCL in water is investigated by dynamic light scattering (DLS) and transmission electron microscopy. DLS results reveal that the diblock copolymers associate into nanoparticles with average hydrodynamic diameters (D(H)) around 100 nm in water, which may be used as drug delivery carriers.

  14. One-pot glovebox-free synthesis, characterization, and self-assembly of novel amphiphilic poly(sarcosine-b-caprolactone) diblock copolymers.

    PubMed

    Cui, Saide; Wang, Xin; Li, Zhenjiang; Zhang, Qiguo; Wu, Wenzhuo; Liu, Jingjing; Wu, Hao; Chen, Cheng; Guo, Kai

    2014-11-01

    Novel amphiphilic polypeptoid-polyester diblock copolymers based on poly(sarcosine) (PSar) and poly(ε-caprolactone) (PCL) are synthesized by a one-pot glovebox-free approach. In this method, sarcosine N-carboxy anhydride (Sar-NCA) is firstly polymerized in the presence of benzylamine under N(2) flow, then the resulting poly(sarcosine) is used in situ as the macro-initiator for the ring-opening polymerization (ROP) of ε-caprolactone using tin(II) octanoate as a catalyst. The degree of poly-merization of each block is controlled by various feed ratios of monomer/initiator. The diblock copolymers with controlled molecular weight and narrow molecular weight distributions (Đ(M) < 1.2) are characterized by (1)H NMR, (13)C NMR, and size-exclusion chromatography. The self-assembly behavior of PSar-b-PCL in water is investigated by dynamic light scattering (DLS) and transmission electron microscopy. DLS results reveal that the diblock copolymers associate into nanoparticles with average hydrodynamic diameters (D(H)) around 100 nm in water, which may be used as drug delivery carriers. PMID:25283643

  15. Tailored Assemblies of Rod-Coil Poly(3-hexylthiophene)-b-Polystyrene Diblock Copolymers: Adaptable Building Blocks for High-Performance Organic Field-Effect Transistors

    SciTech Connect

    Xiao, Kai; Yu, Xiang; Chen, Jihua; Lavrik, Nickolay V; Hong, Kunlun; Sumpter, Bobby; Geohegan, David B

    2011-01-01

    The self-assembly process and resulting structure of a series of conductive diblock copolymer thin films of Poly(3-hexylthiophene)-b-Polystyrene (P3HT-b-PS) have been studied by TEM, SAED, GIXD and AFM and additionally by first principles modeling and simulation. By varying the molecular weight of the P3HT segment, these block copolymers undergo microphase separation and self-assemble into nanostructured sphere, lamellae, nanofiber, and nanoribbon in the films. Within the diblock copolymer thin film, the convalently bonded PS blocks segregated to form amorphous domains, however, the conductive P3HT blocks were crystalline, exhibiting highly-ordered molecular packing with their alkyl side chains aligned along to the normal to the substrate and the - stacking direction of the thiophene rings aligned parallel to the substrate. The conductive P3HY block copolymers exhibited significant improvements in organic feild-effect transistor (OFET) performance and environmental stability as compared to P3HT homopolymers, with up to a factor of two increase in measured moblity (0.08 cm2/Vs ) for the P4 (85 wt% P3HT). Overall, this work demonstrates that the high degree of molecular order induced by bock copolymer phase separation can improve the transport properties and stability of conductive polymer critical for high-performance OFET s.

  16. Sequentially Different AB Diblock and ABA Triblock Copolymers as P3HT:PCBM Interfacial Compatibilizers for Bulk-Heterojunction Photovoltaics.

    PubMed

    Fujita, Hiroyuki; Michinobu, Tsuyoshi; Fukuta, Seijiro; Koganezawa, Tomoyuki; Higashihara, Tomoya

    2016-03-01

    The P3HT:PCBM (P3HT = poly(3-hexylthiophene, PCBM = phenyl-C61-butyric acid methyl ester) bulk-heterojunction (BHJ) organic photovoltaic (OPV) cells using the AB diblock and ABA triblock copolymers (A = polystyrene derivative with donor-acceptor units (PTCNE) and B = P3HT) as compatibilizers were fabricated. Under the optimized blend ratio of the block copolymer, the power conversion efficiency (PCE) was enhanced. This PCE enhancement was clearly related to the increased short-circuit current (J(sc)) and fill factor (FF). The incident photon to current efficiency (IPCE) measurement suggested that the P3HT crystallinity was improved upon addition of the block copolymers. The increased P3HT crystallinity was consistent with the increased photovoltaic parameters, such as J(sc), FF, and consequently the PCE. The surface energies of these block copolymers suggested their thermodynamically stable location at the interface of P3HT:PCBM, showing the efficient compatibilizing performance, resulting in enlarging and fixing the interfacial area and suppressing the recombination of the generated carriers. Grazing incidence X-ray scattering (GIXS) results confirmed the superior compatibilizing performance of the ABA triblock copolymer when compared to the AB diblock copolymer by the fact that, after blending the ABA triblock copolymer in the P3HT:PCBM system, the enhanced crystallinity of matrix P3HT was observed in the excluded areas of the less-aggregated PCBM domains, changing the P3HT crystalline domain orientation from "edge-on" to "isotropic". This is, to the best of our knowledge, the first sequential effect (AB vs ABA) of the block copolymers on the compatibilizing performances based on BHJ OPV device systems. PMID:26864393

  17. Sequentially Different AB Diblock and ABA Triblock Copolymers as P3HT:PCBM Interfacial Compatibilizers for Bulk-Heterojunction Photovoltaics.

    PubMed

    Fujita, Hiroyuki; Michinobu, Tsuyoshi; Fukuta, Seijiro; Koganezawa, Tomoyuki; Higashihara, Tomoya

    2016-03-01

    The P3HT:PCBM (P3HT = poly(3-hexylthiophene, PCBM = phenyl-C61-butyric acid methyl ester) bulk-heterojunction (BHJ) organic photovoltaic (OPV) cells using the AB diblock and ABA triblock copolymers (A = polystyrene derivative with donor-acceptor units (PTCNE) and B = P3HT) as compatibilizers were fabricated. Under the optimized blend ratio of the block copolymer, the power conversion efficiency (PCE) was enhanced. This PCE enhancement was clearly related to the increased short-circuit current (J(sc)) and fill factor (FF). The incident photon to current efficiency (IPCE) measurement suggested that the P3HT crystallinity was improved upon addition of the block copolymers. The increased P3HT crystallinity was consistent with the increased photovoltaic parameters, such as J(sc), FF, and consequently the PCE. The surface energies of these block copolymers suggested their thermodynamically stable location at the interface of P3HT:PCBM, showing the efficient compatibilizing performance, resulting in enlarging and fixing the interfacial area and suppressing the recombination of the generated carriers. Grazing incidence X-ray scattering (GIXS) results confirmed the superior compatibilizing performance of the ABA triblock copolymer when compared to the AB diblock copolymer by the fact that, after blending the ABA triblock copolymer in the P3HT:PCBM system, the enhanced crystallinity of matrix P3HT was observed in the excluded areas of the less-aggregated PCBM domains, changing the P3HT crystalline domain orientation from "edge-on" to "isotropic". This is, to the best of our knowledge, the first sequential effect (AB vs ABA) of the block copolymers on the compatibilizing performances based on BHJ OPV device systems.

  18. Synthesis and self-assembly of biodegradable polyethylene glycol-poly (lactic acid) diblock copolymers as polymersomes for preparation of sustained release system of doxorubicin

    PubMed Central

    Alibolandi, Mona; Sadeghi, Fatemeh; Sazmand, Seyed Hossein; Shahrokhi, Seyed Mohammad; Seifi, Mahmoud; Hadizadeh, Farzin

    2015-01-01

    Introduction: The copolymer of polyethylene glycol (PEG) and polyesters has many interesting properties, such as amphiphilicity, biocompatibility, biodegradability, and self-assembly in an aqueous environment. Diblock copolymers of PEG-polyester can form different structures such as micelles, polymersome, capsules or micro-container in an aqueous environment according to the length of their blocks. Materials and Methods: Herein, a series of poly (lactic acid) (PLA) and PEG diblock copolymers were synthesized through the ring-opening polymerization. The polymerization reaction and the copolymer structures were evaluated by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The corresponding copolymers were implemented for the formation of polymersome structures using film rehydration method. Impact of methoxy PEG chain length and hydrophobic weight fraction on particle size of polymersomes were studied, and the proper ones were selected for loading of doxorubicin (DOX) via pH gradient method. Results and Discussion: Results obtained from 1HNMR and GPC revealed that microwave irradiation is a simple and reliable method for the synthesis of PEG-PLA copolymers. Further analysis indicated the copolymer with relative molecular weight of PLA to PEG ratios of 3 or fEo ~ 25% produced the smallest size polymersomes. Polymersomes prepared from PEG5000 to PLA15000 were more capable in loading and sustained release of DOX than those prepared from PEG2000 to PLA6000. Conclusion: In conclusion copolymers of PEG/PLA with fOE ~25% and relatively higher molecular weight are more suitable for encapsulation and providing sustained release of DOX. PMID:26258054

  19. Mesoscale simulation of polymer reaction equilibrium: Combining dissipative particle dynamics with reaction ensemble Monte Carlo. II. Supramolecular diblock copolymers

    NASA Astrophysics Data System (ADS)

    Lísal, Martin; Brennan, John K.; Smith, William R.

    2009-03-01

    We present an alternative formulation of the reaction ensemble dissipative particle dynamics (RxDPD) method [M. Lísal, J. K. Brennan, and W. R. Smith, J. Chem. Phys. 125, 16490 (2006)], a mesoscale simulation technique for studying polymer systems in reaction equilibrium. The RxDPD method combines elements of dissipative particle dynamics (DPD) and reaction ensemble Monte Carlo (RxMC), and is primarily targeted for the prediction of the system composition, thermodynamic properties, and phase behavior of reaction equilibrium polymer systems. The alternative formulation of the RxDPD method is demonstrated by considering a supramolecular diblock copolymer (SDC) melt in which two homopolymers, An and Bm, can reversibly bond at terminal binding sites to form a diblock copolymer, AnBm. We consider the effect of the terminal binding sites and the chemical incompatibility between A- and B-segments on the phase behavior. Both effects are found to strongly influence the resulting phase behavior. Due to the reversible nature of the binding, the SDC melt can be treated as the reaction equilibrium system An+Bm⇌AnBm. To simulate the An+Bm⇌AnBm melt, the system contains, in addition to full An, Bm, and AnBm polymers, two fractional polymers: one fractional polymer either fAn or fBm, and one fractional polymer fAnBm, which have fractional particles at the ends of the polymer chains. These fractional particles are coupled to the system via a coupling parameter. The time evolution of the system is governed by the DPD equations of motion, accompanied by random changes in the coupling parameter. Random changes in the coupling parameter mimic forward and reverse reaction steps as in the RxMC approach, and they are accepted with a probability derived from the expanded ensemble grand canonical partition function. Unlike the original RxDPD method that considers coupling of entire fractional polymers to the system, the expanded ensemble framework allows a stepwise coupling, thus

  20. RAFT aqueous dispersion polymerization yields poly(ethylene glycol)-based diblock copolymer nano-objects with predictable single phase morphologies.

    PubMed

    Warren, Nicholas J; Mykhaylyk, Oleksandr O; Mahmood, Daniel; Ryan, Anthony J; Armes, Steven P

    2014-01-22

    A poly(ethylene glycol) (PEG) macromolecular chain transfer agent (macro-CTA) is prepared in high yield (>95%) with 97% dithiobenzoate chain-end functionality in a three-step synthesis starting from a monohydroxy PEG113 precursor. This PEG113-dithiobenzoate is then used for the reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA). Polymerizations conducted under optimized conditions at 50 °C led to high conversions as judged by (1)H NMR spectroscopy and relatively low diblock copolymer polydispersities (M(w)/M(n) < 1.25) as judged by GPC. The latter technique also indicated good blocking efficiencies, since there was minimal PEG113 macro-CTA contamination. Systematic variation of the mean degree of polymerization of the core-forming PHPMA block allowed PEG113-PHPMA(x) diblock copolymer spheres, worms, or vesicles to be prepared at up to 17.5% w/w solids, as judged by dynamic light scattering and transmission electron microscopy studies. Small-angle X-ray scattering (SAXS) analysis revealed that more exotic oligolamellar vesicles were observed at 20% w/w solids when targeting highly asymmetric diblock compositions. Detailed analysis of SAXS curves indicated that the mean number of membranes per oligolamellar vesicle is approximately three. A PEG113-PHPMA(x) phase diagram was constructed to enable the reproducible targeting of pure phases, as opposed to mixed morphologies (e.g., spheres plus worms or worms plus vesicles). This new RAFT PISA formulation is expected to be important for the rational and efficient synthesis of a wide range of biocompatible, thermo-responsive PEGylated diblock copolymer nano-objects for various biomedical applications. PMID:24400622

  1. Aqueous self-assembly of poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) copolymers: disparate diblock copolymer compositions give rise to nano- and meso-scale bilayered vesicles

    NASA Astrophysics Data System (ADS)

    Qi, Wei; Ghoroghchian, P. Peter; Li, Guizhi; Hammer, Daniel A.; Therien, Michael J.

    2013-10-01

    Nanoparticles formed from diblock copolymers of FDA approved PEO and PCL have generated considerable interest as in vivo drug delivery vehicles. Herein, we report the synthesis of the most extensive family PEO-b-PCL copolymers that vary over the largest range of number-average molecular weights (Mn: 3.6-57k), PEO weight fractions (fPEO: 0.08-0.33), and PEO chain lengths (0.75-5.8k) reported to date. These polymers were synthesized in order to establish the full range of aqueous phase behaviours of these diblock copolymers and to specifically identify formulations that were able to generate bilayered vesicles (polymersomes). Cryogenic transmission electron microscopy (cryo-TEM) was utilized in order to visualize the morphology of these structures upon aqueous self-assembly of dry polymer films. Nanoscale polymersomes were formed from PEO-b-PCL copolymers over a wide range of PEO weight fractions (fPEO: 0.14-0.27) and PEO molecular weights (0.75-3.8k) after extrusion of aqueous suspensions. Comparative morphology diagrams, which describe the nature of self-assembled structures as a function of diblock copolymer molecular weight and PEO weight fraction, show that in contrast to micron-scale polymersomes, which form only from a limited range of PEO-b-PCL diblock copolymer compositions, a multiplicity of PEO-b-PCL diblock copolymer compositions are able to give rise to nanoscale vesicles. These data underscore that PEO-b-PCL compositions that spontaneously form micron-sized polymersomes, as well as those that have previously been reported to form polymersomes via a cosolvent fabrication system, provide only limited insights into the distribution of PEO-b-PCL diblocks that give rise to nanoscale vesicles. The broad range of polymersome-forming PEO-b-PCL compositions described herein suggest the ability to construct extensive families of nanoscale vesicles of varied bilayer thickness, providing the ability to tune the timescales of vesicle degradation and encapsulant

  2. Directed self-assembly of diblock copolymers in multi-VIA configurations: effect of chemopatterned substrates on defectivity

    NASA Astrophysics Data System (ADS)

    Carpenter, Corinne L.; Delaney, Kris T.; Fredrickson, Glenn H.

    2016-03-01

    Directed self-assembly (DSA) of block copolymers has gained much attention for its potential as a low-cost, high-throughput patterning tool to supplement existing lithographic techniques, and in particular for its ability to easily pattern vertical interconnect accesses (VIAs).1 Single-hole shrink has been extensively explored, but the continued push towards higher-resolution patterns requires more efficient, less space-consuming approaches. The lithographic resolution limits the minimum distance between two features, and the single-hole templates take up valuable real estate on the wafer.2 To accommodate denser features and relax the resolution requirements of the lithographic techniques, it is prudent to move to multi-VIA configurations in which two or more features are assembled in a single guiding template (such as a peanut,3 or a rounded rectangle4). This allows considerably denser feature patterning, but comes at the cost of more plentiful and complicated defect modes than those found in single-hole shrink features. Most systems contain persistent horizontal structures (eg. rings, U-defects, or bars as shown in Figure 1) that prove detrimental to the etch process and yield undesirable configurations. Largely unexplored is the tandem use of chemoepitaxy and graphoepitaxy to suppress defect modes in multi- VIA templates. Specifically, chemically selective patterning of the substrate beneath a template could act synergistically with the template's lateral guidance to lower defectivity. In this study, we use three-dimensional self-consistent field theory (SCFT) simulations to investigate the equilibrium and metastable defective configurations of di-block copolymer DSA systems in the presence of chemically selective or neutral template sidewalls and preferentially attractive striped substrates. We identify chemo-patterning schemes that maximize defect energies, including sidewall interaction strength and chemical preference. In addition, we discuss chemo

  3. Static and dynamic evanescent wave light scattering studies of diblock copolymers adsorbed at the air/water interface

    NASA Astrophysics Data System (ADS)

    Lin, Binhua; Rice, Stuart A.; Weitz, D. A.

    1993-11-01

    We report the results of static and dynamic evanescent wave light scattering studies of a monolayer of a diblock copolymer, polystyrene-b-polymethylmethacrylate (PS-b-PMMA) with weight averaged molecular weights (Mw) of 880 000:290 000 supported at the air/water interface. Our studies probe the interfacial structural and dynamic properties of the monolayer on a length scale which is a fraction of the wavelength of light. The static light scattering studies were carried out as a function of polymer surface coverage and temperature; we also report some preliminary data for the dependence of the static structure function on the relative molecular weights of the PS and PMMA blocks. The complementary dynamic light scattering studies were carried out only as a function of surface coverage. Our data suggest that, upon spreading in the air/water interface, PS-b-PMMA (880:290 K) copolymers form thin disklike aggregates containing about 240 molecules. These data are consistent with a model in which each such aggregate is a ``furry disk'' with a dense core consisting of a layer of collapsed PS blocks atop a thin layer of extended PMMA blocks on the water surface and a brushlike boundary of extended PMMA blocks. The data show that the furry disks diffuse freely when the surface coverage is small, but when the surface coverage is large, they are immobile. Our data also suggest that the furry disks can aggregate to form even larger ``islands'' of disks with an extension greater than 20 μm. The static structure function of the assembly of furry disks is well described, over a wide range of surface coverage, by the structure factor of a two-dimensional hard disk fluid modulated by a two-dimensional hard disk form factor.

  4. Arrangement of Maghemite Nanoparticles via Wet Chemical Self-Assembly in PS-b-PNIPAM Diblock Copolymer Films.

    PubMed

    Yao, Yuan; Metwalli, Ezzeldin; Su, Bo; Körstgens, Volker; Moseguí González, Daniel; Miasnikova, Anna; Laschewsky, Andre; Opel, Matthias; Santoro, Gonzalo; Roth, Stephan V; Müller-Buschbaum, Peter

    2015-06-17

    The structure and magnetic behavior of hybrid films composed of maghemite (γ-Fe2O3) nanoparticles (NPs) and an asymmetric diblock copolymer (DBC) polystyrene61-block-polyN-isopropylacrylamide115 are investigated. The NPs are coated with PS chains, which allow for a selective incorporation inside the PS domains at different NP concentrations. Upon incorporation of low amounts of NPs into the DBC thin films, the initial parallel (to film surface) cylinder morphology changes to a well ordered, perpendicularly oriented one. The characteristic domain distance of the DBC is increased due to the swelling of the PS domains with NPs. At higher NP concentrations, the excess NPs which can no longer be embedded in the PS domains, are accumulated at the film surface, and NP aggregates form. Irrespective of NP concentration, a superparamagnetic behavior of the metal oxide-DBC hybrid films is found. Such superparamagnetic properties make the established hybrid films interesting for high density magnetic storage media and thermoresponsive magnetic sensors.

  5. Functionalization of Cellulose Nanocrystals with PEG-Metal-Chelating Diblock Copolymers via Controlled Conjugation in Aqueous Medium

    NASA Astrophysics Data System (ADS)

    Guo, Melinda

    The surface of cellulose nanocrystals (CNCs) was successfully functionalized with metal chelating diblock copolymers via HyNic-4FB conjugation. Two types of PEG-metal-chelating block polymers with hydrazinonicotinate acetone hydrazine (HyNic) end groups were synthesized: mPEG-PGlu(DTPA) 18-HyNic and mPEG-PGlu(DTPA)25-HyNic. These two polymers both had a methoxy PEG (M ˜ 2000 Da) block that differed in the mean degree of polymerization of the metal-chelating block. They were characterized by 1H NMR spectroscopy and gel-permeation chromatography (GPC). 4-Formylbenzamide (4FB) groups were introduced onto the surface of CNCs and quantified through their reaction with 2-hydrazinopyridine. The polymers were grafted onto the surface of CNCs via bis-aryl hydrazone bond formation, and the kinetics of this reaction was explored by UV/Vis spectroscopy. The CNCs were also labeled with rhodamine and Alexa FluorRTM 488 dyes. Students in our collaborator's group in Pharmacy are examining applications of these materials as radiotherapeutic agents for cancer treatment.

  6. Polystyrene-poly(ethylene oxide) diblock copolymer: the effect of polystyrene and spreading concentration at the air/water interface.

    PubMed

    Glagola, Cameron P; Miceli, Lia M; Milchak, Marissa A; Halle, Emily H; Logan, Jennifer L

    2012-03-20

    Polystyrene-block-poly(ethylene oxide) (PS-PEO) is an amphiphilic diblock copolymer that undergoes microphase separation when spread at the air/water interface, forming nanosized domains. In this study, we investigate the impact of PS by examining a series of PS-PEO samples containing constant PEO (~17,000 g·mol(-1)) and variable PS (from 3600 to 200,000 g·mol(-1)) through isothermal characterization and atomic force microscopy (AFM). The polymers separated into two categories: predominantly hydrophobic and predominantly hydrophilic with a weight percent of PEO of ~20% providing the boundary between the two. AFM results indicated that predominantly hydrophilic PS-PEO forms dots while more hydrophobic samples yield a mixture of dots and spaghetti with continent-like structures appearing at ~7% PEO or less. These structures reflect a blend of polymer spreading, entanglement, and vitrification as the solvent evaporates. Changing the spreading concentration provides insight into this process with higher concentrations representing earlier kinetic stages and lower concentrations demonstrating later ones. Comparison of isothermal results and AFM analysis shows how polymer behavior at the air/water interface correlates with the observed nanostructures. Understanding the impact of polymer composition and spreading concentration is significant in leading to greater control over the nanostructures obtained through PS-PEO self-assembly and their eventual application as polymer templates.

  7. Conformation and structural changes of diblock copolymers with octopus-like micelle formation in the presence of external stimuli

    NASA Astrophysics Data System (ADS)

    Dammertz, K.; Saier, A. M.; Marti, O.; Amirkhani, M.

    2014-04-01

    External stimuli such as vapours and electric fields can be used to manipulate the formation of AB-diblock copolymers on surfaces. We study the conformational variation of PS-b-PMMA (polystyrene-block-poly(methyl methacrylate)), PS and PMMA adsorbed on mica and their response to saturated water or chloroform atmospheres. Using specimens with only partial polymer coverage, new unanticipated effects were observed. Water vapour, a non-solvent for all three polymers, was found to cause high surface mobility. In contrast, chloroform vapour (a solvent for all three polymers) proved to be less efficient. Furthermore, the influence of an additional applied electric field was investigated. A dc field oriented parallel to the sample surface induces the formation of polymer islands which assemble into wormlike chains. Moreover, PS-b-PMMA forms octopus-like micelles (OLMs) on mica. Under the external stimuli mentioned above, the wormlike formations of OLMs are able to align in the direction of the external electric field. In the absence of an electric field, the OLMs disaggregate and exhibit phase separated structures under chloroform vapour.

  8. Occlusion of Sulfate-Based Diblock Copolymer Nanoparticles within Calcite: Effect of Varying the Surface Density of Anionic Stabilizer Chains

    PubMed Central

    2016-01-01

    Polymerization-induced self-assembly (PISA) offers a highly versatile and efficient route to a wide range of organic nanoparticles. In this article, we demonstrate for the first time that poly(ammonium 2-sulfatoethyl methacrylate)-poly(benzyl methacrylate) [PSEM–PBzMA] diblock copolymer nanoparticles can be prepared with either a high or low PSEM stabilizer surface density using either RAFT dispersion polymerization in a 2:1 v/v ethanol/water mixture or RAFT aqueous emulsion polymerization, respectively. We then use these model nanoparticles to gain new insight into a key topic in materials chemistry: the occlusion of organic additives into inorganic crystals. Substantial differences are observed for the extent of occlusion of these two types of anionic nanoparticles into calcite (CaCO3), which serves as a suitable model host crystal. A low PSEM stabilizer surface density leads to uniform nanoparticle occlusion within calcite at up to 7.5% w/w (16% v/v), while minimal occlusion occurs when using nanoparticles with a high PSEM stabilizer surface density. This counter-intuitive observation suggests that an optimum anionic surface density is required for efficient occlusion, which provides a hitherto unexpected design rule for the incorporation of nanoparticles within crystals. PMID:27509298

  9. Inducing an Order–Order Morphological Transition via Chemical Degradation of Amphiphilic Diblock Copolymer Nano-Objects

    PubMed Central

    2016-01-01

    The disulfide-based cyclic monomer, 3-methylidene-1,9-dioxa-5,12,13-trithiacyclopentadecane-2,8-dione (MTC), is statistically copolymerized with 2-hydroxypropyl methacrylate to form a range of diblock copolymer nano-objects via reversible addition–fragmentation chain transfer (RAFT) polymerization. Poly(glycerol monomethacrylate) (PGMA) is employed as the hydrophilic stabilizer block in this aqueous polymerization-induced self-assembly (PISA) formulation, which affords pure spheres, worms or vesicles depending on the target degree of polymerization for the core-forming block. When relatively low levels (<1 mol %) of MTC are incorporated, high monomer conversions (>99%) are achieved and high blocking efficiencies are observed, as judged by 1H NMR spectroscopy and gel permeation chromatography (GPC), respectively. However, the side reactions that are known to occur when cyclic allylic sulfides such as MTC are statistically copolymerized with methacrylic comonomers lead to relatively broad molecular weight distributions. Nevertheless, the worm-like nanoparticles obtained via PISA can be successfully transformed into spherical nanoparticles by addition of excess tris(2-carboxyethyl)phosphine (TCEP) at pH 8–9. Surprisingly, DLS and TEM studies indicate that the time scale needed for this order–order transition is significantly longer than that required for cleavage of the disulfide bonds located in the worm cores indicated by GPC analysis. This reductive degradation pathway may enable the use of these chemically degradable nanoparticles in biomedical applications, such as drug delivery systems and responsive biomaterials. PMID:27228898

  10. Nucleation of the BCC phase from disorder in a diblock copolymer melt: Testing approximate theories through simulation

    NASA Astrophysics Data System (ADS)

    Spencer, Russell K. W.; Curry, Paul F.; Wickham, Robert A.

    2016-10-01

    We examine nucleation of the stable body-centred-cubic (BCC) phase from the metastable uniform disordered phase in an asymmetric diblock copolymer melt. Our comprehensive, large-scale simulations of the time-dependent, mean-field Landau-Brazovskii model find that spherical droplets of the BCC phase nucleate directly from disorder. Near the order-disorder transition, the critical nucleus is large and has a classical profile, attaining the bulk BCC phase in an interior that is separated from disorder by a sharp interface. At greater undercooling, the amplitude of BCC order in the interior decreases and the nucleus interface broadens, leading to a diffuse critical nucleus. This diffuse nucleus becomes large as the simulation approaches the disordered phase spinodal. We show that our simulation follows the same nucleation pathway that Cahn and Hilliard found for an incompressible two-component fluid, across the entire metastable region. In contrast, a classical nucleation theory calculation based on the free energy of a planar interface between coexisting BCC and disordered phases agrees with simulation only in the limit of very small undercooling; we can expand this region of validity somewhat by accounting for the curvature of the droplet interface. A nucleation pathway involving a classical droplet persists, however, to deep undercooling in our simulation, but this pathway is energetically unfavourable. As a droplet grows in the simulation, its interface moves with a constant speed, and this speed is approximately proportional to the undercooling.

  11. Synthesis and Characterization of a Poly(ethylene glycol)-Poly(simvastatin) Diblock Copolymer

    PubMed Central

    Asafo-Adjei, Theodora A.; Dziubla, Thomas D.; Puleo, David A.

    2014-01-01

    Biodegradable polyesters are commonly used as drug delivery vehicles, but their role is typically passive, and encapsulation approaches have limited drug payload. An alternative drug delivery method is to polymerize the active agent or its precursor into a degradable polymer. The prodrug simvastatin contains a lactone ring that lends itself to ring-opening polymerization (ROP). Consequently, simvastatin polymerization was initiated with 5 kDa monomethyl ether poly(ethylene glycol) (mPEG) and catalyzed via stannous octoate. Melt condensation reactions produced a 9.5 kDa copolymer with a polydispersity index of 1.1 at 150 °C up to a 75 kDa copolymer with an index of 6.9 at 250 °C. Kinetic analysis revealed first-order propagation rates. Infrared spectroscopy of the copolymer showed carboxylic and methyl ether stretches unique to simvastatin and mPEG, respectively. Slow degradation was demonstrated in neutral and alkaline conditions. Lastly, simvastatin, simvastatin-incorporated molecules, and mPEG were identified as the degradation products released. The present results show the potential of using ROP to polymerize lactone-containing drugs such as simvastatin. PMID:25431653

  12. Protonation-Induced Microphase Separation in Thin Films of a Polyelectrolyte-Hydrophilic Diblock Copolymer.

    PubMed

    Stewart-Sloan, Charlotte R; Olsen, Bradley D

    2014-05-20

    Block copolymers composed of poly(oligo ethylene glycol methyl ether methacrylate) and poly(2-vinylpyridine) are disordered in the neat state but can be induced to order by protonation of the P2VP block, demonstrating a tunable and responsive method for triggering assembly in thin films. Comparison of protonation with the addition of salts shows that microphase separation is due to selective protonation of the P2VP block. Increasing acid incorporation and increasing 2-vinylpyridine content for P2VP minority copolymers both promote increasingly phase-separated morphologies, consistent with protonation increasing the effective strength of segregation between the two blocks. The self-assembled nanostructures formed after casting from acidic solutions may be tuned based on the amount and type of acid incorporation as well as the annealing treatment applied after casting, where both aqueous and polar organic solvents are shown to be effective. Therefore, POEGMA-b-P2VP is a novel ion-containing block copolymer whose morphologies can be facilely tuned during casting and processing by controlling its exposure to acid. PMID:24910809

  13. Protonation-Induced Microphase Separation in Thin Films of a Polyelectrolyte-Hydrophilic Diblock Copolymer

    PubMed Central

    2015-01-01

    Block copolymers composed of poly(oligo ethylene glycol methyl ether methacrylate) and poly(2-vinylpyridine) are disordered in the neat state but can be induced to order by protonation of the P2VP block, demonstrating a tunable and responsive method for triggering assembly in thin films. Comparison of protonation with the addition of salts shows that microphase separation is due to selective protonation of the P2VP block. Increasing acid incorporation and increasing 2-vinylpyridine content for P2VP minority copolymers both promote increasingly phase-separated morphologies, consistent with protonation increasing the effective strength of segregation between the two blocks. The self-assembled nanostructures formed after casting from acidic solutions may be tuned based on the amount and type of acid incorporation as well as the annealing treatment applied after casting, where both aqueous and polar organic solvents are shown to be effective. Therefore, POEGMA-b-P2VP is a novel ion-containing block copolymer whose morphologies can be facilely tuned during casting and processing by controlling its exposure to acid. PMID:24910809

  14. Self-assembly of rod-coil diblock copolymers within a rod-selective slit: a dissipative particle dynamics simulation study.

    PubMed

    Huang, Jian-Hua; Ma, Ze-Xin; Luo, Meng-Bo

    2014-06-01

    Dissipative particle dynamics simulations are performed to investigate the self-assembly of rod-coil diblock copolymers R(N(R))C(N-N(R)) within a rod-selective slit. The self-assembled structure of the confined system is sensitively dependent on the rigidity kθ and the fraction fR of the rod block and the slit height H. From the phase diagram of structures with respect to kθ and fR for N = 12 and H = 6, we observe four main structures including disordered cylinder (DC) structure, hexagonally packed cylinders (HPC) perpendicular to the slit surfaces, and lamellar structures parallel (L∥) and perpendicular (L⊥) to surfaces. And structure transitions can be achieved by tuning kθ. The effect of the slit height on the self-assembled structure is also studied for R6C6 and R7C5 copolymers with large kθ. For R6C6, different structures near surfaces and in the interior of slit are observed in relatively wide slits. Whereas for R7C5, L⊥ structure, whose lamellar domain spacing decays exponentially with H, is generally generated. Our results suggest an effective way to control the ordering of rod-coil diblock copolymers under nanoscale confinement. PMID:24801931

  15. Self-assembly Morphology and Crystallinity Control of Di-block Copolymer Inspired by Spider Silk

    NASA Astrophysics Data System (ADS)

    Huang, Wenwen; Krishnaji, Sreevidhya; Kaplan, David; Cebe, Peggy

    2012-02-01

    To obtain a fuller understanding of the origin of self-assembly behavior, and thus be able to control the morphology of biomaterials with well defined amino acid sequences for tissue regeneration and drug delivery, we created a family of synthetic silk-based block copolymers inspired by the genetic sequences found in spider dragline, HABn and HBAn (n=1,2,3,6), where B = hydrophilic block, A = hydrophobic block, and H is a histidine tag. We assessed the secondary structure of water cast films by Fourier transform infrared spectroscopy (FTIR). The crystallinity was determined by Fourier self-deconvolution of amide I spectra and confirmed by wide angle X-ray diffraction (WAXD). Results indicate that we can control the self-assembled morphology and the crystallinity by varying the block length, and a minimum of 3 A-blocks are required to form beta sheet crystalline regions in water-cast spider silk block copolymers. The morphology and crystallinity can also be tuned by annealing. Thermal properties of water cast films and films annealed at 120 C were determined by differential scanning calorimetry and thermogravimetry. The sample films were also treated with 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP) to obtain wholly amorphous samples, and crystallized by exposure to methanol. Using scanning and transmission electron microscopies, we observe that fibrillar networks and hollow micelles are formed in water cast and methanol cast samples, but not in samples cast from HFIP.

  16. Chemoepitaxial guiding underlayers for density asymmetric and energetically asymmetric diblock copolymers

    NASA Astrophysics Data System (ADS)

    Nation, Benjamin D.; Ludovice, Peter J.; Henderson, Clifford L.

    2016-04-01

    Block copolymers, polymers composed of two or more homopolymers covalently bonded together, are currently being investigated as a method to extend optical lithography due to their ability to microphase separate on small size scales. In order to drive down the size that these BCPs phase separate, the BCPs with larger Flory-Huggin's χparameter needs to be found. Typically these BCPs are composed of more dissimilar homopolymers. However, changing these interactions also changes how BCPs interact with their guiding underlayers. In this paper, several block copolymers are simulated annealing on chemoepitaxial guiding underlayers using a coarse-grained molecular dynamics model in order to explore the effect that either energetic asymmetry or density asymmetry in the BCP have on the pattern registration. It is found that energetic asymmetry in BCPs causes one of the blocks to desire to skin, which shifts the composition of the background region that leads to well aligned vertical lamellae formation. It is hypothesized that moderate footing and undercutting at the underlayer or slight skinning at the free surface can increase the kinetics of defect annihilation by decreasing the distance that bridges must form. The density asymmetric BCPs simulated in this paper have different mechanical properties which lead to straighter sidewalls in the BCP film and potentially lead to better pattern registration. It is hypothesized that altering the compressibility of the blocks can alter equilibrium defectivity.

  17. The Lifshitz line of the disordered and microemulsion phase in an A/B/A-B three component homopolymer/diblock copolymer mixture

    NASA Astrophysics Data System (ADS)

    Pipich, Vitaliy; Schwahn, Dietmar; Willner, Lutz

    2004-07-01

    Thermal composition fluctuations were measured in a homopolymer blend dPB/PS (dPB/dPS) of critical composition mixed with different amounts of a symmetric diblock copolymer dPB-PS (PB and PS being polybutadiene and polystyrene, respectively) with small-angle neutron scattering (SANS). From thermal fluctuations the two-phase boundary, two critical universality classes and the Lifshitz line were derived. The bicontinuous microemulsion phase could be identified by the characteristic peak positions of samples prepared in bulk, block and film contrast. A non-monotonic Lifshitz line (LL) showing a dependence on temperature was found. LL is located in the disordered and bicontinuous microemulsion phase.

  18. Diblock-copolymer-mediated self-assembly of protein-stabilized iron oxide nanoparticle clusters for magnetic resonance imaging.

    PubMed

    Tähkä, Sari; Laiho, Ari; Kostiainen, Mauri A

    2014-03-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) can be used as efficient transverse relaxivity (T2 ) contrast agents in magnetic resonance imaging (MRI). Organizing small (D<10 nm) SPIONs into large assemblies can considerably enhance their relaxivity. However, this assembly process is difficult to control and can easily result in unwanted aggregation and precipitation, which might further lead to lower contrast agent performance. Herein, we present highly stable protein-polymer double-stabilized SPIONs for improving contrast in MRI. We used a cationic-neutral double hydrophilic poly(N-methyl-2-vinyl pyridinium iodide-block-poly(ethylene oxide) diblock copolymer (P2QVP-b-PEO) to mediate the self-assembly of protein-cage-encapsulated iron oxide (γ-Fe2 O3 ) nanoparticles (magnetoferritin) into stable PEO-coated clusters. This approach relies on electrostatic interactions between the cationic N-methyl-2-vinylpyridinium iodide block and magnetoferritin protein cage surface (pI≈4.5) to form a dense core, whereas the neutral ethylene oxide block provides a stabilizing biocompatible shell. Formation of the complexes was studied in aqueous solvent medium with dynamic light scattering (DLS) and cryogenic transmission electron microcopy (cryo-TEM). DLS results indicated that the hydrodynamic diameter (Dh ) of the clusters is approximately 200 nm, and cryo-TEM showed that the clusters have an anisotropic stringlike morphology. MRI studies showed that in the clusters the longitudinal relaxivity (r1 ) is decreased and the transverse relaxivity (r2 ) is increased relative to free magnetoferritin (MF), thus indicating that clusters can provide considerable contrast enhancement.

  19. On the comparisons between dissipative particle dynamics simulations and self-consistent field calculations of diblock copolymer microphase separation

    NASA Astrophysics Data System (ADS)

    Sandhu, Paramvir; Zong, Jing; Yang, Delian; Wang, Qiang

    2013-05-01

    To highlight the importance of quantitative and parameter-fitting-free comparisons among different models/methods, we revisited the comparisons made by Groot and Madden [J. Chem. Phys. 108, 8713 (1998), 10.1063/1.476300] and Chen et al. [J. Chem. Phys. 122, 104907 (2005), 10.1063/1.1860351] between their dissipative particle dynamics (DPD) simulations of the DPD model and the self-consistent field (SCF) calculations of the "standard" model done by Matsen and Bates [Macromolecules 29, 1091 (1996), 10.1021/ma951138i] for diblock copolymer (DBC) A-B melts. The small values of the invariant degree of polymerization used in the DPD simulations do not justify the use of the fluctuation theory of Fredrickson and Helfand [J. Chem. Phys. 87, 697 (1987), 10.1063/1.453566] by Groot and Madden, and their fitting between the DPD interaction parameters and the Flory-Huggins χ parameter in the "standard" model also has no rigorous basis. Even with their use of the fluctuation theory and the parameter-fitting, we do not find the "quantitative match" for the order-disorder transition of symmetric DBC claimed by Groot and Madden. For lamellar and cylindrical structures, we find that the system fluctuations/correlations decrease the bulk period and greatly suppress the large depletion of the total segmental density at the A-B interfaces as well as its oscillations in A- and B-domains predicted by our SCF calculations of the DPD model. At all values of the A-block volume fractions in the copolymer f (which are integer multiples of 0.1), our SCF calculations give the same sequence of phase transitions with varying χN as the "standard" model, where N denotes the number of segments on each DBC chain. All phase boundaries, however, are shifted to higher χN due to the finite interaction range in the DPD model, except at f = 0.1 (and 0.9), where χN at the transition between the disordered phase and the spheres arranged on a body-centered cubic lattice is lower due to N = 10 in the DPD

  20. Defect structures and ordering behaviours of diblock copolymers self-assembling on spherical substrates.

    PubMed

    Zhang, Liangshun; Wang, Liquan; Lin, Jiaping

    2014-09-21

    One of the main differences of ordered structures constrained on curved surfaces is the nature of topological defects. We here explore the defect structures and ordering behaviours of both lamellar and cylindrical phases of block copolymers confined on spherical substrates by the Landau-Brazovskii theory, which is numerically solved by a highly accurate spectral method with a spherical harmonic basis. For the cylindrical phase, isolated disclinations and scars are generated on the spherical substrates. The number of excess dislocations in a scar depends linearly on the sphere radius. The defect fraction characterizing the ordering dynamics decays exponentially. The scars are formed from the isolated disclinations via mini-scars. For the lamellar phase, three types of defect structures (hedgehog, spiral and quasi-baseball) are identified. The disclination annihilation is the primary ordering mechanism of the lamellar phase.

  1. Prediction of solvent-induced morphological changes of polyelectrolyte diblock copolymer micelles.

    PubMed

    Li, Nan K; Fuss, William H; Tang, Lei; Gu, Renpeng; Chilkoti, Ashutosh; Zauscher, Stefan; Yingling, Yaroslava G

    2015-11-14

    Self-assembly processes of polyelectrolyte block copolymers are ubiquitous in industrial and biological processes; understanding their physical properties can also provide insights into the design of polyelectrolyte materials with novel and tailored properties. Here, we report systematic analysis on how the ionic strength of the solvent and the length of the polyelectrolyte block affect the self-assembly and morphology of the polyelectrolyte block copolymer materials by constructing a salt-dependent morphological phase diagram using an implicit solvent ionic strength (ISIS) method for dissipative particle dynamics (DPD) simulations. This diagram permits the determination of the conditions for the morphological transition into a specific shape, namely vesicles or lamellar aggregates, wormlike/cylindrical micelles, and spherical micelles. The scaling behavior for the size of spherical micelles is predicted, in terms of radius of gyration (R(g,m)) and thickness of corona (Hcorona), as a function of solvent ionic strength (c(s)) and polyelectrolyte length (NA), which are R(g,m) ∼ c(s)(-0.06)N(A)(0.54) and Hcorona ∼ c(s)(-0.11)N(A)(0.75). The simulation results were corroborated through AFM and static light scattering measurements on the example of the self-assembly of monodisperse, single-stranded DNA block-copolynucleotides (polyT50-b-F-dUTP). Overall, we were able to predict the salt-responsive morphology of polyelectrolyte materials in aqueous solution and show that a spherical-cylindrical-lamellar change in morphology can be obtained through an increase in solvent ionic strength or a decrease of polyelectrolyte length. PMID:26315065

  2. Surface characterization of poly(L-lactic acid)-methoxy poly(ethylene glycol) diblock copolymers by static and dynamic contact angle measurements, FTIR, and ATR-FTIR.

    PubMed

    Mert, O; Doganci, E; Erbil, H Y; Demir, A S

    2008-02-01

    The surface composition and surface free energy properties of two types of amphiphilic and semicrystalline diblock copolymers consisting of poly(L-lactic acid) coupled to (methoxy poly(ethylene glycol) (PLLA-MePEG) having differing block lengths of PEG were investigated by using static and dynamic contact angle measurements, transmission Fourier infrared spectroscopy (FTIR), and attenuated total reflection spectroscopy (ATR-FTIR) and compared with results obtained from PLLA and MePEG homopolymers. The contact angle results were evaluated by using the van Oss-Good method (acid-base method), and it was determined that the Lewis base surface tension coefficient (gamma-) of the copolymers increased with an increase of the PEG molar content at the copolymer surface. This result is in good agreement with the transmission FTIR and ATR-FTIR results but not proportional to them, indicating that the surfaces of the copolymers are highly mobile and that the molecular rearrangement takes place upon contact with a polar liquid drop. The dynamic contact angle measurements showed that the strong acid-base interaction between the oxygen atoms in the copolymer backbone of the relatively more hydrophilic PEG segments with the Lewis acidic groups of the polar and hydrogen-bonding water molecules enabled the surface molecules to restructure (conformational change) at the contact area, so that the PEG segments moved upward, whereas the apolar methyl pendant groups of PLLA segments buried downward.

  3. Morphological Phase Behavior of Poly(RTIL)-Containing Diblock Copolymer Melts

    SciTech Connect

    Scalfani, VF; Wiesenauer, EF; Ekblad, JR; Edwards, JP; Gin, DL; Bailey, TS

    2012-05-22

    The development of nanostructured polymeric systems containing directionally continuous poly(ionic liquid) (poly(IL)) domains has considerable implications toward a range of transport-dependent, energy-based technology applications. The controlled, synthetic integration of poly(IL)s into block copolymer (BCP) architectures provides a promising means to this end, based on their inherent ability to self-assemble into a range of defined, periodic morphologies. In this work, we report the melt-state phase behavior of an imidazolium-containing alkyl ionic BCP system, derived from the sequential ring-opening metathesis polymerization (ROMP) of imidazolium- and alkyl-substituted norbornene monomer derivatives. A series of 16 BCP samples were synthesized, varying both the relative volume fraction of the poly(norbornene dodecyl ester) block (f(DOD) = 0.42-0.96) and the overall molecular weights of the block copolymers (M-n values from 5000-20 100 g mol(-1)). Through a combination of small-angle X-ray scattering (SAXS) and dynamic rheology, we were able to delineate clear compositional phase boundaries for each of the classic BCP phases, including lamellae (Lam), hexagonally packed cylinders (Hex), and spheres on a body-centered-cubic lattice (S-BCC). Additionally, a liquid-like packing (LLP) of spheres was found for samples located in the extreme asymmetric region of the phase diagram, and a persistent coexistence of Lam and Hex domains was found in lieu of the bicontinuous cubic gyroid phase for samples located at the intersection of Hex and Lam regions. Thermal disordering was opposed even in very low molecular weight samples, detected only when the composition was highly asymmetric (f(DOD) = 0.96). Annealing experiments on samples exhibiting Lam and Hex coexistence revealed the presence of extremely slow transition kinetics, ultimately selective for one or the other but not the more complex gyroid phase. In fact, no evidence of the bicontinuous network was detected over

  4. Morphological Phase Behavior of Poly(RTIL)-Containing Diblock Copolymer Melts

    SciTech Connect

    Scalfani, Vincent F.; Wiesenauer, Erin F.; Ekblad, John R.; Edwards, Julian P.; Gin, Douglas L.; Bailey, Travis S.

    2012-10-23

    The development of nanostructured polymeric systems containing directionally continuous poly(ionic liquid) (poly(IL)) domains has considerable implications toward a range of transport-dependent, energy-based technology applications. The controlled, synthetic integration of poly(IL)s into block copolymer (BCP) architectures provides a promising means to this end, based on their inherent ability to self-assemble into a range of defined, periodic morphologies. In this work, we report the melt-state phase behavior of an imidazolium-containing alkyl-ionic BCP system, derived from the sequential ring-opening metathesis polymerization (ROMP) of imidazolium- and alkyl-substituted norbornene monomer derivatives. A series of 16 BCP samples were synthesized, varying both the relative volume fraction of the poly(norbornene dodecyl ester) block (f{sub DOD} = 0.42-0.96) and the overall molecular weights of the block copolymers (M{sub n} values from 5000-20,100 g mol{sup -1}). Through a combination of small-angle X-ray scattering (SAXS) and dynamic rheology, we were able to delineate clear compositional phase boundaries for each of the classic BCP phases, including lamellae (Lam), hexagonally packed cylinders (Hex), and spheres on a body-centered-cubic lattice (S{sub BCC}). Additionally, a liquid-like packing (LLP) of spheres was found for samples located in the extreme asymmetric region of the phase diagram, and a persistent coexistence of Lam and Hex domains was found in lieu of the bicontinuous cubic gyroid phase for samples located at the intersection of Hex and Lam regions. Thermal disordering was opposed even in very low molecular weight samples, detected only when the composition was highly asymmetric (f{sub DOD} = 0.96). Annealing experiments on samples exhibiting Lam and Hex coexistence revealed the presence of extremely slow transition kinetics, ultimately selective for one or the other but not the more complex gyroid phase. In fact, no evidence of the bicontinuous

  5. Diblock Copolymer Foams with Adhesive Nano-domains Promote Stem Cell Differentiation

    NASA Astrophysics Data System (ADS)

    Engler, Adam

    2012-02-01

    Adhesions play an important role in cell behavior, including differentiation. Substrates are typically modified with homogeneous protein coatings; extracellular matrices in vivo provide heterogeneous adhesive sites. To mimic adhesive heterogeneity, internal phase emulsion foams were polymerized with polystyrene-polyacrylic acid (PAA) and polystyrene-polyethylene oxide (PEO) to determine if interface de-mixing would form patch-like surfaces. PEO/PAA mole ratios were confirmed by XPS and water contact angle while spatial distribution was measured by chemical force spectroscopy. This method confirmed the presence of patch-like PAA domains. Protein differentially adsorbs on PEO and PAA, so adsorption on foam mixtures was copolymer ratio dependent. Bone marrow-derived mesenchymal stem cell (BMSC) adhesion was ratio dependent, but the highest density and vinculin expression was observed for 75PEO/25PAA. BMSCs appeared to change lineage expression the most on this composition, suggesting that this foam, which exhibits small adhesive PAA domains, may be more biomemetic than uniformally adhesive scaffolds, e.g. 0PEO/100PAA.

  6. Structure and Morphology of PEO-b-PLLA Diblock Copolymer Single Crystal

    NASA Astrophysics Data System (ADS)

    Li, Lingyu

    2005-03-01

    Poly (L-lactide) (PLLA) is an important biodegradable synthetic polymer of interest for medical applications such as controlled drug delivery, resorbable sutures, medical implants, and scaffolds for tissue engineering. Combining PLLA with Poly (ethylene oxide) (PEO) to form a block copolymer PEO-b-PLLA has attracted the interests of material scientists because modifications of physical and chemical properties lead to an accelerated biodegradability. Generally, the rate of degradation strongly depends on the solid state structure of the material therefore clear understanding of crystallization behavior of PEO-b-PLLA is important. Crystallization of PEO-b-PLLA primarily depends on crystallization temperature (Tc). Solution cast thin film crystallization method was used to obtain the PEO-b-PLLA single crystals. At temperatures above Tm of PEO and below that of PLLA, PLLA crystallizes and forms lozenge-shaped single crystal .When cooled to room temperature, PEO begins to crystallize and form fractal-like single crystal on the top of already formed PLLA crystals. However, at temperatures below Tm of PEO, only the fractal-like PEO single crystals were observed. Structure and morphology of this novel single crystal was explored using TEM and AFM.

