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Sample records for block copolymer thin

  1. Microphase separation of block copolymer thin films.

    PubMed

    Zhang, Jilin; Yu, Xinhong; Yang, Ping; Peng, Juan; Luo, Chunxia; Huang, Weihuan; Han, Yanchun

    2010-04-01

    Today, high-ordered micro- and nano-patterned surfaces are widely used in many areas, such as in the preparation of super-thin dielectric films, photonic crystals, antireflective films, super-non-wetting surfaces, bio-compatible surfaces and microelectric devices. Considering the critical fabrication conditions and the irreducible high cost of the photolithography technique in patterning nano-scale structures (<100 nm), the development of other micro- and nano-patterning techniques that can be used to fabricate long-range ordered features - especially nanoscale arrays - is a promising subject in surface science. In contrast to the traditional photolithography patterning technique, block copolymers can spontaneously phase separate into arrays of periodic patterns with length-scales of 10-50 nm, which provides an efficient pathway to pattern nanoscale features. Today, preparing long-range ordered arrays by block copolymer microphase separation is one of the most promising techniques for the fabrication of nanoscale arrays, not only being a simple process but also having a lower cost than traditional methods. In this feature article, we first summarize the many techniques developed to induce ordering in the microphase separation of the block copolymer thin films. Then, evolution, order-order transitions and reversible switching microdomains are considered, since they are very important in the ordered engineering of microphase separation of the block copolymer thin films. Finally, the outlook of this research area will be given.

  2. 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.

  3. Multi-block copolymers in thin films.

    NASA Astrophysics Data System (ADS)

    Maniadis, Panagiotis; Kober, Edward; Lookman, Turab

    2008-03-01

    We study the behavior of an ABn multi-block copolymer confined to a thin film, using self consistent field theory (SCFT) methods. Due to the breaking of symmetry in the direction of confinement, the propagators do not obey the usual diffusion equation. We derive the diffusion equation which correctly describes the confined polymer system and find that it differs from the original in an area which is approximately 3 times the Kuhn length of the polymer, close to the surface of the film. We use the modified diffusion equation to study the structure of the confined polymer.

  4. Rapid ordering of block copolymer thin films

    NASA Astrophysics Data System (ADS)

    Majewski, Pawel W.; Yager, Kevin G.

    2016-10-01

    Block-copolymers self-assemble into diverse morphologies, where nanoscale order can be finely tuned via block architecture and processing conditions. However, the ultimate usage of these materials in real-world applications may be hampered by the extremely long thermal annealing times—hours or days—required to achieve good order. Here, we provide an overview of the fundamentals of block-copolymer self-assembly kinetics, and review the techniques that have been demonstrated to influence, and enhance, these ordering kinetics. We discuss the inherent tradeoffs between oven annealing, solvent annealing, microwave annealing, zone annealing, and other directed self-assembly methods; including an assessment of spatial and temporal characteristics. We also review both real-space and reciprocal-space analysis techniques for quantifying order in these systems.

  5. 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

  6. Orienting Nanostructured Block Copolymer Thin Films via Entropy

    NASA Astrophysics Data System (ADS)

    Lo, Ting-Ya; Dehghan, Ashkan; Georgopanos, Prokopios; Avgeropoulos, Apostolos; Shi, An-Chang; Ho, Rong-Ming

    2015-03-01

    Controlling the orientation of nanostructured thin films of block copolymers (BCPs) is essential for next generation lithography using BCPs. According to conventional wisdom, the orientation of BCPs is mainly determined by molecular interactions (enthalpy-driven orientation). Here, we demonstrate that entropic effect can be used to control the orientation of BCP thin films. Specifically, the architecture of star-block copolymers consisting polystyrene (PS) and poly(dimethylsiloxane) (PDMS) blocks is used to regulate the entropic contribution to the self-assembled nanostructures. Our experimental and theoretical results unequivocally demonstrate that entropy-driven perpendicular orientation of BCP nanostructures can be induced by increasing the arm number of the star-block copolymers with the same volume fractions of PS and PDMS.

  7. Thin film assembly of spider silk-like block copolymers.

    PubMed

    Krishnaji, Sreevidhya T; Huang, Wenwen; Rabotyagova, Olena; Kharlampieva, Eugenia; Choi, Ikjun; Tsukruk, Vladimir V; Naik, Rajesh; Cebe, Peggy; Kaplan, David L

    2011-02-01

    We report the self-assembly of monolayers of spider silk-like block copolymers. Langmuir isotherms were obtained for a series of bioengineered variants of the spider silks, and stable monolayers were generated. Langmuir-Blodgett films were prepared by transferring the monolayers onto silica substrates and were subsequently analyzed by atomic force microscopy (AFM). Static contact angle measurements were performed to characterize interactions across the interface (thin film, water, air), and molecular modeling was used to predict 3D conformation of spider silk-like block copolymers. The influence of molecular architecture and volume fraction of the proteins on the self-assembly process was assessed. At high surface pressure, spider silk-like block copolymers with minimal hydrophobic block (f(A) = 12%) formed oblate structures, whereas block copolymer with a 6-fold larger hydrophobic domain (f(A) = 46%) formed prolate structures. The varied morphologies obtained with increased hydrophobicity offer new options for biomaterials for coatings and related options. The design and use of bioengineered protein block copolymers assembled at air-water interfaces provides a promising approach to compare 2D microstructures and molecular architectures of these amphiphiles, leading to more rationale designs for a range of nanoengineered biomaterial needs as well as providing a basis of comparison to more traditional synthetic block copolymer systems. PMID:21207952

  8. Smectic block copolymer thin films on corrugated substrates.

    PubMed

    Pezzutti, Aldo D; Gómez, Leopoldo R; Vega, Daniel A

    2015-04-14

    In this work we study equilibrium and non-equilibrium structures of smectic block copolymer thin films deposited on a topographically patterned substrate. A Brazovskii free energy model is employed to analyze the coupling between the smectic texture and the local mean curvature of the substrate. The substrate's curvature produces out-of-plane deformations of the block copolymer such that equilibrium textures are modified and dictated by the underlying geometry. For weak curvatures it is shown that the free energy of the block copolymer film follows a Helfrich form, scaling with the square of the mean curvature, with a bending constant dependent on the local pattern orientation. On substrates of varying mean curvature simulations show that topological defects are rapidly expelled from regions with large curvature. These results compare well with available experimental data of poly(styrene)-co-poly(ethylene-alt-propylene) smectic thin films.