  7. Chiral selection of single helix formed by diblock copolymers confined in nanopores.

    PubMed

    Deng, Hanlin; Qiang, Yicheng; Zhang, Tingting; Li, Weihua; Yang, Tao

    2016-09-21

    Chiral selection has attracted tremendous attention from the scientific communities, especially from biologists, due to the mysterious origin of homochirality in life. The self-assembly of achiral block copolymers confined in nanopores offers a simple but useful model of forming helical structures, where the helical structures possess random chirality selection, i.e. equal probability of left-handedness and right-handedness. Based on this model, we study the stimulus-response of chiral selection to external conditions by introducing a designed chiral pattern onto the inner surface of a nanopore, aiming to obtain a defect-free helix with controllable homochirality. A cell dynamics simulation based on the time-dependent Ginzburg-Landau theory is carried out to demonstrate the tuning effect of the patterned surface on the chiral selection. Our results illustrate that the chirality of the helix can be successfully controlled to be consistent with that of the tailored surface patterns. This work provides a successful example for the stimulus response of the chiral selection of self-assembled morphologies from achiral macromolecules to external conditions, and hence sheds light on the understanding of the mechanism of the stimulus response. PMID:27536966

  8. Langmuir structure of poly (2-vinylpyridine-b-hexyl isocyanate) rod-coil diblock copolymers at the air/water Interface

    NASA Astrophysics Data System (ADS)

    Ahmad, Farhan

    2005-03-01

    We conducted a systematic interfacial study for the complete range (5%-90% of rod mole percentage) of an amphiphilic rod-coil system, poly (hexyl isocyanate)-b-(2-vinylpyridine) at the air/water and air/solid interface. We applied Langmuir balance technique, scanning probe microscopy (SPM), transmission electron microscopy (TEM) and X-ray reflectivity for the complete characterization of the monolayer at the interfaces. The phase isotherms showed the well amphiphilic balance for the diblock copolymers, and the formation of stable monolayers. With the increasing rod content, the consistent increase in the monolayer packing density was observed by the phase isotherms and supported by X-ray reflectivity. SPM and TEM characterization showed their interesting surface morphology according to the varying rod mole percentage in the rod-coil system. Rod mole percentage 5%-15% showed micellar morphology. Rod mole percentage 23%-32% showed distinct and dispersed rods, whereas rod mole percentage 70%-90% showed well packed structure similar to lamella phase. We found the tendency of the diblock system to adopt a packed monomolecular structure has increased by the increasing rod content. This lead us to conclude that it is the hexyl-isocyanate (rod part) that governs mostly the interfacial behavior of rod-coil block copolymers.

  9. Broadband pH-Sensing Organic Transistors with Polymeric Sensing Layers Featuring Liquid Crystal Microdomains Encapsulated by Di-Block Copolymer Chains.

    PubMed

    Seo, Jooyeok; Song, Myeonghun; Jeong, Jaehoon; Nam, Sungho; Heo, Inseok; Park, Soo-Young; Kang, Inn-Kyu; Lee, Joon-Hyung; Kim, Hwajeong; Kim, Youngkyoo

    2016-09-14

    We report broadband pH-sensing organic field-effect transistors (OFETs) with the polymer-dispersed liquid crystal (PDLC) sensing layers. The PDLC layers are prepared by spin-coating using ethanol solutions containing 4-cyano-4'-pentyl-biphenyl (5CB) and a diblock copolymer (PAA-b-PCBOA) that consists of LC-philic block [poly(4-cyano-biphenyl-4-oxyundecyl acrylate) (PCBOA)] and acrylic acid block [poly(acrylic acid) (PAA)]. The spin-coated sensing layers feature of 5CB microdomains (<5 μm) encapsulated by the PAA-b-PCBOA polymer chains. The resulting LC-integrated-OFETs (PDLC-i-OFETs) can detect precisely and reproducibly a wide range of pH with only small amounts (10-40 μL) of analyte solutions in both static and dynamic perfusion modes. The positive drain current change is measured for acidic solutions (pH < 7), whereas basic solutions (pH > 7) result in the negative change of drain current. The drain current trend in the present PDLC-i-OFET devices is explained by the shrinking-expanding mechanism of the PAA chains in the diblock copolymer layers. PMID:27557404

  10. Size selective incorporation of gold nanoparticles in diblock copolymer vesicle wall.

    PubMed

    Xu, Jiangping; Han, Yuanyuan; Cui, Jie; Jiang, Wei

    2013-08-20

    A systematic study is conducted to reveal how far the polymeric vesicle wall can embed gold nanoparticles (AuNPs) with different sizes by combining experiments and self-consistent field simulations. Both the experimental and simulative results indicate that the location of AuNPs in vesicle wall or in spherical micelle is heavily size dependent. Whether the AuNPs enter the vesicle wall or not is determined by a ratio of the diameter of AuNPs (D0) to the thickness of the vesicle wall (d(w0)). The 1-dodecanethiol-coated AuNPs (Au(x)R) with D0/d(w0) < 0.3 will stably disperse in the vesicle walls. For polystyrene-coated AuNPs (Au(x)S), a criterion of D0/d(w0) is proposed based on the phase diagram; i.e., the Au(x)S with D0/d(w0) < 0.5 can be located in the vesicle wall. Otherwise, the Au(x)R and the Au(x)S prefer to locate in spherical micelles. Moreover, the contributions of enthalpy and entropy to the total free energy of the system are respectively calculated to reveal the mechanism of the size selective distribution of AuNPs. The results demonstrate that the escape of AuNPs from vesicle walls and their selective distribution in spherical micelles is an entropy-driven process. Our study provides an important guideline for fabricating nanoparticle/block copolymer hybrid vesicles in dilute solution. PMID:23875535

  11. A new formulation of curcumin using poly (lactic-co-glycolic acid)—polyethylene glycol diblock copolymer as carrier material

    NASA Astrophysics Data System (ADS)

    Phuong Tuyen Dao, Thi; Hoai Nguyen, To; To, Van Vinh; Ho, Thanh Ha; Nguyen, Tuan Anh; Chien Dang, Mau

    2014-09-01

    The aim of this study is to fabricate a nanoparticle formulation of curcumin using a relatively new vehicle as the matrix polymer: poly(lactic-co-glycolic acid) (PLGA)- polyethylene glycol (PEG) diblock copolymer, and to investigate the effects of the various processing parameters on the characteristics of nanoparticles (NPs). We successfully synthesized the matrix polymer of PLGA-PEG by conjugation of PLGA copolymer with a carboxylate end group to a heterobifunctional amine-PEG-methoxy using N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide as conjugation crosslinkers. The composition of the formed product (PLGA-PEG) was characterized with 500 MHz 1H nuclear magnetic resonance (NMR). The conjugation of PLGA-PEG was confirmed using Fourier transform infrared (FTIR) spectrum study. This diblock copolymer was then used to prepare the curcumin-loaded NPs through nanoprecipitation technique. With this method, we found that the size distribution depends on the type of solvent, the concentration of polymer and the concentration of surfactant. The particle size and size distribution were measured by dynamic light scattering (DLS). Transmission electron microscope (TEM) and scanning electron microscope (SEM) were used to confirm the size, structure and morphology of the successfully prepared NPs. All of our results showed that they are spherical and quite homologous with mean diameter around of 100-300 nm. Further, we evaluated encapsulation efficiency and some characteristics of NPs through high performance liquid chromatography (HPLC) analyses, zeta-potential measurements and x-ray diffraction studies. The HPLC analyses were performed to determine the amount of curcumin entrapped in NPs. The zeta-potential measurements confirmed the stability of NPs and the successful encapsulation of curcumin within NPs and the x-ray diffraction patterns showed the disordered-crystalline phase of curcumin inside the polymeric matrix.

  12. Confined Cylinders Constructed by a Poly(ethylene oxide)-b-polystyrene Diblock Copolymer and a Blend of Poly(ethylene Oxide)-b-Polystyrene and Polystyrene

    SciTech Connect

    Huang,P.; Guo, Y.; Quirk, R.; Ruan, J.; Lotz, B.; Thomas, E.; Hsiao, B.; Avila-Orta, C.; Sics, I.; Cheng, S.

    2006-01-01

    A poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer with a number average molecular weight of PEO blocks, M{sub N}{sup PEO}=8.8 kg/mol, and a number average molecular weight of PS blocks, M{sub N}{sup PS}=24.5 kg/mol, (volume fraction of the PEO blocks, f{sub PEO}, was 0.26) exhibited a hexagonal cylinder (HC) phase structure. Small angle X-ray scattering results showed that the PEO cylinder diameter was 13.3 nm, and the hexagonal lattice was a=25.1 nm. The cylinder diameter of this HC phase structure was virtually the same as that in the blend system constructed by a PEO-b-PS diblock copolymer (M{sub N}{sup PEO}=8.7 kg/mol and M{sub N}{sup PS}=9.2 kg/mol) and a PS homo-polymer (M{sub N}{sup PS}=4.6 kg/mol) in which the f{sub PEO} was 0.32. The cylinder diameter in this blend sample was 13.7 nm and the hexagonal lattice was a=23.1 nm. Comparing crystal orientation and crystallization behaviors of this PEO-b-PS copolymer with the blend, it was found that the crystal orientation change with respect to crystallization temperature was almost identical. This is attributed to the fact that in both cases the PEO block tethering densities and confinement sizes are very similar. This indicates that when the M{sub N}{sup PS} of PS homo-polymer is lower than the PS blocks, the PS homo-polymer is located inside of the PS matrix rather than at the interface between the PEO and PS in the HC phase structure. On the other hand, a substantial difference of crystallization behaviors was observed between these two samples. The PEO-b-PS copolymer exhibited much more retarded crystallization kinetics than that of the blend. Based on the small angle X-ray scattering results, it was found that in the blend sample, the HC phase structure was not as regularly ordered as that in the PEO-b-PS copolymer, and thus, the HC phase structure contained more defects in the blend. This led to a suggestion that the primary nucleation process in the confined crystallization is a defect

  13. Self-assembly of diblock co-polymers at air-water interface: A microscopy and x-ray scattering study

    NASA Astrophysics Data System (ADS)

    Giri, R. P.; Mukhopadhyay, M. K.

    2016-05-01

    The spontaneous surface aggregation of diblock copolymer, containing polystyrene-polydimethylsiloxane or PS-PDMS, have been studied at air-water interface using Brewster's angle microscopy (BAM) and grazing incidence small angle x-ray scattering (GISAXS) technique. Pronounced differences in the molecular weight and solvent dependence of the size of aggregation on the water surface are observed. Structural characterization is done using atomic force microscopy (AFM) for a monolayer transferred to Si substrate. It shows that, individual polymer chains coalesce to form some disc like micelle aggregation on the Si surface which is also evident from the BAM image of the water floated monolayer. GISAXS study is also corroborating the same result.

  14. Poly(ethylene oxide)-b-poly(L-lactide) diblock copolymer/carbon nanotube-based nanocomposites: LiCl as supramolecular structure-directing agent.

    PubMed

    Meyer, Franck; Raquez, Jean-Marie; Verge, Pierre; Martínez de Arenaza, Inger; Coto, Borja; Van Der Voort, Pascal; Meaurio, Emilio; Dervaux, Bart; Sarasua, Jose-Ramon; Du Prez, Filip; Dubois, Philippe

    2011-11-14

    This work relies on the CNT dispersion in either solution or a polymer matrix through the formation of a three-component supramolecular system composed of PEO-b-PLLA diblock copolymer, carbon nanotubes (CNTs), and lithium chloride. According to a one-pot procedure in solution, the "self-assembly" concept has demonstrated its efficiency using suspension tests of CNTs. Characterizations of the supramolecular system by photon correlation spectroscopy, Raman spectroscopy, and molecular dynamics simulations highlight the charge transfer interaction from the CNTs toward the PEO-b-PLLA/LiCl complex. Finally, this concept was successfully extended in bulk (absence of solvent) via melt-processing techniques by dispersing these complexes in a commercial polylactide (PLA) matrix. Electrical conductivity measurements and transmission electron microscopy attested for the remarkable dispersion of CNTs, confirming the design of high-performance PLA-based materials. PMID:21936499

  15. Formation and Reversible Morphological Transition of Bicontinuous Nanospheres and Toroidal Micelles by the Self-Assembly of a Crystalline-b-Coil Diblock Copolymer.

    PubMed

    Presa-Soto, David; Carriedo, Gabino A; de la Campa, Raquel; Presa Soto, Alejandro

    2016-08-16

    We herein report the formation of two complex nanostructures, toroidal micelles and bicontinuous nanospheres, by the self-assembly of the single structurally simple crystalline-b-coil diblock copolymer poly[bis(trifluoroethoxy)phosphazene]-b-poly(styrene), PTFEP-b-PS, in one solvent (THF) and without additives. The nature of these nanostructures in solution was confirmed by DLS and cryo-TEM experiments. The two morphologies are related by means of a new type of reversible morphological evolution, bicontinuous-to-toroidal, triggered by changes in the polymer concentration. WAXS experiments showed that the degree of crystallinity of the PTFEP chains located at the core of the toroids was higher than that in the bicontinuous nanospheres, thus indicating that the final morphology of the aggregates is mostly determined by the ordering of the PTFEP core-forming blocks. PMID:27455871

  16. Reduction of the inflammatory responses against alginate-poly-L-lysine microcapsules by anti-biofouling surfaces of PEG-b-PLL diblock copolymers.

    PubMed

    Spasojevic, Milica; Paredes-Juarez, Genaro A; Vorenkamp, Joop; de Haan, Bart J; Schouten, Arend Jan; de Vos, Paul

    2014-01-01

    Large-scale application of alginate-poly-L-lysine (alginate-PLL) capsules used for microencapsulation of living cells is hampered by varying degrees of success, caused by tissue responses against the capsules in the host. A major cause is proinflammatory PLL which is applied at the surface to provide semipermeable properties and immunoprotection. In this study, we investigated whether application of poly(ethylene glycol)-block-poly(L-lysine hydrochloride) diblock copolymers (PEG-b-PLL) can reduce the responses against PLL on alginate-matrices. The application of PEG-b-PLL was studied in two manners: (i) as a substitute for PLL or (ii) as an anti-biofouling layer on top of a proinflammatory, but immunoprotective, semipermeable alginate-PLL100 membrane. Transmission FTIR was applied to monitor the binding of PEG-b-PLL. When applied as a substitute for PLL, strong host responses in mice were observed. These responses were caused by insufficient binding of the PLL block of the diblock copolymers confirmed by FTIR. When PEG-b-PLL was applied as an anti-biofouling layer on top of PLL100 the responses in mice were severely reduced. Building an effective anti-biofouling layer required 50 hours as confirmed by FTIR, immunocytochemistry and XPS. Our study provides new insight in the binding requirements of polyamino acids necessary to provide an immunoprotective membrane. Furthermore, we present a relatively simple method to mask proinflammatory components on the surface of microcapsules to reduce host responses. Finally, but most importantly, our study illustrates the importance of combining physicochemical and biological methods to understand the complex interactions at the capsules' surface that determine the success or failure of microcapsules applicable for cell-encapsulation.

  17. High-Pressure Micellar Solutions of Symmetric and Asymmetric Styrene?Diene Diblocks in Compressible Near Critical Solvents: Micellization Pressures and Cloud Pressures Respond but Micellar Cloud Pressures Insensitive to Copolymer Molecular Weight, Concentration, and Block Ratio Changes

    SciTech Connect

    Winoto, Winoto; Tan, Sugata; Shen, Youqin; Radosz, Maciej; Hong, Kunlun; Mays, Jimmy

    2009-01-01

    Micellar solutions of polystyrene-block-polybutadiene and polystyrene-block-polyisoprene in propane are found to exhibit significantly lower cloud pressures than the corresponding hypothetical nonmicellar solutions. Such a cloud-pressure reduction indicates the extent to which micelle formation enhances the apparent diblock solubility in near-critical and hence compressible propane. Concentration-dependent pressure-temperature points beyond which no micelles can be formed, referred to as the micellization end points, are found to depend on the block type, size, and ratio. The cloud-pressure reduction and the micellization end point measured for styrene-diene diblocks in propane should be characteristic of all amphiphilic diblock copolymer solutions that form micelles in compressible solvents.

  18. Semi-crystalline polymethylene-b-poly(acrylic acid) diblock copolymers: aggregation behavior, confined crystallization and controlled growth of semicrystalline micelles from dilute DMF solution.

    PubMed

    Wang, Hongfang; Wu, Cong; Xia, Guangmei; Ma, Zhi; Mo, Guang; Song, Rui

    2015-03-01

    In this paper, we have systematically investigated the aggregation behavior, confined crystallization and controlled growth of a novel polyolefin analogue-containing block copolymers (BCPs), i.e., polymethylene-b-poly(acrylic acid) diblock copolymers (PM-b-PAA). On cooling from a homogenous DMF solution at 80 °C, PM-b-PAA was found to crystallize and aggregate with well-defined disk-like micelles. The aggregate behavior and in-plane morphology of PM-b-PAA could be easily controlled by modifying the block ratio, solution pH and solvent composition (DMF-water), by manipulating the crystallization of PM block and the stretching degree of solvated PAA corona. Further investigation of the crystalline feature of PM-b-PAA indicated that the crystallization of PM was retarded by tethered amorphous PAA segments. The crystalline micelle could construct a nano-confined environment with PM folding as the core into a thickness of the mono-layered polyethylene. Finally, when cultured in dilute DMF solution at 50 °C, the initial crystalline micelles, being as self-seeds, could follow a living growth mechanism and develop into single crystals, with well-defined lozenge-shaped morphology.

  19. Optical and conductive properties of as-synthesized organic-capped TiO₂ nanorods highly dispersible in polystyrene-block-poly(methyl methacrylate) diblock copolymer.

    PubMed

    Cano, Laida; Di Mauro, Angela Evelyn; Striccoli, Marinella; Curri, M Lucia; Tercjak, Agnieszka

    2014-07-23

    As-synthesized organic-capped TiO2 nanorods were incorporated into polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer to achieve TiO2/PS-b-PMMA nanocomposites with enhanced optical and conductive properties. The specific surface chemistry of TiO2 nanorods derived from the colloidal synthetic approach allowed their prompt incorporation in the PS-b-PMMA block copolymer template up to 50 wt %, which resulted in films with an extended coverage of highly dispersed nanoparticles for contents higher than 30 wt %. At such high nanorod contents, the films fabricated by the prepared nanocomposites demonstrated enhanced optical properties. Atomic force microscopy investigation of the nanocomposite films showed a cylindrical morphology for low nanorod contents. Conversely, higher nanorod contents resulted upon removal of the organic component in the nanocomposites with UV treatment in overall nanorod coverage of the film surface with the concomitant formation of charge percolation paths, which led to noticeable conductivity values. EFM and PF-TUNA measurements confirmed the conductive properties of the composites at nanoscale, whereas semiconductor analyzer measurements provided their macroscale characterization. In addition, an increase in the UV-vis absorption was observed with the increase in the nanorod content along with a remarkable conductivity of the overall film.

  20. Formation of Polyion Complex (PIC) Micelles and Vesicles with Anionic pH-Responsive Unimer Micelles and Cationic Diblock Copolymers in Water.

    PubMed

    Ohno, Sayaka; Ishihara, Kazuhiko; Yusa, Shin-Ichi

    2016-04-26

    A random copolymer (p(A/MaU)) of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS) and sodium 11-methacrylamidoundecanate (MaU) was prepared via conventional radical polymerization, which formed a unimer micelle under acidic conditions due to intramolecular hydrophobic interactions between the pendant undecanoic acid groups. Under basic conditions, unimer micelles were opened up to an expanded chain conformation by electrostatic repulsion between the pendant sulfonate and undecanoate anions. A cationic diblock copolymer (P163M99) consisting of poly(3-(methacrylamido)propyl)trimethylammonium chloride (PMAPTAC) and hydrophilic polybetaine, 2-(methacryloyloxy)ethylphosphorylcholine (MPC), blocks was prepared via controlled radical polymerization. Mixing of p(A/MaU) and P163M99 in 0.1 M aqueous NaCl under acidic conditions resulted in the formation of spherical polyion complex (PIC) micelles and vesicles, depending on polymer concentration before mixing. Shapes of the PIC micelles and vesicles changed under basic conditions due to collapse of the charge balance between p(A/MaU) and P163M99. The PIC vesicles can incorporate nonionic hydrophilic guest molecules, and the PIC micelles and vesicles can accept hydrophobic guest molecules in the hydrophobic core formed from p(A/MaU).

  1. Semi-crystalline polymethylene-b-poly(acrylic acid) diblock copolymers: aggregation behavior, confined crystallization and controlled growth of semicrystalline micelles from dilute DMF solution.

    PubMed

    Wang, Hongfang; Wu, Cong; Xia, Guangmei; Ma, Zhi; Mo, Guang; Song, Rui

    2015-03-01

    In this paper, we have systematically investigated the aggregation behavior, confined crystallization and controlled growth of a novel polyolefin analogue-containing block copolymers (BCPs), i.e., polymethylene-b-poly(acrylic acid) diblock copolymers (PM-b-PAA). On cooling from a homogenous DMF solution at 80 °C, PM-b-PAA was found to crystallize and aggregate with well-defined disk-like micelles. The aggregate behavior and in-plane morphology of PM-b-PAA could be easily controlled by modifying the block ratio, solution pH and solvent composition (DMF-water), by manipulating the crystallization of PM block and the stretching degree of solvated PAA corona. Further investigation of the crystalline feature of PM-b-PAA indicated that the crystallization of PM was retarded by tethered amorphous PAA segments. The crystalline micelle could construct a nano-confined environment with PM folding as the core into a thickness of the mono-layered polyethylene. Finally, when cultured in dilute DMF solution at 50 °C, the initial crystalline micelles, being as self-seeds, could follow a living growth mechanism and develop into single crystals, with well-defined lozenge-shaped morphology. PMID:25608942

  2. Structure and Dynamics of Asymmetric Poly(styrene-b-1,4-isoprene) Diblock Copolymer under 1D and 2D Nanoconfinement.

    PubMed

    Kipnusu, Wycliffe K; Elmahdy, Mahdy M; Mapesa, Emmanuel U; Zhang, Jianqi; Böhlmann, Winfried; Smilgies, Detlef-M; Papadakis, Christine M; Kremer, Friedrich

    2015-06-17

    The impact of 1- and 2-dimensional (2D) confinement on the structure and dynamics of poly(styrene-b-1,4-isoprene) P(S-b-I) diblock copolymer is investigated by a combination of Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Grazing-Incidence Small-Angle X-ray Scattering (GISAXS), and Broadband Dielectric Spectroscopy (BDS). 1D confinement is achieved by spin coating the P(S-b-I) to form nanometric thin films on silicon substrates, while in the 2D confinement, the copolymer is infiltrated into cylindrical anodized aluminum oxide (AAO) nanopores. After dissolving the AAO matrix having mean pore diameter of 150 nm, the SEM images of the exposed P(S-b-I) show straight nanorods. For the thin films, GISAXS and AFM reveal hexagonally packed cylinders of PS in a PI matrix. Three dielectrically active relaxation modes assigned to the two segmental modes of the styrene and isoprene blocks and the normal mode of the latter are studied selectively by BDS. The dynamic glass transition, related to the segmental modes of the styrene and isoprene blocks, is independent of the dimensionality and the finite sizes (down to 18 nm) of confinement, but the normal mode is influenced by both factors with 2D geometrical constraints exerting greater impact. This reflects the considerable difference in the length scales on which the two kinds of fluctuations take place. PMID:25660102

  3. Phase structures and morphologies determined by competitions among self-organization, crystallization, and vitrification in a disordered poly(ethylene oxide)-{ital b}-polystyrene diblock copolymer

    SciTech Connect

    Zhu, L.; Chen, Y.; Zhang, A.; Calhoun, B.H.; Chun, M.; Quirk, R.P.; Cheng, S.Z.; Hsiao, B.S.; Yeh, F.; Hashimoto, T.

    1999-10-01

    A poly(ethylene oxide)-{ital b}-polystyrene (PEO-{ital b}-PS) diblock copolymer having a number-average molecular weight ({bar M}{sub n}) of 11&hthinsp;000 g/mol in the PEO blocks and an {bar M}{sub n} of 5200 g/mol in the PS blocks has been synthesized (with a volume fraction of the PEO blocks of 0.66 in the molten state). Differential scanning calorimetry results show that this copolymer possesses a single endotherm, which is attributed to the melting of the PEO-block crystals. Based on real-time resolved synchrotron small-angle x-ray scattering (SAXS) observations, the diblock copolymer is in a disordered state above the glass transition temperature of the PS-rich phase (T{sub g}{sup PS}), which has been determined to be 44.0&hthinsp;{degree}C during cooling using dilatometer mode in thermomechanical measurements. The order-disorder transition temperature (T{sub ODT}) for this diblock copolymer is thus experimentally inaccessible. Depending upon different isothermal crystallization temperatures quenched from the disordered state (T{sub q}s), four cases can be investigated in order to understand the phase relationships among self-organization, crystallization of the PEO blocks, and vitrification of the PS-rich phase: the region where the T{sub q} is above the T{sub g}{sup PS}, the regions where the T{sub q} is near but slightly higher or lower than the T{sub g}{sup PS}; and the region where the T{sub q} is below the T{sub g}{sup PS}. Utilizing simultaneous SAXS and wide angle x-ray-diffraction experiments, it can be seen that lamellar crystals of the PEO blocks in the first case grow with little morphological constraint due to initial disordered phase morphology. As the T{sub q} approaches but is still slightly higher than the T{sub g}{sup PS}, as in the second case, the PEO-block crystals with a greater long period ({ital L}) than that of the disordered state start to grow. The initial disordered phase morphology is gradually destroyed, at least to a major

  4. Phase separations in a copolymer copolymer mixture

    NASA Astrophysics Data System (ADS)

    Zhang, Jin-Jun; Jin, Guojun; Ma, Yuqiang

    2006-01-01

    We propose a three-order-parameter model to study the phase separations in a diblock copolymer-diblock copolymer mixture. The cell dynamical simulations provide rich information about the phase evolution and structural formation, especially the appearance of onion-rings. The parametric dependence and physical reason for the domain growth of onion-rings are discussed.

  5. Poly(ethylene oxide) Crystal Orientation Changes in an Inverse Hexagonal Cylindrical Phase Morphology Constructed by a Poly(ethylene oxide)-block-polystyrene Diblock Copolymer

    SciTech Connect

    Huang,P.; Zheng, J.; Leng, S.; Van Horn, R.; Jeong, K.; Thomas, E.; Hsiao, B.

    2006-01-01

    A poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer with number-average molecular weights of 7.7k g/mol for the PS block and 21.4k g/mol for the PEO block was used to study the PEO crystal orientation changes at different crystallization temperatures (T{sub x}) via small- and wide-angle X-ray scattering techniques. For this diblock copolymer, an inverse hexagonal cylinder (IHC) phase morphology was identified with PX cylinders hexagonally packed within the PEO matrix. In this IHC morphology, the PEO blocks were tethered on the convex interfaces of the PS domains, and the crystallization of PEO blocks was outside of the cylinders. The crystal orientation of the PEO blocks (the c-axis of the PEO crystals) after crystallization among the PS cylinders was, for the first time, found to change with respect to the long cylinder axis, a, depending solely on T{sub x}. At very low T{sub x}'s, when the samples were quenched into liquid nitrogen, the crystals possessed a random orientation. When -30 {sup o}C {<=} T{sub x} {<=} 5 {sup o}C, PEO crystals had an orientation with their c-axis parallel to a. Within the temperature region of 10 {sup o}C < T{sub x} {<=} 20 {sup o}C, the c-axis crystal orientation changed to be tilted with respect to a (the tilting angle was defined to be between the c-axis of the PEO crystals and a). This tilting angle increased with increasing T{sub x}. Finally, a major crystal orientation with the c-axes of PEO crystals perpendicular to a was observed with T{sub x} reached 30 {sup o}C. Furthermore, it was particularly interesting that the PEO crystals in the IHC phase were oriented in two dimensions when T{sub x} = 30 {sup o}C. Namely, the PEO crystal growth was specifically grown along the {l_brace}1010{r_brace} planes of the hexagonal PS cylinders. The crystallite sizes were estimated by the Scherrer equation. The PEO crystal sizes, at least along on dimension, were on the scale of the sizes limited by the distance between the

  6. Poly(ethylene oxide) Crystal Orientation Changes in an Inverse Hexagonal Cylindrical Phase Morphology Constructed by a Poly(ethylene oxide)-block-Polystyrene Diblock Copolymer

    SciTech Connect

    Huang,P.; Zheng, J.; Leng, S.; Van Horn, R.; Jeong, K.; Guo, Y.; Quirk, R.; Cheng, S.; Lotz, B.; et al.

    2007-01-01

    A poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer with number-average molecular weights of 7.7k g/mol for the PS block and 21.4k g/mol for the PEO block was used to study the PEO crystal orientation changes at different crystallization temperatures (T{sub x}) via small- and wide-angle X-ray scattering techniques. For this diblock copolymer, an inverse hexagonal cylinder (IHC) phase morphology was identified with PS cylinders hexagonally packed within the PEO matrix. In this IHC morphology, the PEO blocks were tethered on the convex interfaces of the PS domains, and the crystallization of PEO blocks was outside of the cylinders. The crystal orientation of the PEO blocks (the c-axis of the PEO crystals) after crystallization among the PS cylinders was, for the first time, found to change with respect to the long cylinder axis, {cflx a}, depending solely on T{sub x}. At very low T{sub x}'s, when the samples were quenched into liquid nitrogen, the crystals possessed a random orientation. When -30 C {<=}T{sub x} {<=} 5 C, PEO crystals had an orientation with their c-axis parallel to {cflx a}. Within the temperature region of 10 C {<=} T{sub x} {<=} 20 C, the c-axis crystal orientation changed to be tilted with respect to {cflx a} (the tilting angle was defined to be between the c-axis of the PEO crystals and {cflx a}). This tilting angle increased with increasing T{sub x}. Finally, a major crystal orientation with the c-axes of PEO crystals perpendicular to {cflx a} was observed when Tx reached 30 C. Furthermore, it was particularly interesting that the PEO crystals in the IHC phase were oriented in two dimensions when T{sub x} = 30 C. Namely, the PEO crystal growth was specifically grown along the {l_brace}100{r_brace} planes of the hexagonal PS cylinders. The crystallite sizes were estimated by the Scherrer equation. The PEO crystal sizes, at least along one dimension, were on the scale of the sizes limited by the distance between the neighboring

  7. The secondary structures of poly ( L-alanine) blocks in some diblock copolymers of poly( L-alanine)- b-poly(ethylene glycol) monomethyl ether in the solid state characterized by nuclear magnetic resonance and infrared spectrometry

    NASA Astrophysics Data System (ADS)

    Wu, Guo L.; Sun, Ping C.; Lin, Hai; Ma, Jian B.

    2004-02-01

    The 13C cross-polarization/magic-angle spinning (CP/MAS) spectra of the solid-state nuclear magnetic resonance (NMR) and the infrared spectra of three diblock copolymers, poly ( L-alanine)- block-poly(ethylene glycol) monomethyl ether (PLA- b-MPEG), with various proportions of two blocks were studied in comparison with those of the homopolymer poly( L-alanine), PLA, and the blends of two blocks (PLA and MPEG). The secondary structures such as α-helix and β-sheet of poly ( L-alanine) (PLA) blocks in the block copolymers could be elucidated from the signals in the solid-state 13C CP/MAS NMR spectra and transmittance peaks in the Fourier-transformation infrared (FTIR) spectra. Dramatic differences in the secondary structures were observed for the diblock copolymers, homopolymer PLA and blend samples. It was found that with the increase of the fraction of PLA block in the block copolymers, the ratio of β-sheet to α-helical conformation of PLA block went up although the α-helical conformation was much more than β-sheet conformation in total. It contradicted the general prediction of the secondary structure of homopolypeptides or PLA/PEG blends, in which the β-sheet conformation content decreased with the decrease of the polymerization degree of PLA. The investigation in FTIR spectrometry resulted in the same conclusion.

  8. Custom-made morphologies of ZnO nanostructured films templated by a poly(styrene-block-ethylene oxide) diblock copolymer obtained by a sol-gel technique.

    PubMed

    Sarkar, Kuhu; Rawolle, Monika; Herzig, Eva M; Wang, Weijia; Buffet, Adeline; Roth, Stephan V; Müller-Buschbaum, Peter

    2013-08-01

    Zinc oxide (ZnO) nanostructured films are synthesized on silicon substrates to form different morphologies that consist of foamlike structures, wormlike aggregates, circular vesicles, and spherical granules. The synthesis involves a sol-gel mechanism coupled with an amphiphilic diblock copolymer poly(styrene-block-ethylene oxide), P(S-b-EO), which acts as a structure-directing template. The ZnO precursor zinc acetate dihydrate (ZAD) is incorporated into the poly(ethylene oxide) block. Different morphologies are obtained by adjusting the weight fractions of the solvents and ZAD. The sizes of the structure in solution for different sol-gels are probed by means of dynamic light scattering. Thin-film samples with ZnO nanostructures are prepared by spin coating and solution casting followed by a calcination step. On the basis of various selected combinations of weight fractions of the ingredients used, a ternary phase diagram is constructed to show the compositional boundaries of the investigated morphologies. The evolution and formation mechanisms of the morphologies are addressed in brief. The surface morphologies of the ZnO nanostructures are studied with SEM. The inner structures of the samples are probed by means of grazing incidence small-angle X-ray scattering to complement the SEM investigations. XRD measurements confirm the crystallization of the ZnO in the wurtzite phase upon calcination of the nanocomposite film in air. The optical properties of ZnO are analyzed by FTIR and UV/Vis spectroscopy. PMID:23881752

  9. Final Report: Grant DE-FG02-05ER15682. Simulation of Complex Microphase Formation in Pure and Nanoparticle-filled Diblock Copolymers

    SciTech Connect

    Fernando A. Escobedo

    2009-11-18

    The goal of this project was to use molecular simulation to quantify the impact of additives on the onset and structure of bicontinuous phases in linear diblock copolymers (DBC). The focus was on understanding how additives with selective affinity for a given block will distribute and perturb the structure of complex bicontinuous phases (like gyroid, double diamond, and plumbers nightmare whose minority component block forms two interweaving 3D networks) in DBCs; it was hypothesized that a suitable choice of additive type, size, affinity, and concentration may suppress or stabilize a particular bicontinuous phase. The ultimate goal in this line of investigation is to elucidate the rational design of the optimal additive for which the composition range of stability of a particular bicontinuous phase is maximized. Ours are the first published simulation studies to report on the formation of the gyroid phase in DBC melts and of other bicontinuous phases in DBC-modified by homopolymer. The following tasks were carried out: (i) simulation of bicontinuous phases of pure DBCs via both on-lattice Monte Carlo simulations and continuum-space Monte Carlo and molecular dynamics simulations, (ii) determination of the effect of selective additives (homopolymer) of different sizes on such bicontinuous phases, and (iii) development of novel Monte Carlo methods to map out reliable phase diagrams and improve ergodic sampling; in particular, optimized expanded-ensemble techniques for measuring free-energies and for chemical potential equilibration.

  10. Complementary study based on DFT to describe the structure and properties relationship of diblock copolymer based on PVK and PPV

    NASA Astrophysics Data System (ADS)

    Mbarek, M.; Abbassi, F.; Alimi, K.

    2016-09-01

    The structure-properties relationships of copolymer involving N-vinylcarbazole (PVK) and poly (p-phenylene-vinylene) (PPV) blocks, denoted PVK-PPV, was investigated by calculations based on density functional theory (DFT) and completed by experimental analyses. Thus, vibrational, optical and emission spectra of model compound have been simulated and compared to the experiments observations published recently. Ionization potentials (IPs), electron affinities (EAs) and energy gaps were determined. Furthermore, quantum yields, radiative and nonradiative exciton lifetime was highlighted.

  11. Compatibilization of All-Conjugated Polymer Blends for Organic Photovoltaics.

    PubMed

    Lombeck, Florian; Sepe, Alessandro; Thomann, Ralf; Friend, Richard H; Sommer, Michael

    2016-08-23

    Compatibilization of an immiscible binary blend comprising a conjugated electron donor and a conjugated electron acceptor polymer with suitable electronic properties upon addition of a block copolymer (BCP) composed of the same building blocks is demonstrated. Efficient compatibilization during melt-annealing is feasible when the two polymers are immiscible in the melt, i.e. above the melting point of ∼250 °C of the semicrystalline donor polymer P3HT. To generate immiscibility at these high temperatures, the acceptor polymer PCDTBT is equipped with fluorinated side chains leading to an increased Flory-Huggins interaction parameter. Compatibilization in bulk and thin films is demonstrated, showing that the photovoltaic performance of pristine microphase separated and nanostructured BCPs can also be obtained for compatibilized blend films containing low contents of 10-20 wt % BCP. Thermodynamically stable domain sizes range between several tens of microns for pure blends and ∼10 nm for pure block copolymers. In addition to controlling domain size, the amount of block copolymer added dictates the ratio of edge-on and face-on P3HT crystals, with compatibilized films showing an increasing amount of face-on P3HT crystals with increasing amount of compatibilizer. This study demonstrates the prerequisites and benefits of compatibilizing all-conjugated semicrystalline polymer blends for organic photovoltaics. PMID:27482842

  12. Compatibilization of All-Conjugated Polymer Blends for Organic Photovoltaics.

    PubMed

    Lombeck, Florian; Sepe, Alessandro; Thomann, Ralf; Friend, Richard H; Sommer, Michael

    2016-08-23

    Compatibilization of an immiscible binary blend comprising a conjugated electron donor and a conjugated electron acceptor polymer with suitable electronic properties upon addition of a block copolymer (BCP) composed of the same building blocks is demonstrated. Efficient compatibilization during melt-annealing is feasible when the two polymers are immiscible in the melt, i.e. above the melting point of ∼250 °C of the semicrystalline donor polymer P3HT. To generate immiscibility at these high temperatures, the acceptor polymer PCDTBT is equipped with fluorinated side chains leading to an increased Flory-Huggins interaction parameter. Compatibilization in bulk and thin films is demonstrated, showing that the photovoltaic performance of pristine microphase separated and nanostructured BCPs can also be obtained for compatibilized blend films containing low contents of 10-20 wt % BCP. Thermodynamically stable domain sizes range between several tens of microns for pure blends and ∼10 nm for pure block copolymers. In addition to controlling domain size, the amount of block copolymer added dictates the ratio of edge-on and face-on P3HT crystals, with compatibilized films showing an increasing amount of face-on P3HT crystals with increasing amount of compatibilizer. This study demonstrates the prerequisites and benefits of compatibilizing all-conjugated semicrystalline polymer blends for organic photovoltaics.

  13. Fluorescence Recovery after Photobleaching and Single-Molecule Tracking Measurements of Anisotropic Diffusion within Identical Regions of a Cylinder-Forming Diblock Copolymer Film.

    PubMed

    Tran-Ba, Khanh-Hoa; Higgins, Daniel A; Ito, Takashi

    2015-06-01

    This work demonstrates ensemble and single-molecule diffusion measurements within identical regions of a cylinder-forming polystyrene-poly(ethylene oxide) diblock copolymer (PS-b-PEO) film using fluorescence recovery after photobleaching (FRAP) and single-molecule tracking (SMT). A PS-b-PEO film (∼4 μm thick) with aligned cylindrical PEO microdomains containing 10 μM sulforhodamine B (SRB) was prepared by directional solvent-vapor penetration (SVP) of 1,4-dioxane. The ensemble diffusion behavior of SRB in the microdomains was assessed in FRAP studies of circular photobleached regions (∼7 μm in diameter). The SRB concentration was subsequently reduced by additional photobleaching, and the diffusion of individual SRB molecules was explored using SMT in the identical area (∼16 × 16 μm(2)). The FRAP data showed anisotropic fluorescence recovery, yielding the average microdomain orientation. The extent of fluorescence recovery observed (∼90%) demonstrated long-range microdomain connectivity, while the recovery time dependence provided an ensemble measurement of the SRB diffusion coefficient within the cylindrical microdomains. The SMT data exhibited one-dimensional diffusion of individual SRB molecules along the SVP direction across the entire film thickness, as consistent with the FRAP results. Importantly, the average of the single-molecule diffusion coefficients was close to the value obtained from FRAP in the identical area. In some cases, SMT offered smaller diffusion coefficients than FRAP, possibly due to contributions from SRB molecules confined within short PEO microdomains. The implementation of FRAP and SMT measurements in identical areas provides complementary information on molecular diffusion with minimal influence of sample heterogeneity, permitting direct comparison of ensemble and single-molecule diffusion behavior.

  14. Linker-based control of electron propagation through ferrocene moieties covalently anchored onto insulator-based nanopores derived from a polystyrene-poly(methylmethacrylate) diblock copolymer.

    PubMed

    Li, Feng; Pandey, Bipin; Ito, Takashi

    2012-12-01

    This paper reports the effects of linker length on electron propagation through ferrocene moieties covalently anchored onto insulator-based cylindrical nanopores derived from a cylinder-forming polystyrene-poly(methylmethacrylate) diblock copolymer. These nanopores (24 nm in diameter, 30 nm long) aligned perpendicular to an underlying gold electrode were modified via esterification of their surface COOH groups with OH-terminated ferrocene derivatives having different alkyl linkers (FcCO(CH(2))(n)OH; n = 2, 5, 15). Cyclic voltammograms were measured in 0.1 M NaBF(4) at different scan rates to assess the efficiency of electron propagation through the ferrocene moieties. The redox peaks of the anchored ferrocenes were observed at nanoporous films decorated with FcCO(CH(2))(15)OH and FcCO(CH(2))(5)OH, but not at those with FcCO(CH(2))(2)OH. Importantly, the higher electron propagation efficiency was observed in the use of the longer linker, as shown by the apparent diffusion coefficients (ca. 10(-12) cm(2)/s for n = 15; ca. 10(-13) cm(2)/s for n = 5; no electron propagation for n = 2). The observed electron propagation resulted from electron hopping across relatively large spacing that was controlled by the motion of anchored redox sites (bounded diffusion). The longer linker led to the larger physical displacement range of anchored ferrocene moieties, facilitating the approach of the adjacent ferrocene moieties within a distance required for electron self-exchange reaction. The linker-based control of redox-involved electron propagation on nanostructured, insulating surfaces will provide a means for designing novel molecular electronics and electrochemical sensors.

  15. Testing the Vesicular Morphology to Destruction: Birth and Death of Diblock Copolymer Vesicles Prepared via Polymerization-Induced Self-Assembly

    PubMed Central

    2014-01-01

    Small angle X-ray scattering (SAXS), electrospray ionization charge detection mass spectrometry (CD-MS), dynamic light scattering (DLS), and transmission electron microscopy (TEM) are used to characterize poly(glycerol monomethacrylate)55-poly(2-hydroxypropyl methacrylate)x (G55-Hx) vesicles prepared by polymerization-induced self-assembly (PISA) using a reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization formulation. A G55 chain transfer agent is utilized to prepare a series of G55-Hx diblock copolymers, where the mean degree of polymerization (DP) of the membrane-forming block (x) is varied from 200 to 2000. TEM confirms that vesicles with progressively thicker membranes are produced for x = 200–1000, while SAXS indicates a gradual reduction in mean aggregation number for higher x values, which is consistent with CD-MS studies. Both DLS and SAXS studies indicate minimal change in the overall vesicle diameter between x = 400 and 800. Fitting SAXS patterns to a vesicle model enables calculation of the membrane thickness, degree of hydration of the membrane, and the mean vesicle aggregation number. The membrane thickness increases at higher x values, hence the vesicle lumen must become smaller if the external vesicle dimensions remain constant. Geometric considerations indicate that this growth mechanism lowers the total vesicle interfacial area and hence reduces the free energy of the system. However, it also inevitably leads to gradual ingress of the encapsulated water molecules into the vesicle membrane, as confirmed by SAXS analysis. Ultimately, the highly plasticized membranes become insufficiently hydrophobic to stabilize the vesicle morphology when x exceeds 1000, thus this PISA growth mechanism ultimately leads to vesicle “death”. PMID:25526525

  16. Testing the vesicular morphology to destruction: birth and death of diblock copolymer vesicles prepared via polymerization-induced self-assembly.

    PubMed

    Warren, Nicholas J; Mykhaylyk, Oleksandr O; Ryan, Anthony J; Williams, Mark; Doussineau, Tristan; Dugourd, Philippe; Antoine, Rodolphe; Portale, Giuseppe; Armes, Steven P

    2015-02-11

    Small angle X-ray scattering (SAXS), electrospray ionization charge detection mass spectrometry (CD-MS), dynamic light scattering (DLS), and transmission electron microscopy (TEM) are used to characterize poly(glycerol monomethacrylate)55-poly(2-hydroxypropyl methacrylate)x (G55-Hx) vesicles prepared by polymerization-induced self-assembly (PISA) using a reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization formulation. A G55 chain transfer agent is utilized to prepare a series of G55-Hx diblock copolymers, where the mean degree of polymerization (DP) of the membrane-forming block (x) is varied from 200 to 2000. TEM confirms that vesicles with progressively thicker membranes are produced for x = 200-1000, while SAXS indicates a gradual reduction in mean aggregation number for higher x values, which is consistent with CD-MS studies. Both DLS and SAXS studies indicate minimal change in the overall vesicle diameter between x = 400 and 800. Fitting SAXS patterns to a vesicle model enables calculation of the membrane thickness, degree of hydration of the membrane, and the mean vesicle aggregation number. The membrane thickness increases at higher x values, hence the vesicle lumen must become smaller if the external vesicle dimensions remain constant. Geometric considerations indicate that this growth mechanism lowers the total vesicle interfacial area and hence reduces the free energy of the system. However, it also inevitably leads to gradual ingress of the encapsulated water molecules into the vesicle membrane, as confirmed by SAXS analysis. Ultimately, the highly plasticized membranes become insufficiently hydrophobic to stabilize the vesicle morphology when x exceeds 1000, thus this PISA growth mechanism ultimately leads to vesicle "death".

  17. Testing the vesicular morphology to destruction: birth and death of diblock copolymer vesicles prepared via polymerization-induced self-assembly.

    PubMed

    Warren, Nicholas J; Mykhaylyk, Oleksandr O; Ryan, Anthony J; Williams, Mark; Doussineau, Tristan; Dugourd, Philippe; Antoine, Rodolphe; Portale, Giuseppe; Armes, Steven P

    2015-02-11

    Small angle X-ray scattering (SAXS), electrospray ionization charge detection mass spectrometry (CD-MS), dynamic light scattering (DLS), and transmission electron microscopy (TEM) are used to characterize poly(glycerol monomethacrylate)55-poly(2-hydroxypropyl methacrylate)x (G55-Hx) vesicles prepared by polymerization-induced self-assembly (PISA) using a reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization formulation. A G55 chain transfer agent is utilized to prepare a series of G55-Hx diblock copolymers, where the mean degree of polymerization (DP) of the membrane-forming block (x) is varied from 200 to 2000. TEM confirms that vesicles with progressively thicker membranes are produced for x = 200-1000, while SAXS indicates a gradual reduction in mean aggregation number for higher x values, which is consistent with CD-MS studies. Both DLS and SAXS studies indicate minimal change in the overall vesicle diameter between x = 400 and 800. Fitting SAXS patterns to a vesicle model enables calculation of the membrane thickness, degree of hydration of the membrane, and the mean vesicle aggregation number. The membrane thickness increases at higher x values, hence the vesicle lumen must become smaller if the external vesicle dimensions remain constant. Geometric considerations indicate that this growth mechanism lowers the total vesicle interfacial area and hence reduces the free energy of the system. However, it also inevitably leads to gradual ingress of the encapsulated water molecules into the vesicle membrane, as confirmed by SAXS analysis. Ultimately, the highly plasticized membranes become insufficiently hydrophobic to stabilize the vesicle morphology when x exceeds 1000, thus this PISA growth mechanism ultimately leads to vesicle "death". PMID:25526525

  18. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    SciTech Connect

    An, Hyosung; Mike, Jared; Smith, Kendall A.; Swank, Lisa; Lin, Yen-Hao; L. Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie L.

    2015-09-22

    Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects.

  19. The preparation and characterization of the cross-linked spherical, cylindrical, and vesicular micelles of poly(styrene-b-isoprene) diblock copolymers.

    PubMed

    Park, Soo-Young; Park, Myeong-Hye

    2007-06-01

    PI cores of the micelles of poly(styrene-b-isoprene) (PS-b-PI) diblock copolymers, in PS selective solvents, were cross-linked with sulfur monochloride (S2Cl2). The cross-linked micellar structure was maintained after dialysis in THF (neutral solvent) and did not change during heating. Cross-linking brought about the opportunity for TEM images in a solution state; otherwise, the micellar structure would be destroyed (or changed) during the evaporation of the solvent on a carbon-coated copper grid. The Flory interaction parameter, chi, between the PI block and the solvent was controlled by mixing two selective solvents (DMP/toluene, DMP/DEP and DEP/DBP) which have different degrees of selectivity for the PS block, as well as heating the solutions. Two block copolymers, PS(7.2K)-b-PI(7.8K) and PS(5.5K)-b-PI(18.8K), were studied in order to clarify the effects of the relative chain length of each block on the micelle structure in the selective solvents. PS(7.2K)-b-PI(7.8K), which is nearly symmetric, showed only spherical micelles in the DMP/toluene mixture. The basic spherical micellar shape of PS(7.2K)-b-PI(7.8K) did not change with chi, while the size and aggregation number of the micelles increased as chi increased until 2.05 and then were saturated after that. PS(5.5K)-b-PI(18.8K), which is asymmetric, showed a structural change from spherical to cylindrical to vesicular micelles with an increase in the selectivity of the DMP/DEP and DEP/DBP mixtures (which was also confirmed by TEM and SAXS studies). Giant vesicular micelles with a diameter of approximately 2.5 microm were observed in high-selectivity solvents. The size of the vesicular micelle seemed to decrease as selectivity decreased. The systematic changes of the micellar structures of PS(5.5K)-b-PI(18.8K), via changes in solvent selectivity, could be demonstrated through TEM images, which were prepared by evaporating the solvent of the cross-linked micellar solution onto the carbon-coated grid after

  20. Low-Temperature Synthesis of Thermoresponsive Diblock Copolymer Nano-Objects via Aqueous Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA) using Thermoresponsive Macro-RAFT Agents.

    PubMed

    Tan, Jianbo; Bai, Yuhao; Zhang, Xuechao; Huang, Chundong; Liu, Dongdong; Zhang, Li

    2016-09-01

    Photoinitiated reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of 2-hydroxypropyl methacrylate is conducted in water at low temperature using thermoresponsive copolymers of 2-(2-methoxyethoxy) ethyl methacrylate and oligo(ethylene glycol) methacrylate (Mn = 475 g mol(-1) ) as the macro-RAFT agent. Kinetic studies confirm that quantitative monomer conversion is achieved within 15 min of visible-light irradiation (405 nm, 0.5 mW cm(-2) ), and good control is maintained during the polymerization. The polymerization can be temporally controlled by a simple "ON/OFF" switch of the light source. Finally, thermoresponsive diblock copolymer nano-objects with a diverse set of complex morphologies (spheres, worms, and vesicles) are prepared using this particular formulation. PMID:27439569

  1. Selective confinement of oleylamine capped Au nanoparticles in self-assembled PS-b-PEO diblock copolymer templates.

    PubMed

    Di Mauro, A Evelyn; Striccoli, Marinella; Depalo, Nicoletta; Fanizza, Elisabetta; Cano, Laida; Ingrosso, Chiara; Agostiano, Angela; Curri, M Lucia; Tercjak, Agnieszka

    2014-03-21

    Amphiphilic polystyrene-block-polyethylene oxide (PS-b-PEO) block copolymers (BCPs) have been demonstrated to be effective in directing organization of colloidal Au nanoparticles (NPs). Au NPs have been incorporated into the polymer and the different chemical affinity between the NP surface and the two blocks of the BCP has been used as a driving force of the assembling procedure. The morphology of the nanocomposites, prepared and fabricated as thin films, has been investigated by means of atomic force and scanning electron microscopies as a function of the NP content and BCP molecular weight. NPs have been effectively dispersed in PS-b-PEO hosts at any investigated content (up to 17 wt%) and a clear effect of the BCP properties on the final nanocomposite morphology has been highlighted. Finally, electrostatic force microscopy has demonstrated the conductive properties of the nanocomposite films, showing that the embedded Au NPs effectively convey their conductive properties to the film. The overall investigation has confirmed the selective confinement of the as-prepared surfactant-coated metal NPs in the PS block of PS-b-PEO, thus proposing a very simple and prompt assembling tool for nanopatterning, potentially suitable for optoelectronic, sensing and catalysis applications. PMID:24800269

  2. Core-Corona Functionalization of Diblock Copolymer Micelles by Heterogeneous Metal Nanoparticles for Dual Modality in Chemical Reactions.