  9. Nanostructured anion conducting block copolymer electrolyte thin films

    NASA Astrophysics Data System (ADS)

    Arges, Christopher; Kambe, Yu; Nealey, Paul

    Lamellae forming block copolymer electrolyte (BCE) thin-films with perpendicular aligned orientation were registered with high fidelity over large areas via a self-assembly process followed by a novel chemical vapor infiltration reaction (CVIR) technique. In this scheme, poly(styrene- b-2-vinyl pyridine) (PS bP2VP) block copolymers were self-assembled with perpendicular orientations on neutral chemical brushes using solvent vapor annealing. The ionic groups were selectively introduced into the P2VP block via a Menshutkin reaction that converted the nitrogen in the pyridine to n-methylpyridinium - anion carrier groups. FTIR-ATR and XPS tools confirmed the formation of the aforementioned ionic moieties post CVIR process and structure imaging tools (e.g., SEM and AFM imaging, GI-SAXS and RSOXs) established that incorporation of the ionic groups did not alter the self-assembled nanostructured films nor did subsequent ion-exchange processes. Electrochemical impedance spectroscopy determined the in-plane ion conductivity of different counteranions in the BCE thin films and alteration to the symmetry of the block copolymer film substantially improved (or hindered) BCE ion conductivity if the P2VP block's volume fraction was slightly greater than (or less than) 0.5. U.S. Department of Energy, Office of Science under Contract No. DE-AC02-06CH11357.

  10. Self-assembled phases of block copolymer blend thin films.

    PubMed

    Yager, Kevin G; Lai, Erica; Black, Charles T

    2014-10-28

    The patterns formed by self-assembled thin films of blended cylindrical and lamellar polystyrene-b-poly(methyl methacrylate) block copolymers can be either a spatially uniform, single type of nanostructure or separate, coexisting regions of cylinders and lamellae, depending on fractional composition and molecular weight ratio of the blend constituents. In blends of block copolymers with different molecular weights, the morphology of the smaller molecular weight component more strongly dictates the resulting pattern. Although molecular scale chain mixing distorts microdomain characteristic length scales from those of the pure components, even coexisting morphologies exhibit the same domain spacing. We quantitatively account for the phase behavior of thin-film blends of cylinders and lamellae using a physical, thermodynamic model balancing the energy of chain distortions with the entropy of mixing. PMID:25285733

  11. Simple, generalizable route to highly aligned block copolymer thin films

    NASA Astrophysics Data System (ADS)

    Qiang, Zhe; Cavicchi, Kevin; Vogt, Bryan; University of Akron Team

    Macroscopic alignment of block copolymer domains in thin films is desired for many applications, such as cell responsive surfaces or optical polarizers. Alignment generally requires specialized tools that apply external fields, shear force gradient, or produce topological patterned substrates. This requirement limits the broad academic application of aligned BCPs. Here, we describe a simple modification of commonly utilized solvent vapor annealing (SVA) process for macroscopic alignment of BCPs. Adhering a flat, crosslinked elastomer pad to the BCP film leads to differential swelling between the elastomer pad and BCP to produce a shear force that aligns the ordered BCP domains. The role of elastomer properties, solvent quality, drying rate and degree of segregation of the block copolymer will be discussed to provide generalized rules for alignment with this technique. Cylindrical nanostructures formed in polystyrene-block-polydimethylsiloxane can be transformed into arrays of silica lines and increasing the thickness from a monolayer to bilayer can effectively halve the spacing of the lines. These results illustrate a generalized method for BCP alignment and a potential route for the generation of complex hierarchical assembled structures. A generalized method for block copolymer thin film alignment: solvent vapor annealing with shear.

  12. Simple, generalizable route to highly aligned block copolymer thin films

    NASA Astrophysics Data System (ADS)

    Qiang, Zhe; Cavicchi, Kevin; Vogt, Bryan

    2015-03-01

    Macroscopic alignment of block copolymer domains in thin films is desired for many applications, such as cell responsive surfaces or optical polarizers. Alignment generally requires specialized tools that apply external fields, shear force gradient, or produce topological patterned substrates. This requirement limits the broad academic application of aligned BCPs. Here, we describe a simple modification of commonly utilized solvent vapor annealing (SVA) process for macroscopic alignment of BCPs. Adhering a flat, crosslinked elastomer pad to the BCP film leads to differential swelling between the elastomer pad and BCP to produce a shear force that aligns the ordered BCP domains. The role of elastomer properties, solvent quality, drying rate and degree of segregation of the block copolymer will be discussed to provide generalized rules for alignment with this technique. Cylindrical nanostructures formed in polystyrene-block-polydimethylsiloxane can be transformed into arrays of silica lines and increasing the thickness from a monolayer to bilayer can effectively halve the spacing of the lines. These results illustrate a generalized method for BCP alignment and a potential route for the generation of complex hierarchical assembled structures.

  13. Thin film structure of symmetric rod-coil block copolymers.

    SciTech Connect

    Olsen, B. D.; Li, X.; Wang, J.; Segalman, R. A.; Univ. of Califormia at Berkeley; LBNL

    2007-04-03

    Poly(alkoxyphenylenevinylene-b-isoprene) (PPV-b-PI) rod-coil block copolymers demonstrate novel structures due to the rodlike PPV block. Thin films of the polymers self-assemble into lamellar microphases upon thermal annealing with the lamellae oriented primarily parallel to the substrate. The parallel lamellae show symmetric wetting of PI at both the substrate and vacuum interfaces. Grains of lamellae with parallel orientation are characterized by irregular polygon shapes and are bounded by defect regions where the lamellae are oriented out of the plane of the film. Grazing-incidence small-angle X-ray scattering (GISAXS) shows that these out-of-plane lamellae are strongly oriented perpendicular to the film. The perpendicular lamellae are much straighter than those typically observed in coil-coil block copolymers due to the high bending energy of the liquid crystalline rod nanodomains. Islands or holes form in the films, and domain spacings estimated from the island/hole heights are equal to the bulk domain spacing. The perpendicular 'defect' lamellae mediate the change in thickness required to transition between islands or holes and the surrounding region. Increasing film thickness results in an increasing fraction of the surface covered by perpendicular lamellae, presumably due to limited penetration of the substrate orienting field into the film. At great enough thickness total reorientation of the lamellar structure from parallel to perpendicular orientation at the vacuum interface is observed.

  14. Nanopatterning of ultrananocrystalline diamond thin films via block copolymer lithography.

    SciTech Connect

    Ramanathan, M.; Darling, S. B.; Sumant, A. V.; Auciello, O.

    2010-07-01

    Nanopatterning of diamond surfaces is critical for the development of diamond-based microelectromechanical system/nanoelectromechanical system (MEMS/NEMS), such as resonators or switches. Micro-/nanopatterning of diamond materials is typically done using photolithography or electron beam lithography combined with reactive ion etching (RIE). In this work, we demonstrate a simple process, block copolymer (BCP) lithography, for nanopatterning of ultrananocrystalline diamond (UNCD) films to produce nanostructures suitable for the fabrication of NEMS based on UNCD. In BCP lithography, nanoscale self-assembled polymeric domains serve as an etch mask for pattern transfer. The authors used thin films of a cylinder-forming organic-inorganic BCP, poly(styrene-block-ferrocenyldimethylsilane), PS-b-PFS, as an etch mask on the surface of UNCD films. Orientational control of the etch masking cylindrical PFS blocks is achieved by manipulating the polymer film thickness in concert with the annealing treatment. We have observed that the surface roughness of UNCD layers plays an important role in transferring the pattern. Oxygen RIE was used to etch the exposed areas of the UNCD film underneath the BCP. Arrays of both UNCD posts and wirelike structures have been created using the same starting polymeric materials as the etch mask.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. Factors Influencing Shear Alignment of Cylinder-Forming Block Copolymer Thin Films

    NASA Astrophysics Data System (ADS)

    Davis, Raleigh; Register, Richard; Chaikin, Paul

    2014-03-01

    Application of shear stress to block copolymers is known to preferentially orient the microdomains in the direction of applied shear. While this phenomenon has been well studied for bulk block copolymer systems, the use of shear stress to align microdomains in block copolymer thin films (typically one to several microdomain layers) is still an active area of research. Numerous experimental factors influence the ease with which orientation is achieved as well as the ultimate quality of alignment observed. The present work investigates several of these factors using a series of cylinder-forming poly(styrene)-poly(hexylmethacrylate) copolymers. Parameters studied include film thickness, block copolymer molecular weight and composition, substrate wetting conditions (controlled via grafted polymer brush layers of either polystyrene or polyhexylmethacrylate), and applied shear stress. Quality of alignment is assessed via atomic force microscopy and subsequent computation of an orientational order parameter and the density of defects in the microdomain lattice. The results are compared to a melting-recrystallization model, thus providing greater insight into the fundamental mechanisms and key parameters which control how microdomains order in response to shear. In general monolayers are observed to align more poorly than thicker films, though the influence of film thickness on orientation depends strongly on polymer composition. Alignment quality is ultimately limited by inherent fluctuations in the cylinder trajectories as well as the presence of isolated dislocations.

  20. Hierarchical assembled nanostructures of hydrogen-bonded supramolecular block copolymer thin films

    NASA Astrophysics Data System (ADS)

    Chen, Xiaofang; Cai, Yongchen

    Controlling the microdomain orientation and long-range ordering in block copolymer thin films is very important in a number of applications, such as nanotemplate, nanoporous thin film, and data storage media. The hierarchical assemblies of block copolymers PS- b-P4VP with dendronized small molecules (DM) hydrogen-bonded onto P4VP blocks were investigated in thin films after solvent vapor annealing. P4VP/DM could form lamellar or hexagonal columnar structure with the periodicity around 8 nm, depending on the stoichiometry of the complex. Hierarchical assemblies of PS- b-P4VP(DM)x, including lamellae-within-lamellae, cylinder-within-lamellae, and cylinder-within-cylinder, were simultaneously ordered and oriented in thin films, which have been studied systematically with the help of AFM, TEM and GISAXS technologies. The orientation of supramolecular assembly depends on the P4VP(DM) fraction and can be tailored by varying the DM to P4VP ratio. Structural transitions from cylinders of (P4VP/DM), lamellae, to cylinders of PS could be achieved by simply increasing the ratio of DM to 4VP units in block copolymer systems. This work was supported by the National Natural Science Foundation of China (21174003 and 21474073).

  1. Shear-alignment of metal-containing block copolymer thin films for nanofabrication

    NASA Astrophysics Data System (ADS)

    Kim, So Youn; Register, Richard; Gwyther, Jessica; Manners, Ian; Chaikin, Paul

    2013-03-01

    Cylinder-forming block copolymers can be used as etch masks for the fabrication of nanowire grids, with both fine resolution and scalability. However, achieving a high aspect ratio in these nanostructures, where reactive ion etching is employed for pattern transfer, requires strong etch contrast between two blocks of the copolymer. We achieve this strong contrast by using metal-containing block copolymers: materials which either contain metal as synthesized, or which can be selectively metallized after deposition as thin films. In the first case, iron-containing polystyrene-b-poly(ferrocenylisopropylmethylsilane) (PS-PFS) forming PFS cylinders was employed, and a spin-coated film was aligned by shearing with a polydimethylsiloxane pad. In the second case, polystyrene-b-poly-2-vinylpyridine (PS-P2VP) was deposited as a film, shear-aligned, and then platinum was selectively sequestered within the P2VP cylinders by brief soaking in an aqueous solution of a Pt salt. In both cases, shear stress produced alignment over centimeter-scale areas; this alignment was retained for PS-P2VP during the selective metallization. The line pattern in these aligned block copolymer thin films is then transferred via reactive ion etching into amorphous silicon deposited onto a quartz wafer to fabricate silicon nanowire grid polarizers which can operate at deep ultraviolet wavelengths.