    PubMed

    Jo, Seong Ho; Kim, Hyun Woo; Song, Minkyung; Je, Nam Jin; Oh, Sung-Hoon; Chang, Byoung-Yong; Yoon, Jinhwan; Kim, Joo Hyun; Chung, Bonghoon; Yoo, Seong Il

    2015-08-26

    Nanoscale assemblies composed of different types of nanoparticles (NPs) can reveal interesting aspects about material properties beyond the functions of individual constituent NPs. This research direction may also represent current challenges in nanoscience toward practical applications. With respect to the assembling method, synthetic or biological nanostructures can be utilized to organize heterogeneous NPs in specific sites via chemical or physical interactions. However, those assembling methods often encounter uncontrollable particle aggregation or phase separation. In this study, we anticipated that the self-segregating properties of block copolymer micelles could be particularly useful for organizing heterogeneous NPs, because the presence of chemically distinct domains such as the core and the corona can facilitate the selective placement of constituent NPs in separate domains. Here, we simultaneously functionalized the core and the corona of micelles by Au NPs and Ag NPs, which exhibited plasmonic and catalytic functions, respectively. Our primary question is whether these plasmonic and catalytic functions can be combined in the assembled structures to engineer the kinetics of a model chemical reaction. To test this hypothesis, the catalytic reduction of 4-nitrophenol was selected to evaluate the collective properties of the micellar assemblies in a chemical reaction.

  3. Control of morphology and corona composition in aggregates of mixtures of PS-b-PAA and PS-b-P4VP diblock copolymers: effects of solvent, water content, and mixture composition.

    PubMed

    Vyhnalkova, Renata; Müller, Axel H E; Eisenberg, Adi

    2014-11-11

    The morphologies and corona compositions in aggregates of mixtures of PS-b-PAA and PS-b-P4VP diblock copolymers are influenced by controllable assembly parameters such as water content, block copolymer molar ratios, and solvent effects as well as the hydrophilic block lengths and block length ratios. All these factors can affect the morphology of the aggregates as well as their corona composition, the latter especially in vesicles, where two interfaces are involved. The morphologies and corona compositions of the aggregates were investigated by transmission electron microscopy and electrophoretic mobility, respectively. They depend, to a large extent, on the solubility of P4VP and PAA in the given organic solvent (e.g., DMF, THF, or dioxane), which influences the coil dimensions of the hydrophilic chains. The water content affects both the size and the shape of the block copolymer aggregates as well as the corona composition. Water acts as a precipitant for the hydrophobic block in the common solvent and, therefore, its progressive addition to the solution changes the interaction parameter with the hydrophobic block. The block copolymer molar ratio has an effect on both the morphology and the corona composition of the aggregates. With increasing PS-b-P4VP content in the mixture, the morphology transforms gradually from large compound micelles (LCMs), through coexistence of LCMs and small spherical micelles (SSMs), and eventually to vesicles. As expected, the corona composition of the aggregates is also affected by the block copolymer molar ratio, and changes progressively from pure PAA to a mixture of PAA and P4VP and to pure P4VP with increasing PS-b-P4VP content. It is clear that the use of mixtures of the soluble chains offers the opportunity of fine-tuning the corona composition in block copolymer aggregates under assembly conditions.

  4. Tuning of thermally induced sol-to-gel transitions of moderately concentrated aqueous solutions of doubly thermosensitive hydrophilic diblock copolymers poly(methoxytri(ethylene glycol) acrylate)-b-poly(ethoxydi(ethylene glycol) acrylate-co-acrylic acid).

    PubMed

    Jin, Naixiong; Zhang, Hao; Jin, Shi; Dadmun, Mark D; Zhao, Bin

    2012-03-15

    We report in this article a method to tune the sol-to-gel transitions of moderately concentrated aqueous solutions of doubly thermosensitive hydrophilic diblock copolymers that consist of two blocks exhibiting distinct lower critical solution temperatures (LCSTs) in water. A small amount of weak acid groups is statistically incorporated into the lower LCST block so that its LCST can be tuned by varying solution pH. Well-defined diblock copolymers, poly(methoxytri(ethylene glycol) acrylate)-b-poly(ethoxydi(ethylene glycol) acrylate-co-acrylic acid) (PTEGMA-b-P(DEGEA-co-AA)), were prepared by reversible addition-fragmentation chain transfer polymerization and postpolymerization modification. PTEGMA and PDEGEA are thermosensitive water-soluble polymers with LCSTs of 58 and 9 °C, respectively, in water. A 25 wt % aqueous solution of PTEGMA-b-P(DEGEA-co-AA) with a molar ratio of DEGEA to AA units of 100:5.2 at pH = 3.24 underwent multiple phase transitions upon heating, from a clear, free-flowing liquid (<15 °C) to a clear, free-standing gel (15-46 °C) to a clear, free-flowing hot liquid (47-56 °C), and a cloudy mixture (≥57 °C). With the increase of pH, the sol-to-gel transition temperature (T(sol-gel)) shifted to higher values, while the gel-to-sol transition (T(gel-sol)) and the clouding temperature (T(clouding)) of the sample remained essentially the same. These transitions and the tunability of T(sol-gel) originated from the thermosensitive properties of two blocks of the diblock copolymer and the pH dependence of the LCST of P(DEGEA-co-AA), which were confirmed by dynamic light scattering and differential scanning calorimetry studies. Using the vial inversion test method, we mapped out the C-shaped sol-gel phase diagrams of the diblock copolymer in aqueous buffers in the moderate concentration range at three different pH values (3.24, 5.58, and 5.82, all measured at ~0 °C). While the upper temperature boundaries overlapped, the lower temperature boundary

  5. Control of corona composition and morphology in aggregates of mixtures of PS-b-PAA and PS-b-P4VP diblock copolymers: effects of pH and block length.

    PubMed

    Vyhnalkova, Renata; Müller, Axel H E; Eisenberg, Adi

    2014-05-01

    The corona compositions and morphologies in aggregates of mixtures of amphiphilic polystyrene-block-poly(acrylic acid) (PS-b-PAA) and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymers are influenced by controllable assembly parameters such as the hydrophilic block length and solution pH. The morphologies and corona compositions of the aggregates were investigated by transmission electron microscopy and electrophoretic mobility, respectively. When mineral acids or bases are present during aggregate formation, they can exert a strong influence on the corona composition. Morphology changes were also seen with changing pH, as well as changes in corona composition, specifically for vesicles. Because of complications introduced by the presence of ions, the general hypothesis that the external corona of the vesicles is composed of the longer chains, while the shorter chains form the inner corona, which is valid only in mixtures containing only nonionic chains without any additives (no acids or bases) or within a well-defined narrow pH range. In addition to the numerical block lengths and the pH, the solubility of the hydrophilic blocks can also influence the morphology and as well as the interfacial composition of vesicles; as the numerically longer chains become less soluble, they can contract and move to the interior, while the numerically shorter but more soluble chains go to the external corona. A remarkable morphological feature of the pH continuum is that for some compositions vesicles are observed in four distinct pH regions, separated by pH ranges in which other morphologies dominate. The effect of pH and microion content on coil dimensions of the PVP and PAA chains in the block copolymers is most likely responsible for the observed behavior.

  6. Time-of-flight secondary ion mass spectrometry study of the orientation of a bifunctional diblock copolymer attached to a solid substrate.

    PubMed

    Jasieniak, Marek; Suzuki, Shuko; Monteiro, Michael; Wentrup-Byrne, Edeline; Griesser, Hans J; Grøndahl, Lisbeth

    2009-01-20

    A block copolymer consisting of a phosphate-containing moiety (poly[2-(methacryloyloxy)ethyl phosphate], PMOEP) and a keto-containing moiety (poly[2-(acetoacetoxy)ethyl methacrylate], PAAEMA) showed good stability after attachment to an APS amine-modified glass slide, as did both of the respective homopolymers. The PAAEMA homopolymer can attach to the APS amine groups via covalent linkages, while the PMOEP homopolymer most likely attaches through electrostatic interactions involving deprotonated phosphate and protonated amine groups. To elucidate the conformation of the block copolymer after attachment, particularly with respect to the PMOEP segment orientation, principal component analysis (PCA) of time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra of the surface-attached polymer layers was performed. Comparison with the pure homopolymer spectra and interpretation after PCA indicate that the adsorbed conformation is not random. Rather, the copolymer is adsorbed in a conformation that preferentially exposes the PMOEP block toward the outer surface. We thus conclude that the most likely conformation of PMOEP-b-PAAEMA immobilized onto the APS-modified glass slide is via covalent interfacial linkages involving the PAAEMA block with the result that the surface is enriched in PMOEP tails. This in turn implies that under the conditions applied (dry DMF) the covalent coupling of keto groups to the amine groups of the aminated slide is more efficient than the proton transfer required for the generation of electrostatic attractions. This (partially) preferential orientation of the PMOEP-b-PAAEMA copolymer could have significant implications on interfacial interactions such as those involved in nucleation and the subsequent mineralization sequence of events in hydroxyapatite formation. The present study demonstrates that ToF-SIMS is a powerful tool not only for the investigation of the surface composition of adsorbed layers, but also for probing the molecular

  7. Nanophase segregation and water dynamics in the dendrion diblock copolymer formed from the Fréchet polyaryl ethereal dendrimer and linear PTFE.

    PubMed

    Jang, Seung Soon; Lin, Shiang-Tai; Cagin, Tahir; Molinero, Valeria; Goddard, William A

    2005-05-26

    We propose a new material consisting of a dendrion copolymer formed from (a) a water-soluble dendritic polymer and (b) a hydrophobic backbone. Using molecular dynamics simulations techniques, we determine the structure and dynamics of the dendrion formed by second-generation Fréchet polyaryl ethereal dendrimer as the hydrophilic component and linear polytetrafluoroethylene (PTFE) as the hydrophobic polymer, with 5 and 10 wt % of water. We find that this material produces a well-developed nanoscale structure in which water forms a continuous nanophase, making this new family of compounds promising candidates for applications in fuel cell membranes. We find that the water molecules are incorporated into the dendrimer block of the copolymer to form a nanophase-segregated structure. The well-developed nanophase-segregated structures rendered by this material have characteristic dimensions of segregation ( approximately 30 Angstrom) and dendrimer conformational properties that are independent of water content. Calculations of water dynamics and proton transport in these nanophase-segregated structures indicate that the dendrion copolymer membrane with 10 wt % of water content has a water structure and transport properties equivalent to that of the hydrated Nafion membrane with 20 wt % of water content.

  8. Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions† †Electronic supplementary information (ESI) available: GPC chromatograms, additional transmission electron micrographs, digital photographs, visible absorption spectra and laser diffraction data, further optical and fluorescence micrographs. See DOI: 10.1039/c6nr03856e Click here for additional data file.

    PubMed Central

    Thompson, Kate L.; Derry, Matthew J.; Warren, Nicholas J.; Ratcliffe, Liam P. D.; Williams, Clive N.; Brown, Steven L.

    2016-01-01

    We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56–poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA–PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20–100 μm diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56–poly(benzyl methacrylate)300 [PGMA56–PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56–PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39–poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39–PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to

  9. Flexible Hybrid Electrodes Containing Vanadium Pentoxide (V2O5) and an Electron- and Ion-Conducting Diblock Copolymer for Energy Storage

    NASA Astrophysics Data System (ADS)

    An, Hyosung; Mike, Jared; Smith, Kendall; Swank, Lisa; Lin, Yen-Hao; Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie

    2015-03-01

    Vanadium pentoxide (V2O5) is a promising cathode material for Lithium-ion batteries due to its high capacity, high energy density, and cost-effectiveness. However, its low lithium-ion diffusion coefficient (10-12 - 10-13 cm2/s), low electronic conductivity (10-2 - 10-3 S/cm), and severe volumetric changes during cycling have hindered its application in practical devices. One way to address these problems is to design hybrid electrodes that incorporate a second active material. For this purpose, poly(3-hexylthiophene)-block-poly(ethylene oxide) (P3HT- b-PEO) block copolymer containing electron- and ion-conducting polymer blocks was introduced to a V2O5 electrode system. Cathodes are prepared by mixing aqueous dispersions of block copolymer, V2O5, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and drop casting. The V2O5 and P3HT- b-PEO hybrid electrode showed synergistic results, having improved electrochemical storage performance and mechanical property. We also demonstrated a flexible battery prototype using the P3HT- b-PEO/V2O5 cathode.

  10. Docetaxel-loaded nanoparticles based on star-shaped mannitol-core PLGA-TPGS diblock copolymer for breast cancer therapy.

    PubMed

    Tao, Wei; Zeng, Xiaowei; Liu, Ting; Wang, Zhongyuan; Xiong, Qingqing; Ouyang, Chunping; Huang, Laiqiang; Mei, Lin

    2013-11-01

    A star-shaped biodegradable polymer, mannitol-core poly(d,l-lactide-co-glycolide)-d-α-tocopheryl polyethylene glycol 1000 succinate (M-PLGA-TPGS), was synthesized in order to provide a novel nanoformulation for breast cancer chemotherapy. This novel copolymer was prepared by a core-first approach via three stages of chemical reaction, and was characterized by nuclear magnetic resonance, gel permeation chromatography and thermogravimetric analysis. The docetaxel-loaded M-PLGA-TPGS nanoparticles (NPs), prepared by a modified nanoprecipitation method, were observed to be near-spherical shape with narrow size distribution. Confocal laser scanning microscopy showed that the uptake level of M-PLGA-TPGS NPs was higher than that of PLGA NPs and PLGA-TPGS NPs in MCF-7 cells. A significantly higher level of cytotoxicity was achieved with docetaxel-loaded M-PLGA-TPGS NPs than with commercial Taxotere®, docetaxel-loaded PLGA-TPGS and PLGA NPs. Examination of the drug loading and encapsulation efficiency proved that star-shaped M-PLGA-TPGS could carry higher levels of drug than linear polymer. The in vivo experiment showed docetaxel-loaded M-PLGA-TPGS NPs to have the highest anti-tumor efficacy. In conclusion, the star-like M-PLGA-TPGS copolymer shows potential as a promising drug-loaded biomaterial that can be applied in developing novel nanoformulations for breast cancer therapy.

  11. Genistein-loaded nanoparticles of star-shaped diblock copolymer mannitol-core PLGA-TPGS for the treatment of liver cancer.

    PubMed

    Wu, Binquan; Liang, Yong; Tan, Yi; Xie, Chunmei; Shen, Jin; Zhang, Mei; Liu, Xinkuang; Yang, Lixin; Zhang, Fujian; Liu, Liang; Cai, Shuyu; Huai, De; Zheng, Donghui; Zhang, Rongbo; Zhang, Chao; Chen, Ke; Tang, Xiaolong; Sui, Xuemei

    2016-02-01

    The purpose of this research is to develop nanoparticles (NPs) of star-shaped copolymer mannitol-functionalized PLGA-TPGS for Genistein delivery for liver cancer treatment, and evaluate their therapeutic effects in liver cancer cell line and hepatoma-tumor-bearing nude mice in comparison with the linear PLGA nanoparticles and PLGA-TPGS nanoparticles. The Genistein-loaded M-PLGA-TPGS nanoparticles (MPTN), prepared by a modified nanoprecipitation method, were observed by FESEM and TEM to be near-spherical shape with narrow size distribution. The nanoparticles were further characterized in terms of their size, size distribution, surface charge, drug-loading content, encapsulation efficiency and in vitro drug release profiles. The data showed that the M-PLGA-TPGS nanoparticles were found to be stable, showing almost no change in particle size and surface charge during 3-month storage of their aqueous solution. In vitro Genistein release from the nanoparticles exhibited biphasic pattern with burst release at the initial 4days and sustained release afterwards. The cellular uptake efficiency of fluorescent M-PLGA-TPGS nanoparticles was 1.25-, 1.22-, and 1.29-fold higher than that of the PLGA-TPGS nanoparticles at the nanoparticle concentrations of 100, 250, and 500μg/mL, respectively. In the MPTN group, the ratio of apoptotic cells increased with the drug dose increased, which exhibited dose-dependent effect and a significant difference compared with Genistein solution group (p<0.05). The data also showed that the Genistein-loaded M-PLGA-TPGS nanoparticles have higher antitumor efficacy than that of linear PLGA-TPGS nanoparticles and PLGA nanoparticles in vitro and in vivo. In conclusion, the star-shaped copolymer M-PLGA-TPGS could be used as a potential and promising bioactive material for nanomedicine development for liver cancer treatment.

  12. A novel diblock of copolymer of (monomethoxy poly [ethylene glycol]-oleate) with a small hydrophobic fraction to make stable micelles/polymersomes for curcumin delivery to cancer cells

    PubMed Central

    Erfani-Moghadam, Vahid; Nomani, Alireza; Zamani, Mina; Yazdani, Yaghoub; Najafi, Farhood; Sadeghizadeh, Majid

    2014-01-01

    Curcumin is a potent natural anticancer agent, but its effectiveness is limited by properties such as very low solubility, high rate of degradation, and low rate of absorption of its hydrophobic molecules in vivo. To date, various nanocarriers have been used to improve the bioavailability of this hydrophobic biomaterial. This study investigates the encapsulation of curcumin in a novel nanostructure of monomethoxy poly(ethylene glycol)-oleate (mPEG-OA) and its anticancer effect. Tests were done to determine the critical micelle concentration (CMC), encapsulation efficiency, drug-loading efficiency, and cytotoxicity (against U87MG brain carcinoma cells and HFSF-PI3 cells as normal human fibroblasts) of some nanodevice preparations. The results of fluorescence microscopy and cell-cycle analyses indicated that the in vitro bioavailability of the encapsulated curcumin was significantly greater than that of free curcumin. Cytotoxicity evaluations showed that half maximal inhibitory concentrations of free curcumin and curcumin-loaded mPEG-OA for the U87MG cancer cell line were 48 μM and 24 μM, respectively. The Annexin-V-FLUOS assay was used to quantify the apoptotic effect of the prepared nanostructures. Apoptosis induction was observed in a dose-dependent manner after curcumin-loaded mPEG-OA treatments. Two common self-assembling structures, micelles and polymersomes, were observed by atomic force microscopy and dynamic light scattering, and the abundance of each structure was dependent on the concentration of the diblock copolymer. The mPEG-OA micelles had a very low CMC (13.24 μM or 0.03 g/L). Moreover, atomic force microscopy and dynamic light scattering showed that the curcumin-loaded mPEG-OA polymersomes had very stable structures, and at concentrations 1,000 times less than the CMC, at which the micelles disappear, polymersomes were the dominant structures in the dispersion with a reduced size distribution below 150 nm. Overall, the results from these tests

  13. A novel diblock of copolymer of (monomethoxy poly [ethylene glycol]-oleate) with a small hydrophobic fraction to make stable micelles/polymersomes for curcumin delivery to cancer cells.

    PubMed

    Erfani-Moghadam, Vahid; Nomani, Alireza; Zamani, Mina; Yazdani, Yaghoub; Najafi, Farhood; Sadeghizadeh, Majid

    2014-01-01

    Curcumin is a potent natural anticancer agent, but its effectiveness is limited by properties such as very low solubility, high rate of degradation, and low rate of absorption of its hydrophobic molecules in vivo. To date, various nanocarriers have been used to improve the bioavailability of this hydrophobic biomaterial. This study investigates the encapsulation of curcumin in a novel nanostructure of monomethoxy poly(ethylene glycol)-oleate (mPEG-OA) and its anticancer effect. Tests were done to determine the critical micelle concentration (CMC), encapsulation efficiency, drug-loading efficiency, and cytotoxicity (against U87MG brain carcinoma cells and HFSF-PI3 cells as normal human fibroblasts) of some nanodevice preparations. The results of fluorescence microscopy and cell-cycle analyses indicated that the in vitro bioavailability of the encapsulated curcumin was significantly greater than that of free curcumin. Cytotoxicity evaluations showed that half maximal inhibitory concentrations of free curcumin and curcumin-loaded mPEG-OA for the U87MG cancer cell line were 48 μM and 24 μM, respectively. The Annexin-V-FLUOS assay was used to quantify the apoptotic effect of the prepared nanostructures. Apoptosis induction was observed in a dose-dependent manner after curcumin-loaded mPEG-OA treatments. Two common self-assembling structures, micelles and polymersomes, were observed by atomic force microscopy and dynamic light scattering, and the abundance of each structure was dependent on the concentration of the diblock copolymer. The mPEG-OA micelles had a very low CMC (13.24 μM or 0.03 g/L). Moreover, atomic force microscopy and dynamic light scattering showed that the curcumin-loaded mPEG-OA polymersomes had very stable structures, and at concentrations 1,000 times less than the CMC, at which the micelles disappear, polymersomes were the dominant structures in the dispersion with a reduced size distribution below 150 nm. Overall, the results from these tests

  14. Microdomain contraction in microphase-separated multiblock copolymers

    SciTech Connect

    Smith, S.D. ); Spontak, R.J. ); Satkowski, M.M.; Ashraf, A. ); Lin, J.S. )

    1993-06-01

    Linear multiblock copolymers, like their diblock analogs, undergo microphase separation and order into periodic morphologies when the blocks are sufficiently incompatible. To explore the conformations of such materials, four symmetric poly(styrene-[ital b]-isoprene)[sub [ital n

  15. Fabrication and photoactivity of a tunable-void SiO₂-TiO₂ core-shell structure on modified SiO₂ nanospheres by grafting an amphiphilic diblock copolymer using ARGET ATRP.

    PubMed

    Zhao, Minnan; Zhou, Guowei; Zhang, Lei; Li, Xiuyan; Li, Tianduo; Liu, Fangfang

    2014-02-28

    SiO₂-based composites have important applications in various technological fields. In this work, a tunablevoid SiO₂-TiO₂ core-shell structure was successfully prepared for the first time using SiO₂-polymethyl methacrylate (PMMA)-polyoligo(ethylene glycol)methyl ether methacrylate (PO(EO)nMA) (n = 2, 5, and 8). An amphiphilic copolymer was used as the template, and calcination was performed using tetrabutyl titanate (TBT) as the titanium source. SiO₂-PMMA-b-PO(EO)nMA microspheres were first synthesized through activators regenerated by electron transfer-atom transfer radical polymerization. Methyl methacrylate and O(EO)nMA were grafted with different EO unit numbers onto the surface of the halogen functional group of SiO₂. TBT was hydrolyzed along with the PO(EO)nMA chain through hydrogen bonding, and then the SiO₂-TiO₂ core-shell structure was acquired through calcination to remove the polymer. Simultaneously, amorphous TiO₂ crystallized during calcination. A series of characterizations indicated that the amphiphilic block copolymer was grafted onto SiO₂ mesoparticle surfaces, the titania samples existed only in the anatase phase, and the prepared SiO₂-TiO₂ had hierarchically nanoporous structures. The gradient hydrophilicity of the PMMA-b-PO(EO)nMA copolymer template facilitated the hydrolysis of TBT molecules along the PO(EO)nMA to PMMA segments, thereby tuning the space between the core and the shell. In addition, the space was about 6 nm when the EO number was 2, and the space was about 10 nm when the EO numbers were 5 and 8. The photocatalytic activities of the SiO₂-TiO₂ materials were tested on the photodegradation of methyl orange. PMID:24795964

  16. Antimicrobial Graft Copolymer Gels.

    PubMed

    Harvey, Amanda C; Madsen, Jeppe; Douglas, C W Ian; MacNeil, Sheila; Armes, Steven P

    2016-08-01

    In view of the growing worldwide rise in microbial resistance, there is considerable interest in designing new antimicrobial copolymers. The aim of the current study was to investigate the relationship between antimicrobial activity and copolymer composition/architecture to gain a better understanding of their mechanism of action. Specifically, the antibacterial activity of several copolymers based on 2-(methacryloyloxy)ethyl phosphorylcholine [MPC] and 2-hydroxypropyl methacrylate (HPMA) toward Staphylococcus aureus was examined. Both block and graft copolymers were synthesized using either atom transfer radical polymerization or reversible addition-fragmentation chain transfer polymerization and characterized via (1)H NMR, gel permeation chromatography, rheology, and surface tensiometry. Antimicrobial activity was assessed using a range of well-known assays, including direct contact, live/dead staining, and the release of lactate dehydrogenase (LDH), while transmission electron microscopy was used to study the morphology of the bacteria before and after the addition of various copolymers. As expected, PMPC homopolymer was biocompatible but possessed no discernible antimicrobial activity. PMPC-based graft copolymers comprising PHPMA side chains (i.e. PMPC-g-PHPMA) significantly reduced both bacterial growth and viability. In contrast, a PMPC-PHPMA diblock copolymer comprising a PMPC stabilizer block and a hydrophobic core-forming PHPMA block did not exhibit any antimicrobial activity, although it did form a biocompatible worm gel. Surface tensiometry studies and LDH release assays suggest that the PMPC-g-PHPMA graft copolymer exhibits surfactant-like activity. Thus, the observed antimicrobial activity is likely to be the result of the weakly hydrophobic PHPMA chains penetrating (and hence rupturing) the bacterial membrane. PMID:27409712

  17. Bioinspired catecholic copolymers for antifouling surface coatings.

    PubMed

    Cho, Joon Hee; Shanmuganathan, Kadhiravan; Ellison, Christopher J

    2013-05-01

    We report here a synthetic approach to prepare poly(methyl methacrylate)-polydopamine diblock (PMMA-PDA) and triblock (PDA-PMMA-PDA) copolymers combining mussel-inspired catecholic oxidative chemistry and atom transfer radical polymerization (ATRP). These copolymers display very good solubility in a range of organic solvents and also a broad band photo absorbance that increases with increasing PDA content in the copolymer. Spin-cast thin films of the copolymer were stable in water and showed a sharp reduction (by up to 50%) in protein adsorption compared to those of neat PMMA. Also the peak decomposition temperature of the copolymers was up to 43°C higher than neat PMMA. The enhanced solvent processability, thermal stability and low protein adsorption characteristics of this copolymer makes it attractive for variety of applications including antifouling coatings on large surfaces such as ship hulls, buoys, and wave energy converters.

  18. Crystallization-driven one-dimensional self-assembly of polyethylene-b-poly(tert-butylacrylate) diblock copolymers in DMF: effects of crystallization temperature and the corona-forming block.

    PubMed

    Fan, Bin; Liu, Lei; Li, Jun-Huan; Ke, Xi-Xian; Xu, Jun-Ting; Du, Bin-Yang; Fan, Zhi-Qiang

    2016-01-01

    Crystallization-driven self-assembly of polyethylene-b-poly(tert-butylacrylate) (PE-b-PtBA) block copolymers (BCPs) in N,N-dimethyl formamide (DMF) was studied. It is found that all three PE-b-PtBA BCPs used in this work can self-assemble into one-dimensional crystalline cylindrical micelles. When the BCP solution is cooled to crystallization temperature (Tc) from 130 °C, the seed micelles may be produced via two competitive processes in the initial period: stepwise micellization/crystallization and simultaneous crystallization/micellization. Subsequently, the seed micelles can undergo growth driven by the epitaxial crystallization of the unimers. The lengths of both the seed micelles and the grown micelles are longer for the BCP with a longer PtBA block at a higher Tc. Quasi-living growth of the PE-b-PtBA crystalline cylindrical micelles is achieved at a higher Tc. A longer PtBA block evidently retards the attachment of unimers to the crystalline micelles, leading to a slower growth rate.

  19. Phase Transitions in Thin Block Copolymer Films

    SciTech Connect

    Kramer, Edward J.

    2010-10-08

    David Turnbull's experiments and theoretical insights paved the way for much of our modern understanding of phase transitions in materials. In recognition of his contributions, this lecture will concentrate on phase transitions in a material system not considered by Turnbull, thin diblock copolymer films. Well-ordered block copolymer films are attracting increasing interest as we attempt to extend photolithography to smaller dimensions. In the case of diblock copolymer spheres, an ordered monolayer is hexagonal, but the ordered bulk is body-centered cubic (bcc). There is no hexagonal plane in the bcc structure, so a phase transition must occur as n, the number of layers of spheres in the film, increases. How this phase transition occurs with n and how it can be manipulated is the subject of the first part of my presentation. In the second part of the talk, I show that monolayers of diblock copolymer spheres and cylinders undergo order-to-disorder transitions that differ greatly from those of the bulk. These ordered 2D monolayers are susceptible to phonon-generated disorder as well as to thermal generation of defects, such as dislocations, which, while they are line defects in 3D, are point defects in 2D. The results are compared to the theories of melting of 2D crystals (spheres) and of 2D smectic liquid crystals (cylinders), a comparison that will allow us to understand most, but not all, of the features of these order-disorder transitions that occur as the temperature is increased.

  20. Phase coexistence calculations via a unit-cell Gibbs ensemble formalism for melts of reversibly bonded block copolymers

    NASA Astrophysics Data System (ADS)

    Mester, Zoltan; Lynd, Nathaniel; Fredrickson, Glenn

    2013-03-01

    Melts of block copolymer blends can exhibit coexistence between compositionally and morphologically distinct phases. We derived a unit-cell approach for a field theoretic Gibbs ensemble formalism to rapidly map out such coexistence regions. We also developed a canonical ensemble model for the reversible reaction of supramolecular polymers and integrated it into the Gibbs ensemble scheme. This creates a faster method for generating phase diagrams in complex supramolecular systems than the usual grand canonical ensemble method and allows us to specify the system in experimentally accessible volume fractions rather than chemical potentials. The integrated approach is used to calculate phase diagrams for AB diblock copolymers reversibly reacting with B homopolymers to form a new diblocks we term ``ABB.'' For our case, we use a diblock that is sixty percent A monomer and a homopolymer that is the same length as the diblock. In the limits of infinite reaction favorability (large equilibrium constant), the system approaches cases of an ABB diblock-B homopolymer blend when the AB diblock is the limiting reactant and AB diblock-ABB diblock blend when the homopolymer is the limiting reactant. As reaction favorability is decreased, the phase boundaries shift towards higher homopolymer compositions so that sufficient reaction can take place to produce the ABB diblock that has a deciding role stabilizing the observed phases.

  1. Functionalized block copolymers as adhesion promoters

    SciTech Connect

    Kent, M.S.; Saunders, R.

    1995-03-01

    The goal of this work is to develop novel functionalized block copolymers to promote adhesion at inorganic substrate/polymer interfaces. We envision several potential advantages of functionalized block copolymers over small molecule coupling agents. Greater control over the structure of the interphase region should result through careful design of the backbone of the copolymer. The number of chains per area, the degree of entanglement between the copolymer and the polymer matrix, the number of sites per chain able to attach to the substrate, and the hydrophobicity of the interphase region can all be strongly affected by the choice of block lengths and the monomer sequence. In addition, entanglement between the copolymer and the polymer matrix, if achieved, should contribute significantly to adhesive strength. Our program involves four key elements: the synthesis of suitable functionalized block copolymers, characterization of the conformation of the copolymers at the interface by neutron reflectivity and atomic force microscopy, characterization of the degree of bonding by spectroscopy, and measurement of the mechanical properties of the interface. In this paper we discuss block copolymers designed as adhesion promoters for the copper/epoxy interface. We have synthesized a diblock with one block containing imidazole groups to bond to copper and a second block containing secondary amines to react with the epoxy matrix. We have also prepared a triblock copolymer containing a hydrophobic middle block. Below we describe the synthesis of the block copolymers by living, ring-opening metathesis polymerization (ROMP) and the first characterization data obtained by neutron reflectivity.

  2. Fluctuation Effects on Phase Behavior of Gradient Copolymer Systems

    NASA Astrophysics Data System (ADS)

    Pandav, Gunja; Ganesan, Venkat

    2013-03-01

    We consider the effect of sequence polydispersity on fluctuation induced shift in order-disorder transition (ODT) temperature for symmetric systems of gradient copolymers. Using single chain in mean field simulations, a systematic change in scaling prediction for shift in ODT with Ginzburg parameter is reported. We demonstrate that gradient strength and overall blockiness of sequences has a significant impact on shift in ODT temperature. The weak gradient copolymers having high compositional polydispersity mimic random copolymers whereas, strong gradient copolymers possess inherent blockiness and are close to diblock copolymers. The blockiness parameter has a minimal impact on shift in ODT in strong gradient copolymers. Also, ternary blends of homopolymer/gradient copolymer are investigated to capture effect of compositional polydispersity on phase diagram and formation of microemulsion structures.

  3. Radical-cured block copolymer-modified thermosets

    SciTech Connect

    Redline, Erica M.; Francis, Lorraine F.; Bates, Frank S.

    2013-01-10

    Poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) diblock copolymers were synthesized and added at 4 wt % to 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (BisGMA), a monomer that cures using free radical chemistry. In separate experiments, poly(ethylene glycol) dimethacrylate (PEGDMA) was combined as a secondary monomer with BisGMA and the monomers were loaded with 4 wt % PEP-PEO. The diblock copolymers self-assembled into well-dispersed spherical micelles with PEP cores and PEO coronas. No appreciable change in the final extent of cure of the thermosets was caused by the addition of diblock copolymer, except in the case of BisGMA, where the addition of the block copolymer increased extent of cure by 12%. Furthermore, the extent of cure was increased by 29% and 37% with the addition of 25 and 50 wt % PEGDMA, respectively. Elastic modulus and fracture resistance were also determined, and the values indicate that the addition of block copolymers does not significantly toughen the thermoset materials. This finding is surprising when compared with the large increase in fracture resistance seen in block copolymer-modified epoxies, and an explanation is proposed.

  4. Block Copolymer Bottlebrushes: New Routes to Ever Smaller Microdomain Sizes

    NASA Astrophysics Data System (ADS)

    Mahanthappa, Mahesh; Speetjens, Frank

    Block copolymer self-assembly presents exciting opportunities for the development of nanotemplates for advanced lithography applications, wherein the microdomain sizes (~10-100 nm) are governed by the total copolymer degree of polymerization, N. However, this methodology is limited in its smallest achievable length scale, since AB diblock copolymers self-assemble only above a critical N that depends on the magnitude of the effective segmental interaction parameter χAB. Numerous recent reports have focused on developing ``high χAB'' AB diblocks that self-assemble at low values of N. In this talk we explore the ability of non-linear polymer architectures to induce block copolymer ordering at reduced length scales. Thus, we describe the melt and thin-film self-assembly behavior of block copolymer bottlebrushes derived from linking the block junctions of low molecular weight AB diblocks. We quantitatively demonstrate that increasing the bottlebrush backbone degree of polymerization (Nbackbone) results in a larger reduction in the critical copolymer arm degree of polymerization (Narm) required for self-assembly, thus reducing the length scales at which these materials self-assemble.

  5. Antimicrobial activity of poly(acrylic acid) block copolymers.

    PubMed

    Gratzl, Günther; Paulik, Christian; Hild, Sabine; Guggenbichler, Josef P; Lackner, Maximilian

    2014-05-01

    The increasing number of antibiotic-resistant bacterial strains has developed into a major health problem. In particular, biofilms are the main reason for hospital-acquired infections and diseases. Once formed, biofilms are difficult to remove as they have specific defense mechanisms against antimicrobial agents. Antimicrobial surfaces must therefore kill or repel bacteria before they can settle to form a biofilm. In this study, we describe that poly(acrylic acid) (PAA) containing diblock copolymers can kill bacteria and prevent from biofilm formation. The PAA diblock copolymers with poly(styrene) and poly(methyl methacrylate) were synthesized via anionic polymerization of tert-butyl acrylate with styrene or methyl methacrylate and subsequent acid-catalyzed hydrolysis of the tert-butyl ester. The copolymers were characterized via nuclear magnetic resonance spectroscopy (NMR), size-exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), elemental analysis, and acid-base titrations. Copolymer films with a variety of acrylic acid contents were produced by solvent casting, characterized by atomic force microscopy (AFM) and tested for their antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The antimicrobial activity of the acidic diblock copolymers increased with increasing acrylic acid content, independent of the copolymer-partner, the chain length and the nanostructure.

  6. A Single Diblock Molecular Diode

    NASA Astrophysics Data System (ADS)

    Joshua Obodo, Tobechukwu; Murat, Altynbek; Udo Schwingenschlögl, Udo

    2015-03-01

    We investigate the rectification behavior of the diblock dipyrimidinyldiphenyl molecule and its derivates with increasing donor groups using self-interaction corrected density functional theory combined with the non-equilibrium Green's function method. In particular, we study a tandem setup for the representative optimized rectifier, finding that it significantly improves the rectification behavior of the molecular diode. Moreover, we find that the molecule consisting of donor and acceptor mimics a pn-junction, whereas the tandem setup does not behave as a pn-pn junction, rather like a p-np-n junction. Our results help explain the mechanism behind the experimentally observed rectification behavior of the molecule.

  7. Oxidation effect on templating of metal oxide nanoparticles within block copolymers

    SciTech Connect

    Akcora, Pinar; Briber, Robert M.; Kofinas, Peter

    2009-06-30

    Amphiphilic norbornene-b-(norbornene dicarboxylic acid) diblock copolymers with different block ratios were prepared as templates for the incorporation of iron ions using an ion exchange protocol. The disordered arrangement of iron oxide particles within these copolymers was attributed to the oxidation of the iron ions and the strong interactions between iron oxide nanoparticles, particularly at high iron ion concentrations, which was found to affect the self-assembly of the block copolymer morphologies.

  8. Regulating block copolymer phases via selective homopolymers

    SciTech Connect

    Yang, Shuang E-mail: eqchen@pku.edu.cn; Lei, Zhen; Hu, Nan; Chen, Er-Qiang E-mail: eqchen@pku.edu.cn; Shi, An-Chang

    2015-03-28

    The phase behavior of strongly segregated AB diblock copolymer and selective C homopolymer blends is examined theoretically using a combination of strong stretching theory (SST) and self-consistent field theory (SCFT). The C-homopolymer is immiscible with the B-blocks but strongly attractive with the A-blocks. The effect of homopolymer content on the order-order phase transitions is analyzed. It is observed that, for AB diblock copolymers with majority A-blocks, the addition of the C-homopolymers results in lamellar to cylindrical to spherical phase transitions because of the A/C complexation. For diblock copolymers with minor A-blocks, adding C-homopolymers leads to transitions from spherical or cylindrical morphology with A-rich core to lamellae to inverted cylindrical and spherical morphologies with B-rich core. The results from analytical SST and numerical SCFT are in good agreement within most regions of the phase diagram. But the deviation becomes more obvious when the composition of A-blocks is too small and the content of added C-homopolymers is large enough, where the SCFT predicts a narrow co-existence region between different ordered phases. Furthermore, it is found that the phase behavior of the system is insensitive to the molecular weight of C-homopolymer.

  9. Block and Graft Copolymers of Polyhydroxyalkanoates

    NASA Astrophysics Data System (ADS)

    Marchessault, Robert H.; Ravenelle, François; Kawada, Jumpei

    2004-03-01

    Polyhydroxyalkanoates (PHAs) were modified for diblock copolymer and graft polymer by catalyzed transesterification in the melt and by chemical synthesis to extend the side chains of the PHAs, and the polymers were studied by transmission electron microscopy (TEM) X-ray diffraction, thermal analysis and nuclear magnetic resonance (NMR). Catalyzed transesterification in the melt is used to produce diblock copolymers of poly[3-hydroxybutyrate] (PHB) and monomethoxy poly[ethylene glycol] (mPEG) in a one-step process. The resulting diblock copolymers are amphiphilic and self-assemble into sterically stabilized colloidal suspensions of PHB crystalline lamellae. Graft polymer was synthesized in a two-step chemical synthesis from biosynthesized poly[3-hydroxyoctanoate-co-3-hydroxyundecenoate] (PHOU) containing ca. 25 mol chains. 11-mercaptoundecanoic acid reacts with the side chain alkenes of PHOU by the radical addition creating thioether linkage with terminal carboxyl functionalities. The latter groups were subsequently transformed into the amide or ester linkage by tridecylamine or octadecanol, respectively, producing new graft polymers. The polymers have different physical properties than poly[3-hydroxyoctanoate] (PHO) which is the main component of the PHOU, such as non-stickiness and higher thermal stability. The combination of biosynthesis and chemical synthesis produces a hybrid thermoplastic elastomer with partial biodegradability.

  10. Regulating block copolymer phases via selective homopolymers.

    PubMed

    Yang, Shuang; Lei, Zhen; Hu, Nan; Chen, Er-Qiang; Shi, An-Chang

    2015-03-28

    The phase behavior of strongly segregated AB diblock copolymer and selective C homopolymer blends is examined theoretically using a combination of strong stretching theory (SST) and self-consistent field theory (SCFT). The C-homopolymer is immiscible with the B-blocks but strongly attractive with the A-blocks. The effect of homopolymer content on the order-order phase transitions is analyzed. It is observed that, for AB diblock copolymers with majority A-blocks, the addition of the C-homopolymers results in lamellar to cylindrical to spherical phase transitions because of the A/C complexation. For diblock copolymers with minor A-blocks, adding C-homopolymers leads to transitions from spherical or cylindrical morphology with A-rich core to lamellae to inverted cylindrical and spherical morphologies with B-rich core. The results from analytical SST and numerical SCFT are in good agreement within most regions of the phase diagram. But the deviation becomes more obvious when the composition of A-blocks is too small and the content of added C-homopolymers is large enough, where the SCFT predicts a narrow co-existence region between different ordered phases. Furthermore, it is found that the phase behavior of the system is insensitive to the molecular weight of C-homopolymer. PMID:25833605

  11. Efficacy of Different Block Copolymers in Facilitating Microemulsion Phases in Polymer Blend Systems

    NASA Astrophysics Data System (ADS)

    Pandav, Gunja; Ganesan, Venkat

    2014-03-01

    Polymeric microemulsions are formed in a narrow range of phase diagram when a blend of immiscible homopolymers is compatibilized by copolymers. In this study, we consider the ternary blend system of A and B homopolymers mixed with block copolymers containing A and B segments, and probe the efficacy of different copolymer configurations in promoting the formation of microemulsion phases. Specifically, we consider: (a) Monodisperse diblock copolymers; (b) Diblock copolymers with bidisperse molecular weights (MW); (c) Block copolymers having MW polydispersity in one of the blocks; (d) Diblock copolymers having monodisperse MW but bidispersity in average composition; and (e) Gradient copolymers exhibiting a linear variation in the average composition. Using single chain in mean field simulations effected in two dimensions, we probe the onset of formation and the width of the bicontinuous microemulsion channel in the ternary phase diagram of homopolymer blended with compatibilizer. We rationalize our results by explicitly quantifying the interfacial activity and the influence of fluctuation effects in the respective copolymer systems.

  12. Research Update: Triblock copolymers as templates to synthesize inorganic nanoporous materials

    NASA Astrophysics Data System (ADS)

    Li, Yunqi; Bastakoti, Bishnu Prasad; Yamauchi, Yusuke

    2016-04-01

    This review focuses on the application of triblock copolymers as designed templates to synthesize nanoporous materials with various compositions. Asymmetric triblock copolymers have several advantages compared with symmetric triblock copolymers and diblock copolymers, because the presence of three distinct domains can provide more functional features to direct the resultant nanoporous materials. Here we clearly describe significant contributions of asymmetric triblock copolymers, especially polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (abbreviated as PS-b-P2VP-b-PEO).

  13. Arbitrary lattice symmetries via block copolymer nanomeshes

    PubMed Central

    Majewski, Pawel W.; Rahman, Atikur; Black, Charles T.; Yager, Kevin G.

    2015-01-01

    Self-assembly of block copolymers is a powerful motif for spontaneously forming well-defined nanostructures over macroscopic areas. Yet, the inherent energy minimization criteria of self-assembly give rise to a limited library of structures; diblock copolymers naturally form spheres on a cubic lattice, hexagonally packed cylinders and alternating lamellae. Here, we demonstrate multicomponent nanomeshes with any desired lattice symmetry. We exploit photothermal annealing to rapidly order and align block copolymer phases over macroscopic areas, combined with conversion of the self-assembled organic phase into inorganic replicas. Repeated photothermal processing independently aligns successive layers, providing full control of the size, symmetry and composition of the nanoscale unit cell. We construct a variety of symmetries, most of which are not natively formed by block copolymers, including squares, rhombuses, rectangles and triangles. In fact, we demonstrate all possible two-dimensional Bravais lattices. Finally, we elucidate the influence of nanostructure on the electrical and optical properties of nanomeshes. PMID:26100566

  14. Giant Hexagonal Superstructures in Diblock-Copolymer Membranes

    NASA Astrophysics Data System (ADS)

    Haluska, Christopher K.; Góźdź, Wojciech T.; Döbereiner, Hans-Günther; Förster, Stephan; Gompper, Gerhard

    2002-11-01

    We have observed polymersomes of high genus with their vesicle wall organized on the micrometer scale either in a double bilayer connected by a lattice of passages or a tubular network with hexagonal symmetry. Experimentally found shape classes are identified within a theoretical phase diagram based on the bending energy of the polymer membrane. Pronounced morphological changes could be induced and controlled by temperature.

  15. Encapsulation of Curcumin in Diblock Copolymer Micelles for Cancer Therapy

    PubMed Central

    Alizadeh, Ali Mohammad; Sadeghizadeh, Majid; Najafi, Farhood; Ardestani, Sussan K.; Erfani-Moghadam, Vahid; Khaniki, Mahmood; Rezaei, Arezou; Zamani, Mina; Khodayari, Saeed; Khodayari, Hamid; Mohagheghi, Mohammad Ali

    2015-01-01

    Application of nanoparticles has recently promising results for water insoluble agents like curcumin. In this study, we synthesized polymeric nanoparticle-curcumin (PNPC) and then showed its efficiency, drug loading, stability, and safety. Therapeutic effects of PNPC were also assessed on two cell lines and in an animal model of breast cancer. PNPC remarkably suppressed mammary and hepatocellular carcinoma cells proliferation (P < 0.05). Under the dosing procedure, PNPC was safe at 31.25 mg/kg and lower doses. Higher doses demonstrated minimal hepatocellular and renal toxicity in paraclinical and histopathological examinations. Tumor take rate in PNPC-treated group was 37.5% compared with 87.5% in control (P < 0.05). Average tumor size and weight were significantly lower in PNPC group than control (P < 0.05). PNPC increased proapoptotic Bax protein expression (P < 0.05). Antiapoptotic Bcl-2 protein expression, however, was lower in PNPC-treated animals than the control ones (P < 0.05). In addition, proliferative and angiogenic parameters were statistically decreased in PNPC-treated animals (P < 0.05). These results highlight the suppressing role for PNPC in in vitro and in vivo tumor growth models. Our findings provide credible evidence for superior biocompatibility of the polymeric nanocarrier in pharmacological arena together with an excellent tumor-suppressing response. PMID:25793208

  16. Neutron reflectivity studies of composite nanoparticle - copolymer thin films

    NASA Astrophysics Data System (ADS)

    Lauter-Pasyuk, V.; Lauter, H. J.; Ausserre, D.; Gallot, Y.; Cabuil, V.; Hamdoun, B.; Kornilov, E. I.

    1998-06-01

    Neutron reflection was used for the investigation of a new class of copolymers - composite materials, consisting of symmetric polystyrene-polybuthylmethacrylate (PS-PBMA) diblock copolymer with incorporated nanoparticles γ-Fe 2O 3 of a few nanometers in diameter. The presence of the nanoparticles induces an elastic distortion of the copolymer matrix. From the experiments we obtained information about the lamellar order of the polymer matrix, the distribution of the nanoparticles in the film and the distortion of the interfaces caused by the nanoparticles.

  17. Self-Consistent Field Approach for Cross-Linked Copolymer Materials

    NASA Astrophysics Data System (ADS)

    Schmid, Friederike

    2013-07-01

    A generalized self-consistent field approach for polymer networks with a fixed topology is developed. It is shown that the theory reproduces the localization of cross-links, which is characteristic for gels. The theory is then used to study the order-disorder transition in regular networks of end-linked diblock copolymers. Compared to diblock copolymer melts, the transition is shifted towards lower values of the incompatibility parameter χ (the Flory- Huggins parameter). Moreover, the transition becomes strongly first order already at the mean-field level. If stress is applied, the transition is further shifted and finally vanishes in a critical point.

  18. Directed Assembly of Lamellae Forming Block Copolymer Thin Films near the Order-Disorder Transition

    SciTech Connect

    Kim, Sangwon; Nealey, Paul F.; Bates, Frank S.

    2014-08-07

    The impact of thin film confinement on the ordering of lamellae was investigated using symmetric poly(styrene-b-[isoprene-ran-epoxyisoprene]) diblock copolymers bound by nonpreferential wetting interfaces. The order–disorder transition temperature (TODT) and the occurrence of composition fluctuations in the disordered state are not significantly affected by two-dimensional confinement. Directed self-assembly using chemical patterning is demonstrated near TODT. These results establish the minimum feature size attainable using directed self-assembly of a given diblock copolymer system.

  19. Dispersion characteristics of nanocomposites based on functionalized block copolymers

    NASA Astrophysics Data System (ADS)

    Ke, Linping

    The dispersion characteristics of organoclay nanocomposites based on functionalized block copolymers have been investigated. For the investigation, polystyrene-block-polybutadiene (SB diblock) copolymers synthesized via anionic polymerization were first hydroxylated via hydroboration/oxidation to obtain polystyrene-block-hydroxylated polybutadiene (SBOH diblock) copolymers. Then, the SBOH diblock copolymer was attached with pyridine, pyrimidine, terpyridine, or terpyridine-Ruthenium (Ru) complex functional groups to obtain SB-pyridine, SB-pyrimidine, SB-terpyridine (SB-Terpy), and SB-Terpy-Ru complex diblock copolymers. Subsequently, each of these functionalized block copolymers was used to prepare, via solution blending, organoclay nanocomposites, for which natural clay (montmorillonite, MMT) and two commercial organoclays (Cloisite 30B and Cloisite 15A) were employed. The dispersion characteristics of the organoclay nanocomposites were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and oscillatory rheometry (OR). We have made the following observations. The SBOH/Cloisite 30B nanocomposite had a very high degree of dispersion of Cloisite 30B aggregates, whereas the SBOH/Cloisite 15A and SBOH/MMT nanocomposites had a very low degree of dispersion of the aggregates of Cloisite 15A or MMT. In situ Fourier transform infrared (FTIR) spectroscopy has revealed that hydrogen bonds were formed between the hydroxyl groups in the SBOH diblock copolymer and the surfactant residing at the surface of Cloisite 30B in the former nanocomposite, yielding a very high degree of dispersion of Cloisite 30B aggregates, while no hydrogen bonds were formed in the latter two nanocomposites. The (SB-pyridine)/Cloisite 30B nanocomposite had intercalation of aggregates of Cloisite 30B, while the (SB-pyridine)/Cloisite 15A and (SB-pyridine)/MMT nanocomposites had a very low degree of dispersion of the aggregates of Cloisite 15A or MMT in the SB

  20. Light-emitting block copolymers composition, process and use

    DOEpatents

    Ferraris, John P.; Gutierrez, Jose J.