  2. Surface Modification for Controlling the Orientation of Block Copolymers in thin film and in Cylindrical Nanopores

    NASA Astrophysics Data System (ADS)

    Lin, Xin-Guan; Lin, Feng-Cheng; Tung, Shih-Huang

    2012-02-01

    A series of benzocyclobutene-functionalized random copolymers of styrene and 4-vinylpyridine were synthesized by nitroxide-mediated controlled radical polymerization with BPO and TEMPO. Our research was to use these random copolymers of P(S-r-BCB-r-4VP) to control the orientation of microdomains in block copolymers(BCPs) of poly(styrene-b-4-vinylpyridine)(PS-b-P4VP) thin films and in cylindrical nanopores of anodized aluminum oxide (AAO) membranes. On P(S-r-BCB-r-4VP)-modified substrate,we found that in some particular compositions of random copolymer ,the parallel orientation of the microdomains is switched to be perpendicular in PS-b-P4VP thin film. We also introduced P(S-r-BCB-r-4VP) solution into the nanopores of the AAO and nanotubes formed after solvent evaporation and pyrolysis. And then BCPs of PS-b-P4VP were drawn into the P(S-r-BCB-r-4VP)-modified nanopores in the melt via capillary action to form P(S-r-BCB-r-4VP) coated nanorods of PS-b-P4VP.Similarly,in some particular compositions of random copolymer, we observed that the interactions of the blocks with the walls are not strong or if the interactions are balanced, then the orientation of the microdomains will change from being parallel to being perpendicular to the confining walls.

  3. Nanophase separation in polystyrene-polyfluorene block copolymers thin films prepared through the breath figure procedure.

    PubMed

    Bolognesi, Alberto; Galeotti, Francesco; Giovanella, Umberto; Bertini, Fabio; Yunus, Sami

    2009-05-01

    The amphiphilic block copolymer formed by a hydrophobic body of polystyrene and a hydrophilic head of poly[9,9-di(2-(2-tetrahydropyranyl-oxy)hexyl)fluorene-alt-9,9-dioctylfluorene] was synthesized, and its solution was used to create thin films with ordered pattern of holes, by means of the breath figure technique. These porous films, after a thermal treatment, were found to show ordered aggregates of the pi-conjugated blocks in the place of the cavities. This is probably due to a preorganization of the two different blocks of the copolymer occurring during the breath figure formation, which is driven by the condensation of water microdroplets on the polymer solution, and to a following phase segregation occurring during the thermal annealing. This approach is a promising tool to be employed for the organization of organic materials at the micro and nanoscale.

  4. Morphology Development in Block Copolymer Thin Films via Direct Immersion Annealing

    NASA Astrophysics Data System (ADS)

    Modi, Arvind; Bhaway, Sarang; Vogt, Bryan; Sharma, Ashutosh; Karim, Alamgir

    2015-03-01

    Conventional methods of annealing thin block copolymer (BCP) films include Thermal Annealing and Solvent Vapor Annealing (SVA) processes. Both of the processes have demonstrated excellent control over morphologies and nanostructures. However, both have constraints including long annealing time duration and/or complicated setup requirement. We introduce Direct Immersion Annealing (DIA) of thin block copolymer (BCP) films involving immersion of polymer films directly into the solvent mixture composed of selective non-solvent and solvent for blocks. Non-solvent prevents the dissolution of films while the good solvent permeates the film and plasticizes the blocks. A fine control of swelling ratio can be achieved through an easy and robust control of solvent volume fractions. We studied cylindrical Poly(styrene-block-methyl methacrylate) system in detail and quantified the growth of correlation length (ξ) with time(t) [ ξ = Atn]. We observe a reduction in growth exponent (n) with several fold increase in pre-exponential factor (A) compared to isotropic thermal annealing. We further demonstrate the extension of this strategy to systems with diverse range of χ-parameter, molecular weight and other morphologies.

  5. 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

  6. Evolution of lateral ordering in symmetric block copolymer thin films upon rapid thermal processing.

    PubMed

    Ceresoli, Monica; Ferrarese Lupi, Federico; Seguini, Gabriele; Sparnacci, Katia; Gianotti, Valentina; Antonioli, Diego; Laus, Michele; Boarino, Luca; Perego, Michele

    2014-07-11

    This work reports experimental findings about the evolution of lateral ordering of lamellar microdomains in symmetric PS-b-PMMA thin films on featureless substrates. Phase separation and microdomain evolution are explored in a rather wide range of temperatures (190-340 °C) using a rapid thermal processing (RTP) system. The maximum processing temperature that enables the ordering of block copolymers without introducing any significant degradation of macromolecules is identified. The reported results clearly indicate that the range of accessible temperatures in the processing of these self-assembling materials is mainly limited by the thermal instability of the grafted random copolymer layer, which starts to degrade at T > 300 °C, inducing detachment of the block copolymer thin film. For T ⩽ 290 °C, clear dependence of correlation length (ξ) values on temperature is observed. The highest level of lateral order achievable in the current system in a quasi-equilibrium condition was obtained at the upper processing temperature limit after an annealing time as short as 60 s.

  7. The role of tortuosity on ion conduction in block copolymer electrolyte thin films

    NASA Astrophysics Data System (ADS)

    Kambe, Yu; Arges, Christopher G.; Nealey, Paul F.