    2006-11-14

    Generally, and in one form, the present invention is a composition of light-emitting block copolymer. In another form, the present invention is a process producing a light-emitting block copolymers that intends polymerizing a first di(halo-methyl) aromatic monomer compound in the presence of an anionic initiator and a base to form a polymer and contacting a second di(halo-methyl) aromatic monomer compound with the polymer to form a homopolymer or block copolymer wherein the block copolymer is a diblock, triblock, or star polymer. In yet another form, the present invention is an electroluminescent device comprising a light-emitting block copolymer, wherein the electroluminescent device is to be used in the manufacturing of optical and electrical devices.

  1. Preparation and Morphology of ABn Mictoarm Block Copolymers

    NASA Astrophysics Data System (ADS)

    Takano, Atsushi; Watanabe, Momoka; Asai, Yusuke; Suzuki, Jiro; Matsushita, Yushu

    A series of ABn mictoarm block copolymers (bottle brush copolymers) consisting of polystyrene (S) as a backbone and polyisoprenes (I) as grafts were precisely synthesized by an anionic polymerization, and their microphase-separated structures were investigated by transmission electron microscopy (TEM) and small-angle X-ray scattering(SAXS). A copolymer with composition of φS =0.57 and number of grafts(n) of 10 shows characteristic cylindrical structure, where microdomains of S reveals hexagonal cross section with non-constant mean curvature interface. While a sample with composition of φS =0.37 and number of grafts(n) of 40 shows spherical structure with rather large S isolated domains and characteristic domain packing manner was found. Furthermore composition dependence of microphase-separated structures for SIn mictoarm block copolymers were investigated and compared to SI diblock copolymer system.

  2. Solvent enhanced block copolymer ordering in thin films

    NASA Astrophysics Data System (ADS)

    Misner, Matthew J.

    Diblock copolymer self-assembly of materials is emerging as a key element in the fabrication of functional nanostructured materials. By solvent casting or solvent annealing block copolymer thin films, we have demonstrated methods to produce diblock copolymer films with highly oriented, close-packed arrays of nanoscopic cylindrical domains with a high degree of long-range lateral order with few defects. The solvent imparts a high degree of mobility in the microphase-separated copolymer that enables a rapid removal of defects and a high degree of lateral order. Though the use of a selective cosolvent during solvent casting, it was found that the microdomain size and spacing could be increased, leading to a size-tunable system. Additionally, the presence of water also led to the ability to control the microdomain orientation during solvent annealing. Ionic complexation within cylinder-forming PS- b-EO block copolymer thin films was also investigated, where added salts bind PEO block as the minor component. Small amounts of added salts, on the order a few ions per chain, show large effects on the ordering of the copolymer films during solvent annealing. By using gold or cobalt salts, well-organized patterns of nanoparticles can be generated in the copolymer microdomains. Topographically and chemically patterned surfaces were used as a route to sectorizing and controlling the lattice orientation of copolymer films. Topographically patterned surfaces allow well-defined boundaries to confine the copolymer microdomains on a surface and effectively direct the ordering and grain orientation of the copolymer microdomains. Chemically patterned surfaces provide a route to direct the block copolymer ordering on completely flat surface, which may have advantages in applications where adding additional topography may be undesirable. To generate nanoporous templates from PS-b-PEO bases materials several routs were followed. The first route was through the addition and selective

  3. Nanopatterning of Viruses and Proteins Using Microphase Separated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Cresce, Arthur; Lewandowski, Angela; Bentley, William; Kofinas, Peter

    2006-03-01

    Diblock copolymers containing nickel ions have been prepared that are capable of selectively adsorbing histidine-tagged green fluorescent protein (hisGFP), and also binding tobacco mosaic virus (TMV). A block copolymer of norbornene and norbornene dicarboxylic acid was synthesized using ring-opening metathesis polymerization. A 400/50 block ratio achieved a spherical microphase-separated morphology with roughly 20 nm diameter dicarboxylic acid spheres. The spherical phase was exposed to nickel ions in solution, templating the formation of nickel nanoparticles. This process gave a nickel-loaded diblock copolymer film whose surface was used to chelate hisGFP. Fluorescence spectroscopy and TEM confirmed the presence of the protein on the polymer surface. A sulfonated triblock copolymer was loaded with nickel ions using a similar solution-doping procedure. The morphology of this copolymer was lamellar, and its sulfonated block was loaded with nickel ions. TEM studies revealed the presence of the virus on the surface of the copolymer and showed that the bond between the TMV and the polymer surface can withstand severe detergent washes.

  4. MEAN FIELD AND MONTE CARLO MODELING OF MULTIBLOCK COPOLYMERS

    SciTech Connect

    K. RASMUSSEN; ET AL

    2001-01-01

    The authors discuss and apply extensions needed to treat multiblock copolymers within the mean field theoretical framework for microphase separation in diblock copolymer metals, originally due to Leibler. The mean field calculations are complemented by lattice Monte Carlo realizations using the bond fluctuation model. They find that the microphase separation transition occurs at larger {sub {chi}}N as the number of blocks in increased beyond two (i.e., beyond diblock), and that the characteristic length scale of the emerging morphology decreases as the number of blocks increases. The latter prediction is in qualitative agreement with published experimental results due to Sontak and co-workers for model multiblock poly(styrene-isoprene) systems and recent results due to Hjelm and co-workers for a segmented poly(ester-urethane) relevant to Los Alamos interests. Additionally, the mean field predictions and bond fluctuation realizations yield consistent results.

  5. Comparing Fluid and Elastic Block Copolymer Shells

    NASA Astrophysics Data System (ADS)

    Rozairo, Damith; Croll, Andrew B.

    2014-03-01

    Emulsions can be stabilized with the addition of an amphiphilic diblock copolymer, resulting in droplets surrounded and protected by a polymer monolayer. Such droplets show considerable promise as advanced cargo carriers in pharmaceuticals or cosmetics due to their strength and responsiveness. Diblock copolymer interfaces remain mostly fluid and may not be able to attain the mechanical performance desired by industry. To strengthen block copolymer emulsion droplets we have developed a novel method for creating thin elastic shells using polystyrene-b-poly(acrylic acid)-b-polystyrene (PS-PAA-PS). Characterization of the fluid filled elastic shells is difficult with traditional means which lead us to develop a new and general method of mechanical measurement. Specifically, we use laser scanning confocal microscopy to achieve a high resolution measure of the deformation of soft spheres under the influence of gravity. To prove the resilience of the technique we examine both a polystyrene-b-poly(ethylene oxide) (PS-PEO) stabilized emulsion and the PS-PAA-PS emulsion. The mechanical measurement allows the physics of the polymer at the interface to be examined, which will ultimately lead to the rational development of these technologies.

  6. Frank-Kasper sigma phase stabilized by tailored architectures of block copolymers

    NASA Astrophysics Data System (ADS)

    Li, Weihua; Liu, Meijiao; Xie, Nan; Qiu, Feng; Shi, An-Chang

    Block copolymer self-assembly forms diverse interesting ordered morphologies, of which the spherical phase is of particular interest because it resembles the similar space symmetry as atomic crystals and has a tunable period on nanoscale. Moreover, the packing lattice of spherical domains dictated by the adjustable competition between the entropic and interfacial energies is programmable. For AB diblock copolymers, it has been known that the stable spherical phase is mainly bcc except for a very narrow region of fcc at the vicinity of the order-disorder transition. When introducing variable number of blocks and architectures to form complex AB-type block copolymers, the A15 phase was predicted as stable. However, a striking experiment observed a new spherical phase, the complex Frank-Kasper sigma phase that consists of 30 spheres in a unit cell, in the PI-b-PLA diblock copolymer as well as a SISO tetrablock terpolymer. Inspired by this experiment, we studied the stability of all known spherical phases of fcc, bcc, A15 and sigma in various block copolymers including conformationally asymmetric AB diblock, ABm miktoarm, and BABC tetrablock copolymers. We have revealed the formation mechanism of the nonclassical A15 and sigma phases due to the tailored architectures.

  7. Theory and Simulations of Tapered Diblock Polymers

    NASA Astrophysics Data System (ADS)

    Hall, Lisa M.; Seo, Youngmi; Brown, Jonathan R.

    We study tapered block polymers, AB diblock polymers with a gradient region inserted between the pure A and B blocks such that composition smoothly transitions from A to B (or B to A in the case of inverse tapers). Phase diagrams were created using self consistent field theory (SCFT), and coarse-grained molecular dynamics (MD) simulations were used to study polymer conformations and diffusion, including diffusion of monomer-sized penetrants preferentially dissolved in one of the phases. As has been observed experimentally, we find that tapering makes the A and B blocks more miscible, decreasing domain spacing and shifting the order to disorder transition to lower temperatures. We predict a widening of the bicontinuous double gyroid region of the phase diagram for moderate length normal tapers versus diblocks, suggesting taper length can be used as a control parameter to obtain network phases even at high molecular weight, as may be desirable in transport applications. Additionally, in some inverse tapered systems, SCFT predicts phases not present in the standard AB diblock phase diagram, and MD simulations show how the chains fold back and forth across the interface. In these inverse tapered polymers, as segregation strength is increased, the competing effects of folding and stretching produces lamellae that have domain spacing nearly independent of temperature. We also find that diffusion of penetrants in normal tapers is significantly faster than that in inverse tapers, which is likely related to their unusual conformations. This material is based upon work supported by DOE Grant SC0014209.

  8. Mechanism of Molecular Exchange in Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Choi, Soo-Hyung; Lodge, Timothy; Bates, Frank

    2010-03-01

    Compared to thermodynamic structure, much less has been known about the kinetics of block copolymer micelles which should underlay the attainment of thermodynamic equilibrium. In this presentation, molecular exchange between spherical micelles formed by isotopically labeled diblock copolymers was investigated using time-resolved small-angle neutron scattering. Two pairs of structurally matched poly(styrene-b-ethylene-alt-propylene) (PS-PEP) were synthesized and dispersed in isotopic mixture of squalane, highly selective to PEP block. Each pair includes polymers with fully deuterated (dPS-PEP) and a normal (hPS-PEP) PS blocks. Temperature dependence of the micelle exchange rate R(t) is consistent with melt dynamics for the core polymer. Furthermore, R(t) is significantly sensitive to the core block length N due to the thermodynamic penalty associated with ejecting a core block into the solvent. This hypersensitivity, combined with modest polydispersity in N, leads to an approximately logarithmic decay in R(t).

  9. Graft-through Synthesis and Assembly of Janus Bottlebrush Polymers from A-Branch-B Diblock Macromonomers.

    PubMed

    Kawamoto, Ken; Zhong, Mingjiang; Gadelrab, Karim R; Cheng, Li-Chen; Ross, Caroline A; Alexander-Katz, Alfredo; Johnson, Jeremiah A

    2016-09-14

    We report the synthesis of Janus bottlebrush block copolymers by graft-through polymerization of branched diblock macromonomers. Self-assembly of the bottlebrushes was characterized by small-angle X-ray scattering, atomic force microscopy, and scanning electron microscopy. Phase separation and packing models of the bottlebrushes were computed, and their self-assembly behavior was corroborated experimentally in bulk and in thin films. Lamellar, hexagonal cylinder, and gyroid phases were observed and modeled. The A-branch-B Janus bottlebrush structure provides several unique advantages in the context of bottlebrush polymer assembly, including access to the first examples of gyroid phases.

  10. Graft-through Synthesis and Assembly of Janus Bottlebrush Polymers from A-Branch-B Diblock Macromonomers.

    PubMed

    Kawamoto, Ken; Zhong, Mingjiang; Gadelrab, Karim R; Cheng, Li-Chen; Ross, Caroline A; Alexander-Katz, Alfredo; Johnson, Jeremiah A

    2016-09-14

    We report the synthesis of Janus bottlebrush block copolymers by graft-through polymerization of branched diblock macromonomers. Self-assembly of the bottlebrushes was characterized by small-angle X-ray scattering, atomic force microscopy, and scanning electron microscopy. Phase separation and packing models of the bottlebrushes were computed, and their self-assembly behavior was corroborated experimentally in bulk and in thin films. Lamellar, hexagonal cylinder, and gyroid phases were observed and modeled. The A-branch-B Janus bottlebrush structure provides several unique advantages in the context of bottlebrush polymer assembly, including access to the first examples of gyroid phases. PMID:27580971

  11. Formation of microphase-separated structure with half pitch less than 5.0nm formed by multiblock copolymers for nanolithographic application

    NASA Astrophysics Data System (ADS)

    Kosaka, T.; Kawaguchi, Y.; Himi, T.; Shimizu, T.; Hirahara, K.; Takano, A.; Matsushita, Y.

    2016-03-01

    In this study, we have successfully synthesized polystyrene-b-poly(4-hydroxystyrene) (SH) with molecular weight of 14k and with narrow molecular weight distribution by living anionic polymerization, and the obtained SH diblock copolymer has formed the definite alternative lamellar structure with the half pitch of 10.4nm. In order to achieve narrow half pitch pattern, diblock copolymer (XY) with stronger segregated polymer components with high chi (X and Y) was used, and it was confirmed that the high-chi XY diblock copolymer having molecular weight of 6k showed the clear lamellar structure with the half pitch of 5.5nm. Furthermore syntheses of multiblock copolymers with high chi such as YXY (where X is Si contained polymer) triblock and XYXY (where XYXY is Si contained high χ polymer) tetrablock copolymers were attempted to achieve the narrower half pitch pattern less than 5 nm, and the multiblock copolymers with aimed molecular weight and narrow molecular weight distribution have been successfully obtained. From the highchi multiblock copolymers, it was confirmed that the formation of the definite microphase-separated structure with the half pitch of 4.8nm was observed by TEM and SAXS measurements. Moreover we have developed a large-scale living anionic polymerization apparatus for the preparation of well-defined block copolymers scaled over 3kg.

  12. Chain exchange in triblock copolymer micelles

    NASA Astrophysics Data System (ADS)

    Lu, Jie; Lodge, Timothy; Bates, Frank

    2015-03-01

    Block polymer micelles offer a host of technological applications including drug delivery, viscosity modification, toughening of plastics, and colloidal stabilization. Molecular exchange between micelles directly influences the stability, structure and access to an equilibrium state in such systems and this property recently has been shown to be extraordinarily sensitive to the core block molecular weight in diblock copolymers. The dependence of micelle chain exchange dynamics on molecular architecture has not been reported. The present work conclusively addresses this issue using time-resolved small-angle neutron scattering (TR-SANS) applied to complimentary S-EP-S and EP-S-EP triblock copolymers dissolved in squalane, a selective solvent for the EP blocks, where S and EP refer to poly(styrene) and poly(ethylenepropylene), respectively. Following the overall SANS intensity as a function of time from judiciously deuterium labelled polymer and solvent mixtures directly probes the rate of molecular exchange. Remarkably, the two triblocks display exchange rates that differ by approximately ten orders of magnitude, even though the solvophobic S blocks are of comparable size. This discovery is considered in the context of a model that successfully explains S-EP diblock exchange dynamics.

  13. A one-pot synthesis of polysulfane-bearing block copolymer nanoparticles with tunable size and refractive index.

    PubMed

    Lim, Jeewoo; Cho, Yunshik; Kang, Eun-Hye; Yang, Sanghee; Pyun, Jeffrey; Choi, Tae-Lim; Char, Kookheon

    2016-02-11

    A one-pot synthesis of sulfur-rich polymer nanoparticles through a ring-opening metathesis polymerization is reported. The nanoparticles are formed in situ from diblock copolymers containing a polynorbornene derivative bearing cyclic polysulfanes. The refractive indices of the resulting nanoparticles are readily controlled in the range from 1.54 to nearly 1.65.

  14. Self-assembly of crystalline nanotubes from monodisperse amphiphilic diblock copolypeptoid tiles.

    PubMed

    Sun, Jing; Jiang, Xi; Lund, Reidar; Downing, Kenneth H; Balsara, Nitash P; Zuckermann, Ronald N

    2016-04-12

    The folding and assembly of sequence-defined polymers into precisely ordered nanostructures promises a class of well-defined biomimetic architectures with specific function. Amphiphilic diblock copolymers are known to self-assemble in water to form a variety of nanostructured morphologies including spheres, disks, cylinders, and vesicles. In all of these cases, the predominant driving force for assembly is the formation of a hydrophobic core that excludes water, whereas the hydrophilic blocks are solvated and extend into the aqueous phase. However, such polymer systems typically have broad molar mass distributions and lack the purity and sequence-defined structure often associated with biologically derived polymers. Here, we demonstrate that purified, monodisperse amphiphilic diblock copolypeptoids, with chemically distinct domains that are congruent in size and shape, can behave like molecular tile units that spontaneously assemble into hollow, crystalline nanotubes in water. The nanotubes consist of stacked, porous crystalline rings, and are held together primarily by side-chain van der Waals interactions. The peptoid nanotubes form without a central hydrophobic core, chirality, a hydrogen bond network, and electrostatic or π-π interactions. These results demonstrate the remarkable structure-directing influence of n-alkane and ethyleneoxy side chains in polymer self-assembly. More broadly, this work suggests that flexible, low-molecular-weight sequence-defined polymers can serve as molecular tile units that can assemble into precision supramolecular architectures. PMID:27035944

  15. Self-assembly of crystalline nanotubes from monodisperse amphiphilic diblock copolypeptoid tiles

    PubMed Central

    Sun, Jing; Jiang, Xi; Lund, Reidar; Downing, Kenneth H.; Balsara, Nitash P.; Zuckermann, Ronald N.

    2016-01-01

    The folding and assembly of sequence-defined polymers into precisely ordered nanostructures promises a class of well-defined biomimetic architectures with specific function. Amphiphilic diblock copolymers are known to self-assemble in water to form a variety of nanostructured morphologies including spheres, disks, cylinders, and vesicles. In all of these cases, the predominant driving force for assembly is the formation of a hydrophobic core that excludes water, whereas the hydrophilic blocks are solvated and extend into the aqueous phase. However, such polymer systems typically have broad molar mass distributions and lack the purity and sequence-defined structure often associated with biologically derived polymers. Here, we demonstrate that purified, monodisperse amphiphilic diblock copolypeptoids, with chemically distinct domains that are congruent in size and shape, can behave like molecular tile units that spontaneously assemble into hollow, crystalline nanotubes in water. The nanotubes consist of stacked, porous crystalline rings, and are held together primarily by side-chain van der Waals interactions. The peptoid nanotubes form without a central hydrophobic core, chirality, a hydrogen bond network, and electrostatic or π–π interactions. These results demonstrate the remarkable structure-directing influence of n-alkane and ethyleneoxy side chains in polymer self-assembly. More broadly, this work suggests that flexible, low–molecular-weight sequence-defined polymers can serve as molecular tile units that can assemble into precision supramolecular architectures. PMID:27035944

  16. Effects of Blockiness on the phase behavior of random copolymers

    NASA Astrophysics Data System (ADS)

    Vanderwoude, Gordon; Shi, An-Chang

    Theoretical study of random block copolymers remains a challenging topic due in part to the sheer enormity of their phase space. In this study we use the self-consistent field theory to investigate the phase behaviour of linear (AB)n-type and (AB)n-C-type multiblock copolymers with randomly distributed A and B blocks. In particular, we examine the effect of ``blockiness'' of the random copolymers on the formation of ordered phases. The blockiness can be quantified by the average length of individual A or B blocks, which can be taken as a measure of the heterogeneity of the random copolymers. We observed that the critical value of the χ parameter, at which the order-disorder transition occurs, decreases with increasing blockiness in the (AB)n copolymers. We also observed that the phase behaviour of the (AB)n-C copolymers depends strongly on the blockiness of the random chain. In particular, the blockiness governs whether or not the A/B blocks can phase separate within the A/B domains, thus dictating whether the (AB)n-C behaves as A/B-C diblock copolymers or as ABC terpolymers. The theoretical phase diagrams will be compared with available experiments.

  17. Manipulating Ordering Transitions in Interfacially Modified Block Copolymers

    SciTech Connect

    Singh, N.; Tureau, M; Epps, T

    2009-01-01

    We report a synthetic strategy that allows us to manipulate the interfacial region between blocks and control ordering transitions in poly(isoprene-b-styrene) [P(I-S)] block copolymers. This interfacial modification is accomplished by combining a semi-batch feed with anionic polymerization techniques. Using this approach, we are able to control the segmental composition and molecular interactions in our phase-separated block copolymers, independent of molecular weight and block constituents. A library of copolymers is prepared with various interfacial modifications to examine the effect of interfacial composition on copolymer self-assembly. The morphological characteristics of the self-assembled structures are investigated using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). Normal and inverse tapered block copolymers, containing approximately 15-35 vol% tapered material, show a measurable decrease in the order-disorder transition temperature (TODT) relative to the corresponding non-tapered diblock copolymers, with the inverse tapered materials showing the greatest deviation in TODT. Additionally, TODT was inversely related to the volume fraction of the tapered region in both normal and inverse tapered copolymer materials.

  18. Using Tapered Block Copolymers to Create Conducting Nanomaterials

    NASA Astrophysics Data System (ADS)

    Epps, Thomas, III

    2014-03-01

    Soft materials, such as polymers, colloids, surfactants, and liquid crystals, are a technologically important class of matter employed in a variety of applications. One sub-class of soft material, block copolymers, provides the opportunity to design materials with attractive chemical and mechanical properties based on the ability to assemble into periodic structures with nanoscale domain spacings. Several applications for block copolymers currently under investigation in my group include battery and fuel cell membranes, analytical separations membranes, nano-tool templates, precursors to electronic arrays, and drug delivery vehicles. One area of recent progress in the group focuses on the behavior of conventional block copolymer and tapered block copolymer systems for lithium battery membrane applications. We find that we can tune poly(styrene- b-ethylene oxide) diblock copolymer nanostructures by adjusting the lithium counterion and lithium salt concentration, as well as the taper volume fraction and composition. Additionally, we can estimate the effective interaction parameters (χeff) for the salt-doped copolymers to determine the overall influence of tapering on the energetics of copolymer assembly. These tapered materials allow us to design nanostructured membrane systems with increased conductivity and improved mechanical properties in ion transport devices. We gratefully acknowledge AFOSR-PECASE (FA9550-09-1-0706) and NSF-CAREER (DMR-0645586) for financial support.

  19. Defects in a Noncentrosymmetric Lemellar Block Copolymer Blend

    SciTech Connect

    Chen, Shujun; Gido, Samuel; Tsoukatos, Thodoris; Avgeropoulos, Apostolos; Hadjichristidis, Nikos; Hong, Kunlun; Mays, Jimmy

    2005-01-01

    Here we report results from a defect study on the noncentrosymmetric (NCS) lamellar blend of an ABCD tetrablock copolymer and an AD diblock copolymer. The block copolymers used were polystyrene-block-polybutadiene-block-polyisoprene-block-polycyclohexadiene and polystyrene-block-polycyclohexadiene. Coexisting tetrablock-rich mixed centrosymmetric (CS) and NCS lamellar morphologies were seen in TEM, as predicted by the mean-field theory. NCS grain boundary defects similar to those in CS lamellar systems were observed as well as new defects unique to NCS layered systems, such as chain polarity reversals and kink bands with dilation or compression of the layers. In addition to morphology observations, geometrical and energetic calculations were performed on several new NCS defects, which are in good agreement with experimental results.

  20. High intensity focused ultrasound responsive metallo-supramolecular block copolymer micelles.

    PubMed

    Liang, Bo; Tong, Rui; Wang, Zhenhua; Guo, Shengwei; Xia, Hesheng

    2014-08-12

    The metal-supramolecular diblock copolymer containing mechano-labile bis(terpyridine)-Cu(II) complex linkage in the junction point was synthesized. These metal-ligand containing amphiphilic copolymers are able to self-assemble in aqueous solution to form spherical micelles with poly(propylene glycol) block forming the hydrophobic core. It is found that high intensity focused ultrasound can open the copolymer micelles and trigger the release of the payload in the micelle. The micellar properties and release kinetics of encapsulated guest molecule in response to ultrasound stimuli were investigated. The weak Cu(II)-terpyridine dynamic bond in the copolymer chain can be cleaved under ultrasound and thus leads to the disruption of the copolymer micelle and the release of loaded cargo. This study will open up a new way for the molecular design of ultrasound modulated drug delivery systems. PMID:25072274

  1. Mixing thermodynamics of block-random copolymers

    NASA Astrophysics Data System (ADS)

    Beckingham, Bryan Scott

    Random copolymerization of A and B monomers represents a versatile method to tune interaction strengths between polymers, as ArB random copolymers will exhibit a smaller effective Flory interaction parameter chi; (or interaction energy density X) upon mixing with A or B homopolymers than upon mixing A and B homopolymers with each other, and the ArB composition can be tuned continuously. Thus, the incorporation of a random copolymer block into the classical block copolymer architecture to yield "block-random" copolymers introduces an additional tuning mechanism for the control of structure-property relationships, as the interblock interactions and physical properties can be tuned continuously through the random block's composition. However, typical living or controlled polymerizations produce compositional gradients along the "random" block, which can in turn influence the phase behavior. This dissertation demonstrates a method by which narrow-distribution copolymers of styrene and isoprene of any desired composition, with no measurable down-chain gradient, are synthesized. This synthetic method is then utilized to incorporate random copolymers of styrene and isoprene as blocks into block-random copolymers in order to examine the resulting interblock mixing thermodynamics. A series of well-defined near-symmetric block and block-random copolymers (S-I, Bd-S, I-SrI, S-SrI and Bd-S rI diblocks, where S is polystyrene, I is polyisoprene and Bd is polybutadiene), with varying molecular weight and random-block composition are synthesized and the mixing thermodynamics---via comparison of their interaction energy densities, X---of their hydrogenated derivatives is examined through measurement of the order-disorder transition (ODT) temperature. Hydrogenated derivatives of I-SrI and S-SrI block-random copolymers, both wherein the styrene aromaticity is retained and derivatives wherein the styrene units are saturated to vinylcyclohexane (VCH), are found to hew closely to the

  2. Preparation of shell cross-linked nano-objects from hybrid-peptide block copolymers.

    PubMed

    Rodríguez-Hernández, Juan; Babin, Jérôme; Zappone, Bruno; Lecommandoux, Sébastien

    2005-01-01

    Supramolecular structures formed by self-assembly of diblock copolymers in solution are stable over restricted environmental conditions: concentration, temperature, pH, or ion strength among others. To enlarge their domain of application, it appears necessary to develop stabilization strategies. We report here different strategies to stabilize the shell of micelles formed by self-assembly of amphiphilic polydiene-b-polypeptide diblock copolymers. For this purpose, covalent bonds can be formed between either amine or carboxylic acid groups distributed along the soluble peptide block and a cross-linking agent that contains respectively aldehyde or amine functions. Shell stabilization affords systems with unique properties that combine three main advantages: shape persistence, control of the porosity, and stimuli-responsive behavior. The covalent capture of such macromolecular objects has been studied by light scattering, AFM, and conductimetry measurements.

  3. Modification of Blend Film Pattern Formation with Block Copolymer Additives

    NASA Astrophysics Data System (ADS)

    Sung, L.; Satija, S. K.; Karim, A.; Douglas, J. F.; Han, C. C.

    1997-03-01

    The kinetics of phase separation and morphology of polymer blend films of polystyrene(PS) and polybutadiene(PB) with and without diblock copolymer(PS-b-PB) is examined by optical and atomic force microscropy. The thicker PS/PB binary blend film (2000 Åexhibited essentially no surface pattern formation while spinodal decomposition-like patterns were exhibited by thinner films (<= 1000 ÅThis change is interpreted in terms of a suppression of surface-directed spinodal decomposition in the thinner films. A change in the coarsening kinetics was also observed in the thin films as the thickness was varied from 1000 Åto 200 Åand was interpreted as a crossover from three (bulk-like) to two-dimensional kinetics(Sung et al., Phys. Rev. Lett. 76), 4368 (1996).. The addition of diblock copolymer changed the characteristic dimension at which the surface patterning occurred and the surface pattern formation required thinner film. Neutron reflectivity measurements were carried out to study the density profile of diblcok copolymer on phase separation transverse to the silicon surface to understand this effect.

  4. Acrylic AB and ABA block copolymers based on poly(2-ethylhexyl acrylate) (PEHA) and poly(methyl methacrylate) (PMMA) via ATRP.

    PubMed

    Haloi, Dhruba J; Ata, Souvik; Singha, Nikhil K; Jehnichen, Dieter; Voit, Brigitte

    2012-08-01

    Acrylic block copolymers have several advantages over conventional styrenic block copolymers, because of the presence of a saturated backbone and polar pendant groups. This investigation reports the preparation and characterization of di- and triblock copolymers (AB and ABA types) of 2-ethylhexyl acrylate (EHA) and methyl methacrylate (MMA) via atom transfer radical polymerization (ATRP). A series of block copolymers, PEHA-block-PMMA(AB diblock) and PMMA-block-PEHA-block-PMMA(ABA triblock) were prepared via ATRP at 90 °C using CuBr as catalyst in combination with N,N,N',N″,N″-pentamethyl diethylenetriamine (PMDETA) as ligand and acetone as additive. The chemical structure of the macroinitiators and molar composition of block copolymers were characterized by (1)H NMR analysis, and molecular weights of the polymers were analyzed by GPC analysis. DSC analysis showed two glass transition temperatures (T(g)), indicating formation of two domains, which was corroborated by AFM analysis. Small-angle X-ray scattering (SAXS) analysis of AB and ABA block copolymers showed scattering behavior inside the measuring limits indicating nanophase separation. However, SAXS pattern of AB diblock copolymers indicated general phase separation only, whereas for ABA triblock copolymer an ordered or mixed morphology could be deduced, which is assumed to be the reason for the better mechanical properties achieved with ABA block copolymers than with the AB analogues.

  5. Rectification mechanism in diblock oligomer molecular diodes.

    PubMed

    Oleynik, I I; Kozhushner, M A; Posvyanskii, V S; Yu, L

    2006-03-10

    We investigated a mechanism of rectification in diblock oligomer diode molecules that have recently been synthesized and showed a pronounced asymmetry in the measured I-V spectrum. The observed rectification effect is due to the resonant nature of electron transfer in the system and the localization properties of bound state wave functions of resonant states of the tunneling electron interacting with an asymmetric molecule in an electric field. The asymmetry of the tunneling wave function is enhanced or weakened depending on the polarity of the applied bias. The conceptually new theoretical approach, the Green's function theory of sub-barrier scattering, is able to provide a physically transparent explanation of this rectification effect based on the concept of the bound state spectrum of a tunneling electron. The theory predicts the characteristic features of the I-V spectrum in qualitative agreement with experiment. PMID:16606295

  6. Imidazolium-based Block Copolymers as Solid-State Separators for Alkaline Fuel Cells and Lithium Ion Batteries

    NASA Astrophysics Data System (ADS)

    Nykaza, Jacob Richard

    In this study, polymerized ionic liquid (PIL) diblock copolymers were explored as solid-state polymer separators as an anion exchange membrane (AEM) for alkaline fuel cells AFCs and as a solid polymer electrolyte (SPE) for lithium-ion batteries. Polymerized ionic liquid (PIL) block copolymers are a distinct set of block copolymers that combine the properties of both ionic liquids (e.g., high conductivity, high electrochemical stability) and block copolymers (e.g., self-assembly into various nanostructures), which provides the opportunity to design highly conductive robust solid-state electrolytes that can be tuned for various applications including AFCs and lithium-ion batteries via simple anion exchange. A series of bromide conducting PIL diblock copolymers with an undecyl alkyl side chain between the polymer backbone and the imidazolium moiety were first synthesized at various compositions comprising of a PIL component and a non-ionic component. Synthesis was achieved by post-functionalization from its non-ionic precursor PIL diblock copolymer, which was synthesized via the reverse addition fragmentation chain transfer (RAFT) technique. This PIL diblock copolymer with long alkyl side chains resulted in flexible, transparent films with high mechanical strength and high bromide ion conductivity. The conductivity of the PIL diblock copolymer was three times higher than its analogous PIL homopolymer and an order of magnitude higher than a similar PIL diblock copolymer with shorter alkyl side chain length, which was due to the microphase separated morphology, more specifically, water/ion clusters within the PIL microdomains in the hydrated state. Due to the high conductivity and mechanical robustness of this novel PIL block copolymer, its application as both the ionomer and AEM in an AFC was investigated via anion exchange to hydroxide (OH-), where a maximum power density of 29.3 mW cm-1 (60 °C with H2/O2 at 25 psig (172 kPa) backpressure) was achieved. Rotating disk

  7. Development of new generation of copolymers via reactive extrusion in a twin screw extruder and application in various PVC blends

    NASA Astrophysics Data System (ADS)

    Kim, In

    Polymerization in twin screw extruders has largely involved homopolymers. Here we generalize this and polymerize a range of copolymers and terpolymers including epsilon-caprolactam(CA), o-lauryl lactam(LA), epsilon-caprolactone(CL), and gamma-butyrolactone(GBL) in a modular intermeshing co-rotating twin screw extruder. We considered different types of copolymer structures (di-block, tri-block, and random-block) and different backbones of copolymer(lactams-lactones) as well as the variables of temperature profile, screw speed, monomer feed rate, the ratio of monomer to initiator, and feeding order of co-monomers on reactive extrusion of polyamides-polylactones based (co)polymers. Specially designed block copolymers have played a role as compatibilizing agents in the system of immiscible polymer blends. We apply the di-block copolymer(P(LA-b-CL)) and random block copolymer (P(LA/CA-b-CL)) produced by reactive extrusion as a compatibilizing agent in immiscible polymer blend systems: (i) poly(vinyl chloride) (PVC)/polyamide 12 (PA12), (ii) PVC/polypropylene(PP), and (iii) PVC/Ethylene-propylene-non-conjugated diene elastomer(EPDM).

  8. Self-assembly of block copolymers grafted onto a flat substrate: Recent progress in theory and simulations

    NASA Astrophysics Data System (ADS)

    Zheng, Wang; Bao-Hui, Li

    2016-01-01

    Block copolymers are a class of soft matter that self-assemble to form ordered morphologies on the scale of nanometers, making them ideal materials for various applications. These applications directly depend on the shape and size of the self-assembled morphologies, and hence, a high degree of control over the self-assembly is desired. Grafting block copolymer chains onto a substrate to form copolymer brushes is a versatile method to fabricate functional surfaces. Such surfaces demonstrate a response to their environment, i.e., they change their surface topography in response to different external conditions. Furthermore, such surfaces may possess nanoscale patterns, which are important for some applications; however, such patterns may not form with spun-cast films under the same condition. In this review, we summarize the recent progress of the self-assembly of block copolymers grafted onto a flat substrate. We mainly concentrate on the self-assembled morphologies of end-grafted AB diblock copolymers, junction point-grafted AB diblock copolymers (i.e., Y-shaped brushes), and end-grafted ABA triblock copolymers. Special emphasis is placed on theoretical and simulation progress. Project supported by the National Natural Science Foundation of China (Grant Nos. 20990234, 20925414, and 91227121), the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT1257), the Programme of Introducing Talents of Discipline to Universities, China, and by the Tianhe No. 1, China.

  9. Sulfonated Polymerized Ionic Liquid Block Copolymers.

    PubMed

    Meek, Kelly M; Elabd, Yossef A

    2016-07-01

    The successful synthesis of a new diblock copolymer, referred to as sulfonated polymerized ionic liquid (PIL) block copolymer, poly(SS-Li-b-AEBIm-TFSI), is reported, which contains both sulfonated blocks (sulfonated styrene: SS) and PIL blocks (1-[(2-acryloyloxy)ethyl]-3-butylimidazolium: AEBIm) with both mobile cations (lithium: Li(+) ) and mobile anions (bis(trifluoromethylsulfonyl)imide: TFSI(-) ). Synthesis consists of polymerization via reversible addition-fragmentation chain transfer, followed by post-functionalization reactions to covalently attach the imidazolium cations and sulfonic acid anions to their respective blocks, followed by ion exchange metathesis resulting in mobile Li(+) cations and mobile TFSI(-) anions. Solid-state films containing 1 m Li-TFSI salt dissolved in ionic liquid result in an ion conductivity of >1.5 mS cm(-1) at 70 °C, where small-angle X-ray scattering data indicate a weakly ordered microphase-separated morphology. These results demonstrate a new ion-conducting block copolymer containing both mobile cations and mobile anions. PMID:27125600

  10. Stabilization of amphiphilic block copolymer nanotubes and vesicles by photopolymerization

    NASA Astrophysics Data System (ADS)

    Kishore, R.; Jofre, A.; Hutchison, J. B.; Allegrini, M.; Locascio, L. E.; Helmerson, K.

    2006-12-01

    We create long polymer nanotubes by directly pulling on the membrane of polymersomes using either optical tweezers or a micropipette. The polymersomes are composed of amphiphilic diblock copolymers and the nanotubes formed have an aqueous core connected to the aqueous interior of the polymersome. Stabilized membranes of nanotubes and vesicles were formed by the directed selfassembly of poly(ethylene oxide)-block-polybutadiene, followed by photopolymerization, initiated by UV light, to a maximum double bond conversion of 15%. The photopolymerized nanotubes are extremely robust. The applicability of photopolymerization for biophysics and bioanalytical science is demonstrated by electrophoresing DNA molecules through a stabilized nanotube with an integrated vesicle reservoir.

  11. Surface Engineering of Styrene/PEGylated-Fluoroalkyl Styrene Block Copolymer Thin Films

    SciTech Connect

    Martinelle, E.; Menghetti, S; Galli, G; Glisenti, A; Krishnan, S; Paik, M; Ober, C; Smilgies, D; Fischer, D

    2009-01-01

    A series of diblock copolymers prepared from styrenic monomers was synthesized using atom transfer radical polymerization. One block was derived from styrene, whereas the second block was prepared from a styrene modified with an amphiphilic PEGylated-fluoroalkyl side chain. The surface properties of the resulting polymer films were carefully characterized using dynamic contact angle, XPS, and NEXAFS measurements. The polymer morphology was investigated using atomic force microscope and GISAXS studies. The block copolymers possess surfaces dominated by the fluorinated unit in the dry state and a distinct phase separated microstructure in the thin film. The microstructure of these polymers is strongly influenced by the thin film structure in which it is investigated.

  12. Effect of Macromolecular Architecture on the Morphology of Polystyrene Polyisoprene Block Copolymers

    SciTech Connect

    Kumar, Rajeev; Goswami, Monojoy; Mays, Jimmy; Sides, Scott; Sumpter, Bobby G; Dadmun, Mark D; Dyer, Caleb W; Driva, Paraskevi; Chen, Jihua

    2013-01-01

    The impact of block connectivity on the morphologies of four block copolymers of varying architecture containing polystyrene (PS) and polyisoprene (PI) has been studied. The volume fraction of PS and molecular weight are held constant while varying the architecture from a linear PS-PI diblock copolymer to three different miktoarm star architectures: PS2PI, PSPI2, and PS2PI2. Morphologies of the PS2PI and PSPI2 miktoarm stars are different from those observed for the linear copolymer and dependent on the connectivity of the copolymer blocks. The change in morphology with connectivity indicates that combining two chains at a junction point leads to chain crowding, where subsequent excluded volume effects drive the change in morphology for each sample. The PS2PI2 miktoarm star exhibits the same morphology as the linear diblock but with a reduction in the size of the domains. The extent of the decrease in domain size indicates that chain stretching impacts the formation of this morphology. Experimentally observed morphologies for different chain architectures are generally consistent with three-dimensional self-consistent field theory simulations, taking into account conformational asymmetry and experimental uncertainty in the copolymer composition. Furthermore, these results generally agree with analytical theory predictions that account for architectural and conformational asymmetry.

  13. Patterning square and rectangular arrays using shear-aligned block copolymer thin films

    NASA Astrophysics Data System (ADS)

    Kim, So Youn; Davis, Raleigh L.; Register, Richard A.; Gwyther, Jessica; Nunns, Adam; Manners, Ian; Chaikin, Paul M.

    2014-03-01

    Microphase separation of block copolymers in thin films can generate periodic structures: hexagonally packed arrays of dots from spherical or cylindrical phase block copolymers, or periodic stripes from cylindrical or lamellar phase block copolymers. Square or rectangular patterns, however, do not naturally form by spontaneous self-assembly of a simple diblock copolymer, and are a challenge to create. We present a simple way to create nano-square/rectangular arrays by building up a double-layer film of a cylinder-forming diblock, where each layer is sequentially deposited, shear-aligned independently, and cross-linked. Any block copolymer with at least one crosslinkable block can in principle be employed; in this study we use cylinder-forming polystyrene-b-poly(ferrocenylisopropylmethylsilane) and polystyrene-b-poly(hexylmethacrylate). The pitch of the array is tunable by varying polymer molecular weight. Oxygen reactive ion etching is used to reveal the grid structures, and these grids can in turn form nano-wells in the silicon substrate when the cylinder-forming block is very etch-resistant under the conditions used for silicon etching. Additionally, metal dots ordered in square arrays can be created using these grids as templates, via metal evaporation and lift-off.

  14. Aqueous dispersion polymerization: a new paradigm for in situ block copolymer self-assembly in concentrated solution.

    PubMed

    Sugihara, Shinji; Blanazs, Adam; Armes, Steven P; Ryan, Anthony J; Lewis, Andrew L

    2011-10-01

    Reversible addition-fragmentation chain transfer polymerization has been utilized to polymerize 2-hydroxypropyl methacrylate (HPMA) using a water-soluble macromolecular chain transfer agent based on poly(2-(methacryloyloxy)ethylphosphorylcholine) (PMPC). A detailed phase diagram has been elucidated for this aqueous dispersion polymerization formulation that reliably predicts the precise block compositions associated with well-defined particle morphologies (i.e., pure phases). Unlike the ad hoc approaches described in the literature, this strategy enables the facile, efficient, and reproducible preparation of diblock copolymer spheres, worms, or vesicles directly in concentrated aqueous solution. Chain extension of the highly hydrated zwitterionic PMPC block with HPMA in water at 70 °C produces a hydrophobic poly(2-hydroxypropyl methacrylate) (PHPMA) block, which drives in situ self-assembly to form well-defined diblock copolymer spheres, worms, or vesicles. The final particle morphology obtained at full monomer conversion is dictated by (i) the target degree of polymerization of the PHPMA block and (ii) the total solids concentration at which the HPMA polymerization is conducted. Moreover, if the targeted diblock copolymer composition corresponds to vesicle phase space at full monomer conversion, the in situ particle morphology evolves from spheres to worms to vesicles during the in situ polymerization of HPMA. In the case of PMPC(25)-PHPMA(400) particles, this systematic approach allows the direct, reproducible, and highly efficient preparation of either block copolymer vesicles at up to 25% solids or well-defined worms at 16-25% solids in aqueous solution. PMID:21854065

  15. Directed Assembly of Supramolecular Copolymers in Thin Films: Thermodynamic and Kinetic Advantages

    NASA Astrophysics Data System (ADS)

    Daoulas, Kostas Ch.; Cavallo, Anna; Shenhar, Roy; Müller, Marcus

    2010-09-01

    Using computer simulation of a coarse-grained model for supramolecular polymers, we investigate the potential of quasiblock copolymers (QBCPs) assembled on chemically patterned substrates for creating device-oriented nanostructures. QBCPs are comprised of AB diblock copolymers and supramolecular B segments that can reversibly bond to any available B terminus, on either the copolymers or the B oligomers, creating a polydisperse blend of B homopolymers, and AB and ABA copolymers. We demonstrate the defect-free replication of patterns with perpendicularly crossing, A-preferential lines, where the same QBCP can simultaneously replicate patterns differing by up to 50% in their length scales. We demonstrate how the pattern affects the distribution of molecular architectures and the key role of supramolecular associations for replicating patterns with different length scales.

  16. Influence of Architecture on the Behavior of Microphase Separated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Speetjens, Frank W., II

    The nanoscale self-assembly of block copolymers at the ˜10-100 nm length scale has exciting potential applications in next-generation nanolithography and nanotemplating, wherein the feature sizes are governed by the overall copolymer degree of polymerization, N. However, the thermodynamics of block copolymer microphase separation intrinsically limit the size of the smallest features accessible by this approach. This limitation stems from the fact that AB diblock copolymer self-assembly only occurs above a critical N that depends inversely on the magnitude of the effective interaction parameter Chi, which quantifies the energetic repulsions between the dissimilar monomer segments. In this dissertation, we first provide an overview of current routes to smaller periodicities in self-assembled block copolymers. While numerous reports have focused on developing "high Chi" AB diblocks that self-assemble at smaller values of N, the use of complex macromolecular architectures to stabilize ordered block copolymer nanostructures remains relatively unexplored. We report the melt-phase self-assembly behavior of block copolymer bottlebrushes derived from linking the block junctions of low molecular weight, symmetric poly(styrene-b-lactide) (PS-b-PLA) copolymers. These studies quantitatively demonstrate that increasing the bottlebrush backbone degree of polymerization (Nbackbone) reduces the critical PS-b-PLA copolymer arm degree of polymerization (Narm) required for self-assembly into lamellar mesophases by as much as 75%, thus reducing the nanoscale feature sizes accessible with this monomer chemistry. In studies of asymmetric block copolymer bottlebrushes, we observe a less significant reduction in the Narm required for self-assembly into a hexagonally-packed cylinders morphology. These results are rationalized in terms of how monomer concentration fluctuation effects manifest upon ordering a disordered copolymer into either a lamellar or cylindrical morphology. Finally, the

  17. Electrostatic Self-Assembly in Copolymers-Nanoparticles Systems

    NASA Astrophysics Data System (ADS)

    Berret, Jean-Francois

    2004-03-01

    We have investigated the phase behavior of neutral/polyelectrolyte block copolymers (also called double-hydrophilic block copolymers) with oppositely charged surfactants [1,2]. When the neutral part of the copolymer is long enough as compared to the charged block, in aqueous solutions the copolymers associate with the surfactant micelles so as to form colloidal complexes of typical sizes 100 nm. We call the mechanism of formation of the complexes electrostatic self-assembly. Using scattering experiments (neutron, x-ray, light) we have found that the colloids have a core-shell microstructure. The core is constituted by densely packed surfactant micelles connected by the polyelectrolyte chains. More recently, we have shown that neutral/polyelectrolyte copolymers also associate with a wide variety of oppositely charged species, such as multivalent counterions, globular proteins and solid nanoparticles. In this communication, we demonstrate the ability of charged diblocks to generate nanostructures of adjustable sizes and morphologies. [1] P. Hervé et al., Europhys. Lett. 58, 912 (2002). J.-F. Berret et al., Eur. Phys. J. E 9, 301 (2002). [2] J.-F. Berret et al., J. Phys. Chem. B 107, 8111 (2003)

  18. Adsorption of diblock polypeptides on polystyrene latex.

    PubMed

    Jain, Ritesh; Forciniti, Daniel

    2012-10-30

    The adsorption of peptides at solid/liquid interfaces is affected by peptide/surface and peptide/peptide hydrophobic and electrostatic forces. Three diblock copolypeptides and two homopeptides were adsorbed on poly(styrene) nanospheres from water, water/methanol, and water/glycerol mixtures at different pH's to study both of these effects. Peptides with one hydrophilic (glutamic acid or lysine) and one nonpolar block (alanine) or with both hydrophilic blocks with opposite charges (glutamic acid and lysine) were chemically synthesized and used as adsorbates in this study. The amount adsorbed was determined, and dynamic light scattering (DLS) was used to measure the adsorbed layer thickness. It was found that peptide/surface and peptide/peptide electrostatic interactions dominate the adsorption process. Hydrophobic forces also play a role, but secondary to electrostatic forces. Positively charged blocks show high affinity for the surface, whereas negatively charged blocks were excluded from it. Poly(Lys) has the highest affinity by the surface, while (Glu)(14)-b-(Ala)(5) has the lowest. Adsorption of all peptides was inhibited by methanol and promoted by glycerol. The adsorption for (Lys)(5)-b-(Glu)(6) was extremely sensitive to pH, irrespective of cosolvent, whereas the thickness for (Lys)(30)-b-(Ala)(41) was sensitive to pH as well as cosolvent. Aggregation was observed in the presence of the nanosurfaces but not in the bulk peptides under some pH and solvent conditions. PMID:23009064

  19. Unexpected consequences of block polydispersity on the self-assembly of ABA triblock copolymers.

    PubMed

    Widin, Joan M; Schmitt, Adam K; Schmitt, Andrew L; Im, Kyuhyun; Mahanthappa, Mahesh K

    2012-02-29

    Controlled/"living" polymerizations and tandem polymerization methodologies offer enticing opportunities to enchain a wide variety of monomers into new, functional block copolymer materials with unusual physical properties. However, the use of these synthetic methods often introduces nontrivial molecular weight polydispersities, a type of chain length heterogeneity, into one or more of the copolymer blocks. While the self-assembly behavior of monodisperse AB diblock and ABA triblock copolymers is both experimentally and theoretically well understood, the effects of broadening the copolymer molecular weight distribution on block copolymer phase behavior are less well-explored. We report the melt-phase self-assembly behavior of SBS triblock copolymers (S = poly(styrene) and B = poly(1,4-butadiene)) comprised of a broad polydispersity B block (M(w)/M(n) = 1.73-2.00) flanked by relatively narrow dispersity S blocks (M(w)/M(n) = 1.09-1.36), in order to identify the effects of chain length heterogeneity on block copolymer self-assembly. Based on synchrotron small-angle X-ray scattering and transmission electron microscopy analyses of seventeen SBS triblock copolymers with poly(1,4-butadiene) volume fractions 0.27 ≤ f(B) ≤ 0.82, we demonstrate that polydisperse SBS triblock copolymers self-assemble into periodic structures with unexpectedly enhanced stabilities that greatly exceed those of equivalent monodisperse copolymers. The unprecedented stabilities of these polydisperse microphase separated melts are discussed in the context of a complete morphology diagram for this system, which demonstrates that narrow dispersity copolymers are not required for periodic nanoscale assembly. PMID:22280467

  20. Unexpected Consequences of Block Polydispersity on the Self-Assembly of ABA Triblock Copolymers

    SciTech Connect

    Widin, Joan M.; Schmitt, Adam K.; Schmitt, Andrew L.; Im, Kyuhyun; Mahanthappa, Mahesh K.