    This talk discusses the role of grain tortuosity on ion conductivity in block copolymer electrolyte (BCE) thin films. In particular, we studied lamellae forming BCEs with both domains oriented perpendicular to the substrate surface and connected directly from one electrode to another - i.e., tortuosity of one. The BCE is composed of ion-conducting, poly(2-vinyl n-methylpyridinium) blocks and non-ionic polystyrene blocks. Prior to creating the BCE, the pristine block copolymer, poly(styrene- b-2-vinyl pyridine), was directly self-assembled (DSA) on topographical or chemical patterns via graphoepitaxy and chemoepitaxy. A chemical vapor infiltration reaction modified the P2VP block into positively charged, fixed quaternary ammonium groups paired with mobile counteranions. The graphoepitaxy process utilized topographical interdigitated gold nanoelectrodes (100s of nanometers spacing between electrodes) created via e-beam lithography. Alternatively, chemical patterns had gold electrodes incorporated into them with 10s to 100s of microns spacing using conventional optical lithography. The interdigitated gold electrodes enabled in-plane ion conductivity measurements of the DSA BCEs to study the role of grain tortuosity on ion conductivity. U.S. Department of Energy Office of Science: Contract No. DE-AC02-06CH11357.

  8. Directed Ordering of Block Copolymer Thin Films with Flexible Interfaces for Functional Materials

    NASA Astrophysics Data System (ADS)

    Karim, Alamgir

    2012-02-01

    Orientation control of block copolymer (BCP) films is important for advanced technological applications. We present studies on directed ordering of block copolymer thin films on rigid substrates such as quartz to elastomeric PDMS and flexible Kapton substrates for tunable orientation of microphase separated poly (styrene) -- block -poly (methylmethacrylate) (PS-PMMA) cylinder and lamellae forming BCP films. Although the crosslinked PDMS has low surface energy, its surface energy can be tuned by exposing to UV-Ozone (UVO) that presents an opportunity to change BCP-PDMS interfacial energy to control BCP orientation across full range of orientation and film wettability. On the other hand, Kapton offers a near neutral surface for PS-PMMA without surface modification. Via a modified version of a dynamic thermal processing termed cold zone annealing-sharp (CZA-S), we obtain a wide range of orientations of the block copolymer films in unfilled and nanoparticle filled systems with an interest in photovoltaic systems. With CZA-S, vertical orientation of PS-PMMA can be obtained in films as thick as 1 micron with etchable PMMA domains for membrane applications. GISAXS characterization of these etched BCP membranes reveals up to 5 orders of diffraction indicating hexagonally packed vertical nanopores that extend throughout the film. Under similar thermal gradient, but static conditions, temporally stable vertical cylinders form only within a narrow zone of maximum temperature gradient. Primary CZA-S ordering mechanism thus involves propagating this narrow vertically oriented zone of BCP cylinders created at the maximum thermal gradient section, across the film. An optimal speed is needed since the process competes with preferential surface wetting dynamics that favors parallel orientation. These results are reproduced on large area flexible films on a prototype dynamic R2R assembly platform with incorporated multi-CZA gradient for thin (100 nm) BCP films currently.

  9. 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

  10. Process Controlled Multiscale Morphologies in Metal-containing Block Copolymer Thin Films

    SciTech Connect

    Ramanathan, Nathan Muruganathan; Kilbey, II, S Michael; Darling, Seth B.

    2014-01-01

    Poly(styrene-block-ferrocenyldimethylsilane) (PS-b-PFS) is a metal-containing block copolymer that exhibits certain advantages as a mask for lithographic applications. These advantages include compatibility with a wide range of substrates, ease of control over domain morphologies and robust stability to etch plasma, which aid in the development of high-aspect-ratio patterns. An asymmetric cylinder-forming PS-b-PFS copolymer is subjected to different processing to manipulate the morphology of the phase-separated domains. Control of film structure and domain morphology is achieved by adjusting the film thickness, mode of annealing, and/or annealing time. Changing the process from thermal or solvent annealing to hybrid annealing (thermal and then solvent annealing in sequence) leads to the formation of mesoscale spherulitic and dendritic morphologies. In this communication, we show that reversing the order of the hybrid annealing (solvent annealing first and then thermal annealing) of relatively thick films (>100 nm) on homogeneously thick substrates develops disordered lamellar structure. Furthermore, the same processing applied on a substrate with a thin, mechanically flexible window in the center leads to the formation of sub-micron scale concentric ring patterns. Enhanced material mobility in the thick film during hybrid annealing along with dynamic rippling effects that may arise from the vibration of the thin window during spin casting are likely causes for these morphologies.

  11. Synergistic templated self-assembly of cellulose nanocrystals in thin block copolymer films

    NASA Astrophysics Data System (ADS)

    Grolman, Danielle; Gilman, Jeffrey; Davis, Chelsea; Karim, Alamgir

    2015-03-01

    Nanofillers in thin polymer films offer unique advantage to potentially modify the film's thermal, optical, electrical and mechanical properties due to the high surface area to volume ratio and intrinsic property change at the nanoscale. Nanofilled polymer films have been shown to exhibit unusual film stability to dewetting with a nonmonotonic behavior with nanofiller loading, potentially arising from factors such as competitive phase behavior and filler aggregation, particularly in the high nanofiller concentration limit. In this regard, block copolymer films can act as ideal nanoscale structured templates to selectively sequester and organize nanofillers. In conjunction with incorporated cellulose nanocrystals (CNCs), we seek to understand how individual anisotropic nanofillers can provide synergistic reinforcement to inherently anisotropic nanostructured block copolymer films. A clear enhancement in the Young's Modulus was observed with increased CNC loading using strain-induced elastic buckling instability for mechanical measurements (SIEBIMM) for thin films. To this end, we examine the nanoscale to microscale morphology of the blend film through AFM, TEM and grazing incidence small-angle x-ray scattering (GISAXS), and CNC dispersion and percolation through high-intensity grazing incidence wide-angle x-ray scattering (GIWAXS) analysis.

  12. Directed self-assembly of block copolymer films on atomically-thin graphene chemical patterns

    PubMed Central

    Chang, Tzu-Hsuan; Xiong, Shisheng; Jacobberger, Robert M.; Mikael, Solomon; Suh, Hyo Seon; Liu, Chi-Chun; Geng, Dalong; Wang, Xudong; Arnold, Michael S.; Ma, Zhenqiang; Nealey, Paul F.

    2016-01-01

    Directed self-assembly of block copolymers is a scalable method to fabricate well-ordered patterns over the wafer scale with feature sizes below the resolution of conventional lithography. Typically, lithographically-defined prepatterns with varying chemical contrast are used to rationally guide the assembly of block copolymers. The directed self-assembly to obtain accurate registration and alignment is largely influenced by the assembly kinetics. Furthermore, a considerably broad processing window is favored for industrial manufacturing. Using an atomically-thin layer of graphene on germanium, after two simple processing steps, we create a novel chemical pattern to direct the assembly of polystyrene-block-poly(methyl methacrylate). Faster assembly kinetics are observed on graphene/germanium chemical patterns than on conventional chemical patterns based on polymer mats and brushes. This new chemical pattern allows for assembly on a wide range of guiding periods and along designed 90° bending structures. We also achieve density multiplication by a factor of 10, greatly enhancing the pattern resolution. The rapid assembly kinetics, minimal topography, and broad processing window demonstrate the advantages of inorganic chemical patterns composed of hard surfaces. PMID:27528258

  13. Directed self-assembly of block copolymer films on atomically-thin graphene chemical patterns.

    PubMed

    Chang, Tzu-Hsuan; Xiong, Shisheng; Jacobberger, Robert M; Mikael, Solomon; Suh, Hyo Seon; Liu, Chi-Chun; Geng, Dalong; Wang, Xudong; Arnold, Michael S; Ma, Zhenqiang; Nealey, Paul F

    2016-01-01

    Directed self-assembly of block copolymers is a scalable method to fabricate well-ordered patterns over the wafer scale with feature sizes below the resolution of conventional lithography. Typically, lithographically-defined prepatterns with varying chemical contrast are used to rationally guide the assembly of block copolymers. The directed self-assembly to obtain accurate registration and alignment is largely influenced by the assembly kinetics. Furthermore, a considerably broad processing window is favored for industrial manufacturing. Using an atomically-thin layer of graphene on germanium, after two simple processing steps, we create a novel chemical pattern to direct the assembly of polystyrene-block-poly(methyl methacrylate). Faster assembly kinetics are observed on graphene/germanium chemical patterns than on conventional chemical patterns based on polymer mats and brushes. This new chemical pattern allows for assembly on a wide range of guiding periods and along designed 90° bending structures. We also achieve density multiplication by a factor of 10, greatly enhancing the pattern resolution. The rapid assembly kinetics, minimal topography, and broad processing window demonstrate the advantages of inorganic chemical patterns composed of hard surfaces.

  14. Directed self-assembly of block copolymer films on atomically-thin graphene chemical patterns

    NASA Astrophysics Data System (ADS)

    Chang, Tzu-Hsuan; Xiong, Shisheng; Jacobberger, Robert M.; Mikael, Solomon; Suh, Hyo Seon; Liu, Chi-Chun; Geng, Dalong; Wang, Xudong; Arnold, Michael S.; Ma, Zhenqiang; Nealey, Paul F.

    2016-08-01

    Directed self-assembly of block copolymers is a scalable method to fabricate well-ordered patterns over the wafer scale with feature sizes below the resolution of conventional lithography. Typically, lithographically-defined prepatterns with varying chemical contrast are used to rationally guide the assembly of block copolymers. The directed self-assembly to obtain accurate registration and alignment is largely influenced by the assembly kinetics. Furthermore, a considerably broad processing window is favored for industrial manufacturing. Using an atomically-thin layer of graphene on germanium, after two simple processing steps, we create a novel chemical pattern to direct the assembly of polystyrene-block-poly(methyl methacrylate). Faster assembly kinetics are observed on graphene/germanium chemical patterns than on conventional chemical patterns based on polymer mats and brushes. This new chemical pattern allows for assembly on a wide range of guiding periods and along designed 90° bending structures. We also achieve density multiplication by a factor of 10, greatly enhancing the pattern resolution. The rapid assembly kinetics, minimal topography, and broad processing window demonstrate the advantages of inorganic chemical patterns composed of hard surfaces.

  15. Directed self-assembly of block copolymer films on atomically-thin graphene chemical patterns.

    PubMed

    Chang, Tzu-Hsuan; Xiong, Shisheng; Jacobberger, Robert M; Mikael, Solomon; Suh, Hyo Seon; Liu, Chi-Chun; Geng, Dalong; Wang, Xudong; Arnold, Michael S; Ma, Zhenqiang; Nealey, Paul F

    2016-01-01

    Directed self-assembly of block copolymers is a scalable method to fabricate well-ordered patterns over the wafer scale with feature sizes below the resolution of conventional lithography. Typically, lithographically-defined prepatterns with varying chemical contrast are used to rationally guide the assembly of block copolymers. The directed self-assembly to obtain accurate registration and alignment is largely influenced by the assembly kinetics. Furthermore, a considerably broad processing window is favored for industrial manufacturing. Using an atomically-thin layer of graphene on germanium, after two simple processing steps, we create a novel chemical pattern to direct the assembly of polystyrene-block-poly(methyl methacrylate). Faster assembly kinetics are observed on graphene/germanium chemical patterns than on conventional chemical patterns based on polymer mats and brushes. This new chemical pattern allows for assembly on a wide range of guiding periods and along designed 90° bending structures. We also achieve density multiplication by a factor of 10, greatly enhancing the pattern resolution. The rapid assembly kinetics, minimal topography, and broad processing window demonstrate the advantages of inorganic chemical patterns composed of hard surfaces. PMID:27528258

  16. Structured block copolymer thin film composites for ultra-high energy density capacitors

    NASA Astrophysics Data System (ADS)

    Samant, Saumil; Hailu, Shimelis; Grabowski, Christopher; Durstock, Michael; Raghavan, Dharmaraj; Karim, Alamgir