    2012-05-09

    Controlled/'living' polymerizations and tandem polymerization methodologies offer enticing opportunities to enchain a wide variety of monomers into new, functional block copolymer materials with unusual physical properties. However, the use of these synthetic methods often introduces nontrivial molecular weight polydispersities, a type of chain length heterogeneity, into one or more of the copolymer blocks. While the self-assembly behavior of monodisperse AB diblock and ABA triblock copolymers is both experimentally and theoretically well understood, the effects of broadening the copolymer molecular weight distribution on block copolymer phase behavior are less well-explored. We report the melt-phase self-assembly behavior of SBS triblock copolymers (S = poly(styrene) and B = poly(1,4-butadiene)) comprised of a broad polydispersity B block (M{sub w}/M{sub n} = 1.73-2.00) flanked by relatively narrow dispersity S blocks (M{sub w}/M{sub n} = 1.09-1.36), in order to identify the effects of chain length heterogeneity on block copolymer self-assembly. Based on synchrotron small-angle X-ray scattering and transmission electron microscopy analyses of seventeen SBS triblock copolymers with poly(1,4-butadiene) volume fractions 0.27 {le} f{sub B} {le} 0.82, we demonstrate that polydisperse SBS triblock copolymers self-assemble into periodic structures with unexpectedly enhanced stabilities that greatly exceed those of equivalent monodisperse copolymers. The unprecedented stabilities of these polydisperse microphase separated melts are discussed in the context of a complete morphology diagram for this system, which demonstrates that narrow dispersity copolymers are not required for periodic nanoscale assembly.

  1. Correlated disorder in random block copolymers

    NASA Astrophysics Data System (ADS)

    Westfahl, Harry, Jr.; Schmalian, Jörg

    2005-07-01

    We study the effect of a random Flory-Huggins parameter in a symmetric diblock copolymer melt which is expected to occur in a copolymer where one block is near its structural glass transition. In the clean limit the microphase segregation between the two blocks causes a weak, fluctuation induced first order transition to a lamellar state. Using a renormalization group approach combined with the replica trick to treat the quenched disorder, we show that beyond a critical disorder strength, which depends on the length of the polymer chain, the character of the transition is changed. The system becomes dominated by strong randomness and a glassy rather than an ordered lamellar state occurs. A renormalization of the effective disorder distribution leads to nonlocal disorder correlations that reflect strong compositional fluctuation on the scale of the radius of gyration of the polymer chains. The reason for this behavior is shown to be the chain length dependent role of critical fluctuations, which are less important for shorter chains and become increasingly more relevant as the polymer length increases and the clean first order transition becomes weaker.

  2. Effect of Copolymer Chain Architecture on Active Layer Morphology and Device Performance

    NASA Astrophysics Data System (ADS)

    Amonoo, Jojo; Li, Anton; Sykes, Matthew; Huang, Bingyuan; Palermo, Edmund; McNeil, Anne; Shtein, Max; Green, Peter

    2014-03-01

    The optimum morphological structure that determines the device performance of bulk heterojunction thin film polymer solar cells is greatly influenced by the extent of phase separation between the polymer and fullerene components, which ultimately defines the length scales and purity of the donor- and acceptor-rich phases. Block copolymer thin films have been widely studied for their ability to microphase separate into well-defined nanostructures. Nickel-catalyzed chain-growth copolymerizations of thiophene and selenophene derivatives afforded well-defined π-conjugated copolymers of poly(3-hexylthiophene) (P3HT) and poly(3-hexylselenophene) (P3HS) to achieve diblock, random and gradient copolymer chain architectures. This allowed us to study the effect of copolymer sequence and nanoscale morphology of P3HT-P3HS copolymer/[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) on device performance. With the use of energy-filtered transmission electron microscopy and conductive and photoconductive atomic force microscopy we found that copolymer sequence strongly influences the phase separation capabilities of the copolymer-fullerene blend in bulk heterojunction organic photovoltaic devices.

  3. Directed assembly of supramolecular copolymers in thin films

    NASA Astrophysics Data System (ADS)

    Muller, Marcus; Daoulas, Kostas Ch.; Cavallo, Anna; Shenhar, Roy

    2011-03-01

    Using computer simulation of a coarse-grained model for supramolecular polymers we investigate the potential of quasi-block copolymers (QBCP) assembled on chemically patterned substrates for creating device-oriented nanostructures. QBCP are comprised of AB diblock copolymers and supramolecular B segments that can reversibly bond to any available B terminus, either on the copolymers or the B oligomers, creating a polydisperse blend of B homopolymers, AB and ABA copolymers. We focus on an AB incompatibility, χ , and strength of supramolecular bonds where a lamellar morphology, a bicontinous structure and a macrophase-separated state have comparable free energy in the bulk. We consider substrate patterns with perpendicularly crossing, A-preferential lines and demonstrate their defect-free replication by QBCP. The same QBCP replicates simultaneously patterns differing by up to 50 % in their length scales, illustrating the high versatility of QBCP materials. We discuss the interplay between pattern geometry and distribution of molecular architectures and verify the key role of supramolecular associations for replicating patterns with different length scales.

  4. Rapidly recovering hydrogel scaffolds from self-assembling diblock copolypeptide amphiphiles

    NASA Astrophysics Data System (ADS)

    Nowak, Andrew P.; Breedveld, Victor; Pakstis, Lisa; Ozbas, Bulent; Pine, David J.; Pochan, Darrin; Deming, Timothy J.

    2002-05-01

    Protein-based hydrogels are used for many applications, ranging from food and cosmetic thickeners to support matrices for drug delivery and tissue replacement. These materials are usually prepared using proteins extracted from natural sources, which can give rise to inconsistent properties unsuitable for medical applications. Recent developments have utilized recombinant DNA methods to prepare artificial protein hydrogels with specific association mechanisms and responsiveness to various stimuli. Here we synthesize diblock copolypeptide amphiphiles containing charged and hydrophobic segments. Dilute solutions of these copolypeptides would be expected to form micelles; instead, they form hydrogels that retain their mechanical strength up to temperatures of about 90°C and recover rapidly after stress. The use of synthetic materials permits adjustment of copolymer chain length and composition, which we varied to study their effect on hydrogel formation and properties. We find that gelation depends not only on the amphiphilic nature of the polypeptides, but also on chain conformations-α-helix, β-strand or random coil. Indeed, shape-specific supramolecular assembly is integral to the gelation process, and provides a new class of peptide-based hydrogels with potential for applications in biotechnology.

  5. Junction-Controlled Elasticity of Single-Walled Carbon Nanotube Dispersions in Acrylic Copolymer Gels and Solutions

    SciTech Connect

    Schoch, Andrew B.; Shull, Kenneth R.; Brinson, L. Catherine

    2008-08-26

    Oscillatory shear rheometry is used to study the mechanical response of single-walled carbon nanotubes dispersed in solutions of acrylic diblock or triblock copolymers in 2-ethyl-1-hexanol. Thermal transitions in the copolymer solutions provide a route for the easy processing of these composite materials, with excellent dispersion of the nanotubes as verified by near-infrared photoluminescence spectroscopy. The nanotube dispersions form elastic networks with properties that are controlled by the junction points between nanotubes, featuring a temperature-dependent elastic response that is controlled by the dynamic properties of the matrix copolymer solution. The data are consistent with the formation of micelle-like aggregates around the nanotubes. At low temperatures the core-forming poly(methyl methacrylate) blocks are glassy, and the overall mechanical response of the composite does not evolve with time. At higher temperatures the enhanced mobility of the core-forming blocks enables the junctions to achieve more intimate nanotube-nanotube contact, and the composite modulus increases with time. These aging effects are observed in both diblock and triblock copolymer solutions but are partially reversed in the triblock solutions by cooling through the gel transition of the triblock copolymer. This result is attributed to the generation of internal stresses during gelation and the ability of these stresses to break or weaken the nanotube junctions.

  6. The effect of block copolymer on the phase behavior of a polymer blend

    SciTech Connect

    Sung, L.; Jackson, C.L.; Hess, D.

    1995-12-31

    The effect of an interfacial modifier on the phase behavior of a blend has been investigated using time-resolved fight scattering and small angle neutron scattering techniques. A low molecular weight binary blend of deuterated polystyrene/polybutadiene (PSD/PB) with PSD-PB diblock copolymer as the added interfacial modifier was studied. We observed that the critical temperature of the blend decreases with increasing copolymer content and the kinetics of the phase separation (via spinodal decomposition) slows down in the presence of the copolymer. The transition from early to late stage spinodal decomposition in a near critical mixture of the binary blend was analyzed and compared to available theories. In addition, transmission electron microscopy and optical microscopy studies were used to examine the morphology of the system under various temperature quench conditions.

  7. The influence of pendant hydroxyl groups on enzymatic degradation and drug delivery of amphiphilic poly[glycidol-block-(epsilon-caprolactone)] copolymers.

    PubMed

    Mao, Jing; Gan, Zhihua

    2009-11-10

    An amphiphilic diblock copolymer PG-b-PCL with well-controlled structure and pendant hydroxyl groups along hydrophilic block was synthesized by sequential anionic ring-opening polymerization. The micellization and drug release of PG-b-PCL copolymers using pyrene as a fluorescence probe were investigated for determining the influences of copolymer composition and lipase concentration on drug loading capacity and controlled release behavior. The biodegradation of PG-b-PCL copolymers was studied with microspheres as research samples. It has been concluded that the polar hydroxyl groups along each repeat unit of hydrophilic PG block in PG-b-PCL copolymer have great influences on drug encapsulation, drug release, and enzymatic degradation of micelles and microspheres.

  8. Dynamics of Block Copolymer Nanocomposites

    SciTech Connect

    Mochrie, Simon G. J.

    2014-09-09

    A detailed study of the dynamics of cadmium sulfide nanoparticles suspended in polystyrene homopolymer matrices was carried out using X-ray photon correlation spectroscopy for temperatures between 120 and 180 °C. For low molecular weight polystyrene homopolymers, the observed dynamics show a crossover from diffusive to hyper-diffusive behavior with decreasing temperatures. For higher molecular weight polystyrene, the nanoparticle dynamics appear hyper-diffusive at all temperatures studied. The relaxation time and characteristic velocity determined from the measured hyper-diffusive dynamics reveal that the activation energy and underlying forces determined are on the order of 2.14 × 10-19 J and 87 pN, respectively. We also carried out a detailed X-ray scattering study of the static and dynamic behavior of a styrene– isoprene diblock copolymer melt with a styrene volume fraction of 0.3468. At 115 and 120 °C, we observe splitting of the principal Bragg peak, which we attribute to phase coexistence of hexagonal cylindrical and cubic double- gyroid structure. In the disordered phase, above 130 °C, we have characterized the dynamics of composition fluctuations via X-ray photon correlation spectroscopy. Near the peak of the static structure factor, these fluctuations show stretched-exponential relaxations, characterized by a stretching exponent of about 0.36 for a range of temperatures immediately above the MST. The corresponding characteristic relaxation times vary exponentially with temperature, changing by a factor of 2 for each 2 °C change in temperature. At low wavevectors, the measured relaxations are diffusive with relaxation times that change by a factor of 2 for each 8 °C change in temperature.

  9. Biological materials: Part A. tuning LCST of raft copolymers and gold/copolymer hybrid nanoparticles and Part B. Biobased nanomaterials

    NASA Astrophysics Data System (ADS)

    Chen, Ning

    The research described in this dissertation is comprised of two major parts. The first part studied the effects of asymmetric amphiphilic end groups on the thermo-response of diblock copolymers of (oligo/di(ethylene glycol) methyl ether (meth)acrylates, OEGA/DEGMA) and the hybrid nanoparticles of these copolymers with a gold nanoparticle core. Placing the more hydrophilic end group on the more hydrophilic block significantly increased the cloud point compared to a similar copolymer composition with the end group placement reversed. For a given composition, the cloud point was shifted by as much as 28 °C depending on the placement of end groups. This is a much stronger effect than either changing the hydrophilic/hydrophobic block ratio or replacing the hydrophilic acrylate monomer with the equivalent methacrylate monomer. The temperature range of the coil-globule transition was also altered. Binding these diblock copolymers to a gold core decreased the cloud point by 5-15 °C and narrowed the temperature range of the coil-globule transition. The effects were more pronounced when the gold core was bound to the less hydrophilic block. Given the limited numbers of monomers that are approved safe for in vivo use, employing amphiphilic end group placement is a useful tool to tune a thermo-response without otherwise changing the copolymer composition. The second part of the dissertation investigated the production of value-added nanomaterials from two biorefinery "wastes": lignin and peptidoglycan. Different solvents and spinning methods (melt-, wet-, and electro-spinning) were tested to make lignin/cellulose blended and carbonized fibers. Only electro-spinning yielded fibers having a small enough diameter for efficient carbonization (≤ 5-10 μm), but it was concluded that cellulose was not a suitable binder. Cellulose lignin fibers before carbonization showed up to 90% decrease in moisture uptake compared to pure cellulose. Peptidoglycan (a bacterial cell wall

  10. Facile fabrication of diblock methoxy poly(ethylene glycol)-poly(tetramethylene carbonate) and its self-assembled micelles as drug carriers.

    PubMed

    Feng, Jun; Su, Wei; Wang, Hua-fen; Huang, Fu-wei; Zhang, Xian-zheng; Zhuo, Ren-xi

    2009-12-01

    AB type diblock methoxy poly(ethylene glycol)-b-poly(tetramethylene carbonate) (mPEG-PTeMC) copolymers were designed for the first time and used as carriers for the sustained release of the hydrophobic drug ibuprofen. In this paper, we developed a facile ring-opening polymerization (ROP) method to prepare mPEG-PTeMC copolymers under the catalysis of Novozym-435 lipase. Attractively, the polymerization has been successfully performed at 30 degrees C, close to room temperature. The data show that the copolymer compositions agree well with the feed ratio of TeMC to mPEG, indicating the controllable feature of the polymerization. The copolymer structures were characterized by (1)H NMR, IR, SEC, and DSC measurements. mPEG-PTeMC exhibits no apparent in vitro cytotoxicity toward human embryonic kidney transformed 293T cells. Those amphiphilic copolymers can readily self-assemble into nanosized micelles (about 150 nm) in aqueous solution. Their critical micelle concentrations are in the range of (1.6-9.3) x 10(-7) mol/L, determined by fluorescence spectroscopy. The micelles present high stability in PBS solution, with no obvious change in micelle diameters over 5 days. Ibuprofen can be loaded effectively in mPEG-PTeMC micelles, and its sustained release behavior is observed. Transmission electron microscopy shows that the well-dispersed spherical micelles are around 25 nm in diameter, while the diameter is 30 nm after loading ibuprofen. The release rate increases when the chain length of the PTeMC block decreases. These properties show that the micelles self-assembled from mPEG-PTeMC copolymers would have great potential as carriers for the effective encapsulation as well as sustained release of hydrophobic drugs.

  11. Synthesis and Self-Assembly of Discrete Dimethylsiloxane-Lactic Acid Diblock Co-oligomers: The Dononacontamer and Its Shorter Homologues.

    PubMed

    van Genabeek, Bas; de Waal, Bas F M; Gosens, Mark M J; Pitet, Louis M; Palmans, Anja R A; Meijer, E W

    2016-03-30

    Most of the theoretical and computational descriptions of the phase behavior of block copolymers describe the chain ensembles of perfect and uniform polymers. In contrast, experimental studies on block copolymers always employ materials with disperse molecular makeup. Although most polymers are so-called monodisperse, they still have a molecular weight dispersity. Here, we describe the synthesis and properties of a series of discrete length diblock co-oligomers, based on oligo-dimethylsiloxane (oDMS) and oligo-lactic acid (oLA), diblock co-oligomers with highly noncompatible blocks. By utilizing an iterative synthetic protocol, co-oligomers with molar masses up to 6901 Da, ultralow molar mass dispersities (Đ ≤ 1.00002), and unique control over the co-oligomer composition are synthesized and characterized. This specific block co-oligomer required the development of a new divergent strategy for the oDMS structures by which both bis- and monosubstituted oDMS derivatives up to 59 Si-atoms became available. The incompatibility of the two blocks makes the final coupling more demanding the longer the blocks become. These optimized synthetic procedures granted access to multigram quantities of most of the block co-oligomers, useful to study the lower limits of block copolymer phase segregation in detail. Cylindrical, gyroid, and lamellar nanostructures, as revealed by DSC, SAXS, and AFM, were generated. The small oligomeric size of the block co-oligomers resulted in exceptionally small feature sizes (down to 3.4 nm) and long-range organization. PMID:26999049

  12. Amphiphilic Diblock Terpolymer PMAgala-b-P(MAA-co-MAChol)s with Attached Galactose and Cholesterol Grafts and Their Intracellular pH-Responsive Doxorubicin Delivery.

    PubMed

    Wang, Zhao; Luo, Ting; Sheng, Ruilong; Li, Hui; Sun, Jingjing; Cao, Amin

    2016-01-11

    In this work, a series of diblock terpolymer poly(6-O-methacryloyl-D-galactopyranose)-b-poly(methacrylic acid-co-6-cholesteryloxy hexyl methacrylate) amphiphiles bearing attached galactose and cholesterol grafts denoted as the PMAgala-b-P(MAA-co-MAChol)s were designed and prepared, and these terpolymer amphiphiles were further exploited as a platform for intracellular doxorubicin (DOX) delivery. First, employing a sequential RAFT strategy with preliminarily synthesized poly(6-O-methacryloyl-1,2:3,4-di-O-isopropylidene-d-galactopyranose) (PMAIpGP) macro-RAFT initiator and a successive trifluoroacetic acid (TFA)-mediated deprotection, a series of amphiphilic diblock terpolymer PMAgala-b-P(MAA-co-MAChol)s were prepared, and were further characterized by NMR, Fourier transform infrared spectrometer (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and a dynamic contact angle testing instrument (DCAT). In aqueous media, spontaneous micellization of the synthesized diblock terpolymer amphiphiles were continuously examined by critical micellization concentration assay, dynamic light scattering (DLS), and transmission electron microscopy (TEM), and the efficacies of DOX loading by these copolymer micelles were investigated along with the complexed nanoparticle stability. Furthermore, in vitro DOX release of the drug-loaded terpolymer micelles were studied at 37 °C in buffer under various pH conditions, and cell toxicities of as-synthesized diblock amphiphiles were examined by MTT assay. Finally, with H1299 cells, intracellular DOX delivery and localization by the block amphiphile vectors were investigated by invert fluorescence microscopy. As a result, it was revealed that the random copolymerization of MAA and MAChol comonomers in the second block limited the formation of cholesterol liquid-crystal phase and enhanced DOX loading efficiency and complex nanoparticle stability, that ionic interactions between the DOX and MAA comonomer

  13. NEUTRON REFLECTIVITY OF LINEAR-DENDRITIC DIBLOCK COPOLYMER MONOLAYERS. (R825224)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  14. Symmetry Transition in Thin Films of Diblock Copolymer/Homopolymer Blends

    SciTech Connect

    Mishra, Vindhya; Hur, Su-mi; Cochran, Eric W.; Stein, Gila E.; Fredrickson, Glenn H.; Kramer, Edward J.

    2010-03-30

    The effect of blending small weight fractions of low molecular weight majority block homopolymer on the structure of multilayer films of spherical morphology poly(styrene-b-2vinylpyridine) [PS-P2VP] has been studied. The structure of the films was characterized with grazing-incidence small-angle X-ray scattering (GISAXS) and transmission electron microscopy (TEM). In multilayer films of PS-P2VP, competition between hexagonal packing of the spherical domains preferred at the surfaces with the BCC (110) packing preferred by the internal layers leads to a transition in the packing symmetry as the number of sphere layers (n) is increased.(1) Neat PS-P2VP exhibits hexagonal close-packed (HCP) symmetry up through n = 4, but at four layers coexistence of hexagonal and face-centered orthorhombic phases is observed. At n = n* = 5 the face-centered orthorhombic structure (FCO) is the stable phase. On increasing n further, the FCO phase continuously distorts to approach the arrangement of the BCC (110) plane. We observe that blending a small weight fraction of low molecular weight PS homopolymer with PS-P2VP suppresses this transition and stabilizes the hexagonal close-packed arrangement beyond four layers. Moreover, n* increases with increasing weight fraction of incorporated homopolymer for the small weight fractions of homopolymer used in this study. Self-consistent-field theory simulations designed to mimic the experimental system corroborate that n* is expected to increase and show that the PS homopolymer segregates to the interstices of the HCP unit cell. This suggests that the homopolymer reduces the stretching of the PS block and the free energy penalty of HCP relative to BCC inner layers. This result is consistent with the hypothesis that the excessive stretching requirement in an HCP arrangement is the cause of its higher free energy as compared to the BCC lattice.

  15. Patterned carbon nanotubes fabricated by the combination of microcontact printing and diblock copolymer micelles.

    PubMed

    Xu, Peng; Ji, Xin; Qi, Junlei; Yang, Hongmin; Zheng, Weitao; Abetz, Volker; Jiang, Shimei; Shen, Jiacong

    2010-01-01

    A convenient approach to synthesize patterned carbon nanotubes (CNTs) of three morphologies on printed substrates by combination of microcontact printing (microCP) and a plasma-enhanced chemical vapor deposition (PECVD) process is presented. Micelles of polystyrene-block-poly-(2-vinylpyridine) (PS-b-P2VP) in toluene were used as nanoreactors to fabricate FeCl3 in the core domains, and the complex solution was used as an ink to print films with polydimethylsiloxane (PDMS) stamps, different morphologies (porous, dots and stripes patterns) of the FeCl3-loaded micellar films were left onto silicon substrates after printed. After removing the polymer by thermal decomposition, the left iron oxide cluster arrays on the substrate were used as catalysts for the growth of CNTs by the process of PECVD, where the CNTs uniformly distributed on the substrates according to the morphologies of patterned catalysts arrays. PMID:20352884

  16. Fabrication of Nanohole Array via Nanodot Array Using Simple Self-Assembly Process of Diblock Copolymer

    NASA Astrophysics Data System (ADS)

    Matsuyama, Tsuyoshi; Kawata, Yoshimasa

    2007-06-01

    We present a simple self-assembly process for fabricating a nanohole array via a nanodot array on a glass substrate by dripping ethanol onto the nanodot array. It is found that well-aligned arrays of nanoholes as well as nanodots are formed on the whole surface of the glass. A dot is transformed into a hole, and the alignment of the nanodots strongly reflects that of the nanoholes. We find that the change in the depth of holes agrees well with the change in the surface energy with the ethanol concentration in the aqueous solution. We believe that the interfacial energy between the nanodots and the dripped ethanol causes the transformation from nanodots into nanoholes. The nanohole arrays are directly applicable to molds for nanopatterned media used in high-density near-field optical data storage. The bit data can be stored and read out using probes with small apertures.

  17. STRUCTURE OF DIBLOCK COPOLYMERS IN SUPERCRITICAL CARBON DIOXIDE AND CRITICAL MICELLIZATION PRESSURE. (R826115)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  18. Vertical Conducting Nanodomains Self-Assembled from Poly(3-hexylthiophene)-Based Diblock Copolymer Thin Films

    SciTech Connect

    Y Lee; S Kim; H Yang; M Jang; S Hwang; H Lee; K Baek

    2011-12-31

    We have synthesized {pi}-conjugated poly(3-hexyl thiophene)-block-poly(methyl methacrylate) (P3HT-b-PMMA) with a P3HT molecular weight of 11 kDa and a PMMA volume fraction of 0.53, which potentially has several organic electronic applications. Its phase-separation behavior was investigated for various thicknesses cast from organic solvents. When cast onto 300 nm thick SiO{sub 2} dielectrics from toluene, in which the P3HT segments have limited solubility, the P3HT-b-PMMA films consist of nanofibrillar self-assemblies of laterally {pi}-stacked P3HT chains. In contrast, the P3HT segments were found to be highly mobile in chlorobenzene, generating a typical phase-separation morphology consisting of vertically conducting P3HT nanodomains on these dielectrics. As the thickness of the cast films increased, however, the topmost surface becomes covered with {pi}-conjugated nanofibrils that are laterally oriented with respect to the surface. Due to the anisotropic domain orientations of P3HT, top-gate organic field-effect transistors (OFETs) containing the P3HT-b-PMMA films exhibited enhanced electrical performance compared to bottom-gate OFETs.

  19. LANGMUIR BEHAVIOR AND ULTRATHIN FILMS OF NEW LINEAR-DENDRITIC DIBLOCK COPOLYMERS. (R825224)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  20. Interfacial reactivity of block copolymers: understanding the amphiphile-to-hydrophile transition.

    PubMed

    Napoli, Alessandro; Bermudez, Harry; Hubbell, Jeffrey A

    2005-09-27

    Block copolymers offer an interesting platform to study chemically triggered transitions in self-assembled structures. We have previously reported the oxidative degradation of vesicles made of poly(propylene sulfide)-poly(ethylene glycol) (PPS-PEG) copolymers. Here we propose a mechanism for vesicle degradation deduced from copolymer conformational changes occurring at the air/water interface in a Langmuir trough together with a reactive subphase. The hydrophobic PPS block is converted into hydrophilic poly(propylene sulfoxide) and poly(propylene sulfone) by oxidation upon exposure to 1% aqueous H(2)O(2) subphase. As a result, a dramatic increase in area per molecule at constant surface pressure (Pi) was observed, followed by an apparent decrease (recorded as decrease in area at constant Pi) due to copolymer dissolution. For monolayers at the air/water surface, the large interfacial tensions present suppress increases in local curvature for alleviating the increased hydrophilicity of the copolymer chains. By contrast, vesicles can potentially rearrange molecules in their bilayers to accommodate a changing hydrophilic-lipophilic balance (HLB). Similar time scales for monolayer rearrangement and vesicle degradation imply a common copolymer chain solubilization mechanism, which in vesicles lead to an eventual transition to aggregates of higher curvature, such as cylindrical and spherical micelles. Subtle differences in response to the applied surface pressure for the diblock compared to the triblock suggest an effect of the different chain mobility. PMID:16171345

  1. The influence of shear on the ordering temperature of a triblock copolymer melt

    NASA Astrophysics Data System (ADS)

    Nakatani, Alan I.; Morrison, Faith A.; Douglas, Jack F.; Mays, Jimmy W.; Jackson, Catheryn L.; Muthukumar, M.; Han, Charles C.

    1996-01-01

    The effect of shear on the ordering temperature of a triblock copolymer melt of polystyrene-polybutadiene-polystyrene (SBS) is examined by in situ small angle neutron scattering (SANS). Results obtained by SANS are compared to the rheologically determined order-disorder transition temperature, TRODT=115±5 °C. The SANS measurements from a Couette geometry shear cell are then used to construct a ``dynamical phase diagram'' based on characteristic changes in the scattering with temperature and shear rate, γ˙. A shear rate dependent ordering temperature, Tord(γ˙), is identified as the system is sheared isothermally from the disordered state. The scattering behavior is shown to be highly strain dependent. We compare our findings on the shear rate dependence of the ordering transition in triblock materials with previous observations on diblock copolymer materials and theoretical expectations for the shear rate dependence of the order-disorder transition temperature. A simple scaling argument leads to a good description of the shear rate dependence of Tord(γ˙) in both diblock and triblock copolymer measurements over the range of shear rates examined.

  2. Thermodynamics of coil-hyperbranched poly(styrene-b-acrylated epoxidized soybean oil) block copolymers

    NASA Astrophysics Data System (ADS)

    Lin, Fang-Yi; Hohmann, Austin; Hernández, Nacú; Cochran, Eric

    Here we present the phase behavior of a new type of coil-hyperbranched diblock copolymer: poly(styrene- b-acrylated epoxidized soybean oil), or PS-PAESO. PS-PAESO is an example of a biorenewable thermoplastic elastomer (bio-TPE). To date, we have shown that bio-TPEs can be economical commercial substitutes for their petrochemically derived analogues--such as poly(styrene- b-butadiene- b-styrene) (SBS)--in a range of applications including pressure sensitive adhesives and bitumen modification. From a polymer physics perspective, PS-PAESO is an interesting material in that it couples a linear coil-like block with a highly branched block. Thus in contrast to the past five decades of studies on linear AB diblock copolymers, coil-hyperbranched block copolymers are relatively unknown to the community and can be expected to deviate substantially from the standard ``universal'' phase behavior in the AB systems. To explore these new materials, we have constructed a library of PS-PAESO materials spanning a range of molecular weight and composition values. The phase transition behavior and the morphology information will be interpreted by isochronal temperature scanning in dynamic shear rheology, small angle X-ray scattering and the corresponding transmission electron microscopy.

  3. Melt and Solid-State Structures of Polydisperse Polyolefin Multiblock Copolymers

    SciTech Connect

    Li, Sheng; Register, Richard A.; Weinhold, Jeffrey D.; Landes, Brian G.

    2012-10-23

    Crystallization in polydisperse ethylene-octene multiblock copolymers, polymerized via chain shuttling chemistry, is examined using two-dimensional synchrotron small- and wide-angle X-ray scattering on flow-aligned specimens. The multiblocks are composed of alternating crystalline (hard) blocks of low 1-octene content and amorphous (soft) blocks of high 1-octene content; the block lengths and the number of blocks per chain are characterized by most-probable distributions. These polymers self-assemble into lamellar domain morphologies in the melt, and the melt morphology is retained in the solid state. Despite extensive mixing between hard and soft blocks, the high crystallinity (>50%) of the hard blocks leads to an alignment of the crystallites within the domain structure, with the orthorhombic polyethylene c-axis generally perpendicular to the lamellar domain normal. The interlamellar domain spacings exhibited by the multiblocks, which exceed 100 nm, are estimated to be 5 times larger than those in near-monodisperse block copolymers having a similar chemical composition and a number-average molecular weight equivalent to the multiblock's 'constituent diblock' repeating unit. This swelling factor exceeds the value of 3 previously reported for analogous polydisperse olefin diblock copolymers, due to the lower segregation strength and enhanced phase mixing of the multiblocks studied here.

  4. Influencing the structure of block copolymer micelles with small molecule additives

    NASA Astrophysics Data System (ADS)

    Robertson, Megan; Singh, Avantika; Cooksey, Tyler; Kidd, Bryce; Piemonte, Rachele; Wang, Shu; Mai Le, Kim; Madsen, Louis

    Amphiphilic block copolymer micelles in water are under broad exploration for drug delivery applications due to their high loading capacity and targeted drug delivery. We aim to understand the kinetic and thermodynamic processes that underlie the self-assembly of diblock copolymer micelle systems. The present work focuses on diblock copolymers containing poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic polymer), which spontaneously self-assemble into spherical micelles in water. Addition of a common good solvent (a co-solvent) for both of the constituting blocks, such as tetrahydrofuran (THF), reduces the interfacial tension at the core-corona interface. We are currently investigating the effect of this phenomenon on the micelle structural properties, using small-angle scattering and nuclear magnetic resonance. We have characterized the hydrodynamic radius, core radius, corona thickness, aggregation number, degree of swelling of the micelle core with the co-solvent, and unimer (free chain) concentration, as a function of the co-solvent concentration. Fundamental knowledge from these studies will inform design of drug delivery systems by allowing us to tailor micelle properties for optimal cargo loading.

  5. "Hairy" Nanoparticles in Block Copolymers and Homopolymers: Modeling using Hybrid Self-Consistent Field Theory

    NASA Astrophysics Data System (ADS)

    Ginzburg, Valeriy

    2011-03-01

    Today, dispersed nanoparticles play important role in various applications (toughened plastics, healthcare, personal care, etc.) Mesoscale simulations and theory are important in understanding what governs the morphology of nanoparticles under various conditions. In particular, for nanoparticle/block copolymer mixtures, two popular simulation methods are Self-Consistent Field/Density Functional Theory (SCF-DFT) (Thompson, Ginzburg, Matsen, and Balazs, Science 292, 2469 [2001]), and Hybrid Self-Consistent Field Theory (HSCFT) (Sides et al., Phys Rev Lett 96, 250601 [2006]). The two methods are shown to be very similar in their assumptions and end-results; the choice of the method to be used can depend on the specific problem. Here, we use modified HSCFT to explicitly account for the complicated role of short-chain ligands grafted onto nanoparticles to promote dispersion. In particular, we discuss the phase diagrams of such ``hairy'' nanoparticles in diblock copolymers as function of diblock composition, nanoparticle volume fraction, and ligand length. Depending on the particle size and ligand coverage, particles could segregate into favorable domain, stay close to the interface, or phase-separate from the block copolymer altogether. We also consider the dispersion of ``hairy'' nanoparticles in a homopolymer and analyze the morphologies of particle clusters as function of ligand length. The results could have interesting implications for the design of new nanocomposite materials.

  6. Thermo-/pH-responsive behaviours of base-rich diblock polyampholytes in aqueous solution: experiment and simulation

    NASA Astrophysics Data System (ADS)

    Han, Xia; Feng, Jian; Dong, Fang; Zhang, Xuxia; Liu, Honglai; Hu, Ying

    2014-08-01

    We report on the thermo-responsive and pH-responsive behaviours exhibited by two poly(acrylic acid)-poly(2-(dimethylamino)ethyl methacrylate) diblock copolymers with unbalanced acid-base compositions, PAA40-PDMAEMA120 and PAA40-PDMAEMA285, in water, a selective solvent. Using a combination of ultraviolet-visible (UV-vis) spectroscopy and dynamic light scattering, the dual-stimuli responsive behaviours can be clearly detected. The ζ-potential decreases sharply for a symmetrical counterpart PAA60-PDMAEMA70 solution, while it changes evenly for PAA40-PDMAEMA120 and PAA40-PDMAEMA285 solutions because of the asymmetrical compositions. The lower critical solution temperature of the PAA40-PDMAEMA285 solution is always less than that of the PAA40-PDMAEMA120 solution at the same solution concentration and pH values. The molecular dynamics simulation is used to explore the molecular mechanism of the responsive behaviour. The simulation also evidences the presence of dual-stimuli responsive behaviour of the copolymer with respect to changes in temperature and pH in aqueous solutions. The radius of gyration Rg and the end-to-end distance Re of the asymmetric polyampholyte A20-B60 are smaller than those of the symmetric one A40-B40 at all simulated temperatures, which indicates increased aggregation behaviour and the compact aggregates of asymmetric polyampholyte chains. The effect of polymer molecular mass MW on the aggregation behaviour seems to be more profound than that of polymer composition, which may be attributed to the fact that increasing the molecular weight of the copolymer increases the variability of the micelle sizes. Additionally, hydrophobic interaction plays a key role in the aggregation process.

  7. Composition and properties of porous blend membranes containing tertiary amine based amphiphilic copolymers with different sequence structures.

    PubMed

    Yao, Zhikan; Cui, Yue; Zheng, Ke; Zhu, Baoku; Zhu, Liping

    2015-01-01

    Four tertiary amine based amphiphilic copolymers with similar composition but different sequence structures in terms of diblock (Poly(dimethylamino-2-ethyl methacrylate-b-methyl methacrylate) (P(MMA-b-DMAEMA))), triblock (P(DMAEMA-b-MMA-b-DMAEMA)), four-armed diblock (P(MMA-b-DMAEMA)4) and random (P(MMA-r-DMAEMA)) were synthesized and used for fabricating functional porous membranes by blending method. The retention ratios and surface enrichment ratios of the copolymers in blend membranes were determined by hydrogen nuclear magnetic resonance ((1)H-NMR) and X-ray photoelectron spectroscopy (XPS). The composition of the formed membranes was investigated and the durability was experimentally tested. The hydrophilicity of the membranes was evaluated by water contact angle measurement. The performance of membranes under different conditions including water fluxes at different pH and various ionic strength, the adsorption capabilities for Cr(VI) and negatively charged dye sunset yellow at different pH was studied. The results show that tertiary amine based amphiphilic copolymers with block and multi-armed sequence structures enable the blend membranes with higher copolymer retention ratios, more surface tertiary amine groups contents and better composition stability as well as more sensitive to the variation of pH, ionic strength, higher equilibrium anions, and negatively charged dyes uptakes.

  8. Design of block copolymer templated solid state batteries

    NASA Astrophysics Data System (ADS)

    Bullock, Steven Edward

    The advent of portable electronics has placed a great demand on the power requirements of battery systems. High power batteries for small devices, such as cell phones, laptop computers, and personal data assistants (PDA's) have focused primarily on lithium ion batteries. With the introduction of large flexible panel displays, the need for a flexible battery system is apparent. Ring Opening Metathesis Polymerization (ROMP) is a facile method for synthesizing block copolymers with polar functional groups. These functional groups allow the formation of metal oxide clusters via a template of the microphase separated block copolymer domains. In this thesis, the synthesis of a flexible polymer battery system is described. Diblock copolymers of an ionically conductive unsaturated polyethylene oxide block with a carboxylic acid functionalized block were synthesized and characterized with NMR, IR and Gel Permeation Chromatography (GPC). Characterization of polymer templated LiMn2O 4 clusters and nanocomposites synthesized for the study have a distributed cluster morphology within the polymer matrix. The nanocomposites were analyzed with transmission electron microscopy to determine the morphology of the nanocomposites. Battery performance was characterized with cyclic voltammetry and galvanostatic charge/discharge cycling for power capacity. The ionic conductivity was measured with impedance spectroscopy. The novel room temperature templating strategy used for the synthesis of these ionically conductive nanocomposites requires no thermal cycling steps. This makes it attractive for processing of sheet structures to power flexible displays.

  9. Morphology and Proton Transport in Humidified Phosphonated Peptoid Block Copolymers

    PubMed Central

    2016-01-01

    Polymers that conduct protons in the hydrated state are of crucial importance in a wide variety of clean energy applications such as hydrogen fuel cells and artificial photosynthesis. Phosphonated and sulfonated polymers are known to conduct protons at low water content. In this paper, we report on the synthesis phosphonated peptoid diblock copolymers, poly-N-(2-ethyl)hexylglycine-block-poly-N-phosphonomethylglycine (pNeh-b-pNpm), with volume fractions of pNpm (ϕNpm) values ranging from 0.13 to 0.44 and dispersity (Đ) ≤ 1.0003. The morphologies of the dry block copolypeptoids were determined by transmission electron microscopy and in both the dry and hydrated states by synchrotron small-angle X-ray scattering. Dry samples with ϕNpm > 0.13 exhibited a lamellar morphology. Upon hydration, the lowest molecular weight sample transitioned to a hexagonally packed cylinder morphology, while the others maintained their dry morphologies. Water uptake of all of the ordered samples was 8.1 ± 1.1 water molecules per phosphonate group. In spite of this, the proton conductivity of the ordered pNeh-b-pNpm copolymers ranged from 0.002 to 0.008 S/cm. We demonstrate that proton conductivity is maximized in high molecular weight, symmetric pNeh-b-pNpm copolymers. PMID:27134312

  10. Proton Conductivities of Lamellae-Forming Bioinspired Block Copolymer Thin Films Containing Silver Nanoparticles.

    PubMed

    Yabu, Hiroshi; Matsui, Jun; Hara, Mitsuo; Nagano, Shusaku; Matsuo, Yasutaka; Nagao, Yuki

    2016-09-20

    Size-controlled metal nanoparticles (NPs) were spontaneously formed when the amphiphilic diblock copolymers consisting of poly(vinyl catechol) and polystyrene (PVCa-b-PSt) were used as reductants and templates for NPs. In the present study, the proton conductivity of well-aligned lamellae structured PVCa-b-PSt films with Ag NPs was evaluated. We found that the proton conductivity of PVCa-b-PSt film was increased 10-fold by the addition of Ag NPs into the proton conduction channels filled with catechol moieties. In addition, the effect of humidity and the origin of proton conductivity enhancement was investigated. PMID:27589224

  11. Proton Conductivities of Lamellae-Forming Bioinspired Block Copolymer Thin Films Containing Silver Nanoparticles.

    PubMed

    Yabu, Hiroshi; Matsui, Jun; Hara, Mitsuo; Nagano, Shusaku; Matsuo, Yasutaka; Nagao, Yuki

    2016-09-20

    Size-controlled metal nanoparticles (NPs) were spontaneously formed when the amphiphilic diblock copolymers consisting of poly(vinyl catechol) and polystyrene (PVCa-b-PSt) were used as reductants and templates for NPs. In the present study, the proton conductivity of well-aligned lamellae structured PVCa-b-PSt films with Ag NPs was evaluated. We found that the proton conductivity of PVCa-b-PSt film was increased 10-fold by the addition of Ag NPs into the proton conduction channels filled with catechol moieties. In addition, the effect of humidity and the origin of proton conductivity enhancement was investigated.

  12. Conformational Antibody Binding to a Native, Cell-Free Expressed GPCR in Block Copolymer Membranes

    PubMed Central

    de Hoog, Hans-Peter M.; Lin JieRong, Esther M.; Banerjee, Sourabh; Décaillot, Fabien M.; Nallani, Madhavan

    2014-01-01

    G-protein coupled receptors (GPCRs) play a key role in physiological processes and are attractive drug targets. Their biophysical characterization is, however, highly challenging because of their innate instability outside a stabilizing membrane and the difficulty of finding a suitable expression system. We here show the cell-free expression of a GPCR, CXCR4, and its direct embedding in diblock copolymer membranes. The polymer-stabilized CXCR4 is readily immobilized onto biosensor chips for label-free binding analysis. Kinetic characterization using a conformationally sensitive antibody shows the receptor to exist in the correctly folded conformation, showing binding behaviour that is commensurate with heterologously expressed CXCR4. PMID:25329156

  13. Protein based Block Copolymers

    PubMed Central

    Rabotyagova, Olena S.; Cebe, Peggy; Kaplan, David L.

    2011-01-01

    Advances in genetic engineering have led to the synthesis of protein-based block copolymers with control of chemistry and molecular weight, resulting in unique physical and biological properties. The benefits from incorporating peptide blocks into copolymer designs arise from the fundamental properties of proteins to adopt ordered conformations and to undergo self-assembly, providing control over structure formation at various length scales when compared to conventional block copolymers. This review covers the synthesis, structure, assembly, properties, and applications of protein-based block copolymers. PMID:21235251

  14. Dynamics of structure formation in crystallizable block copolymers

    SciTech Connect

    Rangarajan, P.; Register, R.A.; Adamson, D.H.

    1995-12-31

    Isothermal crystallization of polyolefin diblock copolymers from homogeneous and weakly segregated melts has been tracked using simultaneous, synchrotron-based small and wide-angle x-ray scattering (SAXS and WAXS). The polymers are prepared by hydrogenating polydiene diblocks, and contain crystallizable polyethylene ({open_quotes}E{close_quotes}; hydrogenated high 1,4-polybutadiene) blocks and a variety of amorphous polyolefin blocks. All polymers exhibit a well-ordered lamellar morphology at room temperature, as evidenced by 2-3 clear SAXS reflections, even for compositions containing as little as 12% E. In polymers crystallizing from homogeneous melts, the WAXS reflections from the E crystallites grow in parallel with the 3-4 SAXS reflections, so microphase separation is driven by crystallization. These structures, which are reminiscent of strong segregation (as indicated by the multiple SAXS reflections), are obtained by cooling only 20{degrees}C below the melting point. For a polymer having a weakly segregated melt, crystallization eradicates the melt morphology, but larger domain spacings were observed for higher crystallization temperatures, unlike the path-independent values obtained on crystallization from single-phase melts, suggesting that melt segregation hinders the development of the equilibrium crystallization-driven structure.

  15. Reflectivity studies on adsorbed block copolymers under shear

    SciTech Connect

    Smith, G.S.; Wages, S.; Baker, S.M.; Toprakcioglu, C.; Hadziioannou, G.

    1994-12-01

    The authors report neutron reflectivity data on (poly)styrene-(poly)ethylene oxide (PS-PEO) diblock copolymers adsorbed onto quartz from the selective solvent cyclohexane (a non-solvent for PEO and a poor solvent for PS). The PEO ``anchor block`` adsorbs strongly to form a thin layer on the quartz substrate, while the deuterated PS chains dangle into the solvent. They find that under static conditions the density profile of the PS block in a poor solvent can be well described by a Schultz function which is indicative of a polymer ``mushroom.`` Furthermore, they have studied the same system under shear at shear rates from 0--400s{sup {minus}1}. They find that there is a dramatic increase in the thickness of the PS layer under shear in cyclohexane and that the relaxation time from the shear-on profile back to the static profile is on the order of several days.

  16. Investigation of the colloidal Cr2O3 removal possibilities from aqueous solution using the ionic polyamino acid block copolymers.

    PubMed

    Ostolska, Iwona; Wiśniewska, Małgorzata

    2015-06-15

    Disposal of the environmentally dangerous metal oxide suspensions from the waste water is an essential problem. The polymers adsorption can be one of the most effective and suitable methods. In the presented paper the ionic diblock copolymers impact on the Cr2O3 suspensions was investigated. The copolymer adsorption layers structure was determined on the basis of the adsorption and electrokinetic (surface charge density and zeta potential) tests. The polymers adsorption amount was measured using the static method from aqueous solutions. Additionally, the application of the turbidimetric method enabled determination of the interactions between the system constituents. Analysis of this data allows the estimation of the most probable stabilization (or destabilization) mechanism of the Cr2O3 suspensions in the presence of the studied macromolecular compounds. Hence, the Cr2O3 suspensions are unstable in the presence of the anionic copolymer at pH 3 and the cationic one in the alkaline medium. PMID:25746566

  17. Molecular Exchange Dynamics in Block Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Bates, Frank; Lu, Jie; Choi, Soohyung; Lodge, Timothy

    2012-02-01

    Poly(styrene-b-ethylene propylene) (PS-PEP) diblock copolymers were mixed with squalane (C30H62) at 1% by weight resulting in the formation of spherical micelles. The structure and dynamics of molecular exchange were characterized by synchrotron small-angle x-ray scattering (SAXS) and time resolved small-angle neutron scattering (TR-SANS), respectively, between 100 C and 160 C. TR-SANS measurements were performed with solutions initially containing deuterium labeled micelle cores and normal cores dispersed in a contrast matched squalane. Monitoring the reduction in scattering intensity as a function of time at various temperatures revealed molecular exchange dynamics highly sensitive to the core molecular weight and molecular weight distribution. Time-temperature superposition of data acquired at different temperatures produced a single master curve for all the mixtures. Experiments conducted with isotopically labeled micelle cores, each formed from two different but relatively mondisperse PS blocks, confirmed a simple dynamical model based on first order kinetics and core Rouse single chain relaxation. These findings demonstrate a dramatic transition to nonergodicity with increasing micelle core molecular weight and confirm the origins of the logarithmic exchange kinetics in such systems.

  18. Study on the preparation of nifedipine-loaded oral copolymer micelles and its pharmacokinetics in rats.

    PubMed

    Yang, Yue-Hui; Ding, Ping-Tian

    2015-01-01

    The objective of this paper was to prepare nifedipine-loaded oral copolymer micelles and to improve bioavailability of hydrophobic drugs. The methoxy poly(ethylene glycol)-b-polycaprolactone diblock copolymer (mPEG-b-PCL) we developed was the research object; solvent evaporation method was utilized to prepare nifedipine-loaded copolymer micelles, and the drug concentration, drug-loaded amount, and entrapment efficiency were also determined. Transmission electron microscopy and dynamic light scattering were used to characterize the morphology and size distributions of micelles, and the in vivo pharmacokinetics were studied in rats with the research objects of nifedipine-loaded oral copolymer micelles. The drug concentration, drug-loaded amount, and entrapment efficiency of mPEG-b-PCL-nifedipine micelles were (69.39 ± 4.33) μg mL(-1), (3.35 ± 0.21)%, and (8.67 ± 0.54)%, respectively. The micelles were globular shaped with a narrow size distribution and a mean diameter of (34.8 ± 3.2) nm, and the relative bioavailability of the micelles we developed was 246.20% when compared with the tablets available in the market. The mPEG-b-PCL-nifedipine oral copolymer micelles can improve the bioavailability of hydrophobic drugs. Oral polymer micelles drug delivery system has a good prospect.

  19. Ionic Interactions for Aqueous Templating of Biofunctional Molecules in Block Copolymer Nanostructures

    NASA Astrophysics Data System (ADS)

    Olsen, Bradley; Kim, Bokyung; Lam, Christopher; Stewart-Sloan, Charlotte; Gkikas, Emmanouil

    2013-03-01

    The use of ionic interactions to direct both biomolecular templating and block copolymer self-assembly into nanopatterned films with only aqueous processing conditions is demonstrated using block copolymers containing both thermally responsive and pH responsive blocks. Reversible addition-fragmentation chain transfer (RAFT) polymerization is employed to synthesize diblock copolymers with one neutral thermoresponsive and one polycationic block and the pH-dependnent complexation between model proteins or biomimetic J-aggregating chromophores and the polycationic block is demonstrated. Spin casting is used to prepare nanostructured films from the protein-block copolymer and chromophore-block copolymer coacervates. After film formation, the lower critical solution temperature (LCST) of the thermoresponsive block allows the nanomaterial to be effectively immobilized in aqueous environments at physiological temperatures, enabling use of the materials for biomolecule immobilization and controlled release. In the case of protein nanotemplating, the ionic environment in which the protein is confined enables the majority of the protein (80%) to retain its activity, even after having been dehydrated in vacuum and confined in the thin film.

  20. The Tricontinuous 3ths(5) Phase: A New Morphology in Copolymer Melts

    NASA Astrophysics Data System (ADS)

    Fischer, Michael; de Campo, Liliana; Kirkensgaard, Jacob; Hyde, Stephen; Schroeder-Turk, Gerd

    2015-03-01

    Self-assembly remains one of the most efficient routes to the formation of ordered nanostructures, including the double gyroid network phase in diblock copolymers based on two intergrown network domains. This talk demonstrates the use of self-consistent field theory to show that a tricontinuous structure with monoclinic symmetry, called 3ths(5), based on the intergrowth of three distorted ths nets, is an equilibrium phase of triblock star-copolymer melts when an extended molecular core is introduced. The introduction of the core enhances the role of chain stretching by enforcing larger structural length scales, thus destabilizing the hexagonal columnar phase in favor of morphologies with less packing frustration. This study further demonstrates that the introduction of molecular cores is a general concept for tuning the relative importance of entropic and enthalpic free energy contributions, hence providing a tool to stabilize an extended repertoire of self-assembled nanostructured materials.

  1. Mechanism for hierarchical self-assembly of nanoparticles on scaffolds derived from block copolymers.

    SciTech Connect

    Darling, S. B.

    2007-07-01

    Lithographically patterned substrates can direct the self-assembly of block copolymer films into aligned structures that, in turn, template the self-organization of colloidal nanoparticles. Deposition on pristine diblock copolymer films does not lead to reproducible selective decoration, but films modified to have nanoscale corrugation act as scaffolds for highly selective nanoparticle adsorption. The mechanism for this selectivity relies on the lateral forces inherent to spin casting to remove all of the nanoparticle suspension not confined within the nanoscopic trenches. This technique does not rely on interactions between the surfactant capping molecules and the polymer and is therefore general to a wide class of nanoparticle materials. Prospects to obtain long-range ordering and associated potential applications are discussed.

  2. The hydration and ordering of lamellar block copolymer films prior to the formation of polymer vesicles

    NASA Astrophysics Data System (ADS)

    Kamata, Yohei; Parnell, Andrew; Dennison, Andrew; Barker, Robert; Gutfreund, Philipp; Skoda, Maximilian; Mai, Shaomin; Jones, Richard

    2012-02-01

    Polymersomes -- vesicles based on self-assembled bilayers in turn composed of amphiphilic copolymers -- are good candidates for molecular delivery systems; hydrophilic molecules can be enclosed within the aqueous core, to be released by a trigger, which disrupts the vesicle's wall. The key to the use of these polymer vesicles as effective molecular delivery system is in the ability to efficiently encapsulate a molecular payload within the vesicle. To understand the formation mechanism of polymer vesicles via the thin film rehydration method, we have evaluated the hydration and ordering of PEO-PBO diblock copolymer thin films in a controlled water vapor atmosphere. We have performed Neutron Reflectivity, Ellipsometry and Atomic Force Microscopy measurements during the hydration process. These results show that the film swells slowly in the initial stage. It then swells rapidly at a certain critical point and makes ordered structure at the same time. The lamellae are gradually oriented parallel to the substrate with increasing water absorption.