    2014-03-01

    Development of high energy density capacitors is essential for future applications like hybrid vehicles and directed energy weaponry. Fundamentally, energy density is governed by product of dielectric permittivity ɛ and breakdown strength Vbd. Hence, improvements in energy density are greatly reliant on improving either ɛ or Vbd or a combination of both. Polymer films are widely used in capacitors due to high Vbd and low loss but they suffer from very low permittivities. Composite dielectrics offer a unique opportunity to combine the high ɛ of inorganic fillers with the high Vbd of a polymer matrix. For enhancement of dielectric properties, it is essential to improve matrix-filler interaction and control the spatial distribution of fillers for which nanostructured block copolymers BCP act as ideal templates. We use Directed Self-assembly of block copolymers to rapidly fabricate highly aligned BCP-TiO2 composite nanostructures in thin films under dynamic thermal gradient field to synergistically combine the high ɛ of functionalized TiO2 and high Vbd of BCP matrix. The results of impact of BCP morphology, processing conditions and concentration of TiO2 on capacitor performance will be reported. U.S. Air Force of Scientific Research under contract FA9550-12-1-0306

  17. Morphological Evolution of Gyroid-Forming Block Copolymer Thin Films with Varying Solvent Evaporation Rate.

    PubMed

    Wu, Yi-Hsiu; Lo, Ting-Ya; She, Ming-Shiuan; Ho, Rong-Ming

    2015-08-01

    In this study, we aim to examine the morphological evolution of block copolymer (BCP) nanostructured thin films through solvent evaporation at different rates for solvent swollen polystyrene-block-poly(l-lactide) (PS-PLLA). Interesting phase transitions from disorder to perpendicular cylinder and then gyroid can be found while using a partially selective solvent for PS to swell PS-PLLA thin film followed by solvent evaporation. During the transitions, gyroid-forming BCP thin film with characteristic crystallographic planes of (111)G, (110)G, and (211)G parallel to air surface can be observed, and will gradually transform into coexisting (110)G and (211)G planes, and finally transforms to (211)G plane due to the preferential segregation of constituted block to the surface (i.e., the thermodynamic origin for self-assembly) that affects the relative amount of each component at the air surface. With the decrease on the evaporation rate, the disorder phase will transform to parallel cylinder and then directly to (211)G without transition to perpendicular cylinder phase. Most importantly, the morphological evolution of PS-PLLA thin films is strongly dependent upon the solvent removal rate only in the initial stage of the evaporation process due to the anisotropy of cylinder structure. Once the morphology is transformed back to the isotropic gyroid structure after long evaporation, the morphological evolution will only relate to the variation of the surface composition. Similar phase transitions at the substrate can also be obtained by controlling the ratio of PLLA-OH to PS-OH homopolymers to functionalize the substrate. As a result, the fabrication of well-defined nanostructured thin films with controlled orientation can be achieved by simple swelling and deswelling with controlled evaporation rate.

  18. Get in Line: Orienting Cylinders in Block Copolymer Thin Films via Shear

    NASA Astrophysics Data System (ADS)

    Davis, Raleigh; Register, Richard; Chaikin, Paul

    2015-03-01

    Block copolymer thin films have garnered much attention for their potential as nanolithographic masks. For many patterning applications, however, the need to impart well-defined order to the microdomains is paramount. One method to achieve long-range orientational order in thin films is through the use of shear. The ease with which orientation is achieved as well as the ultimate quality of alignment is strongly influenced by the copolymer composition and molecular weight, film thickness, and shearing conditions, as revealed using a series of cylinder-forming poly(styrene)-poly(hexylmethacrylate) (PS-PHMA) copolymers. Quality of in-plane alignment is assessed via atomic force microscopy, quantified through an orientational order parameter (Ψ2) . The ease with which alignment is achieved is determined by measuring Ψ2 as a function of applied shear stress and comparing the results to a melting-recrystallization model which allows for the determination of two key alignment parameters: the critical stress needed for alignment (σc) , and an orientation rate constant (Γ) . The Ψ2 vs. stress behavior, including the time-dependence, is well captured by the model. For monolayers, as PS weight fraction or overall molecular weight increases, σc also increases, while Γ greatly decreases. As the number of cylinder layers is increased, σc decreases to a plateau. The ultimate quality of alignment is studied by comparing Ψ2 vs. lattice defect density for well-aligned films; Ψ2is limited by both undulations in the cylinder trajectories as well as the presence of isolated dislocations.

  19. Nanoporous membrane based on block copolymer thin film for protein drug delivery

    NASA Astrophysics Data System (ADS)

    Yang, Seung Yun; Yang, Jeong-A.; Kim, Eung-Sam; Jeon, Gumhye; Oh, Eun Ju; Choi, Kwan Yong; Hahn, Sei Kwang; Kim, Jin Kon

    2010-03-01

    We studied long term and controlled release of protein drugs by using nanoporous membranes with various pore sizes. Nanoporous membrane consists of the separation layer prepared by polystyrene-block-poly(methylmethacrylate) copolymer thin film and conventional microfiltration membrane as a support. We demonstrate a long-term constant in vitro release of bovine serum albumin (BSA)and human growth hormone ) (hGH) without their denaturation up to 2 months. A nearly constant serum concentration of hGH was maintained up to 3 weeks in SD rats. The long-term constant delivery based on this membrane for protein drugs within the therapeutic range can be highly appreciated for the patients with hormone- deficiency.

  20. Nanofabrication of Block Copolymer Bulk and Thin Films: Microdomain Structures as Templates

    NASA Astrophysics Data System (ADS)

    Hashimoto, Takeji; Fukunaga, Kenji

    In this chapter we shall discuss applications of block copolymers (bcps) to nanotechnologies and nanosciences. Our objectives here are to explore the methods and principles concerning fabrications of ordered structures of bcps having various symmetries with nano-sized periodicity to create new materials with interesting structures and properties. We define this kind of fabrication as nano-fabrication. In other words we aim to control or manipulate self- organized microdomain structures of bcps, in both nonequilibrium and equi- librium states, and utilize them as templates for further nano-fabrication to- ward advanced devices and materials, such as tunable photonic crystals [1-4], quantum dots and nanowires [5-9], nanohybrids with inorganic materials and nanometal particles [10-12], photovoltaics and photoluminescence [13-16], etc. We shall present the bcp templates in both bulk (Sect. 2) and thin films (Sect. 3).

  1. 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.