  3. Computational Investigation of Block Copolymer Surfactants for Stabilizing Fluctuation-Induced Polymeric Microemulsions

    NASA Astrophysics Data System (ADS)

    Delaney, Kris; Fredrickson, Glenn

    2013-03-01

    High molecular weight diblock copolymers introduced into a blend of immiscible homopolymers can act as a surfactant to suppress macroscopic two-fluid phase separation. With variation of block copolymer composition, the crossover between low-temperature ordering into microphase or macrophase separated states is marked by a mean-field isotropic Lifshitz multi-critical point. Strong fluctuations close to the Lifshitz point are observed to suppress the low-temperature ordering; a microemulsion state emerges, with large, co-continuous domains of segregated fluid lacking any long-range order. We study this phenomenon with fully fluctuating field-theoretic simulations based on complex Langevin sampling, and we attempt to design new block polymer surfactants that can produce the microemulsion state with a wider composition tolerance.

  4. Effective repair of traumatically injured spinal cord by nanoscale block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Shi, Yunzhou; Kim, Sungwon; Huff, Terry B.; Borgens, Richard B.; Park, Kinam; Shi, Riyi; Cheng, Ji-Xin

    2010-01-01

    Spinal cord injury results in immediate disruption of neuronal membranes, followed by extensive secondary neurodegenerative processes. A key approach for repairing injured spinal cord is to seal the damaged membranes at an early stage. Here, we show that axonal membranes injured by compression can be effectively repaired using self-assembled monomethoxy poly(ethylene glycol)-poly(D,L-lactic acid) di-block copolymer micelles. Injured spinal tissue incubated with micelles (60 nm diameter) showed rapid restoration of compound action potential and reduced calcium influx into axons for micelle concentrations much lower than the concentrations of polyethylene glycol, a known sealing agent for early-stage spinal cord injury. Intravenously injected micelles effectively recovered locomotor function and reduced the volume and inflammatory response of the lesion in injured rats, without any adverse effects. Our results show that copolymer micelles can interrupt the spread of primary spinal cord injury damage with minimal toxicity.

  5. Effective repair of traumatically injured spinal cord by nanoscale block copolymer micelles.

    PubMed

    Shi, Yunzhou; Kim, Sungwon; Huff, Terry B; Borgens, Richard B; Park, Kinam; Shi, Riyi; Cheng, Ji-Xin

    2010-01-01

    Spinal cord injury results in immediate disruption of neuronal membranes, followed by extensive secondary neurodegenerative processes. A key approach for repairing injured spinal cord is to seal the damaged membranes at an early stage. Here, we show that axonal membranes injured by compression can be effectively repaired using self-assembled monomethoxy poly(ethylene glycol)-poly(d,l-lactic acid) di-block copolymer micelles. Injured spinal tissue incubated with micelles (60 nm diameter) showed rapid restoration of compound action potential and reduced calcium influx into axons for micelle concentrations much lower than the concentrations of polyethylene glycol, a known sealing agent for early-stage spinal cord injury. Intravenously injected micelles effectively recovered locomotor function and reduced the volume and inflammatory response of the lesion in injured rats, without any adverse effects. Our results show that copolymer micelles can interrupt the spread of primary spinal cord injury damage with minimal toxicity.

  6. Tailor-Made Stereoblock Copolymers of Poly(lactic acid) by a Truly Living Polymerization Catalyst.

    PubMed

    Rosen, Tomer; Goldberg, Israel; Venditto, Vincenzo; Kol, Moshe

    2016-09-21

    Poly(lactic acid) (PLA) is a biodegradable polymer prepared by the catalyzed ring opening polymerization of lactide. An ideal catalyst should enable a sequential polymerization of the lactide enantiomers to afford stereoblock copolymers with predetermined number and lengths of blocks. We describe a magnesium based catalyst that combines very high activity with a true-living nature, which gives access to PLA materials of unprecedented microstructures. Full consumption of thousands of equivalents of L-LA within minutes gave PLLA of expected molecular weights and narrow molecular weight distributions. Precise PLLA-b-PDLA diblock copolymers having block lengths of up to 500 repeat units were readily prepared within 30 min, and their thermal characterization revealed a stereocomplex phase only with very high melting transitions and melting enthalpies. The one pot sequential polymerization was extended up to precise hexablocks having "dialed-in" block lengths. PMID:27602949

  7. Thermoresponsive diblock glycopolymer by RAFT polymerization for lectin recognition.

    PubMed

    Sun, Kan; Xu, Muru; Zhou, Kaichun; Nie, Huali; Quan, Jing; Zhu, Limin

    2016-11-01

    A thermoresponsive double-hydrophilic diblock glycopolymer, poly(diethyl- eneglycol methacrylate)-block-poly(6-O-vinyladipoyl-d-glucose) (PDEGMA-b-POVAG), was successfully prepared by a combination of enzymatic synthesis and reversible addition-fragment chain transfer (RAFT) polymerization protocols using poly(diethyl- eneglycol methacrylate) (PDEGMA) as macro-RAFT agent. The block glycopolymer was characterized by (1)H NMR and GPC. UV-vis, DLS and TEM studies revealed that the glycopolymer PDEGMA-b-POVAG was thermoresponsive with LCST at 31.0°C, and was able to self-assemble into spherical micelles of various sizes in aqueous solution. The glucose pendants in the glycopolymer could interact with the lectin Concanavalin A (Con A), the average hydrodynamic diameters of glycopolymer micelles increased to 170nm from 110nm after recognizing Con A. The diblock glycopolymer micelles have excellent biocompatibility with pig iliac endothelial cells, as measured using the MTT assay, but micelles loaded with Con A could be used to induce apoptosis in human hepatoma SMMC-7721 cells. PMID:27524009

  8. Connecting Molecular Dynamics Simulations and Fluids Density Functional Theory of Block Copolymers

    NASA Astrophysics Data System (ADS)

    Hall, Lisa

    Increased understanding and precise control over the nanoscale structure and dynamics of microphase separated block copolymers would advance development of mechanically robust but conductive materials for battery electrolytes, among other applications. Both coarse-grained molecular dynamics (MD) simulations and fluids (classical) density functional theory (fDFT) can capture the microphase separation of block copolymers, using similar monomer-based chain models and including local packing effects. Equilibrium free energies of various microphases are readily accessible from fDFT, which allows us to efficiently determine the equilibrium nanostructure over a large parameter space. Meanwhile, MD allows us to visualize specific polymer conformations in 3D over time and to calculate dynamic properties. The fDFT density profiles are used to initialize the MD simulations; this ensures the MD proceeds in the appropriate microphase separated state rather than in a metastable structure (useful especially for nonlamellar structures). The simulations equilibrate more quickly than simulations initialized with a random state, which is significant especially for long chains. We apply these methods to study the interfacial behavior and microphase separated structure of diblock and tapered block copolymers. Tapered copolymers consist of pure A and B monomer blocks on the ends separated by a tapered region that smoothly varies from A to B (or from B to A for an inverse taper). Intuitively, tapering increases the segregation strength required for the material to microphase separate and increases the width of the interfacial region. Increasing normal taper length yields a lower domain spacing and increased polymer mobility, while larger inverse tapers correspond to even lower domain spacing but decreased mobility. Thus the changes in dynamics with tapering cannot be explained by mapping to a diblock system at an adjusted effective segregation strength. This material is based upon work

  9. Widely Tunable Morphologies in Block Copolymer Thin Films Through Solvent Vapor Annealing Using Mixtures of Selective Solvents

    PubMed Central

    Chavis, Michelle A.; Smilgies, Detlef-M.; Wiesner, Ulrich B.; Ober, Christopher K.

    2015-01-01

    Thin films of block copolymers are extremely attractive for nanofabrication because of their ability to form uniform and periodic nanoscale structures by microphase separation. One shortcoming of this approach is that to date the design of a desired equilibrium structure requires synthesis of a block copolymer de novo within the corresponding volume ratio of the blocks. In this work, we investigated solvent vapor annealing in supported thin films of poly(2-hydroxyethyl methacrylate)-block-poly(methyl methacrylate) [PHEMA-b-PMMA] by means of grazing incidence small angle X–ray scattering (GISAXS). A spin-coated thin film of lamellar block copolymer was solvent vapor annealed to induce microphase separation and improve the long-range order of the self-assembled pattern. Annealing in a mixture of solvent vapors using a controlled volume ratio of solvents (methanol, MeOH, and tetrahydrofuran, THF), which are chosen to be preferential for each block, enabled selective formation of ordered lamellae, gyroid, hexagonal or spherical morphologies from a single block copolymer with a fixed volume fraction. The selected microstructure was then kinetically trapped in the dry film by rapid drying. To our knowledge, this paper describes the first reported case where in-situ methods are used to study the transition of block copolymer films from one initial disordered morphology to four different ordered morphologies, covering much of the theoretical diblock copolymer phase diagram. PMID:26819574

  10. Phase behavior of block copolymers in compressed carbon dioxide and as single domain-layer, nanolithographic etch resists for sub-10 nm pattern transfer

    NASA Astrophysics Data System (ADS)

    Chandler, Curran Matthew

    Diblock copolymers have many interesting properties, which first and foremost include their ability to self-assemble into various ordered, regularly spaced domains with nanometer-scale feature sizes. The work in this dissertation can be logically divided into two parts -- the first and the majority of this work describes the phase behavior of certain block copolymer systems, and the second discusses real applications possible with block copolymer templates. Many compressible fluids have solvent-like properties dependent on fluid pressure and can be used as processing aids similar to liquid solvents. Here, compressed CO2 was shown to swell several thin homopolymer films, including polystyrene and polyisoprene, as measured by high pressure ellipsometry at elevated temperatures and pressures. The ellipsometric technique was modified to produce accurate data at these conditions through a custom pressure vessel design. The order-disorder transition (ODT) temperatures of several poly(styrene-bisoprene) diblock copolymers were also investigated by static birefringence when dilated with compressed CO2. Sorption of CO2 in each copolymer resulted in significant depressions of the ODT temperature as a function of fluid pressure, and the data above was used to estimate the quantitative amount of solvent in each of the diblock copolymers. These depressions were not shown to follow dilution approximation, and showed interesting, exaggerated scaling of the ODT at near-bulk polymer concentrations. The phase behavior of block copolymer surfactants was studied when blended with polymer or small molecule additives capable of selective hydrogen bonds. This work used small angle X-ray scattering (SAXS) to identify several low molecular weight systems with strong phase separation and ordered domains as small as 2--3 nanometers upon blending. One blend of a commercially-available surfactant with a small molecule additive was further developed and showed promise as a thin-film pattern

  11. Aggregation of poly(acrylic acid)-containing elastin-mimetic copolymers

    PubMed Central

    Paik, Bradford A.; Blanco, Marco A.; Jia, Xinqiao; Roberts, Christopher J.; Kiick, Kristi L.

    2015-01-01

    Polymer-peptide conjugates were produced via the copper-catalyzed alkyne-azide cycloaddition of poly(tert butyl acrylate) (PtBA) and elastin-like peptides. An azide-functionalized polymer was produced via atom-transfer radical polymerization (ATRP) followed by conversion of bromine end groups to azide groups. Subsequent reaction of the polymer with a bis-alkyne-functionalized, elastin-like peptide proceeded with high efficiency, yielding di- and tri-block conjugates, which after deprotection, yielded poly(acrylic acid) (PAA)-based diblock and triblock copolymers. These conjugates were solubilized in dimethyl formamide, and titration of phosphate buffered saline (PBS) induced aggregation. The presence of polydisperse spherical aggregates was confirmed by dynamic light scattering and transmission electron microscopy. Additionally, a coarse-grained molecular model was designed to reasonably capture inter- and intramolecular interactions for the conjugates and its precursors. This model was used to assess the effect of the different interacting molecular forces on the conformational thermodynamic stability of the copolymers. Our results indicated that the PAA’s ability to hydrogen-bond with both itself and the peptide is the main interaction for stabilizing the diblocks and triblocks and driving their self-assembly, while interactions between peptides are suggested to play only a minor role on the conformational and thermodynamic stability of the conjugates. PMID:25611563

  12. Phase diagram of selectively cross-linked block copolymers shows chemically microstructured gel.

    PubMed

    von der Heydt, Alice; Zippelius, Annette

    2015-02-01

    We study analytically the intricate phase behavior of cross-linked AB diblock copolymer melts, which can undergo two main phase transitions due to quenched random constraints. Gelation, i.e., spatially random localisation of polymers forming a system-spanning cluster, is driven by increasing the number parameter μ of irreversible, type-selective cross-links between random pairs of A blocks. Self-assembly into a periodic pattern of A/B-rich microdomains (microphase separation) is controlled by the AB incompatibility χ inversely proportional to temperature. Our model aims to capture the system's essential microscopic features, including an ensemble of random networks that reflects spatial correlations at the instant of cross-linking. We identify suitable order parameters and derive a free-energy functional in the spirit of Landau theory that allows us to trace a phase diagram in the plane of μ and χ. Selective cross-links promote microphase separation at higher critical temperatures than in uncross-linked diblock copolymer melts. Microphase separation in the liquid state facilitates gelation, giving rise to a novel gel state whose chemical composition density mirrors the periodic AB pattern. PMID:25662662

  13. Micelles, Lamellaes and Connected Bilayer Membranes in Block Copolymer Melts, Blends and Solutions

    NASA Astrophysics Data System (ADS)

    Mortensen, Kell

    1997-03-01

    Block copolymers of poly(ethylene oxide), PEO, and poly(propylene oxide), PPO, provide a unique model system for studies of aqueous systems of amphilic macromolecules, as the amphiphilic character can be changed continuously by changing temperature(K Mortensen, W Brown, B. Nordén , Phys. Rev. Letters 13 2340 (1992)) or pressure(K Mortensen, D Schwahn S Janssen Phys. Rev. Letters 71 1728 (1993)). The structural characteristics of aqueous solutions of the PEO-PPO-PEO copolymers and their self-associated assemblies are reviewed(K Mortensen, J. Phys. Cond. Matter 8 A103 (1996)). It is shown by small-angle neutron scattering that at low temperatures and/or concentration the individual copolymers exist in solution as individual unimers. Depending on molecular design, i.e. size of the individual blocks, various aggregates are formed, including spherical, worm-like and disc-shaped micelles. The spherical micelles provide the basis for liquid-crystalline mesophases of cubic structure. The crystallization can be understood as a simple hard-sphere condensation. Worm- or rod-like micelles may form nematic or hexagonally ordered structures, whereas the discs may condense into lamellar phases. While bi-continuous microemulsions frequently appear in ternary phase diagrams of oil, water and low-molecular surfactants, there has only recently been observations of such phases in binary systems of block copolymers and solvent. The first observation was made in an aqueous solution of a low PEO-content PEO-PPO-PEO triblock copolymer(E Hecht, K Mortensen, H Hoffmann, Macromolecules 28 5465, 1995). More recently, the microemulsion sponge phase has been observed in a system of tri-block copolymers dissolved in homopolymers( JH Laurer, JC Fung, JW Sedat, DA Agard, SD Schmit, J Samseth, K Mortensen, RJ Spontak, Langmuir, submitted) and in a ternary systems of diblock copolymer and homopolymers(FS Bates, WW Maurer, PM Lipic MA Hillmyer, KA Almdal, K Mortensen, TP Lodge Science, submitted).

  14. Optoelectronics using block copolymers.

    SciTech Connect

    Botiz, I.; Darling, S. B.; Center for Nanoscale Materials

    2010-05-01

    Block copolymers, either as semiconductors themselves or as structure directors, are emerging as a promising class of materials for understanding and controlling processes associated with both photovoltaic energy conversion and light emitting devices.

  15. Hydrogen-bonded side chain liquid crystalline block copolymer: Molecular design, synthesis, characterization and applications

    NASA Astrophysics Data System (ADS)

    Chao, Chi-Yang

    Block copolymers can self-assemble into highly regular, microphase-separated morphologies with dimensions at nanometer length scales. Potential applications such as optical wavelength photonic crystals, templates for nanolithographic patterning, or nanochannels for biomacromolecular separation take advantage of the well-ordered, controlled size microdomains of block copolymers. Side-chain liquid crystalline block copolymers (SCLCBCPs) are drawing increasing attention since the incorporation of liquid crystallinity turns their well-organized microstructures into dynamic functional materials. As a special type of block copolymer, hydrogen-bonded SCLCBCPs are unique, compositionally tunable materials with multiple dynamic functionalities that can readily respond to thermal, electrical and mechanical fields. Hydrogen-bonded SCLCBCPs were synthesized and assembled from host poly(styrene- b-acrylic acid) diblock copolymers with narrow molecular weight distributions as proton donors and guest imidazole functionalized mesogenic moieties as proton acceptors. In these studies non-covalent hydrogen bonding is employed to connect mesogenic side groups to a block copolymer backbone, both for its dynamic character as well as for facile materials preparation. The homogeneity and configuration of the hydrogen-bonded complexes were determined by both the molecular architecture of imidazolyl side groups and the process conditions. A one-dimensional photonic crystal composed of high molecular weight hydrogen-bonded SCLCBCP, with temperature dependent optical wavelength stop bands was successfully produced. The microstructures of hydrogen-bonded complexes could be rapidly aligned in an AC electric field at temperatures below the order-disorder transition but above their glass transitions. Remarkable dipolar properties of the mesogenic groups and thermal dissociation of hydrogen bonds are key elements to fast orientation switching. Studies of a wide range of mesogen and polymer

  16. Structure-directing star-shaped block copolymers: supramolecular vesicles for the delivery of anticancer drugs.

    PubMed

    Yang, Chuan; Liu, Shao Qiong; Venkataraman, Shrinivas; Gao, Shu Jun; Ke, Xiyu; Chia, Xin Tian; Hedrick, James L; Yang, Yi Yan

    2015-06-28

    Amphiphilic polycarbonate/PEG copolymer with a star-like architecture was designed to facilitate a unique supramolecular transformation of micelles to vesicles in aqueous solution for the efficient delivery of anticancer drugs. The star-shaped amphipilic block copolymer was synthesized by initiating the ring-opening polymerization of trimethylene carbonate (TMC) from methyl cholate through a combination of metal-free organo-catalytic living ring-opening polymerization and post-polymerization chain-end derivatization strategies. Subsequently, the self-assembly of the star-like polymer in aqueous solution into nanosized vesicles for anti-cancer drug delivery was studied. DOX was physically encapsulated into vesicles by dialysis and drug loading level was significant (22.5% in weight) for DOX. Importantly, DOX-loaded nanoparticles self-assembled from the star-like copolymer exhibited greater kinetic stability and higher DOX loading capacity than micelles prepared from cholesterol-initiated diblock analogue. The advantageous disparity is believed to be due to the transformation of micelles (diblock copolymer) to vesicles (star-like block copolymer) that possess greater core space for drug loading as well as the ability of such supramolecular structures to encapsulate DOX. DOX-loaded vesicles effectively inhibited the proliferation of 4T1, MDA-MB-231 and BT-474 cells, with IC50 values of 10, 1.5 and 1.0mg/L, respectively. DOX-loaded vesicles injected into 4T1 tumor-bearing mice exhibited enhanced accumulation in tumor tissue due to the enhanced permeation and retention (EPR) effect. Importantly, DOX-loaded vesicles demonstrated greater tumor growth inhibition than free DOX without causing significant body weight loss or cardiotoxicity. The unique ability of the star-like copolymer emanating from the methyl cholate core provided the requisite modification in the block copolymer interfacial curvature to generate vesicles of high loading capacity for DOX with significant

  17. Structure-directing star-shaped block copolymers: supramolecular vesicles for the delivery of anticancer drugs.

    PubMed

    Yang, Chuan; Liu, Shao Qiong; Venkataraman, Shrinivas; Gao, Shu Jun; Ke, Xiyu; Chia, Xin Tian; Hedrick, James L; Yang, Yi Yan

    2015-06-28

    Amphiphilic polycarbonate/PEG copolymer with a star-like architecture was designed to facilitate a unique supramolecular transformation of micelles to vesicles in aqueous solution for the efficient delivery of anticancer drugs. The star-shaped amphipilic block copolymer was synthesized by initiating the ring-opening polymerization of trimethylene carbonate (TMC) from methyl cholate through a combination of metal-free organo-catalytic living ring-opening polymerization and post-polymerization chain-end derivatization strategies. Subsequently, the self-assembly of the star-like polymer in aqueous solution into nanosized vesicles for anti-cancer drug delivery was studied. DOX was physically encapsulated into vesicles by dialysis and drug loading level was significant (22.5% in weight) for DOX. Importantly, DOX-loaded nanoparticles self-assembled from the star-like copolymer exhibited greater kinetic stability and higher DOX loading capacity than micelles prepared from cholesterol-initiated diblock analogue. The advantageous disparity is believed to be due to the transformation of micelles (diblock copolymer) to vesicles (star-like block copolymer) that possess greater core space for drug loading as well as the ability of such supramolecular structures to encapsulate DOX. DOX-loaded vesicles effectively inhibited the proliferation of 4T1, MDA-MB-231 and BT-474 cells, with IC50 values of 10, 1.5 and 1.0mg/L, respectively. DOX-loaded vesicles injected into 4T1 tumor-bearing mice exhibited enhanced accumulation in tumor tissue due to the enhanced permeation and retention (EPR) effect. Importantly, DOX-loaded vesicles demonstrated greater tumor growth inhibition than free DOX without causing significant body weight loss or cardiotoxicity. The unique ability of the star-like copolymer emanating from the methyl cholate core provided the requisite modification in the block copolymer interfacial curvature to generate vesicles of high loading capacity for DOX with significant

  18. Molecular exchange in block copolymer micelles: when corona chains overlap

    NASA Astrophysics Data System (ADS)

    Lu, Jie; Lodge, Timothy; Bates, Frank; Choi, Soohyung

    2013-03-01

    The chain exchange kinetics of poly(styrene-b-ethylenepropylene) (PS-PEP) diblock copolymer micelles in squalane (C30H62) was investigated using time-resolved small angle neutron scattering (TR-SANS). The solvent is a mixture of h-squalane and d-squalane that contrast-matches a mixed 50/50 h/d PS micelle core. As isotope labeled chains exchange, the core contrast decreases, leading to a reduction in scattering intensity. This strategy therefore allows direct probing of the chain exchange rate. Separate copolymer micellar solutions containing either deuterium labeled (dPS) or normal (hPS) poly(styrene) core blocks were prepared and mixed at room temperature, below the core glass transition temperature. The samples were heated to several temperatures (around 100 °C) and monitored by TR-SANS every 5 min. As polymer concentration was increased from 1% to 15% by volume, we observed a significant slowing down of chain exchange rate. Similar retarded kinetics was found when part of the solvent in the 1% solution was replaced by homopolymer PEP (comparable size as corona block). Furthermore, if all the solvent is replaced with PEP, no exchange was detected for up to 3hr at 200 °C. These results will be discussed in terms of a molecular model for chain exchange Infineum, Iprime, NIST, ORNL

  19. Nanowire polarizers by guided self-assembly of block copolymers

    NASA Astrophysics Data System (ADS)

    Roberts, Philip M. S.; Baum, Alexandra; Karamath, James; Evans, Allan; Shibata, Satoshi; Walton, Harry

    2014-01-01

    Wire-grid polarizers (WGPs) are currently limited by their wafer-scale manufacturing methods to sizes of approximately 12 to 18 in. For large-size displays, a new method for the production of large-area WGPs is required. Large-area WGPs were simulated using the finite-difference-time-domain method, and a scaleable method for their production based on a block copolymer (BCP)-nanostructured template was implemented. The nanostructured template is globally aligned through the use of a cylinder-forming liquid crystal (LC) diblock copolymer, which is first aligned on a rubbed polyimide substrate. A surface-relief template is produced using the differential dry etch rates of the cylinder-forming component and LC polymer matrix component of the BCP. The template is metalized to produce a WGP. Polarizers of arbitrary size with polarization efficiency up to 0.6 have been made in close agreement with calculated values for idealized structures. The choice of the cylinder-forming polymer is critical to the degree of alignment of the template, and the thermal stability of the LC polymer matrix is critical to the stability of the template during etching.

  20. Effect of monomer sequences on conformations of copolymers grafted on spherical nanoparticles: A Monte Carlo simulation study

    SciTech Connect

    Seifpour, Arezou; Spicer, Philip; Nair, Nitish; Jayaraman, Arthi

    2010-04-28

    Functionalizing nanoparticles with organic ligands, such as oligomers, polymers, DNA, and proteins, is an attractive way to manipulate the interfacial interactions between the nanoparticles and the medium the particles are placed in, and thus control the nanoparticle assembly. In this paper we have conducted a Monte Carlo simulation study on copolymer grafted spherical nanoparticles to show the tremendous potential of using monomer sequence on the copolymers to tune the grafted chain conformation, and thus the effective interactions between copolymer grafted nanoparticles. We have studied AB copolymers with alternating, multiblock, or diblock sequences, where either A monomers or B monomers have monomer-monomer attractive interactions. Our focus has been to show the nontrivial effect of monomer sequence on the conformations of the grafted copolymers at various particle diameters, grafting densities, copolymer chain lengths, and monomer-monomer interactions in an implicit small molecule solvent. We observe that the monomer sequence, particle diameter, and grafting density dictate whether (a) the grafted chains aggregate to bring attractive monomers from multiple grafted chains together (interchain and intrachain monomer aggregation) if the enthalpy gained by doing so offsets the entropic loss caused by stretching of chains, or (b) each grafted chain folds onto itself to bring its attractive monomers together (only intrachain monomer aggregation) if the entropic loss from interchain aggregation cannot be overcome by the enthalpic gain. For six copolymers of chain length N=24 grafted on a spherical particle of diameter D=4, interchain and intrachain monomer aggregation occurs, and the radius of gyration varies nonmonotonically with increasing blockiness of the monomer sequence. At larger particle diameters the grafted chains transition to purely intrachain monomer aggregation. The radius of gyration varies monotonically with monomer sequence for intrachain monomer

  1. Stable domain size and conformational segregation of short and long blocks during microphase separation in random block copolymers

    NASA Astrophysics Data System (ADS)

    Markina, A.; Chertovich, A.

    2015-03-01

    In this Letter we use computer simulations and test microphase separation for AB-diblock copolymers with different block's statistics. We show that the domain size during microphase separation is stable only for the system with large enough polydispersity, namely with exponential (Flory-type) block length distribution. The reason for stable domain size is a conformational segregation of short and long blocks during the increase of the incompatibility in the system. While short blocks became elongated and occupy the surface of the interphase region, long blocks pushed out to the center of the domain and formed their compact conformations.

  2. Polymerization-Induced Self-Assembly of Block Copolymer Nano-objects via RAFT Aqueous Dispersion Polymerization

    PubMed Central

    2014-01-01

    In this Perspective, we discuss the recent development of polymerization-induced self-assembly mediated by reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization. This approach has quickly become a powerful and versatile technique for the synthesis of a wide range of bespoke organic diblock copolymer nano-objects of controllable size, morphology, and surface functionality. Given its potential scalability, such environmentally-friendly formulations are expected to offer many potential applications, such as novel Pickering emulsifiers, efficient microencapsulation vehicles, and sterilizable thermo-responsive hydrogels for the cost-effective long-term storage of mammalian cells. PMID:24968281

  3. A Comparative Study of Cellular Uptake and Subcellular Localization of Doxorubicin Loaded in Self-Assemblies of Amphiphilic Copolymers with Pendant Dendron by MDA-MB-231 Human Breast Cancer Cells.

    PubMed

    Viswanathan, Geetha; Hsu, Yu-Hsuan; Voon, Siew Hui; Imae, Toyoko; Siriviriyanun, Ampornphan; Lee, Hong Boon; Kiew, Lik Voon; Chung, Lip Yong; Yusa, Shin-Ichi

    2016-06-01

    Previously synthesized amphiphilic diblock copolymers with pendant dendron moieties have been investigated for their potential use as drug carriers to improve the delivery of an anticancer drug to human breast cancer cells. Diblock copolymer (P71 D3 )-based micelles effectively encapsulate the doxorubicin (DOX) with a high drug-loading capacity (≈95%, 104 DOX molecules per micelle), which is approximately double the amount of drug loaded into the diblock copolymer (P296 D1 ) vesicles. DOX released from the resultant P71 D3 /DOX micelles is approximately 1.3-fold more abundant, at a tumoral acidic pH of 5.5 compared with a pH of 7.4. The P71 D3 /DOX micelles also enhance drug potency in breast cancer MDA-MB-231 cells due to their higher intracellular uptake, by approximately twofold, compared with the vesicular nanocarrier, and free DOX. Micellar nanocarriers are taken up by lysosomes via energy-dependent processes, followed by the release of DOX into the cytoplasm and subsequent translocation into the nucleus, where it exert its cytotoxic effect.

  4. Rich Variety of Three-Dimensional Nanostructures Enabled by Geometrically Constraining Star-like Block Copolymers.

    PubMed

    Wang, Chao; Xu, Yuci; Li, Weihua; Lin, Zhiqun

    2016-08-01

    The influence of star-like architecture on phase behavior of star-like block copolymer under cylindrical confinement differs largely from the bulk (i.e., nonconfinement). A set of intriguing self-assembled morphologies and the corresponding phase diagrams of star-like (AB)f diblock copolymers with different numbers of arms f (i.e., f = 3, 9, 15, and 21) in four scenarios (ϕA = 0.3 and V0 > 0; ϕA = 0.3 and V0 < 0; ϕA = 0.7 and V0 > 0; and ϕA = 0.7 and V0 < 0 (where ϕA is the volume fraction of A block) and V0 < 0 and V0 > 0 represent that the pore wall of cylindrical confinement prefers the inner A block (i.e., A-preferential) and B block (i.e., B-preferential), respectively) were for the first time scrutinized by employing the pseudospectral method of self-consistent mean-field theory. Surprisingly, a new nanoscopic phase, that is, perforated-lamellae-on-cylinder (denoted PC), was observed in star-like (AB)3 diblock copolymer at ϕA = 0.3 and V0 > 0. With a further increase in f, a single lamellae (denoted L1) was found to possess a larger phase region. Under the confinement of A-preferential wall (i.e., V0 < 0) at ϕA = 0.3, PC phase became metastable and its free energy increased as f increased. Quite intriguingly, when ϕA = 0.7 and V0 > 0, where an inverted cylinder was formed in bulk, the PC phase became stable, and its free energy decreased as f increased, suggesting the propensity to form PC phase under this condition. Moreover, in stark contrast to the phase transition of C1 → L1 → PC (C1, a single cylindrical microdmain) at ϕA = 0.3 and V0 > 0, when subjected to the A-preferential wall (ϕA = 0.7), a different phase transition sequence (i.e., C1 → PC → L1) was identified due to the formation of a double-layer structure. On the basis of our calculations, the influence of star-like architecture on (AB)f diblock copolymer under the imposed cylindrical confinement, particularly the shift of the phase boundaries as a function of f, was thoroughly

  5. Rich Variety of Three-Dimensional Nanostructures Enabled by Geometrically Constraining Star-like Block Copolymers.

    PubMed

    Wang, Chao; Xu, Yuci; Li, Weihua; Lin, Zhiqun

    2016-08-01

    The influence of star-like architecture on phase behavior of star-like block copolymer under cylindrical confinement differs largely from the bulk (i.e., nonconfinement). A set of intriguing self-assembled morphologies and the corresponding phase diagrams of star-like (AB)f diblock copolymers with different numbers of arms f (i.e., f = 3, 9, 15, and 21) in four scenarios (ϕA = 0.3 and V0 > 0; ϕA = 0.3 and V0 < 0; ϕA = 0.7 and V0 > 0; and ϕA = 0.7 and V0 < 0 (where ϕA is the volume fraction of A block) and V0 < 0 and V0 > 0 represent that the pore wall of cylindrical confinement prefers the inner A block (i.e., A-preferential) and B block (i.e., B-preferential), respectively) were for the first time scrutinized by employing the pseudospectral method of self-consistent mean-field theory. Surprisingly, a new nanoscopic phase, that is, perforated-lamellae-on-cylinder (denoted PC), was observed in star-like (AB)3 diblock copolymer at ϕA = 0.3 and V0 > 0. With a further increase in f, a single lamellae (denoted L1) was found to possess a larger phase region. Under the confinement of A-preferential wall (i.e., V0 < 0) at ϕA = 0.3, PC phase became metastable and its free energy increased as f increased. Quite intriguingly, when ϕA = 0.7 and V0 > 0, where an inverted cylinder was formed in bulk, the PC phase became stable, and its free energy decreased as f increased, suggesting the propensity to form PC phase under this condition. Moreover, in stark contrast to the phase transition of C1 → L1 → PC (C1, a single cylindrical microdmain) at ϕA = 0.3 and V0 > 0, when subjected to the A-preferential wall (ϕA = 0.7), a different phase transition sequence (i.e., C1 → PC → L1) was identified due to the formation of a double-layer structure. On the basis of our calculations, the influence of star-like architecture on (AB)f diblock copolymer under the imposed cylindrical confinement, particularly the shift of the phase boundaries as a function of f, was thoroughly

  6. Mechanistic approaches on the antibacterial activity of poly(acrylic acid) copolymers.

    PubMed

    Gratzl, Günther; Walkner, Sarah; Hild, Sabine; Hassel, Achim Walter; Weber, Hedda Katrin; Paulik, Christian

    2015-02-01

    The availability of polymeric antimicrobially active surfaces, which are mainly based on cationic surface effects, is limited. We have previously reported the discovery that, in addition to cationic surfaces, anionic surfaces based on poly(acrylic acid) (PAA) copolymers have a bactericidal effect. In this study, poly(styrene)-poly(acrylic acid)-diblock copolymers (PS-b-PAA) are used to describe the major variables causing the material to have a bactericidal effect on Escherichia coli ATCC 25922 in aqueous suspensions. Upon contact with water, the surface structure of the copolymer changes, the pH value decreases, and the PAA-block migrates toward the surface. Systematically modified antimicrobial tests show that the presence of acid-form PAA provides maximum antimicrobial activity of the material in slightly acidic conditions, and that an ion-exchange effect is the most probable mechanism. Antimicrobially inactive counter-ions inhibit the bactericidal activity of the copolymers, but the material can be regenerated by treatment with acids. PMID:25543987

  7. When block copolymer self-assembly in hierarchically ordered honeycomb films depicts the breath figure process.

    PubMed

    Escalé, Pierre; Save, Maud; Billon, Laurent; Ruokolainen, Janne; Rubatat, Laurent

    2016-01-21

    Nowadays, a challenge in the preparation of hierarchically ordered materials is the control of concomitant and interacting self-organization processes occurring in time at different length scales. In the present paper, the breath figure process is combined with block copolymer nano-phase segregation to elaborate hierarchically structured honeycomb porous films. Copolymer ordering, at the nanometer length scale, is observed and described in detail with respect to the array of pores of micrometer dimension, hence pointing out the structural interplays between both length-scales. The study is focused on two diblock copolymers made of polystyrene and poly(tert-butyl acrylate) (PS-b-PtBA) with compositions producing lamellae or hexagonal packing of cylinders at thermodynamical equilibrium. Transmission Electron Microscopy completed with Small and Ultra-Small Angle Scattering are performed to evidence the inner morphologies of the honeycomb. The structural data are discussed in the light of the honeycomb film formation process establishing the interest in using kinetically trapped block copolymer self-organization as an imprint to elucidate the complex breath figure process. PMID:26528753

  8. Mechanistic approaches on the antibacterial activity of poly(acrylic acid) copolymers.

    PubMed

    Gratzl, Günther; Walkner, Sarah; Hild, Sabine; Hassel, Achim Walter; Weber, Hedda Katrin; Paulik, Christian

    2015-02-01

    The availability of polymeric antimicrobially active surfaces, which are mainly based on cationic surface effects, is limited. We have previously reported the discovery that, in addition to cationic surfaces, anionic surfaces based on poly(acrylic acid) (PAA) copolymers have a bactericidal effect. In this study, poly(styrene)-poly(acrylic acid)-diblock copolymers (PS-b-PAA) are used to describe the major variables causing the material to have a bactericidal effect on Escherichia coli ATCC 25922 in aqueous suspensions. Upon contact with water, the surface structure of the copolymer changes, the pH value decreases, and the PAA-block migrates toward the surface. Systematically modified antimicrobial tests show that the presence of acid-form PAA provides maximum antimicrobial activity of the material in slightly acidic conditions, and that an ion-exchange effect is the most probable mechanism. Antimicrobially inactive counter-ions inhibit the bactericidal activity of the copolymers, but the material can be regenerated by treatment with acids.

  9. Influence of copolymer architectures on adhesion and compatibilization of polymers at interfaces

    NASA Astrophysics Data System (ADS)

    Guo, Lantao

    Adhesion and compatibilization of immiscible homopolymers by a variety of copolymer architectures were studied. The work is arranged into 5 chapters: In Chapter 1, an introduction to recent studies on improvement of adhesion and compatibilization of polymer blends using copolymers was made including the advantages and shortcomings of interfacial reinforcement by a diblock copolymer architecture. Emphasis is on the novel ways to improve adhesion at polymer interfaces by a variety of copolymer architectures, including physical entanglement and chemical modification and chemical bonding. In Chapter 2, a series of Polystyrene-Poly(methyl methacrylate) (PS-PMMA) graft copolymers were introduced to modify the PS and PMMA homopolymer interface and was found to increase the interfacial fracture toughness to a large extent, depending on the detailed architectural variables such as the graft number per chain, the lengths of the backbone and the grafts, and the total molecular weights of the graft copolymers. It was also found that there was an optimal number of grafts per chain which can be interpreted based on the graft length and inter-branch length of the backbone of the copolymer. Effect of in-situ grafting via a chemical reaction between Polystyrene-Poly(vinyl phenol) (PS-PSOH) and oxazoline containing Styrene-Acrylonitril (SAN) was also discussed compared with the physical grafting of a graft copolymer of different structural parameters. In Chapter 3, hydrogen bonding was utilized to toughen the interface between PS and PAA poly(acrylic acid)) or PMMA using a random copolymer architecture of Polystyrene-Poly(vinyl pyridine) (PS-PVP). It was shown that random copolymer architecture is not only economically feasible due to its low cost of producing but also very effective on adhesion because it not only overcomes the issue of micelle formation which is an unavoidable situation in the diblock and graft cases but the enhancement of adhesion is much higher utilizing a H

  10. Morphology phase diagram of ultrathin anatase TiO2 films templated by a single PS-b-PEO block copolymer.

    PubMed

    Cheng, Ya-Jun; Gutmann, Jochen S

    2006-04-12

    Ultrathin TiO2 films showing rich morphologies are prepared on Si(100) substrates using sol-gel chemistry coupled with an amphilic polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer as a structure-directing agent. The block copolymer undergoes a good-poor solvent pair induced phase separation in a mixed solution of 1,4-dioxane, concentrated hydrochloric acid (HCl), and titanium tetraisopropoxide (TTIP). By adjusting the weight fractions of 1,4-dioxane, HCl, and TTIP, inorganic block copolymer composite films containing a variety of different morphologies are obtained. On the basis of the results a ternary phase diagram of the morphologies is mapped. By calcination, anatase TiO2 films are achieved. The morphologies and crystallographic phase of the films are studied with AFM, SEM, and XRD, respectively, and the formation mechanisms of the different morphologies are discussed. PMID:16594703

  11. Formation of nanoscale networks: selectively swelling amphiphilic block copolymers with CO2-expanded liquids

    NASA Astrophysics Data System (ADS)

    Gong, Jianliang; Zhang, Aijuan; Bai, Hua; Zhang, Qingkun; Du, Can; Li, Lei; Hong, Yanzhen; Li, Jun

    2013-01-01

    Polymeric films with nanoscale networks were prepared by selectively swelling an amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with the CO2-expanded liquid (CXL), CO2-methanol. The phase behavior of the CO2-methanol system was investigated by both theoretical calculation and experiments, revealing that methanol can be expanded by CO2, forming homogeneous CXL under the experimental conditions. When treated with the CO2-methanol system, the spin cast compact PS-b-P4VP film was transformed into a network with interconnected pores, in a pressure range of 12-20 MPa and a temperature range of 45-60 °C. The formation mechanism of the network, involving plasticization of PS and selective swelling of P4VP, was proposed. Because the diblock copolymer diffusion process is controlled by the activated hopping of individual block copolymer chains with the thermodynamic barrier for moving PVP segments from one to another, the formation of the network structures is achieved in a short time scale and shows ``thermodynamically restricted'' character. Furthermore, the resulting polymer networks were employed as templates, for the preparation of polypyrrole networks, by an electrochemical polymerization process. The prepared porous polypyrrole film was used to fabricate a chemoresistor-type gas sensor which showed high sensitivity towards ammonia.Polymeric films with nanoscale networks were prepared by selectively swelling an amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with the CO2-expanded liquid (CXL), CO2-methanol. The phase behavior of the CO2-methanol system was investigated by both theoretical calculation and experiments, revealing that methanol can be expanded by CO2, forming homogeneous CXL under the experimental conditions. When treated with the CO2-methanol system, the spin cast compact PS-b-P4VP film was transformed into a network with interconnected pores, in a pressure range of 12-20 MPa and a

  12. A X-Ray Scattering of Ordering in Block Copolymers.

    NASA Astrophysics Data System (ADS)

    Harkless, Curtis Ray

    1990-01-01

    The block copolymer, a novel system for studying the kinetics of first-order phase transitions, is investigated. Solutions of the block copolymer polystyrene-polybutadiene exhibit two types of phase transitions presently of great interest to the science community. Studies of the process by which these transformations occur can broaden our understanding of kinetic phenomena and aid in the identification of universal features such as nonequilibrium scaling. This thesis represents the first attempt to probe the kinetics of these transitions using synchrotron x-ray diffraction. The block copolymer molecule is composed of two different polymer chains joined by a covalent bond. When the chains are incompatible mesophases form through the process of microphase separation. The system also exhibits an ordering transition which results in a characteristic superlattice of the microdomains. A brief discussion of first-order phase transition kinetics is given followed by a detailed review of the relevant literature on block copolymers. High quality diblock and triblock copolymer solutions were prepared. The structure of each system was determined from the x-ray scattering profiles as a function of temperature after which kinetic measurements were performed. Each kinetic measurement involved annealing the sample above the dissolution temperature and rapidly quenching the sample temperature to a fixed point below. The subsequent transformation process was observed through the x-ray scattering profile. Due to the resolution obtained at the synchrotron, the scattering contributions from the ordered and disordered states are identified and separated for the first time. As a result several new features are observed such as the presence of fine structure in the x-ray scattering profile. Fast kinetic measurements reveal that transformation occurs as a two-stage process and that the ordering transition exhibits an unexpected crossover in behavior consistent with two dimensional

  13. Block copolymers for alkaline fuel cell membrane materials

    NASA Astrophysics Data System (ADS)

    Li, Yifan

    Alkaline fuel cells (AFCs) using anion exchange membranes (AEMs) as electrolyte have recently received considerable attention. AFCs offer some advantages over proton exchange membrane fuel cells, including the potential of non-noble metal (e.g. nickel, silver) catalyst on the cathode, which can dramatically lower the fuel cell cost. The main drawback of traditional AFCs is the use of liquid electrolyte (e.g. aqueous potassium hydroxide), which can result in the formation of carbonate precipitates by reaction with carbon dioxide. AEMs with tethered cations can overcome the precipitates formed in traditional AFCs. Our current research focuses on developing different polymer systems (blend, block, grafted, and crosslinked polymers) in order to understand alkaline fuel cell membrane in many aspects and design optimized anion exchange membranes with better alkaline stability, mechanical integrity and ionic conductivity. A number of distinct materials have been produced and characterized. A polymer blend system comprised of poly(vinylbenzyl chloride)-b-polystyrene (PVBC-b-PS) diblock copolymer, prepared by nitroxide mediated polymerization (NMP), with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) or brominated PPO was studied for conversion into a blend membrane for AEM. The formation of a miscible blend matrix improved mechanical properties while maintaining high ionic conductivity through formation of phase separated ionic domains. Using anionic polymerization, a polyethylene based block copolymer was designed where the polyethylene-based block copolymer formed bicontinuous morphological structures to enhance the hydroxide conductivity (up to 94 mS/cm at 80 °C) while excellent mechanical properties (strain up to 205%) of the polyethylene block copolymer membrane was observed. A polymer system was designed and characterized with monomethoxy polyethylene glycol (mPEG) as a hydrophilic polymer grafted through substitution of pendent benzyl chloride groups of a PVBC

  14. Self-Assembly of Amphiphilic Block Copolymers Containing Poly(n-octadecyl acrylate) Block in Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Akiba, Isamu; Akino, Yusuke; Masunaga, Hiroyasu; Sakurai, Kazuo

    2010-11-01

    Synchrotron small-angle X-ray scattering (SAXS) experiments were carried out for poly(acrylic acid)-block-poly(n-octadecyl acrylate) (PAA-b-PODA) and PAA-b-PODA-b-PAA micelles in aqueous solutions. SAXS results indicated that PAA-b-PODA and PAA-b-PODA-b-PAA formed core-shell micelles with disk-like morphology below melting temperature of PODA in aqueous solutions. The thickness of PAA-b-PODA (diblock copolymer) micelle was larger than that of PAA-b-PODA-b-PAA (triblock copolymer) micelle. The difference of sizes between these micelles was related to difference of molecular architectures of PAA-b-PODA and PAA-b-PODA-b-PAA. PAA-b-PODA micelle showed morphological transition from disk to spherical shape with elevating temperature. On the contrary, PAA-b-PODA-b-PAA micelle maintained disk-like shape above melting temperature, although enlargement of micelle thickness is caused.

  15. Block coordination copolymers

    DOEpatents

    Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

    2012-11-13

    The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

  16. Block coordination copolymers

    DOEpatents

    Koh, Kyoung Moo; Wong-Foy, Antek G.; Matzger, Adam J.; Benin, Annabelle I.; Willis, Richard R.

    2012-12-04

    The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

  17. Block coordination copolymers

    DOEpatents

    Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

    2014-11-11

    The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

  18. Ultraviolet absorbing copolymers

    DOEpatents

    Gupta, Amitava; Yavrouian, Andre H.

    1982-01-01

    Photostable and weather stable absorping copolymers have been prepared from acrylic esters such as methyl methacrylate containing 0.1 to 5% of an 2-hydroxy-allyl benzophenone, preferably the 4,4' dimethoxy derivative thereof. The pendant benzophenone chromophores protect the acrylic backbone and when photoexcited do not degrade the ester side chain, nor abstract hydrogen from the backbone.

  19. Synthesis and Self-Assembly of Rod2Coil Miktoarm Star Copolymers of Poly(3-dodecxylthiophene) and Poly(methyl methacrylate) with high rod fractions

    NASA Astrophysics Data System (ADS)

    Park, Jicheol; Moon, Hong Chul; Choi, Chung-Royng; Kim, Jin Kon

    2015-03-01

    Poly(3-dodecylthiophene)-b-poly(methyl methacrylate) diblock copolymer (P3DDT- b-PMMA) can self-assembled into various microdomains such as spheres, cylinders, and lamellae depending on weight fraction of P3DDT. However, only filbril morphology was formed when weight fraction of P3DDT (wP 3 DDT) was major (wP 3 DDT ~ 0.76). Here, we introduce a new approach to obtain microdomain structures even at high wP 3 DDT by using well-defined A2B miktoarm star copolymer composed of P3DDT and PMMA ((P3DDT)2PMMA. We found via small angle X-ray scattering and transmission electron microscopy that (P3DDT)2PMMA showed PMMA cylinder packed hexagonally in the matrix of P3DDT and body-centered-cubic spheres of PMMA for wP 3 DDT of 0.66 and 0.75, respectively. This because of much reduction of the rod-rod interaction in (P3DDT)2PMMA compared with P3DDT- b-PMMA diblock copolymers.

  20. Formation of sub-7 nm feature size PS-b-P4VP block copolymer structures by solvent vapour process

    NASA Astrophysics Data System (ADS)

    Chaudhari, Atul; Ghoshal, Tandra; Shaw, Matthew T.; Cummins, Cian; Borah, Dipu; Holmes, Justin D.; Morris, Michael A.

    2014-03-01

    The nanometer range structure produced by thin films of diblock copolymers makes them a great of interest as templates for the microelectronics industry. We investigated the effect of annealing solvents and/or mixture of the solvents in case of symmetric Poly (styrene-block-4vinylpyridine) (PS-b-P4VP) diblock copolymer to get the desired line patterns. In this paper, we used different molecular weights PS-b-P4VP to demonstrate the scalability of such high χ BCP system which requires precise fine-tuning of interfacial energies achieved by surface treatment and that improves the wetting property, ordering, and minimizes defect densities. Bare Silicon Substrates were also modified with polystyrene brush and ethylene glycol self-assembled monolayer in a simple quick reproducible way. Also, a novel and simple in situ hard mask technique was used to generate sub-7nm Iron oxide nanowires with a high aspect ratio on Silicon substrate, which can be used to develop silicon nanowires post pattern transfer.

  1. "Schizophrenic" hemocompatible copolymers via switchable thermoresponsive transition of nonionic/zwitterionic block self-assembly in human blood.

    PubMed

    Shih, Yu-Ju; Chang, Yung; Deratani, Andre; Quemener, Damien

    2012-09-10

    "Schizophrenic" diblock copolymers containing nonionic and zwitterionic blocks were prepared with well-controlled molecular weights via atom-transfer radical polymerization (ATRP). In this work, we report a systematic study of how morphological changes of poly(N-isopropylacrylamide)-block-poly(sulfobetaine methacrylate) (PNIPAAm-b-PSBMA) copolymers affect hemocompatibility in human blood solution. The "schizophrenic" behavior of PNIPAAm-b-PSBMA was observed by (1)H NMR, dynamic light scattering (DLS), and turbidity measurement with double morphological transition, exhibiting both lower critical solution temperature (LCST) and upper critical solution temperature (UCST) in aqueous solution. Below the UCST of PSBMA block, micelles were obtained with a core of insoluble PSBMA association and a shell of soluble PNIPAAm, whereas the opposite micelle structure was observed above the LCST of PNIPAAm block. In between the UCST and LCST, unimers with both soluble blocks were detected. Hydrodynamic size of prepared polymers and copolymers is determined to illustrate the correlations between intermolecular nonionic/zwitterionic associations and blood compatibility of PNIPAAm, PNIPAAm-b-PSBMA, and PSBMA suspension in human blood. Human fibrinogen adsorption onto the PNIPAAm-b-PSBMA copolymers from single-protein solutions was measured by DLS to determine the nonfouling stability of copolymer suspension. The new nonfouling nature of PNIPAAm-b-PSBMA copolymers was demonstrated to show extremely high anticoagulant activity and antihemolytic activity in human blood over a wide range of explored temperatures from 4 to 40 °C. The temperature-independent blood compatibility of nonionic/zwitterionic block copolymer along with their schizophrenic phase behavior in aqueous solution suggests their potential in blood-contacting applications. PMID:22838402

  2. "Non-equilibrium" block copolymer micelles with glassy cores: a predictive approach based on theory of equilibrium micelles.

    PubMed

    Nagarajan, Ramanathan

    2015-07-01

    Micelles generated in water from most amphiphilic block copolymers are widely recognized to be non-equilibrium structures. Typically, the micelles are prepared by a kinetic process, first allowing molecular scale dissolution of the block copolymer in a common solvent that likes both the blocks and then gradually replacing the common solvent by water to promote the hydrophobic blocks to aggregate and create the micelles. The non-equilibrium nature of the micelle originates from the fact that dynamic exchange between the block copolymer molecules in the micelle and the singly dispersed block copolymer molecules in water is suppressed, because of the glassy nature of the core forming polymer block and/or its very large hydrophobicity. Although most amphiphilic block copolymers generate such non-equilibrium micelles, no theoretical approach to a priori predict the micelle characteristics currently exists. In this work, we propose a predictive approach for non-equilibrium micelles with glassy cores by applying the equilibrium theory of micelles in two steps. In the first, we calculate the properties of micelles formed in the mixed solvent while true equilibrium prevails, until the micelle core becomes glassy. In the second step, we freeze the micelle aggregation number at this glassy state and calculate the corona dimension from the equilibrium theory of micelles. The condition when the micelle core becomes glassy is independently determined from a statistical thermodynamic treatment of diluent effect on polymer glass transition temperature. The predictions based on this "non-equilibrium" model compare reasonably well with experimental data for polystyrene-polyethylene oxide diblock copolymer, which is the most extensively studied system in the literature. In contrast, the application of the equilibrium model to describe such a system significantly overpredicts the micelle core and corona dimensions and the aggregation number. The non-equilibrium model suggests ways to

  3. Field-theoretic studies of phase coexistence and supramolecular assembly in block copolymers

    NASA Astrophysics Data System (ADS)

    Mester, Zoltan

    with respect to the compositions within each cell. The solutions are restricted to those where the mass conservation constraints and the volumetric constraints between coexisting phases are satisfied. The Gibb ensemble SCFT method is extended to supramolecular self-assembly by developing a canonical formalism for reversibly bonded multiblock copolymers. The case of AB diblock copolymers that reversibly react at their B termini with monofunctional B homopolymers to produce longer ABB diblock copolymers is specifically addressed with the new methodology.

  4. Structure of colloidal complexes obtained from neutral/poly- electrolyte copolymers and oppositely charged surfactants

    NASA Astrophysics Data System (ADS)

    Berret, J.-F.; Cristobal, G.; Hervé, P.; Oberdisse, J.; Grillo, I.

    2002-11-01

    We report on the phase behavior and scattering properties of colloidal complexes made from block copolymers and surfactants. The copolymer is poly(sodium acrylate)-b-poly(acrylamide), hereafter abbreviated as PANa-PAM, with molecular weight 5000 g/mol for the first block and 30000 g/mol for the second. In aqueous solutions and neutral pH, poly(sodium acrylate) is a weak polyelectrolyte, whereas poly(acrylamide) is neutral and in good-solvent conditions. The surfactant is dodecyltrimethylammonium bromide (DTAB) and is of opposite charge with respect to the polyelectrolyte block. Combining dynamical light scattering and small-angle neutron scattering, we show that in aqueous solutions PANa-PAM diblocks and DTAB associate into colloidal complexes. For surfactant-to-polymer charge ratios Z lower than a threshold (Z_C sim 0.3), the complexes are single surfactant micelles decorated by few copolymers. Above the threshold, the colloidal complexes reveal an original core-shell microstructure. We have found that the core of typical radius 100 200 Å is constituted from densely packed surfactant micelles connected by the polyelectrolyte blocks. The outer part of the colloidal complex is a corona and is made from the neutral poly(acrylamide) chains. Typical hydrodynamic sizes for the whole aggregate are around 1000 Å. The aggregation numbers expressed in terms of numbers of micelles and copolymers per complex are determined and found to be comprised between 100 400, depending on the charge ratio Z and on the total concentration. We have also shown that the sizes of the complexes depend on the exact procedure of the sample preparation. We propose that the driving mechanism for the complex formation is similar to that involved in the phase separation of homopolyelectrolyte/surfactant systems. With copolymers, the presence of the neutral blocks prevents the macroscopic phase separation from occurring.

  5. Organization of Gold Nanorods in Cylinder-Forming Block Copolymer Films

    NASA Astrophysics Data System (ADS)

    Jian, Guoquian; Riggleman, Robert; Composto, Russell

    2012-02-01

    The addition of gold nanorods (AuNRs) to copolymer films can impart unique optical and electrical properties. To take full advantage of this system, the AuNRs must be dispersed in a self-organizing copolymer that directs the orientation of the anisotropic particle. In the present work, AuNRs with aspect ratio 3.6 (8 nm x 29 nm) are grafted with poly(2-vinyl pyridine) (P2VP) brushes and dispersed in a cylindrical forming diblock copolymer of polystyrene-b-P2VP (180K-b-77K, 29.6 wt% P2VP). Films are spun cast and solvent annealed in chloroform to produce a perpendicular cylindrical morphology at the surface. Using TEM and UV-ozone etching combined with AFM, the AuNRs are well dispersed and co-locate (top down view) with the P2VP cylinders, ˜50nm diameter. However, the AuNRs mainly lie parallel to the surface indicating that they likely locate at the junction created at the intersection between P2VP cylinders and P2VP brush layer adjacent to the silicon oxide surface. Self-consistent field calculations of the Au:PS-b-P2VP morphology as well as the effect of adding P2VP homopolymer to the nanocomposite will be discussed.

  6. Micellar cathodes from self-assembled nitroxide-containing block copolymers in battery electrolytes.

    PubMed

    Hauffman, Guillaume; Maguin, Quentin; Bourgeois, Jean-Pierre; Vlad, Alexandru; Gohy, Jean-François

    2014-01-01

    This contribution describes the synthesis of block copolymers containing electrochemically active blocks, their micellization, and finally their use as micellar cathodes in a lithium battery. The self-assembly of the synthesized poly(styrene)-block-poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PS-b-PTMA) diblock copolymers is realized in a typical battery electrolyte made of 1 m lithium trifluoromethanesulfonate dissolved in a mixture of ethylene carbonate/diethyl carbonate/dimethyl carbonate(1:1:1, in volume). Dynamic light scattering and atomic force micro-scopy indicate the formation of well-defined spherical micelles with a PS core and a PTMA corona. The electrochemical properties of those micelles are further investigated. Cyclic voltammograms show a reversible redox reaction at 3.6 V (vs Li(+) /Li). The charge/discharge profiles indicate a flat and reversible plateau around 3.6 V (vs Li(+) /Li). Finally, the cycling performances of the micellar cathodes are demonstrated. Such self-assembled block copolymers open new opportunities for nanostructured organic radical batteries. PMID:24127365

  7. Formation of interconnected morphologies via nanorod inclusion in the confined assembly of symmetric block copolymers.

    PubMed

    Park, Jay Hoon; Joo, Yong Lak

    2014-05-21

    We have investigated the effect of nanorods on the symmetry breaking of a model diblock copolymer under cylindrical confinement using coarse-grained molecular dynamics. Unlike nanoparticles, nanorods can readily be interconnected with each other and also induce connection across self-assembly domains at much lower loading than nanoparticles. Such interconnecting nanorods, when incorporated within the nanofiber confined assembled block copolymer, have great potential for providing highly conductive pathways for energy applications, such as battery electrodes and separators. Symmetric block copolymers (BCP) under cylindrical confinement with a nanorod aspect ratio (N) of 1, 5, and 10 are examined with three different types of nanorod-BCP attractions: (a) neutral nanorods, (b) A (wall-attractive phase)-attractive nanorods, and (c) B (wall-repulsive phase)-attractive nanorods. The system was studied with both selective and neutral walls, which affect the orientation of the interconnected nanorod network. Upon close examination of the BCP-nanorod self-assembly, we discovered that the ratio of the interphase distance to the nanorod aspect ratio (I/N) can be correlated to the onset of nanorod interconnectivity and formation of asymmetrical interconnected BCP morphology. By developing a phase diagram with respect to I/N, one can predict the formation of desired BCP morphology and the critical loading of nanorods for connected morphologies in cylindrical confinement. PMID:24682243

  8. Thermoregulated formation and disintegration of cationic block copolymer vesicles: fluorescence resonance energy transfer study.

    PubMed

    Maiti, Chiranjit; Dey, Debabrata; Mandal, Sarthak; Dhara, Dibakar

    2014-02-27

    Formation and disintegration of self-assembled nanostructures in response to external stimuli are important phenomena that have been widely explored for a variety of biomedical applications. In this contribution, we report the thermally triggered assembly of block copolymer molecules in aqueous solution to form vesicles (polymersomes) and their disassembly on reduction of temperature. A new thermoresponsive diblock copolymer of poly(N-isopropylacrylamide) poly((3-methacrylamidopropyl)trimethylammonium chloride) (PNIPA-b-PMAPTAC) was synthesized by reversible addition-fragmentation chain transfer technique. The solution properties and self-assembling behavior of the block copolymer molecules were studied by turbidimetry, temperature-dependent proton nuclear magnetic resonance, fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. Fluorescence resonance energy transfer studies between coumarin-153 (C-153, donor) and rhodamine 6G (R6G, acceptor) have been performed by steady-state and picosecond-resolved fluorescence spectroscopy to probe the structural and dynamic heterogeneity of the vesicles. The occurrence of efficient energy transfer was evident from the shortening of donor lifetime in the presence of the acceptor. The capability of the vesicles to encapsulate both hydrophobic and hydrophilic molecules and release them in response to decrease in temperature makes them potentially useful as drug delivery vehicles. PMID:24490812

  9. Synthesis and characterization of an elastin-mimetic amphiphilic block copolymer protein

    NASA Astrophysics Data System (ADS)

    Lee, Terrence Anita-Talley

    2000-10-01

    The overall goal in material science is to be able to control the molecular architecture of a material and thus its end properties. There is no method that offers greater control than the biological synthesis of proteins. From the DNA sequence to the final synthesized protein, the entire process is finitely controlled. This present work describes methods developed and used to synthesize protein polymers by manipulating this process. From the initial DNA sequence chosen, the end properties that the protein polymer will have are dictated. An amphiphilic diblock copolymer was designed based on environmentally responsive elastin-mimetic peptide sequences [(Val/Ile)-Pro-Gly-Xaa-Gly] (Xaa = Ala or Glu for the hydrophilic block, Val or Phe for the hydrophobic block) and synthesized using a genetic engineering approach. Differential scanning calorimetry measurements in aqueous solution revealed that reversible hydrophobic folding and assembly of the copolymer occurs above the inverse temperature transition, Tt, of the hydrophobic block. This process results in the formation of 50 nm protein-based micellar aggregates, which were characterized by electron microscopy and temperature-dependent dynamic light scattering techniques. The distribution of micellar aggregates can be altered reproducibly through variation of environmental conditions including pH and temperature. The uniform and defined macromolecular architecture of this protein copolymer permits greater control over the physical properties of the micelles, which therefore may facilitate applications in controlled release of small molecules.

  10. Ionic Conductivity and Gas Permeability of Polymerized Ionic Liquid Block Copolymer Membranes

    NASA Astrophysics Data System (ADS)

    Evans, Christopher; Sanoja, Gabriel; Schneider, Yanika; Modestino, Miguel; Segalman, Rachel; Joint CenterArtificial Photosynthesis Team

    2014-03-01

    Polymer membranes for many energy applications, such as solar-to-hydrogen fuel production, require ionic conductivity while acting as gas diffusion barriers. We have synthesized a diblock copolymer consisting of poly(styrene-block-(4-(2-methacrylamidoethyl)-imidazolium trifluoroacetate) by treating poly(styrene-block-histamine methacrylamide) (PS- b-PHMA) with trifluoroacetic acid. The PS block serves as the structural support while the imidazolium derivative is an ion conducting polymerized ionic liquid (PIL). Small angle X-ray scattering and transmission electron microscopy demonstrate that the block copolymer self-assembles into well-ordered nanostructures, with lamellae and hexagonally packed cylindrical morphologies. The ionic conductivities of the PS-b-PHMA materials were as high as 2 x 10-4 S/cm while an order of magnitude increase in conductivity was observed upon conversion to PS-b-PIL. The ionic conductivity of the PS-b-PIL increased by a factor of ~ 4 up to 1.2 x 10-3 S/cm as the PIL domain size increased from 20 to 40 nm. These insights allow for the rational design of high performance ion conducting membranes with even greater conductivities via precise morphological control. Additionally, the role of thermal annealing on the ionic conductivity and gas permeability of copolymer membranes was investigated.

  11. Micellar cathodes from self-assembled nitroxide-containing block copolymers in battery electrolytes.

    PubMed

    Hauffman, Guillaume; Maguin, Quentin; Bourgeois, Jean-Pierre; Vlad, Alexandru; Gohy, Jean-François

    2014-01-01

    This contribution describes the synthesis of block copolymers containing electrochemically active blocks, their micellization, and finally their use as micellar cathodes in a lithium battery. The self-assembly of the synthesized poly(styrene)-block-poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PS-b-PTMA) diblock copolymers is realized in a typical battery electrolyte made of 1 m lithium trifluoromethanesulfonate dissolved in a mixture of ethylene carbonate/diethyl carbonate/dimethyl carbonate(1:1:1, in volume). Dynamic light scattering and atomic force micro-scopy indicate the formation of well-defined spherical micelles with a PS core and a PTMA corona. The electrochemical properties of those micelles are further investigated. Cyclic voltammograms show a reversible redox reaction at 3.6 V (vs Li(+) /Li). The charge/discharge profiles indicate a flat and reversible plateau around 3.6 V (vs Li(+) /Li). Finally, the cycling performances of the micellar cathodes are demonstrated. Such self-assembled block copolymers open new opportunities for nanostructured organic radical batteries.

  12. Block copolymer battery separator

    DOEpatents

    Wong, David; Balsara, Nitash Pervez

    2016-04-26

    The invention herein described is the use of a block copolymer/homopolymer blend for creating nanoporous materials for transport applications. Specifically, this is demonstrated by using the block copolymer poly(styrene-block-ethylene-block-styrene) (SES) and blending it with homopolymer polystyrene (PS). After blending the polymers, a film is cast, and the film is submerged in tetrahydrofuran, which removes the PS. This creates a nanoporous polymer film, whereby the holes are lined with PS. Control of morphology of the system is achieved by manipulating the amount of PS added and the relative size of the PS added. The porous nature of these films was demonstrated by measuring the ionic conductivity in a traditional battery electrolyte, 1M LiPF.sub.6 in EC/DEC (1:1 v/v) using AC impedance spectroscopy and comparing these results to commercially available battery separators.

  13. Imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1992-01-01

    Imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly(arylene ethers) in polar aprotic solvents and by chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The resulting block copolymers have one glass transition temperature or two, depending upon the particular structure and/or the compatibility of the block units. Most of these block copolymers form tough, solvent resistant films with high tensile properties.

  14. Interactions in random copolymers

    NASA Astrophysics Data System (ADS)

    Marinov, Toma; Luettmer-Strathmann, Jutta

    2002-04-01

    The description of thermodynamic properties of copolymers in terms of simple lattice models requires a value for the effective interaction strength between chain segments, in addition to parameters that can be derived from the properties of the corresponding homopolymers. If the monomers are chemically similar, Berthelot's geometric-mean combining rule provides a good first approximation for interactions between unlike segments. In earlier work on blends of polyolefins [1], we found that the small-scale architecture of the chains leads to corrections to the geometric-mean approximation that are important for the prediction of phase diagrams. In this work, we focus on the additional effects due to sequencing of the monomeric units. In order to estimate the effective interaction for random copolymers, the small-scale simulation approach developed in [1] is extended to allow for random sequencing of the monomeric units. The approach is applied here to random copolymers of ethylene and 1-butene. [1] J. Luettmer-Strathmann and J.E.G. Lipson. Phys. Rev. E 59, 2039 (1999) and Macromolecules 32, 1093 (1999).

  15. Reduction-sensitive amphiphilic triblock copolymers self-assemble into stimuli-responsive micelles for drug delivery.

    PubMed

    Toughraï, Smahan; Malinova, Violeta; Masciadri, Raffaello; Menon, Sindhu; Tanner, Pascal; Palivan, Cornelia; Bruns, Nico; Meier, Wolfgang

    2015-04-01

    Polymeric nanostructures obtained through self-assembly of reduction-sensitive amphiphilic triblock copolymers were investigated as potential drug delivery systems. The characteristic feature of these polymers is their cleavable disulfide bond in the center of the hydrophobic block. Therefore, the triblock copolymers can be cleaved into amphiphilic diblock copolymers. A poly(2-hydroxyethyl methacrylate)-b-poly(butyl methacrylate)-S-S-poly(butyl methacrylate)-b-poly(2-hydroxyethyl methacrylate) (PHEMA-b-(PBMA-S-S-PBMA)-b-PHEMA) triblock copolymer was synthesized. It self-assembled into micelles which were used to encapsulate hydrophobic dye molecules (Nile Red, BodiPy 630/650) as model payloads. The self-assembled nanostructures disintegrated upon reduction of the disulfide bond, releasing their cargo and yielding larger particles that formed aggregates in solution after 24 h. A burst release of payload was shown within the first 15 min, followed by a constant release over several hours. As concentration gradients of reducing agents are commonly found in biological systems, the micelles could be used as redox-sensitive nanocarriers for the intracellular delivery of drugs.

  16. Fabrication of platinum nanoparticles in aqueous solution and solid phase using amphiphilic PB-b-PEO copolymer nanoreactors

    SciTech Connect

    Hoda, Numan; Budama, Leyla; Çakır, Burçin Acar; Topel, Önder; Ozisik, Rahmi

    2013-09-01

    Graphical abstract: TEM image of Pt nanoparticles produced by reducing by NaBH{sub 4} within PB-b-PEO micelles in aqueous media (scale bar 1 nm). - Highlights: • Pt nanoparticles were synthesized within amphiphilic diblock copolymer micelles. • The effects of reducing agents and precursor dose on Pt np size were investigated. • The effect on fabrication of Pt np by reducing in aqueous and solid phases was compared. • The size of nanoparticles was about 1.4 nm for all doses and reducing agents types. - Abstract: Fabrication of Pt nanoparticles using an amphiphilic copolymer template in aqueous solution was achieved via polybutadiene-block-polyethyleneoxide copolymer micelles, which acted as nanoreactors. In addition, Pt nanoparticles were synthesized using hydrogen gas as the reducing agent in solid state for the first time to compare against solution synthesis. The influences of loaded precursor salt amount to micelles and the type of reducing agent on the size of nanoparticles were investigated through transmission electron microscopy. It was found that increasing the ratio of precursor salt to copolymer and using different type of reducing agent, even in solid phase reduction, did not affect the nanoparticle size. The average size of Pt nanoparticles was estimated to be 1.4 ± 0.1 nm. The reason for getting same sized nanoparticles was discussed in the light of nucleation, growth process, stabilization and diffusion of nanoparticles within micelles.

  17. Manipulating Interfaces through Surface Confinement of Poly(glycidyl methacrylate)-block-poly(vinyldimethylazlactone), a Dually Reactive Block Copolymer

    SciTech Connect

    Lokitz, Bradley S; Wei, Jifeng; Hinestrosa Salazar, Juan P; Ivanov, Ilia N; Browning, James B; Ankner, John Francis; Kilbey, II, S Michael; Messman, Jamie M

    2012-01-01

    The assembly of dually reactive, well-defined diblock copolymers incorporating the chemoselective/functional monomer, 4,4-dimethyl-2-vinylazlactone (VDMA) and the surface-reactive monomer glycidyl methacrylate (GMA) is examined to understand how competition between surface attachment and microphase segregation influences interfacial structure. Reaction of the PGMA block with surface hydroxyl groups not only anchors the copolymer to the surface, but limits chain mobility, creating brush-like structures comprising PVDMA blocks, which contain reactive azlactone groups. The block copolymers are spin coated at various solution concentrations and annealed at elevated temperature to optimize film deposition to achieve a molecularly uniform layer. The thickness and structure of the polymer thin films are investigated by ellipsometry, infrared spectroscopy, and neutron reflectometry. The results show that deposition of PGMA-b-PVDMA provides a useful route to control film thickness while preserving azlactone groups that can be further modified with biotin-poly(ethylene glycol)amine to generate designer surfaces. The method described herein offers guidance for creating highly functional surfaces, films, or coatings through the use of dually reactive block copolymers and postpolymerization modification.

  18. Preparation of biocompatible zwitterionic block copolymer vesicles by direct dissolution in water and subsequent silicification within their membranes.

    PubMed

    Du, Jianzhong; Armes, Steven P

    2009-08-18

    The facile preparation of block copolymer vesicles in pure water and their subsequent stabilization by sol-gel chemistry within the vesicle membrane is described. An amphiphilic biocompatible zwitterionic diblock copolymer, poly(epsilon-caprolactone)-block-poly[2-(methacryloyloxy)ethyl phosphorylcholine], PCL-b-PMPC, was synthesized by (i) ring-opening polymerization of epsilon-caprolactone, (ii) end-group modification by esterification, and (iii) atom transfer radical polymerization (ATRP) of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC). Unusually, block copolymer vesicles were formed instantly upon adding dried copolymer powder into hot water without using organic cosolvents, pH adjustment, or even stirring. This protocol is much more convenient than previously reported methods such as solvent-switching and film rehydration. The PCL vesicle membrane is moderately hydrophobic and fully biodegradable. The highly biocompatible PMPC chains are expressed on both the exterior and interior surface of the membrane. These vesicles can be stabilized by aqueous sol-gel chemistry within the hydrophobic PCL vesicle membrane by using tetramethyl orthosilicate (TMOS) as the silica precursor in the absence of any external catalyst. The water-immiscible TMOS precursor is initially solubilized within the hydrophobic membrane prior to its in situ transformation into silica. The vesicles were characterized by 1H NMR spectroscopy, atomic force microscopy, transmission electron microscopy, and dynamic light scattering.

  19. Microphase Separation in Thin Films of Block Copolymer Supramolecular Assemblies: Composition Dependent Morphological Transitions and Molecular Architecture Effect

    NASA Astrophysics Data System (ADS)

    Nandan, Bhanu; Stamm, Manfred

    2010-03-01

    Block copolymer based supramolecular assemblies (SMAs) recently have attracted lot of attention because of their potential application as nanotemplates. These SMAs are prepared by attaching small molecules selectively to one of the blocks of the copolymer through physical interactions. In the present study, the phase behavior of SMAs formed by polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) with 2-(4'-hydroxybenzeneazo)benzoic acid (HABA) was investigated with respect to the molar ratio (X) between HABA and 4VP monomer unit in bulk as well as in thin films. It will be shown that these SMAs show some interesting composition dependent and solvent induced pathway dependent phase transitions. Moreover, the orientation of cylindrical or lamellar microdomains of P4VP(HABA) depends on the selectivity of the solvent as well as on the degree of swelling of the thin film. Furthermore, it will be shown that the molecular architecture of the block copolymer influences the orientation and ordering of microdomains in the SMA. Hence, whereas, the cylindrical and lamellar microdomains of SMA composed of a P4VP-b-PS-b-P4VP triblock copolymer were perpendicular to the substrate, those composed from a PS-b-P4VP diblock of similar composition had in-plane orientation of the microdomains.

  20. Mixed-Salt Effects on the Ionic Conductivity of Lithium-Doped PEO-Containing Block Copolymers

    SciTech Connect

    Young, Wen-Shiue; Albert, Julie N.L.; Schantz, A. Benjamin; Epps, III, Thomas H.

    2012-10-10

    We demonstrate a simple, yet effective, mixed-salt method to increase the room temperature ionic conductivity of lithium-doped block copolymer electrolyte membranes by suppressing the crystalline phases in the conducting block. We examined a mixed-salt system of LiClO{sub 4} and LiN(SO{sub 2}CF{sub 3}){sub 2} (LiTFSI) doped into a lamellae-forming poly(styrene-b-ethylene oxide) (PS-PEO) diblock copolymer. The domain spacings, morphologies, thermal behavior, and crystalline phases of salt-doped PS-PEO samples were characterized, and the ionic conductivities of block copolymer electrolytes were obtained through ac impedance measurements. Comparing the ionic conductivity profiles of salt-doped PS-PEO samples at different mixed-salt ratios and total salt concentrations, we found that the ionic conductivity at room temperature can be improved by more than an order of magnitude when coinhibition of crystallite growth is promoted by the concerted behavior of the PEO:LiClO{sub 4} and PEO:LiTFSI phases. Additionally, we examined the influence of mixed-salt ratio and total salt concentration on copolymer energetics, and we found that the slope of the effective interaction parameter ({chi}{sub eff}) vs salt concentration in our lamellae-forming PS-PEO system was lower than that reported for a cylinder-forming PS-PEO system due to the balance between chain stretching and salt segregation in the PEO domains.

  1. Interaction chromatography for characterization and large-scale fractionation of chemically heterogeneous copolymers

    NASA Astrophysics Data System (ADS)

    Han, Junwon

    The remarkable development of polymer synthesis techniques to make complex polymers with controlled chain architectures has inevitably demanded the advancement of polymer characterization tools to analyze the molecular dispersity in polymeric materials beyond size exclusion chromatography (SEC). In particular, man-made synthetic copolymers that consist of more than one monomer type are disperse mixtures of polymer chains that have distributions in terms of both chemical heterogeneity and chain length (molar mass). While the molecular weight distribution has been quite reliably estimated by the SEC, it is still challenging to properly characterize the chemical composition distribution in the copolymers. Here, I have developed and applied adsorption-based interaction chromatography (IC) techniques as a promising tool to characterize and fractionate polystyrene-based block, random and branched copolymers in terms of their chemical heterogeneity. The first part of this thesis is focused on the adsorption-desorption based purification of PS-b-PMMA diblock copolymers using nanoporous silica. The liquid chromatography analysis and large scale purification are discussed for the PS-b-PMMA block copolymers that have been synthesized by sequential anionic polymerization. SEC and IC are compared to critically analyze the contents of PS homopolymers in the as-synthesized block copolymers. In addition, I have developed an IC technique to provide faster and more reliable information on the chemical heterogeneity in the as-synthesized block copolymers. Finally, a large scale (multi-gram) separation technique is developed to obtain "homopolymer-free" block copolymers via a simple chromatographic filtration technique. By taking advantage of the large specific surface area of nanoporous silica (≈300m 2/g), large scale purification of neat PS-b-PMMA has successfully been achieved by controlling adsorption and desorption of the block copolymers on the silica gel surface using a

  2. Block copolymer investigations

    NASA Astrophysics Data System (ADS)

    Yufa, Nataliya A.

    The research presented in this thesis deals with various aspects of block copolymers on the nanoscale: their behavior at a range of temperatures, their use as scaffolds, or for creation of chemically striped surfaces, as well as the behavior of metals on block copolymers under the influence of UV light, and the healing behavior of copolymers. Invented around the time of World War II, copolymers have been used for decades due to their macroscopic properties, such as their ability to be molded without vulcanization, and the fact that, unlike rubber, they can be recycled. In recent years, block copolymers (BCPs) have been used for lithography, as scaffolds for nano-objects, to create a magnetic hard drive, as well as in photonic and other applications. In this work we used primarily atomic force microscopy (AFM) and transmission electron microscopy (TEM), described in Chapter II, to conduct our studies. In Chapter III we demonstrate a new and general method for positioning nanoparticles within nanoscale grooves. This technique is suitable for nanodots, nanocrystals, as well as DNA. We use AFM and TEM to demonstrate selective decoration. In Chapters IV and V we use AFM and TEM to study the structure of polymer surfaces coated with metals and self-assembled monolayers. We describe how the surfaces were created, exhibit their structure on the nanoscale, and prove that their macroscopic wetting properties have been altered compared to the original polymer structures. Finally, Chapters VI and VII report out in-situ AFM studies of BCP at high temperatures, made possible only recently with the invention of air-tight high-temperature AFM imaging cells. We locate the transition between disordered films and cylinders during initial ordering. Fluctuations of existing domains leading to domain coarsening are also described, and are shown to be consistent with reptation and curvature minimization. Chapter VII deals with the healing of PS-b-PMMA following AFM-tip lithography or

  3. Solid-supported polymer bilayers formed by coil-coil block copolymers.

    PubMed

    Yang, Yan-Ling; Tsao, Heng-Kwong; Sheng, Yu-Jane

    2016-08-14

    The formation and physical properties of solid-supported polymer bilayers (SPBs) on an adhesive substrate have been explored by dissipative particle dynamics simulations. A SPB is developed by the adsorption of vesicles formed by diblock copolymers in a selective solvent. The adsorbed vesicle can remain intact or become ruptured into a SPB, depending on the interaction between solvophobic blocks and solvent and the interaction between solvophilic blocks and the substrate. The morphological phase diagram of adsorbed vesicles is acquired. The influence of polymer adhesion strength and solvophobicity on the geometrical and mechanical properties of a SPB is systematically studied as well. It is found that vesicular disruption is easily triggered for strong adhesion strength. Moreover, for strong adhesion strength and weak solvophobicity, the fluctuation of membrane height is impeded while the area of fluctuation is enhanced. PMID:27418114

  4. Effects of compositional asymmetry in phase behavior of ABA triblock copolymer melts from Monte Carlo simulation.

    PubMed

    Wołoszczuk, S; Banaszak, M

    2010-12-01

    We simulate ABA triblock copolymer melts using a lattice Monte Carlo method, known as cooperative motion algorithm, probing various degrees of compositional asymmetry. Selected order-disorder transition lines are determined in terms of the segment incompatibility, quantified by product χN , and the triblock asymmetry parameters, α and β. We correlate the results of the simulation with the self-consistent field theory and an experimental study of polyisoprene-polystyrene-polyisoprene triblock melt by Hamersky and coworkers. In particular, we confirm the mean-field prediction that for highly asymmetric triblocks the short A -block is localized in the middle of the B -domain due to an entropic advantage. This results in the middle block relaxation and is consistent with the experimental data indicating that as the relatively short A -blocks are grown into AB diblock, from the B -block side, the order-disorder transition temperature is considerably depressed.

  5. Nanoscale engineering of two-dimensional disordered hyperuniform block-copolymer assemblies

    NASA Astrophysics Data System (ADS)

    Zito, Gianluigi; Rusciano, Giulia; Pesce, Giuseppe; Malafronte, Anna; Di Girolamo, Rocco; Ausanio, Giovanni; Vecchione, Antonio; Sasso, Antonio

    2015-11-01

    Disordered hyperuniform (DH) media have been recognized as a new state of disordered matter that broadens our vision of material engineering. Here, long-range correlated disordered two-dimensional patterns are fabricated by self-assembling of spherical diblock-copolymer (BCP) micelles. Control of the self-assembling parameters leads to the formation of DH patterns of micelles that can host nanoscale material inclusions, therefore providing an effective strategy for fabricating multimaterial DH structures at molecular scale. Centroidal patterns are accurately determined by virtue of BCP micelles loaded with metal nanoparticles. Our analysis reveals the signature of nearly ideal DH BCP assemblies in the local density fluctuation and a dominant linear scaling in the local number fluctuation.

  6. Coatings with Thermally Switchable Surface Energy Produced From Block Copolymer Films

    NASA Astrophysics Data System (ADS)

    Davis, Raleigh; Register, Richard

    2015-03-01

    Polymer-based coatings are employed across a wide array of sectors. One application of such coatings is to impart a prescribed surface energy, i . e . hydrophilic or hydrophobic character. The present work explores an approach to create surfaces with thermally switchable wetting behavior by employing coatings based on block copolymers which possess both hydrophilic and hydrophobic segments. The amphiphilic block copolymers were synthesized by coupling allyl-ended poly(ethylene oxide) (PEO) and hydride-ended poly(dimethylsiloxane) (PDMS) oligomers via a Pt catalyst. One PEO-PDMS diblock possessed an order-disorder-transition-temperature (TODT) of 64°C as characterized by small angle x-ray scattering. Above the TODT the polymer is a disordered melt, but below this temperature it self-assembles into alternating lamellae with a repeat spacing of 7.7 nm. When cooled through the TODT in vacuum or dry air, the PDMS-enriched domains wet the film's surface, producing a hydrophobic surface with a contact angle (CA) ~ 90° as measured from CA goniometry. However, when cooled under water or in humid air, a PEO-rich hydrophilic surface is produced, yielding CAs ranging from 20-40°. The coatings can then be reversibly switched between the two states by reheating above the TODT, exposing to the appropriate environment, and re-cooling, ideally ``locking in'' the structure until the next processing cycle. The TODT, and thus the switching temperature, can be continuously tuned by blending with PEO-PDMS diblocks of different molecular weights.

  7. Adsorption of block copolymers on solid surfaces: A Monte Carlo study.

    PubMed

    Słyk, Edyta; Rżysko, Wojciech; Bryk, Paweł

    2014-07-28

    Using hyper-parallel tempering Monte Carlo simulation, multiple histogram reweighting method, and finite size scaling, we investigate the adsorption of fully flexible and rod-coil chains on the square lattice. We find that the phase behaviour changes with the chain length and flexibility. For homonuclear rod-coil chains, the phase diagram consists of only gas-disorder liquid critical point. Weakening of the interaction energy between the segments belonging to two different subunits gives rise to an order-disorder transition. The topology of the resulting phase diagram depends on the chain length and flexibility. For short chains, both fully flexible and rod-coil diblock copolymers form lamellar ordered phase with fully stretched chains, and the order-disorder transition is of the first order. The phase diagrams are similar for both chain architectures and consist of two binodals meeting in the triple point. When the chain length increases the order-disorder transition becomes second-order and the difference in the phase behaviour between the fully flexible and the rod-coil diblock copolymers becomes more pronounced. While for the former chain architecture the topology of the phase diagram involves a λ-line which meets the gas-disordered liquid binodal in the critical end-point, in the latter case the λ-line meets the gas-disordered liquid critical point and forms the tricritical point. We trace back these changes to the change in the morphology of the ordered phase. The mechanism of the order-disorder transition involves the formation of domains resembling those observed during the spinodal decomposition process. The domains subsequently merge and arrange into lamellae. These observations are supported by integral geometry analysis. PMID:25084959

  8. Dynamics of Chain Exchange in Block Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Lodge, Timothy

    Block copolymer micelles are rarely at equilibrium. The primary reason is the large number of repeat units in the insoluble block, Ncore, which makes the thermodynamic penalty for extracting a single chain (``unimer exchange'') substantial. As a consequence, the critical micelle concentration (CMC) is rarely accessed experimentally; however, in the proximity of a critical micelle temperature (CMT), equilibration is possible. We have been using time-resolved small angle neutron scattering (TR-SANS) to obtain a detailed picture of the mechanisms and time scales for chain exchange, at or near equilibrium. Our model system is poly(styrene)-block-poly(ethylene-alt-propylene)) (PS-PEP), in the PEP-selective solvent squalane (C30H62) . Equivalent micelles with either normal (hPS) or perdeuterated (dPS) cores are initially mixed in a blend of isotopically substituted squalane, designed to contrast-match a 50:50 hPS:dPS core. Samples are then annealed at a target temperature, and chain exchange is revealed quantitatively by the temporal decay in scattered intensity. The rate of exchange as function of concentration, temperature, Ncore, Ncorona, and chain architecture (diblock versus triblock) will be discussed.

  9. Preparation, Stability, and Bio-Compatability of Block Copolymer Vesicles

    NASA Astrophysics Data System (ADS)

    Discher, Dennis; Lee, James C.-M.; Bermudez, Harry; Bates, Frank; Discher, Bohdana

    2001-03-01

    Vesicles made completely from diblock copolymers polymersomes can be stably prepared by a wide range of techniques common to liposomes. Processes such as film rehydration, sonication, and extrusion can generate many micron giants as well as monodisperse, 100 nm vesicles of PEO-PEE (polyethyleneoxide polyethylethylene) or PEO PBD (polyethyleneoxide polybutadiene). These thick-walled vesicles of polymer can encapsulate macromolecules just as liposomes can, but, unlike many pure liposome systems, these polymersomes exhibit no in-surface thermal transitions and a sub-population even survive autoclaving. Suspension in blood plasma has no immediate ill-effect on vesicle stability, and neither adhesion nor stimulation of phagocytes are apparent when giant polymersomes are held in direct, protracted contact. Proliferating cells, in addition, are unaffected when cultured for an extended time with an excess of polymersomes, and several injections of 10 mg doses into rats show no ill-effect. The results are consistent with the steric stabilization that PEG-lipid can impart to liposomes, but the present single-component polymersomes are far more stable mechanically and are not limited by PEG driven micellization.

  10. Confinement effects on the miscibility of block copolymer blends.

    PubMed

    Spencer, Russell K W; Matsen, Mark W

    2016-04-01

    Thin films of long and short symmetric AB diblock copolymers are examined using self-consistent field theory (SCFT). We focus on hard confining walls with a preference for the A component, such that the lamellar domains orient parallel to the film with an even number ν of monolayers. For neat melts, confinement causes the lamellar period, D, to deviate from its bulk value, Db, in order to be commensurate with the film thickness, i.e., L = νD/2. For blends, however, the melt also has the option of macrophase separating into ν(l) large and ν((s)) small monolayers so as to provide a better fit, where L = ν(l)D(l)/2 + ν(s)D((s))/2. In addition to performing full SCFT calculations of the entire film, we develop a semi-analytical calculation for the coexistence of thick and thin monolayers that helps explain the complicated interplay between miscibility and commensurability. PMID:27106106

  11. A density functional theory of chiral block copolymer melts.

    PubMed

    Wang, Shih-Hao; Kawakatsu, Toshihiro; Chen, Peilong; Lu, Chun-Yi David

    2013-05-21

    A density functional theory is developed for the diblock copolymer melt, where one block contains the segment orientation dependent chiral interaction. In addition to the standard (scalar) pair interaction between the two types of monomers, the chiral block has the additional pairwise interaction, which is linear in the tangent vectors of the segments. We construct a density functional, which contains both the scalar density field and the vector chain alignment field. The quadratic part of the density functional comes from the mean field theory of the microscopic model, whereas the fourth order terms are introduced phenomenologically in the spatially local form. From the stability analysis of this model, we find that the additional chiral interaction shifts the order-disorder transition, which is consistent with the behavior of experimental system. Further numerical calculation reveals a new metastable chiral helical cylinder structure, which is similar to the one found experimentally. Another similar metastable structure but with zigzag modulation is also observed. As the helical and zigzag structures disappear when the chiral interaction is switched off, we understand that the chiral effect is the driving force for the formation of these exotic metastable structures.

  12. LIGHT SCATTERING STUDY OF DIBLOCK COPOLYMERS IN SUPERCRITICAL CARBON DIOXIDE CO2 DENSITY-INDUCED MICELLIZATION TRANSITION. (R826115)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  13. Cellular internalization of a membrane binding two-photon probe by a complex of anionic diblock copolymer and cationic surfactant

    NASA Astrophysics Data System (ADS)

    Nag, Okhil Kumar; Woo, Han Young; Chen, Wei R.

    2012-03-01

    We report a two-photon (TP) absorbing molecular probe 1,4-bis(4'-(N,N-bis(6''-(N,N,N-trimethylammonium)hexyl)amino)-styryl)benzene tetrabromide (C1) and its interaction with cells upon encapsulation with polymeric vesicles. Two-photon microscopy (TPM) revealed that the free C1 specifically could bind to the plasma membrane and shows bright TP emission. However, C1 encapsulated with polymeric vesicles internalized into the cytosol. In addition, fluorescence quantum efficiency and TP cross section of encapsulated C1 enhanced by 2-fold. These results not only show useful guidelines for the development of efficient TP probes, but also underscore the possibility of using this type of nanostructure for intracellular delivery of the bioactive therapeutics.

  14. Pathways of cylindrical orientations in PS-b-P4VP diblock copolymer thin films upon solvent vapor annealing.

    PubMed

    Gowd, E Bhoje; Koga, Tadanori; Endoh, Maya K; Kumar, Kamlesh; Stamm, Manfred

    2014-10-21

    The orientation changes of perpendicular cylindrical microdomains in polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) thin films upon annealing in different solvent vapors were investigated by in situ grazing incidence small-angle X-ray scattering (GISAXS) and ex situ scanning force microscopy (SFM). The swelling of P4VP perpendicular cylinders (C⊥) in chloroform, a non-selective solvent vapor, leads to the reorientation to in-plane cylinders through a disordered state in a particular kinetic pathway in the phase diagram upon drying. On the other hand, the swelling of the P4VP perpendicular cylinders in a selective solvent vapor (i.e., 1,4-dioxane) induces a morphological transition from cylindrical to ellipsoidal as a transient structure to spherical microdomains; subsequent solvent evaporation resulted in shrinkage of the matrix in the vertical direction, merging the ellipsoidal domains into the perpendicularly aligned cylinders. In this paper, we have discussed the mechanism based on the selectivity of the solvent to the constituting blocks that is mainly responsible for the orientation changes. PMID:25142254

  15. Polyether/Polyester Graft Copolymers

    NASA Technical Reports Server (NTRS)

    Bell, Vernon L., Jr.; Wakelyn, N.; Stoakley, D. M.; Proctor, K. M.

    1986-01-01

    Higher solvent resistance achieved along with lower melting temperature. New technique provides method of preparing copolymers with polypivalolactone segments grafted onto poly (2,6-dimethyl-phenylene oxide) backbone. Process makes strong materials with improved solvent resistance and crystalline, thermally-reversible crosslinks. Resulting graft copolymers easier to fabricate into useful articles, including thin films, sheets, fibers, foams, laminates, and moldings.

  16. Amphiphilic poly(D- or L-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) block copolymers: controlled synthesis, characterization, and stereocomplex formation.

    PubMed

    Spasova, Mariya; Mespouille, Laetitia; Coulembier, Olivier; Paneva, Dilyana; Manolova, Nevena; Rashkov, Iliya; Dubois, Philippe

    2009-05-11

    Novel well-defined amphiphilic poly(D-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) (PDLA-b-PDMAEMA) and poly(L-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) (PLLA-b-PDMAEMA) copolymers were obtained. The synthesis strategy consisted of a three-step procedure: (i) controlled ring-opening polymerization (ROP) of (D- or L-)lactide initiated by Al(O(i)Pr)(3), followed by (ii) quantitative conversion of the polylactide (PLA) hydroxyl end-groups with bromoisobutyryl bromide and (iii) atom transfer radical polymerization (ATRP) of DMAEMA. The PLA block molecular weight was kept below 5000 g/mol. The macromolecular parameters of the (co)polymers were determined by (1)H NMR spectroscopy and size exclusion chromatography (SEC). The stereocomplexes of PDLA-b-PDMAEMA/PLLA-b-PDMAEMA diblock copolymers were prepared via solvent casting. The stereocomplex formation was evidenced by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. The obtained stereocomplexes had melting temperature of about 65 degrees C above that of the individual copolymers and exhibited diffraction patterns assigned to the stereocomplex crystallites. In addition, for the first time it was shown that the replacement of one of the PLA partners with high molecular weight PLLA or PDLA did not hamper the stereocomplex formation. The presence of PDMAEMA blocks proved to impart hydrophilicity of the synthesized copolymers and related stereocomplexes, as determined by static water contact angle measurements. PMID:19331403

  17. Cooperation of Amphiphilicity and Crystallization for Regulating the Self-Assembly of Poly(ethylene glycol)-block-poly(lactic acid) Copolymers.

    PubMed

    Wang, Zhen; Cao, Yuanyuan; Song, Jiaqi; Xie, Zhigang; Wang, Yapei

    2016-09-20

    Tuning the amphiphilicity of block copolymers has been extensively exploited to manipulate the morphological transition of aggregates. The introduction of crystallizable moieties into the amphiphilic copolymers also offers increasing possibilities for regulating self-assembled structures. In this work, we demonstrate a detailed investigation of the self-assembly behavior of amphiphilic poly(ethylene glycol)-block-poly(l-lactic acid) (PEG-b-PLLA) diblock copolymers with the assistance of a common solvent in aqueous solution. With a given length of the PEG block, the molecular weight of the PLA block has great effect on the morphologies of self-assembled nanoaggregates as a result of varying molecular amphiphilicity and polymer crystallization. Common solvents including N,N-dimethylformamide, dioxane, and tetrahydrofuran involved in the early stage of self-assembly led to the change in chain configuration, which further influences the self-assembly of block copolymers. This study expanded the scope of PLA-based copolymers and proposed a possible mechanism of the sphere-to-lozenge and platelet-to-cylinder morphological transitions. PMID:27496056

  18. Flash NanoPrecipitation of organic actives via confined micromixing and block copolymer stabilization

    NASA Astrophysics Data System (ADS)

    Johnson, Brian K.

    to quantify the induction time through knowledge of the mixing lifetime. Copolymer aggregation without an organic active to kinetically frozen nanoparticles occurs by a "fusion only" mechanism. By analogy to classical precipitation kinetics, the interfacial free energy of a diblock copolymer nanoparticle is determined for the first time. The composite dissertation provides a clear picture of Flash NanoPrecipitation for future research and applications.

  19. Lateral structuring and stability phenomena induced by block copolymers and core-shell nanogel particles at immiscible polymer/polymer interfaces

    NASA Astrophysics Data System (ADS)

    Gozen, Arif Omer

    We have investigated the parameters such as copolymer/nanoparticle concentration, architecture and molecular weight combined with film thickness, time and temperature in order to develop a molecular-level insight on how lateral interfacial structuring occurs at immiscible polymer/polymer interfaces. I order to develop a molecular-level understanding of how these 'smart' self-assembling materials and core-shell nanogel particles interact both intra- and inter-molecularly and form ordered structures in bulk, as well as at immiscible interfaces, we first focused on the response of core-shell polymer nanoparticles, designated CSNGs, composed of a cross-linked divinylbenzene core and poly(methyl methacrylate) (PMMA) arms as they segregate from PMMA homopolymer. We have demonstrated that these nanogel particles exhibit autophobic character when dispersed in high molecular weight homopolymer matrices and segregate to the interface with another fluid. We have further explored the migration of these new-generation nanogel particles (CSNG-Rs) segregating from PS homopolymer to PS/PMMA interfaces. Unlike the instability patterns observed with the CSNGs, which exhibit classical nucleation and growth mechanism with circular hole formation, we have observed an intriguing dewetting pattern and CSNG-Rs forming lateral aggregates and tentacle-like structures at the interface. In parallel with our core-shell particle studies, we have also explored the structuring of copolymer molecules that are far from equilibrium in bulk and complex laminate of polymer thin films. Our early triblock copolymer studies have proven that molecular asymmetry has a profound effect on order-disorder transition temperature. We focused primarily on the effect of the copolymer chemical composition (i.e., block sizes) on the dewetting behavior of PS/SM thin films on PMMA. We elucidate the interfacial segregation and concurrent micellization of diblock copolymers in a dynamically evolving environment with

  20. Effect of PEG-PDMAEMA Block Copolymer Architecture on Polyelectrolyte Complex Formation with Heparin.

    PubMed

    Välimäki, Salla; Khakalo, Alexey; Ora, Ari; Johansson, Leena-Sisko; Rojas, Orlando J; Kostiainen, Mauri A

    2016-09-12

    Heparin is a naturally occurring polyelectrolyte consisting of a sulfated polysaccharide backbone. It is widely used as an anticoagulant during major surgical operations. However, the associated bleeding risks require rapid neutralization after the operation. The only clinically approved antidote for heparin is protamine sulfate, which is, however, ineffective against low molecular weight heparin and can cause severe adverse reactions in patients. In this study, the facile synthesis of cationic-neutral diblock copolymers and their effective heparin binding is presented. Poly(ethylene glycol)-poly(2-(dimethylamino)ethyl methacrylate) (PEG-PDMAEMA) block copolymers were synthesized in two steps via atom-transfer radical polymerization (ATRP) using PEG as a macroinitiator. Solution state binding between heparin and a range of PEG-PDMAEMA block copolymers and one homopolymer was studied with dynamic light scattering and methylene blue displacement assay. Also in vitro binding in plasma was studied by utilizing a chromogenic heparin anti-Xa assay. Additionally, quartz crystal microbalance and multiparametric surface plasmon resonance were used to study the surface adsorption kinetics of the polymers on a heparin layer. It was shown that the block copolymers and heparin form electrostatically bound complexes with varying colloidal properties, where the block lengths play a key role in controlling the heparin binding affinity, polyelectrolyte complex size and surface charge. With the optimized polymers (PEG114PDMAEMA52 and PEG114PDMAEMA100), heparin could be neutralized in a dose-dependent manner, and bound efficiently into small neutral complexes, with a hydrodynamic radius less than 100 nm. These complexes had only a limited effect on cell viability. Based on these studies, our approach paves the way for the development of new polymeric heparin binding agents. PMID:27477891

  1. Phthalimide Copolymer Solar Cells

    NASA Astrophysics Data System (ADS)

    Xin, Hao; Guo, Xugang; Ren, Guoqiang; Kim, Felix; Watson, Mark; Jenekhe, Samson

    2010-03-01

    Photovoltaic properties of bulk heterojunction solar cells based on phthalimide donor-acceptor copolymers have been investigated. Due to the strong π-π stacking of the polymers, the state-of-the-art thermal annealing approach resulted in micro-scale phase separation and thus negligible photocurrent. To achieve ideal bicontinuous morphology, different strategies including quickly film drying and mixed solvent for film processing have been explored. In these films, nano-sale phase separation was achieved and a power conversion efficiency of 3.0% was obtained. Absorption and space-charge limited current mobility measurements reveal similar light harvesting and hole mobilities in all the films, indicating that the morphology is the dominant factor determining the photovoltaic performance. Our results demonstrate that for highly crystalline and/or low-solubility polymers, finding a way to prevent polymer aggregation and large scale phase separation is critical to realizing high performance solar cells.

  2. Phase Behavior of Binary Blends of AB+AC Block Copolymers with compatible B and C blocks

    NASA Astrophysics Data System (ADS)

    Pryamitsyn, Victor; Ganesan, Venkat

    2012-02-01

    Recently the experimental studies of phase behavior of binary blends of PS-b-P2VP and PS-b-PHS demonstrated an interesting effect: blends of symmetric PS-b-P2VP and shorter symmetric (PS-b-PHS) formed cylindrical HEX and spherical BCC phases, while each pure component formed lamellas. The miscibility of P2VP and PHS is caused by the hydrogen bonding between P2VP and PHS,which can be described as a negative Flory ?-parameter between P2VP and PHS. We developed a theory of the microphase segregation of AB+AC blends of diblock copolymers based on strong stretching theory. The main result of our theory is that in the copolymer brush-like layer formed by longer B chain and shorter C chains, the attraction between B and shorter C chains causes relative stretching of short C chains and compression of longer B chains. The latter manifests in an excessive bending force towards the grafting surface (BC|AA interface). Such bending force causes a transition from a symmetric lamella phase to a HEX cylinder or BCC spherical phases with the BC phase being a ``matrix'' component. In a blend of asymmetric BCC sphere forming copolymers (where B and C segments are the minor components), such bending force may unfold BCC spherical phase to a HEX cylinder phase, or even highly uneven lamella phases.

  3. Thermodynamics of the multi-stage self-assembly of pH-sensitive gradient copolymers in aqueous solutions.

    PubMed

    Černochová, Zulfiya; Bogomolova, Anna; Borisova, Olga V; Filippov, Sergey K; Černoch, Peter; Billon, Laurent; Borisov, Oleg V; Štěpánek, Petr

    2016-08-10

    The self-assembly thermodynamics of pH-sensitive di-block and tri-block gradient copolymers of acrylic acid and styrene was studied for the first time using isothermal titration calorimetry (ITC) and dynamic light scattering (DLS) performed at varying pH. We were able to monitor each step of micellization as a function of decreasing pH. The growth of micelles is a multi-stage process that is pH dependent with several exothermic and endothermic components. The first step of protonation of the acrylic acid monomer units was accompanied mainly by conformational changes and the beginning of self-assembly. In the second stage of self-assembly, the micelles become larger and the number of micelles becomes smaller. While solution acidity increases, the isothermal calorimetry data show a broad deep minimum corresponding to an exothermic process attributed to an increase in the size of hydrophobic domains and an increase in the structure's hydrophobicity. The minor change in heat capacity (ΔCp) confirms the structural changes during this exothermic process. The exothermic process terminates deionization of acrylic acid. The pH-dependence of the ζ-potential of the block gradient copolymer micelles exhibits a plateau in the regime corresponding to the pH-controlled variation of the micellar dimensions. The onset of micelle formation and the solubility of the gradient copolymers were found to be dependent on the length of the gradient block. PMID:27451979

  4. Real-Time observation of PS-PDMS block copolymer self-assembly under solvent vapor annealing

    NASA Astrophysics Data System (ADS)

    Bai, Wubin; Yager, Kevin; Ross, Caroline

    2015-03-01

    Solvent annealing provides a convenient way to produce microphase separation in films of block copolymers, but the morphology transition of the film during the solvent absorption, equilibrium solvent-BCP concentration and solvent desorption process are not well known. An in situ study of solvent annealing of polystyrene-block-polydimethylsiloxane (PS-PDMS, 16 kg/mol, fPDMS = 30%, period 17 nm) diblock copolymer was carried by synchrotron grazing-incidence small-angle X-ray scattering (GISAXS). The swollen film morphology was found to be strongly dependent on swelling ratio. A transition from the disordered state to a highly ordered state which contained multiple layers of in-plane cylinders was observed at a swelling ratio around 1.45 from samples with 100nm to 1000nm as-cast thickness. The rate of solvent absorption was found to be less important to the dried morphology, while the time of equilibrium solvent-BCP concentration stage was found to influence the orientation of self-assembled microdomains and the drying rate was found to affect the degree of structure deformation. The implications of the results to pattern generation for block copolymer directed self-assembly will be discussed. Semiconductor Research Corporation, National Science Foundation.

  5. Flory-Huggins parameter χ, from binary mixtures of Lennard-Jones particles to block copolymer melts.

    PubMed

    Chremos, Alexandros; Nikoubashman, Arash; Panagiotopoulos, Athanassios Z

    2014-02-01

    In this contribution, we develop a coarse-graining methodology for mapping specific block copolymer systems to bead-spring particle-based models. We map the constituent Kuhn segments to Lennard-Jones particles, and establish a semi-empirical correlation between the experimentally determined Flory-Huggins parameter χ and the interaction of the model potential. For these purposes, we have performed an extensive set of isobaric-isothermal Monte Carlo simulations of binary mixtures of Lennard-Jones particles with the same size but with asymmetric energetic parameters. The phase behavior of these monomeric mixtures is then extended to chains with finite sizes through theoretical considerations. Such a top-down coarse-graining approach is important from a computational point of view, since many characteristic features of block copolymer systems are on time and length scales which are still inaccessible through fully atomistic simulations. We demonstrate the applicability of our method for generating parameters by reproducing the morphology diagram of a specific diblock copolymer, namely, poly(styrene-b-methyl methacrylate), which has been extensively studied in experiments. PMID:24511981

  6. Flory-Huggins parameter χ, from binary mixtures of Lennard-Jones particles to block copolymer melts

    SciTech Connect

    Chremos, Alexandros; Nikoubashman, Arash Panagiotopoulos, Athanassios Z.

    2014-02-07

    In this contribution, we develop a coarse-graining methodology for mapping specific block copolymer systems to bead-spring particle-based models. We map the constituent Kuhn segments to Lennard-Jones particles, and establish a semi-empirical correlation between the experimentally determined Flory-Huggins parameter χ and the interaction of the model potential. For these purposes, we have performed an extensive set of isobaric–isothermal Monte Carlo simulations of binary mixtures of Lennard-Jones particles with the same size but with asymmetric energetic parameters. The phase behavior of these monomeric mixtures is then extended to chains with finite sizes through theoretical considerations. Such a top-down coarse-graining approach is important from a computational point of view, since many characteristic features of block copolymer systems are on time and length scales which are still inaccessible through fully atomistic simulations. We demonstrate the applicability of our method for generating parameters by reproducing the morphology diagram of a specific diblock copolymer, namely, poly(styrene-b-methyl methacrylate), which has been extensively studied in experiments.

  7. Selective Area Control of Self-Assembled Pattern Architecture Using a Lithographically Patternable Block Copolymer

    SciTech Connect

    Black, C.T.; Bosworth, J.K.; Obert C.K.

    2009-07-01

    We leverage distinctive chemical properties of the diblock copolymer poly({alpha}-methylstyrene)-block-poly(4-hydroxystyrene) to create for the first time high-resolution selective-area regions of two different block copolymer phase morphologies. Exposure of thin films of poly({alpha}-methylstyrene)-block-poly(4-hydroxystyrene) to nonselective or block-selective solvent vapors results in polymer phase separation and self-assembly of patterns of cylindrical-phase or kinetically trapped spherical-phases, respectively. Poly(4-hydroxystyrene) acts as a high-resolution negative-tone photoresist in the presence of small amounts of a photoacid generator and cross-linker, undergoing radiation-induced cross-linking upon exposure to ultraviolet light or an electron beam. We use lithographic exposure to lock one self-assembled phase morphology in specific sample areas as small as 100 nm in width prior to film exposure to a subsequent solvent vapor to form a second self-assembled morphology in unexposed wafer areas.

  8. Block copolymers confined in a nanopore: Pathfinding in a curving and frustrating flatland

    NASA Astrophysics Data System (ADS)

    Sevink, G. J. A.; Zvelindovsky, A. V.

    2008-02-01

    We have studied structure formation in a confined block copolymer melt by means of dynamic density functional theory. The confinement is two dimensional, and the confined geometry is that of a cylindrical nanopore. Although the results of this study are general, our coarse-grained molecular model is inspired by an experimental lamella-forming polysterene-polybutadiene diblock copolymer system [K. Shin et al., Science 306, 76 (2004)], in which an exotic toroidal structure was observed upon confinement in alumina nanopores. Our computational study shows that a zoo of exotic structures can be formed, although the majority, including the catenoid, helix, and double helix that were also found in Monte Carlo nanopore studies, are metastable states. We introduce a general classification scheme and consider the role of kinetics and elongational pressure on stability and formation pathway of both equilibrium and metastable structures in detail. We find that helicity and threefold connections mediate structural transitions on a larger scale. Moreover, by matching the remaining parameter in our mesoscopic method, the Flory-Huggins parameter χ, to the experimental system, we obtain a structure that resembles the experimental toroidal structure in great detail. Here, the most important factor seems to be the roughness of the pore, i.e., small variations of the pore radius on a scale that is larger than the characteristic size in the system.

  9. The plumber's nightmare: a new morphology in block copolymer-ceramic nanocomposites and mesoporous aluminosilicates.

    PubMed

    Finnefrock, Adam C; Ulrich, Ralph; Toombes, Gilman E S; Gruner, Sol M; Wiesner, Ulrich

    2003-10-29

    A novel cubic bicontinuous morphology is found in polymer-ceramic nanocomposites and mesoporous aluminosilicates that are derived by an amphiphilic diblock copolymer, poly(isoprene-b-ethylene oxide) (PI-b-PEO), used as a structure-directing agent for an inorganic aluminosilicate. Small-angle X-ray scattering (SAXS) was employed to unambiguously identify the Im(-)3m crystallographic symmetry of the materials by fitting individual Bragg peak positions in the two-dimensional X-ray images. Structure factor calculations, in conjunction with results from transmission electron microscopy, were used to narrow the range of possible structures consistent with the symmetry and showed the plumber's nightmare morphology to be consistent with the data. The samples are made by deposition onto a substrate that imposes a strain field, generating a lattice distortion. This distortion is quantitatively analyzed and shown to have resulted in shrinkage of the crystallites by approximately one-third in a direction perpendicular to the substrate, in both as-made composites and calcined ceramic materials. Finally, the observation of the bicontinuous block-copolymer-derived hybrid morphology is discussed in the context of a pseudo-ternary morphology diagram and compared to existing studies of ternary phase diagrams of amphiphiles in a mixture of two solvents. The calcined mesoporous materials have potential applications in the fields of catalysis, separation technology, and microelectronics.

  10. Simulations on a swollen gyroid nanostructure in thin films relevant to systems of ionic block copolymers.

    PubMed

    Knychała, P; Banaszak, M

    2014-07-01

    Self-assembly of symmetric A/S-B copolymer melt to gyroid nanostructure, partitioning space into interpenetrating nano-labyrinths (channels), in thin films, is investigated using a minimal lattice model with short-range interactions. This model is relevant to poly(styrenesulfonate)-b -polymethylbutylene melt consisting of three types of segments, A, B and S, corresponding to styrene, methylbutylene and styrenesulfonate, respectively. A single sequence of A, B, and S is used in simulations and the fraction of S segments is fixed at p = 0.647 which corresponds to experimental data. The film thickness, L(z), is restricted to nine values (L(z) = 17 , 22, 26, 30, 34, 42, 51, 60, and 68 in units of the underlying lattice constant). The gyroid nanostructure is found to be stable if the film thickness is equal to or greater than the bulk period of the nanophase. The observed gyroid is referred to as swollen since the volume fraction of two continuous networks made of the B segments is anomalous with respect to that of conventional diblock copolymers. In contrast to bulk state, we do not directly observe the order-disorder transition to the gyroid nanophase for thin films. In this case, however, simulations indicate a direct order-disorder transition to a lamellar phase and the order-disorder transition temperature is higher than that in the bulk state, varying strongly with the film thickness. PMID:25080175

  11. Morphology and Ionic Conductivity of Oriented Block Copolymer/Ionic Liquid Mixtures

    NASA Astrophysics Data System (ADS)

    Sharick, Sharon; Winey, Karen I.

    2015-03-01

    Ion-containing block copolymers with increased continuity and long-range order of ion-containing microdomains were prepared to probe the impact of grain boundaries and microdomain orientation on ion transport. We studied poly(styrene- b-methyl methacrylate) diblock copolymers swollen with 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonylimide) (SbMMA/IL), and characterized the thermal transitions, morphologies, and ionic conductivities by differential scanning calorimetry, small-angle X-ray scattering, and electrochemical impedance spectroscopy over a range of compositions. Two glass transition temperatures (Tgs) are observed, corresponding to PS and PMMA/IL microdomains, and Tg,PMMA/IL is modeled well by the Gordon-Taylor expression. SbMMA/IL films prepared by solvent evaporation exhibit strongly microphase-separated lamellar morphology with long-range order. Slower rates of solvent evaporation produce films with lamellae preferentially oriented to be in the plane. In-plane conductivities increase with both increasing ionic liquid content and with better parallel alignment of lamellae. The Sax and Ottino model will be used to compare the conductivity of SbMMA/IL with the homopolymer/IL mixture, PMMA/IL, and to discuss the ion transport mechanism.

  12. Substrate-bound growth of Au-Pd diblock nanowire and hybrid nanorod-plate

    NASA Astrophysics Data System (ADS)

    He, Jiating; Wang, Yawen; Fan, Zhanxi; Lam, Zhenhui; Zhang, Hua; Liu, Bin; Chen, Hongyu

    2015-04-01

    We expand the scope of the previously developed Active Surface Growth mode for growing substrate-bound ultrathin Pd (d = 4 nm) and Ag nanowires (d = 30 nm) in aqueous solution under ambient conditions. Using Au nanorods as the seeds, selective growth at the contact line between the rod and the substrate eventually leads to an attached Pd nanoplate. The unique growth mode also allows sequential growth of different materials via a single seed, giving substrate-bound Au-Pd diblock nanowires. The new abilities to use seed shape to pre-define the active sites and to apply sequential growth open windows for new pathways to hybrid nanostructures.We expand the scope of the previously developed Active Surface Growth mode for growing substrate-bound ultrathin Pd (d = 4 nm) and Ag nanowires (d = 30 nm) in aqueous solution under ambient conditions. Using Au nanorods as the seeds, selective growth at the contact line between the rod and the substrate eventually leads to an attached Pd nanoplate. The unique growth mode also allows sequential growth of different materials via a single seed, giving substrate-bound Au-Pd diblock nanowires. The new abilities to use seed shape to pre-define the active sites and to apply sequential growth open windows for new pathways to hybrid nanostructures. Electronic supplementary information (ESI) available: Supporting TEM and SEM images of control experiments with different reaction conditions and another type of diblock nanowires. See DOI: 10.1039/c5nr00361j

  13. Skin delivery by block copolymer nanoparticles (block copolymer micelles).

    PubMed

    Laredj-Bourezg, Faiza; Bolzinger, Marie-Alexandrine; Pelletier, Jocelyne; Valour, Jean-Pierre; Rovère, Marie-Rose; Smatti, Batoule; Chevalier, Yves

    2015-12-30

    Block copolymer nanoparticles often referred to as "block copolymer micelles" have been assessed as carriers for skin delivery of hydrophobic drugs. Such carriers are based on organic biocompatible and biodegradable materials loaded with hydrophobic drugs: poly(lactide)-block-poly(ethylene glycol) copolymer (PLA-b-PEG) nanoparticles that have a solid hydrophobic core made of glassy poly(d,l-lactide), and poly(caprolactone)-block-poly(ethylene glycol) copolymer (PCL-b-PEG) nanoparticles having a liquid core of polycaprolactone. In vitro skin absorption of all-trans retinol showed a large accumulation of retinol in stratum corneum from both block copolymer nanoparticles, higher by a factor 20 than Polysorbate 80 surfactant micelles and by a factor 80 than oil solution. Additionally, skin absorption from PLA-b-PEG nanoparticles was higher by one order of magnitude than PCL-b-PEG, although their sizes (65nm) and external surface (water-swollen PEG layer) were identical as revealed by detailed structural characterizations. Fluorescence microscopy of histological skin sections provided a non-destructive picture of the storage of Nile Red inside stratum corneum, epidermis and dermis. Though particle cores had a different physical states (solid or liquid as measured by (1)H NMR), the ability of nanoparticles for solubilization of the drug assessed from their Hildebrand solubility parameters appeared the parameter of best relevance regarding skin absorption.

  14. Morphological and physical characterization of poly(styrene-isobutylene-styrene) block copolymers and ionomers thereof

    NASA Astrophysics Data System (ADS)

    Baugh, Daniel Webster, III

    Poly(styrene-isobutylene-styrene) block copolymers made by living cationic polymerization using a difunctional initiator and the sequential monomer addition technique were analyzed using curve-resolution software in conjunction with high-resolution GPC. Fractional precipitation and selective solvent extraction were applied to a representative sample in order to confirm the identity of contaminating species. The latter were found to be low molecular weight polystyrene homopolymer, diblock copolymer, and higher molecular weight segmented block copolymers formed by intermolecular electrophilic aromatic substitution linking reactions occurring late in the polymerization of the styrene outer blocks. Solvent-cast films of poly(styrene-isobutylene-styrene) (PS-PIB-PS) block copolymers and block ionomers were analyzed using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Four block copolymer samples with center block molecular weights of 52,000 g/mol and PS volume fractions (o sbPS) ranging from 0.17 to 0.31 were studied. All samples exhibited hexagonally packed cylinders of PS within the PIB matrix. Cylinder spacing was in the range 32 to 36 nm for most samples, while cylinder diameters varied from 14 to 21 nm. Porod analysis of the scattering data indicated the presence of isolated phase mixing and sharp phase boundaries. PS-PIB-PS block copolymers and ionomers therefrom were analyzed using dynamic mechanical analysis (DMA) and tensile testing. The study encompassed five block copolymer samples with similar PIB center blocks with molecular weights of approx52,000 g/mol and PS weight fractions ranging from 0.127 to 0.337. Ionomers were prepared from two of these materials by lightly sulfonating the PS outer blocks. Sulfonation levels varied from 1.7 to 4.7 mol % and the sodium and potassium neutralized forms were compared to the parent block copolymers. Dynamic mechanical analysis (DMA) of the block copolymer films indicated the existence

  15. Copolymer Crystallization: Approaching Equilibrium

    NASA Astrophysics Data System (ADS)

    Crist, Buckley; Finerman, Terry

    2002-03-01

    Random ethylene-butene copolymers of uniform chemical composition and degree of polymerization are crystallized by evaporation of thin films (1 μ m - 5 μ m) from solution. Macroscopic films ( 100 μm) formed by sequential layer deposition are characterized by density, calorimetry and X-ray techniques. Most notable is the density, which in some cases implies a crystalline fraction nearly 90% of the equilibrium value calculated from Flory theory. Melting temperature of these solution deposited layers is increased by as much as 8 ^oC over Tm for the same polymer crystallized from the melt. Small-angle X-ray scattering indicates that the amorphous layer thickness is strongly reduced by this layered crystallization process. X-ray diffraction shows a pronounced orientation of chain axes and lamellar normals parallel to the normal of the macroscopic film. It is clear that solvent enhances chain mobility, permitting proper sequences to aggregate and crystallize in a manner that is never achieved in the melt.

  16. Distinct Adsorption Configurations and Self-Assembly Characteristics of Fibrinogen on Chemically Uniform and Alternating Surfaces including Block Copolymer Nanodomains

    PubMed Central

    2015-01-01

    Understanding protein–surface interactions is crucial to solid-state biomedical applications whose functionality is directly correlated with the precise control of the adsorption configuration, surface packing, loading density, and bioactivity of protein molecules. Because of the small dimensions and highly amphiphilic nature of proteins, investigation of protein adsorption performed on nanoscale topology can shed light on subprotein-level interaction preferences. In this study, we examine the adsorption and assembly behavior of a highly elongated protein, fibrinogen, on both chemically uniform (as-is and buffered HF-treated SiO2/Si, and homopolymers of polystyrene and poly(methyl methacrylate)) and varying (polystyrene-block-poly(methyl methacrylate)) surfaces. By focusing on high-resolution imaging of individual protein molecules whose configurations are influenced by protein–surface rather than protein–protein interactions, fibrinogen conformations characteristic to each surface are identified and statistically analyzed for structural similarities/differences in key protein domains. By exploiting block copolymer nanodomains whose repeat distance is commensurate with the length of the individual protein, we determine that fibrinogen exhibits a more neutral tendency for interaction with both polystyrene and poly(methyl methacrylate) blocks relative to the case of common globular proteins. Factors affecting fibrinogen–polymer interactions are discussed in terms of hydrophobic and electrostatic interactions. In addition, assembly and packing attributes of fibrinogen are determined at different loading conditions. Primary orientations of fibrinogen and its rearrangements with respect to the underlying diblock nanodomains associated with different surface coverage are explained by pertinent protein interaction mechanisms. On the basis of two-dimensional stacking behavior, a protein assembly model is proposed for the formation of an extended fibrinogen network

  17. A multiscale modeling study of loss processes in block-copolymer-based solar cell nanodevices.

    PubMed

    Donets, Sergii; Pershin, Anton; Christlmaier, Martin J A; Baeurle, Stephan A

    2013-03-01

    Flexible photovoltaic devices possess promising perspectives in opto-electronic technologies, where high mobility and/or large-scale applicability are important. However, their usefulness in such applications is currently still limited due to the low level of optimization of their performance and durability. For the improvement of these properties, a better understanding and control of small-scale annihilation phenomena involved in the photovoltaic process, such as exciton loss and charge carrier loss, is necessary, which typically implicates multiple length- and time-scales. Here, we study the causes for their occurrence on the example of nanostructured diblock- and triblock-copolymer systems by making use of a novel solar-cell simulation algorithm and explore new routes to optimize their photovoltaic properties. A particular focus is set on the investigation of exciton and charge carrier loss phenomena and their dependence on the inter-monomeric interaction strength, chain architecture, and external mechanical loading. Our simulation results reveal that in the regime from low up to intermediate χ-parameters an increasing number of continuous percolation paths is created. In this parameter range, the internal quantum efficiency (IQE) increases up to a maximum, characterized by a minimum in the number of charge losses due to charge recombination. In the regime of high χ-parameters both block-copolymer systems form nanostructures with a large number of bottlenecks and dead ends. These lead to a large number of charge losses due to charge recombination, charge trapping, and a deteriorated exciton dissociation, resulting in a significant drop in the IQE. Moreover, we find that the photovoltaic performance of the triblock-copolymer material decreases with increasing mechanical loading, caused by a growing number of charge losses due to charge recombination and charge accumulation. Finally, we demonstrate that the process of charge trapping in defects can be reversed

  18. A multiscale modeling study of loss processes in block-copolymer-based solar cell nanodevices

    NASA Astrophysics Data System (ADS)

    Donets, Sergii; Pershin, Anton; Christlmaier, Martin J. A.; Baeurle, Stephan A.

    2013-03-01

    Flexible photovoltaic devices possess promising perspectives in opto-electronic technologies, where high mobility and/or large-scale applicability are important. However, their usefulness in such applications is currently still limited due to the low level of optimization of their performance and durability. For the improvement of these properties, a better understanding and control of small-scale annihilation phenomena involved in the photovoltaic process, such as exciton loss and charge carrier loss, is necessary, which typically implicates multiple length- and time-scales. Here, we study the causes for their occurrence on the example of nanostructured diblock- and triblock-copolymer systems by making use of a novel solar-cell simulation algorithm and explore new routes to optimize their photovoltaic properties. A particular focus is set on the investigation of exciton and charge carrier loss phenomena and their dependence on the inter-monomeric interaction strength, chain architecture, and external mechanical loading. Our simulation results reveal that in the regime from low up to intermediate χ-parameters an increasing number of continuous percolation paths is created. In this parameter range, the internal quantum efficiency (IQE) increases up to a maximum, characterized by a minimum in the number of charge losses due to charge recombination. In the regime of high χ-parameters both block-copolymer systems form nanostructures with a large number of bottlenecks and dead ends. These lead to a large number of charge losses due to charge recombination, charge trapping, and a deteriorated exciton dissociation, resulting in a significant drop in the IQE. Moreover, we find that the photovoltaic performance of the triblock-copolymer material decreases with increasing mechanical loading, caused by a growing number of charge losses due to charge recombination and charge accumulation. Finally, we demonstrate that the process of charge trapping in defects can be reversed

  19. Optimization of Brush-like Cationic Copolymers for Non-viral Gene Delivery

    PubMed Central

    Wei, Hua; Pahang, JoshuelA; Pun, Suzie H.

    2012-01-01

    Polyethylenimine (PEI) is one of the most broadly used polycations for gene delivery due to its high transfection efficiency and commercial availability but materials are cytotoxic and often polydisperse. The goal of current work is to develop an alternative family of polycations based on controlled living radical polymerization (CLRP) and to optimize the polymer structure for efficient gene delivery. In this study, well-defined poly(glycidyl methacrylate)(P(GMA)) homopolymers were synthesized using reversible addition fragmentation chain transfer (RAFT) polymerization followed by decoration using three different types of oligoamines, i.e., tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), and tris(2-aminoethyl)amine (TREN), respectively, to generate various P(GMA-oligoamine) homopolycations. The effect of P(GMA) backbone length and structure of oligoamine on gene transfer efficiency was then determined. The optimal polymer, P(GMA-TEPA)50, provided comparable transfection efficiency but lower cytotoxicity than PEI. P(GMA-TEPA)50 was then used as the cationic block in di-block copolymers containing hydrophilic N-(2-hydroxypropyl) methacrylamide (HPMA) and oligo(ethylene glycol) monomethyl ether methacrylate (OEGMA). Polyplexes of block copolymers were stable against aggregation in physiological salt condition and in Opti-MEM due to the shielding effect of P(HPMA) and P(OEGMA). However, the presence of the HPMA/OEGMA block significantly decreased the transfection efficacy of P(GMA-TEPA)50homopolycation. To compensate for reduced cell uptake caused by the hydrophilic shell of polyplex, the integrin-binding peptide, RGD, was conjugated to the hydrophilic chain end of P(OEGMA)15-b-P(GMA-TEPA)50 copolymer by Michael-type addition reaction. At low polymer to DNA ratios, the RGD-functionalized polymer showed increased gene delivery efficiency to HeLa cells compared to analogous polymers lacking RGD. PMID:23240866

  20. Copolymers For Capillary Gel Electrophoresis

    DOEpatents

    Liu, Changsheng; Li, Qingbo

    2005-08-09

    This invention relates to an electrophoresis separation medium having a gel matrix of at least one random, linear copolymer comprising a primary comonomer and at least one secondary comonomer, wherein the comonomers are randomly distributed along the copolymer chain. The primary comonomer is an acrylamide or an acrylamide derivative that provides the primary physical, chemical, and sieving properties of the gel matrix. The at least one secondary comonomer imparts an inherent physical, chemical, or sieving property to the copolymer chain. The primary and secondary comonomers are present in a ratio sufficient to induce desired properties that optimize electrophoresis performance. The invention also relates to a method of separating a mixture of biological molecules using this gel matrix, a method of preparing the novel electrophoresis separation medium, and a capillary tube filled with the electrophoresis separation medium.

  1. Loading of Silica Nanoparticles in Block Copolymer Vesicles during Polymerization-Induced Self-Assembly: Encapsulation Efficiency and Thermally Triggered Release.

    PubMed

    Mable, Charlotte J; Gibson, Rebecca R; Prevost, Sylvain; McKenzie, Beulah E; Mykhaylyk, Oleksandr O; Armes, Steven P

    2015-12-30

    Poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) diblock copolymer vesicles can be prepared in the form of concentrated aqueous dispersions via polymerization-induced self-assembly (PISA). In the present study, these syntheses are conducted in the presence of varying amounts of silica nanoparticles of approximately 18 nm diameter. This approach leads to encapsulation of up to hundreds of silica nanoparticles per vesicle. Silica has high electron contrast compared to the copolymer which facilitates TEM analysis, and its thermal stability enables quantification of the loading efficiency via thermogravimetric analysis. Encapsulation efficiencies can be calculated using disk centrifuge photosedimentometry, since the vesicle density increases at higher silica loadings while the mean vesicle diameter remains essentially unchanged. Small angle X-ray scattering (SAXS) is used to confirm silica encapsulation, since a structure factor is observed at q ≈ 0.25 nm(-1). A new two-population model provides satisfactory data fits to the SAXS patterns and allows the mean silica volume fraction within the vesicles to be determined. Finally, the thermoresponsive nature of the diblock copolymer vesicles enables thermally triggered release of the encapsulated silica nanoparticles simply by cooling to 0-10 °C, which induces a morphological transition. These silica-loaded vesicles constitute a useful model system for understanding the encapsulation of globular proteins, enzymes, or antibodies for potential biomedical applications. They may also serve as an active payload for self-healing hydrogels or repair of biological tissue. Finally, we also encapsulate a model globular protein, bovine serum albumin, and calculate its loading efficiency using fluorescence spectroscopy. PMID:26600089

  2. Mechano-responsive hydrogels crosslinked by reactive block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Xiao, Longxi

    Hydrogels are crosslinked polymeric networks that can swell in water without dissolution. Owing to their structural similarity to the native extracelluar matrices, hydrogels have been widely used in biomedical applications. Synthetic hydrogels have been designed to respond to various stimuli, but mechanical signals have not incorporated into hydrogel matrices. Because most tissues in the body are subjected to various types of mechanical forces, and cells within these tissues have sophisticated mechano-transduction machinery, this thesis is focused on developing hydrogel materials with built-in mechano-sensing mechanisms for use as tissue engineering scaffolds or drug release devices. Self-assembled block copolymer micelles (BCMs) with reactive handles were employed as the nanoscopic crosslinkers for the construction of covalently crosslinked networks. BCMs were assembled from amphiphilic diblock copolymers of poly(n-butyl acrylate) and poly(acrylic acid) partially modified with acrylate. Radical polymerization of acrylamide in the presence of micellar crosslinkers gave rise to elastomeric hydrogels whose mechanical properties can be tuned by varying the BCM composition and concentration. TEM imaging revealed that the covalently integrated BCMs underwent strain-dependent reversible deformation. A model hydrophobic drug, pyrene, loaded into the core of BCMs prior to the hydrogel formation, was dynamically released in response to externally applied mechanical forces, through force-induced reversible micelle deformation and the penetration of water molecules into the micelle core. The mechano-responsive hydrogel has been studied for tissue repair and regeneration purposes. Glycidyl methacrylate (GMA)-modified hyaluronic acid (HA) was photochemically crosslinked in the presence of dexamethasone (DEX)-loaded crosslinkable BCMs. The resultant HA gels (HAxBCM) contain covalently integrated micellar compartments with DEX being sequestered in the hydrophobic core. Compared

  3. Using click chemistry to modify block copolymers and their morphologies

    NASA Astrophysics Data System (ADS)

    Wollbold, Johannes

    Microphase separated block copolymers (BCPs) are emerging as promising templates and scaffolds for the fabrication of nanostructured materials. To achieve the desired nanostructures, it is necessary to establish convenient approaches to control the morphology of BCPs. It remains challenging to induce morphological transitions of BCPs via external fields. Click chemistry, especially alkyne/azide click chemistry, has been widely used to synthesize novel functionalized materials. Here, we demonstrate that alkyne/azide click chemistry can be used as an efficient approach to chemically modify BCPs and therefore induce morphological transitions. Alkyne-functionalized diblock copolymers (di-BCPs) poly(ethylene oxide)- block-poly(n-butyl methacrylate-random-propargyl methacrylate) (PEO-b-P(nBMA-r-PgMA)) have been successfully synthesized. When the di-BCP is blended with an azide additive Rhodamine B azide and annealed at elevated temperatures, click reaction occurs between the two components. With the Rhodamine B structure attached to the polymer backbone, the di-BCP shows dramatic change in the interactions between the two blocks and the volume fraction of each block. As a result, morphological transitions, such as disorder-to-order transitions (DOTs) and order-to-order transitions (OOTs), are observed. The reaction kinetics and morphology evolution during the click chemistry induced DOTs have been investigated by in-situ and ex-situ characterizations, and fast kinetics properties are observed. Microphase separated morphologies after the DOTs or OOTs are dictated by the composition of neat di-BCPs and the mole ratio between the alkyne and azide groups. The DOTs of PEO-b-P(nBMA-r-PgMA) di-BCPs induced by alkyne/azide click chemistry have also been achieved in thin film geometries, with comparable kinetics to bulk samples. The orientation of the microdomains is dependent on the grafting density of Rhodamine B structure as well as film thickness. At higher grafting densities

  4. Crystalline imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1995-01-01

    Crystalline imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly)arylene ethers) in polar aprotic solvents and chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The block copolymers of the invention have one glass transition temperature or two, depending on the particular structure and/or the compatibility of the block units. Most of these crystalline block copolymers for tough, solvent resistant films with high tensile properties. While all of the copolymers produced by the present invention are crystalline, testing reveals that copolymers with longer imide blocks or higher imide content have increased crystallinity.

  5. Polyether-polyester graft copolymer

    NASA Technical Reports Server (NTRS)

    Bell, Vernon L. (Inventor)

    1987-01-01

    Described is a polyether graft polymer having improved solvent resistance and crystalline thermally reversible crosslinks. The copolymer is prepared by a novel process of anionic copolymerization. These polymers exhibit good solvent resistance and are well suited for aircraft parts. Previous aromatic polyethers, also known as polyphenylene oxides, have certain deficiencies which detract from their usefulness. These commercial polymers are often soluble in common solvents including the halocarbon and aromatic hydrocarbon types of paint thinners and removers. This limitation prevents the use of these polyethers in structural articles requiring frequent painting. In addition, the most popular commercially available polyether is a very high melting plastic. This makes it considerably more difficult to fabricate finished parts from this material. These problems are solved by providing an aromatic polyether graft copolymer with improved solvent resistance and crystalline thermally reversible crosslinks. The graft copolymer is formed by converting the carboxyl groups of a carboxylated polyphenylene oxide polymer to ionic carbonyl groups in a suitable solvent, reacting pivalolactone with the dissolved polymer, and adding acid to the solution to produce the graft copolymer.

  6. Impacts of Repeat Unit Structure and Copolymer Architecture on Thermal and Solution Properties in Homopolymers, Copolymers, and Copolymer Blends

    NASA Astrophysics Data System (ADS)

    Marrou, Stephen Raye

    Gradient copolymers are a relatively new type of copolymer architecture in which the distribution of comonomers gradually varies over the length of the copolymer chain, resulting in a number of unusual properties derived from the arrangement of repeat units. For example, nanophase-segregated gradient copolymers exhibit extremely broad glass transition temperatures (Tgs) resulting from the wide range of compositions present in the nanostructure. This dissertation presents a number of studies on how repeat unit structure and copolymer architecture dictate bulk and solution properties, specifically taking inspiration from the gradient copolymer architecture and comparing the response from this compositionally heterogeneous material to other more conventional materials. The glass transition behavior of a range of common homopolymers was studied to determine the effects of subunit structure on Tg breadth, observing a significant increase in T g breadth with increasing side chain length in methacrylate-based homopolymers and random copolymers. Additionally, increasing the composition distribution of copolymers, either by blending individual random copolymers of different overall composition or synthesizing random copolymers to high conversion, resulted in significant increases to Tg breadth. Plasticization of homopolymers and random copolymers with low molecular weight additives also served to increase the Tg breadth; the most dramatic effect was observed in the selective plasticization of a styrene/4-vinylpyridine gradient copolymer with increases in T g breadth to values above 100 °C. In addition, the effects of repeat unit structure and copolymer architecture on other polymer properties besides Tg were also investigated. The intrinsic fluorescence of styrene units in styrene-containing copolymers was studied, noting the impact of repeat unit structure and copolymer architecture on the resulting fluorescence spectra in solution. The impact of repeat unit structure on

  7. Some aspects of the orientational order distribution of flexible chains in a diblock mesophase

    SciTech Connect

    Lorthioir, Cédric Randriamahefa, Solo

    2013-12-14

    The segmental motions of flexible chains in the lamellar structure of a strongly segregated poly(styrene)-poly(dimethylsiloxane) (PS-PDMS) diblock were investigated over a time scale of a few tens of microseconds. {sup 2}H NMR experiments were performed on the PDMS block, selectively perdeuterated. Transverse relaxation measurements show that the main part of the PDMS repeat units display anisotropic reorientational motions within the diblock lamellae and such a segmental ordering essentially results from interchain steric repulsions. {sup 2}H double quantum-based experiments evidenced a non-uniform local stretching of PDMS chains and enabled the underlying distribution of the orientational order parameter to be determined quantitatively. Besides, a fraction of the PDMS chain segments, about 14%, were found to display isotropic – or nearly isotropic – reorientations, which could be assigned to repeat units located within a thin sublayer (about 1–2 nm) at the lamellae midplane, but also deeper in the lamellae, close to folded parts of the chains. These experimental results were confronted to theoretical descriptions of opposing polymer brushes and, in particular, to the strong-stretching theory (SST) including the entropic contribution of free chain ends.

  8. Cellular Interactions and Biocompatibility of Self-Assembling Diblock Polypeptide Hydrogels

    NASA Astrophysics Data System (ADS)

    Pakstis, Lisa; Ozbas, Bulent; Pochan, Darrin; Robinson, Clifford; Nowak, Andrew; Deming, Timothy

    2002-03-01

    Self-assembling peptide based hydrogels having a unique nano- and microscopic morphology are being studied for potential use as tissue engineering scaffolds. Low molecular weight ( ~20 kg/mol), amphiphilic, diblock polypeptides of hydrophilic lysine (K) or glutamic acid (E) and hydrophobic leucine (L) or valine (V) form hydrogels in aqueous solution at neutral pH and at very low volume fraction of polymer (vol. fraction polypeptide >=0.5 wt%). The morphology of these hydrogels has been characterized using laser confocal microscopy (LCM), small angle neutron scattering (SANS), and cryogenic transmission electron microscopy (cryoTEM) imaging. Studies of the interactions of the hydrogels with bacterial and mammalian cells reveal that these materials are non-cytotoxic and biocompatible. Hence, the chemistry of the assembled diblock polypeptides allows for cellular proliferation whereas the same chemistry in the homopolyeric form is cytotoxic. Current research is directed at the design and incorporation of binding sites within the polypeptide to specifically target interactions of the hydrogel with desired cells types.

  9. Surface Mechanical and Rheological Behaviors of Biocompatible Poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA-PEG) and Poly((D,L-lactic acid-ran-glycolic acid-ran-ε-caprolactone)-block-ethylene glycol) (PLGACL-PEG) Block Copolymers at the Air-Water Interface.

    PubMed

    Kim, Hyun Chang; Lee, Hoyoung; Khetan, Jawahar; Won, You-Yeon

    2015-12-29

    Air-water interfacial monolayers of poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA-PEG) exhibit an exponential increase in surface pressure under high monolayer compression. In order to understand the molecular origin of this behavior, a combined experimental and theoretical investigation (including surface pressure-area isotherm, X-ray reflectivity (XR) and interfacial rheological measurements, and a self-consistent field (SCF) theoretical analysis) was performed on air-water monolayers formed by a PLGA-PEG diblock copolymer and also by a nonglassy analogue of this diblock copolymer, poly((D,L-lactic acid-ran-glycolic acid-ran-caprolactone)-block-ethylene glycol) (PLGACL-PEG). The combined results of this study show that the two mechanisms, i.e., the glass transition of the collapsed PLGA film and the lateral repulsion of the PEG brush chains that occur simultaneously under lateral compression of the monolayer, are both responsible for the observed PLGA-PEG isotherm behavior. Upon cessation of compression, the high surface pressure of the PLGA-PEG monolayer typically relaxes over time with a stretched exponential decay, suggesting that in this diblock copolymer situation, the hydrophobic domain formed by the PLGA blocks undergoes glass transition in the high lateral compression state, analogously to the PLGA homopolymer monolayer. In the high PEG grafting density regime, the contribution of the PEG brush chains to the high monolayer surface pressure is significantly lower than what is predicted by the SCF model because of the many-body attraction among PEG segments (referred to in the literature as the "n-cluster" effects). The end-grafted PEG chains were found to be protein resistant even under the influence of the "n-cluster" effects.

  10. Discovering Complex Ordered Phases of Block Copolymers

    NASA Astrophysics Data System (ADS)

    Shi, An-Chang

    2012-02-01

    Block copolymers with their rich phase behavior and ordering transitions have become a paradigm for the study of structured soft materials. Understanding the structures and phase transitions in block copolymers has been one of the most active research areas in polymer science in the past two decades. One of the achievements is the self-consistent field theory (SCFT), which provides a powerful framework for the study of ordered phase of block copolymers. I will present a generic strategy to discover complex ordered phases of block copolymers within the SCFT framework. Specifically, a combination of real-space and reciprocal-space techniques is used to explore possible ordered phases in multiblock copolymer melts. These candidate phases can then be used to construct phase diagrams. Application of this strategy to linear and star ABC triblock copolymers has led to the discovery of a rich array of ordered phases.

  11. Mixed interactions in random copolymers

    NASA Astrophysics Data System (ADS)

    Marinov, Toma; Luettmer-Strathmann, Jutta

    2002-03-01

    The description of thermodynamic properties of copolymers in terms of simple lattice models requires a value for the mixed interaction strength (ɛ_12) between unlike chain segments, in addition to parameters that can be derived from the properties of the corresponding homopolymers. If the monomers are chemically similar, Berthelot's geometric-mean combining rule provides a good first approximation for ɛ_12. In earlier work on blends of polyolefins [1], we found that the small-scale architecture of the chains leads to corrections to the geometric-mean approximation that are important for the prediction of phase diagrams. In this work, we focus on the additional effects due to sequencing of the monomeric units. In order to estimate the mixed interaction ɛ_12 for random copolymers, the small-scale simulation approach developed in [1] is extended to allow for random sequencing of the monomeric units. The approach is applied here to random copolymers of ethylene and 1-butene. [1] J. Luettmer-Strathmann and J.E.G. Lipson. Phys. Rev. E 59, 2039 (1999) and Macromolecules 32, 1093 (1999).

  12. Phase Behavior of Symmetric Sulfonated Block Copolymers

    SciTech Connect

    Park, Moon Jeong; Balsara, Nitash P.

    2008-08-21

    Phase behavior of poly(styrenesulfonate-methylbutylene) (PSS-PMB) block copolymers was studied by varying molecular weight, sulfonation level, and temperature. Molecular weights of the copolymers range from 2.9 to 117 kg/mol. Ordered lamellar, gyroid, hexagonally perforated lamellae, and hexagonally packed cylinder phases were observed in spite of the fact that the copolymers are nearly symmetric with PSS volume fractions between 0.45 and 0.50. The wide variety of morphologies seen in our copolymers is inconsistent with current theories on block copolymer phase behavior such as self-consistent field theory. Low molecular weight PSS-PMB copolymers (<6.2 kg/mol) show order-order and order-disorder phase transitions as a function of temperature. In contrast, the phase behavior of high molecular weight PSS-PMB copolymers (>7.7 kg/mol) is independent of temperature. Due to the large value of Flory-Huggins interaction parameter, x, between the sulfonated and non-sulfonated blocks, PSS-PMB copolymers with PSS and PMB molecular weights of 1.8 and 1.4 kg/mol, respectively, show the presence of an ordered gyroid phase with a 2.5 nm diameter PSS network. A variety of methods are used to estimate x between PSS and PMB chains as a function of sulfonation level. Some aspects of the observed phase behavior of PSS-PMB copolymers can be rationalized using x.

  13. Copolymers of fluorinated polydienes and sulfonated polystyrene

    DOEpatents

    Mays, Jimmy W.; Gido, Samuel P.; Huang, Tianzi; Hong, Kunlun

    2009-11-17

    Copolymers of fluorinated polydienes and sulfonated polystyrene and their use in fuel cell membranes, batteries, breathable chemical-biological protective materials, and templates for sol-gel polymerization.

  14. Self-assembly of Random Copolymers

    PubMed Central

    Li, Longyu; Raghupathi, Kishore; Song, Cunfeng; Prasad, Priyaa; Thayumanavan, S.

    2014-01-01

    Self-assembly of random copolymers has attracted considerable attention recently. In this feature article, we highlight the use of random copolymers to prepare nanostructures with different morphologies and to prepare nanomaterials that are responsive to single or multiple stimuli. The synthesis of single-chain nanoparticles and their potential applications from random copolymers are also discussed in some detail. We aim to draw more attention to these easily accessible copolymers, which are likely to play an important role in translational polymer research. PMID:25036552

  15. Enhancement of deoxyribozyme activity by cationic copolymers.

    PubMed

    Gao, Jueyuan; Shimada, Naohiko; Maruyama, Atsushi

    2015-02-01

    Deoxyribozymes, or DNAzymes, are DNA molecules with enzymatic activity. DNAzymes with ribonuclease activity have various potential applications in biomedical and bioanalytical fields; however, most constructs have limited turnover despite optimization of reaction conditions and DNAzyme structures. A cationic comb-type copolymer accelerates DNA hybridization and strand exchange rates, and we hypothesized that the copolymer would enhance deoxyribozyme activity by promoting turnover. The copolymer did not change DNAzyme activity under single-turnover conditions, suggesting that the copolymer affects neither the folding structure of DNAzyme nor the association of a divalent cation, a catalytic cofactor, to DNAzyme. The copolymer enhanced activity of the evaluated DNAzyme over a wide temperature range under multiple-turnover conditions. The copolymer increased the DNAzyme kcat/KM by fifty-fold at 50 °C, the optimal temperature for the DNAzyme in the absence of the copolymer. The acceleration effect was most significant when the reaction temperature was slightly higher than the melting temperature of the enzyme/substrate complex; acceleration of two orders of magnitude was observed. We concluded that the copolymer accelerated the turnover step without influencing the chemical cleavage step. In contrast to the copolymer, a cationic surfactant, CTAB, strongly inhibited the DNAzyme activity under either single- or multiple-turnover conditions. PMID:26218121

  16. Facile Synthesis of Novel Polyethylene-Based A-B-C Block Copolymers Containing Poly(methyl methacrylate) Using a Living Polymerization System.

    PubMed

    Song, Xiangyang; Ma, Qiong; Cai, Zhengguo; Tanaka, Ryo; Shiono, Takeshi; Grubbs, Robert B

    2016-02-01

    Ethylene-propylene-methyl methacrylate (MMA) and ethylene-hexene-MMA A-B-C block copolymers with high molecular weight (>100,000) are synthesized using fluorenylamide-ligated titanium complex activated by modified methylaluminoxane and 2,6-di-tert-butyl-4-methylphenol for the first time. After diblock copolymerization of olefin is conducted completely, MMA is added and activated by aluminum Lewis acid to promote anionic polymerization. The length of polyolefin and poly (methyl methacrylate) (PMMA) is controllable precisely by the change of the additive amount of olefin and polymerization time, respectively. A soft amorphous polypropylene or polyhexene segment is located between two hard segments of semicrystalline polyethylene and glassy PMMA blocks.

  17. ABC Triblock Copolymer Worms: Synthesis, Characterization, and Evaluation as Pickering Emulsifiers for Millimeter-Sized Droplets

    PubMed Central

    2016-01-01

    Polymerization-induced self-assembly (PISA) is used to prepare linear poly(glycerol monomethacrylate)–poly(2-hydroxypropyl methacrylate)–poly(benzyl methacrylate) [PGMA–PHPMA–PBzMA] triblock copolymer nano-objects in the form of a concentrated aqueous dispersion via a three-step synthesis based on reversible addition–fragmentation chain transfer (RAFT) polymerization. First, GMA is polymerized via RAFT solution polymerization in ethanol, then HPMA is polymerized via RAFT aqueous solution polymerization, and finally BzMA is polymerized via “seeded” RAFT aqueous emulsion polymerization. For certain block compositions, highly anisotropic worm-like particles are obtained, which are characterized by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The design rules for accessing higher order morphologies (i.e., worms or vesicles) are briefly explored. Surprisingly, vesicular morphologies cannot be accessed by targeting longer PBzMA blocks—instead, only spherical nanoparticles are formed. SAXS is used to rationalize these counterintuitive observations, which are best explained by considering subtle changes in the relative enthalpic incompatibilities between the three blocks during the growth of the PBzMA block. Finally, the PGMA–PHPMA–PBzMA worms are evaluated as Pickering emulsifiers for the stabilization of oil-in-water emulsions. Millimeter-sized oil droplets can be obtained using low-shear homogenization (hand-shaking) in the presence of 20 vol % n-dodecane. In contrast, control experiments performed using PGMA–PHPMA diblock copolymer worms indicate that these more delicate nanostructures do not survive even these mild conditions. PMID:27795581

  18. Directed Self-Assembly of Block Copolymers for High Breakdown Strength Polymer Film Capacitors.

    PubMed

    Samant, Saumil P; Grabowski, Christopher A; Kisslinger, Kim; Yager, Kevin G; Yuan, Guangcui; Satija, Sushil K; Durstock, Michael F; Raghavan, Dharmaraj; Karim, Alamgir

    2016-03-01

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ∼50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the "barrier effect", where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. This approach opens a new nanomaterial paradigm for designing high energy density dielectric materials. PMID:26942835

  19. Directed self-assembly of block copolymers for high breakdown strength polymer film capacitors

    DOE PAGES

    Samant, Saumil P.; Grabowski, Christopher A.; Kisslinger, Kim; Yager, Kevin G.; Yuan, Guangcui; Satija, Sushil K.; Durstock, Michael F.; Raghavan, Dharmaraj; Karim, Alamgir

    2016-03-04

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayeredmore » films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ~50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the “barrier effect”, where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. Lastly, this approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.« less

  20. Directed Self-Assembly of Block Copolymers for High Breakdown Strength Polymer Film Capacitors.

    PubMed

    Samant, Saumil P; Grabowski, Christopher A; Kisslinger, Kim; Yager, Kevin G; Yuan, Guangcui; Satija, Sushil K; Durstock, Michael F; Raghavan, Dharmaraj; Karim, Alamgir

    2016-03-01

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ∼50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the "barrier effect", where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. This approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.

  1. Curcumin loaded pH-sensitive hybrid lipid/block copolymer nanosized drug delivery systems.

    PubMed

    Jelezova, Ivelina; Drakalska, Elena; Momekova, Denitsa; Shalimova, Natalia; Momekov, Georgi; Konstantinov, Spiro; Rangelov, Stanislav; Pispas, Stergios

    2015-10-12

    Curcumin is a perspective drug candidate with pleiotropic antineoplastic activity, whose exceptionally low aqueous solubility and poor pharmacokinetic properties have hampered its development beyond the preclinical level. A possible approach to overcome these limitations is the encapsulation of curcumin into nano-carriers, incl. liposomes. The present contribution is focused on feasibility of using hybrid pH-sensitive liposomes, whereby curcumin is entrapped as a free drug and as a water soluble inclusion complex with PEGylated tert-butylcalix[4]arene, which allows the drug to occupy both the phospholipid membranes and the aqueous core of liposomes. The inclusion complexes were encapsulated in dipalmithoylphosphathydilcholine:cholesterol liposomes, whose membranes were grafted with a poly(isoprene-b-acrylic acid) diblock copolymer to confer pH-sensitivity. The liposomes were characterized by DLS, ζ-potential measurements, cryo-TEM, curcumin encapsulation efficacy, loading capacity, and in vitro release as a function of pH. Free and formulated curcumin were further investigated for cytotoxicity, apoptosis-induction and caspase-8, and 9 activation in chemosensitive HL-60 and its resistant sublines HL-60/Dox and HL-60/CDDP. Formulated curcumin was superior cytotoxic and apoptogenic agent vs. the free drug. The mechanistic assay demonstrated that the potent proapoptotic effects of pH-sensitive liposomal curcumin presumably mediated via recruitment of both extrinsic and intrinsic apoptotic pathways in both HL-60 and HL-60/CDDP cells.

  2. Magnetic field alignment of supramolecular perylene/block copolymer complexes for electro-optic thin films

    NASA Astrophysics Data System (ADS)

    Gopinadhan, Manesh; Majewski, Pawel; Shade, Ryan; Dell, Emma; Gupta, Nalini; Campos, Luis; Osuji, Chinedum

    2012-02-01

    The realization of nanostructured electro-optic materials by self-assembly is complicated by the persistence of structural defects which render the system properties isotropic on macroscopic length scales. Here we demonstrate the use of magnetic fields to facilitate large area alignment of a supramolecular system consisting of a poly(styrene-b-acrylic acid) (PS-b-PAA) diblock copolymer host and a semiconducting perylene ligand. Hydrogen bonding between the carboxylic acid groups of PAA and imidazole head group of the perylene species results in hierarchically ordered materials with smectic perylene layers in a matrix of hexagonally