  2. Multiple Replicas of Block Copolymer Thin Films from a Brushless Organosilicate Substrate

    NASA Astrophysics Data System (ADS)

    Suh, Hyo Seon; Yoon, Hyunsik; Char, Kookheon

    2011-03-01

    The chain end-grafted polymer brushes or cross-linked polymer mats have typically been utilized as the surface modification layers to induce the perpendicular orientation of block copolymer (BCP) thin films. Instead of such polymer-based approaches, we have recently introduced a new concept to control the BCP orientation using the brushless organosilicate (OS) substrates, whose surface energy can be finely tuned with thermal treatment. In this brushless case, the BCP chains do not penetrate into the underlying hard OS substrates during thermal annealing of BCP films, therefore, the BCP chains at the interface have no entangled structure with fairly weak adhesion of BCP films against the substrate. Owing to such weak adhesion of BCP films against the OS substrate, the perpendicularly oriented BCP film on a neutral OS substrate could be easily peeled off and transferred to a UV-curable resin applied onto the BCP film. The OS substrate after the peel-off process of a BCP film could regenerate the perpendicularly oriented BCP films since the surface energy of the OS substrate remains intact during the peel-off process. Furthermore, the direct-assembled BCP films on chemically patterned OS substrates could also be peeled off and transferred on to a UV-curable resin, allowing us to produce multiple replicas of direct-assembled BCP thin films from a single chemically patterned OS substrate.

  3. Formation of Lamellar Heterolattices in Block Copolymer Thin Films by Sequential Electrospray Deposition

    NASA Astrophysics Data System (ADS)

    Choo, Youngwoo; Hu, Hanqiong; Toth, Kristof; Osuji, Chinedum

    Electrospray deposition (ESD) of block copolymers (BCPs) on a heated substrate provides precise control over the formation of BCP thin films. This continuous deposition process allows one to fabricate heterogeneously assembled thin films by altering the deposition materials. Here, we demonstrate such the sequential ESD of lamellae-forming poly(styrene- b-4-vinylpyridine) BCPs with differing molecular weights and explore the morphology of the composite films. The resulting structure of the heterolattice interface was a strong function of temperature. Sharp interfaces with abrupt changes in the lamellar period (L0) were observed at lower deposition temperatures (150 - 170 °C), while higher temperature (190 °C) produced a smooth variation in the lamellar period from one molecular weight to the next. Furthermore, the ordering kinetics of a secondary layer which was deposited onto the primary layer could be substantially enhanced depending on the molecular weight of the polymer present in the underlying primary layer. We elucidate these findings in the context of temperature and molecular weight dependent diffusion dynamics of the polymers in the melt which control the inter-mixing of the layers. We gratefully acknowledge funding by NSF DRM-1410568.

  4. Automated Defect and Correlation Length Analysis of Block Copolymer Thin Film Nanopatterns

    PubMed Central

    Murphy, Jeffrey N.; Harris, Kenneth D.; Buriak, Jillian M.

    2015-01-01

    Line patterns produced by lamellae- and cylinder-forming block copolymer (BCP) thin films are of widespread interest for their potential to enable nanoscale patterning over large areas. In order for such patterning methods to effectively integrate with current technologies, the resulting patterns need to have low defect densities, and be produced in a short timescale. To understand whether a given polymer or annealing method might potentially meet such challenges, it is necessary to examine the evolution of defects. Unfortunately, few tools are readily available to researchers, particularly those engaged in the synthesis and design of new polymeric systems with the potential for patterning, to measure defects in such line patterns. To this end, we present an image analysis tool, which we have developed and made available, to measure the characteristics of such patterns in an automated fashion. Additionally we apply the tool to six cylinder-forming polystyrene-block-poly(2-vinylpyridine) polymers thermally annealed to explore the relationship between the size of each polymer and measured characteristics including line period, line-width, defect density, line-edge roughness (LER), line-width roughness (LWR), and correlation length. Finally, we explore the line-edge roughness, line-width roughness, defect density, and correlation length as a function of the image area sampled to determine each in a more rigorous fashion. PMID:26207990

  5. 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.

  6. 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

  7. Dynamic thermal field-induced gradient soft-shear for highly oriented block copolymer thin films.

    PubMed

    Singh, Gurpreet; Yager, Kevin G; Berry, Brian; Kim, Ho-Cheol; Karim, Alamgir

    2012-11-27

    As demand for smaller, more powerful, and energy-efficient devices continues, conventional patterning technologies are pushing up against fundamental limits. Block copolymers (BCPs) are considered prime candidates for a potential solution via directed self-assembly of nanostructures. We introduce here a facile directed self-assembly method to rapidly fabricate unidirectionally aligned BCP nanopatterns at large scale, on rigid or flexible template-free substrates via a thermally induced dynamic gradient soft-shear field. A localized differential thermal expansion at the interface between a BCP film and a confining polydimethylsiloxane (PDMS) layer due to a dynamic thermal field imposes the gradient soft-shear field. PDMS undergoes directional expansion (along the annealing direction) in the heating zone and contracts back in the cooling zone, thus setting up a single cycle of oscillatory shear (maximum lateral shear stress ∼12 × 10(4) Pa) in the system. We successfully apply this process to create unidirectional alignment of BCP thin films over a wide range of thicknesses (nm to μm) and processing speeds (μm/s to mm/s) using both a flat and patterned PDMS layer. Grazing incidence small-angle X-ray scattering measurements show absolutely no sign of isotropic population and reveal ≥99% aligned orientational order with an angular spread Δθ(fwhm) ≤ 5° (full width at half-maximum). This method may pave the way to practical industrial use of hierarchically patterned BCP nanostructures. PMID:23106286

  8. Controlling Directed Self-Assembly and Sintering of Gold Nanorods in Patterned Block Copolymer Thin Films

    NASA Astrophysics Data System (ADS)

    Lai, Fengyuan

    As the miniaturization of electronic devices continues, proper thermal management is crucial to ensure the optimum performance and reliability of such devices within their specification. Of primary interest are the so-called thermal interface materials to minimize the thermal resistance between the heat source and the heat sink. To this end, polymer nanocomposites composed of a polymer matrix and nanoscale fillers with high thermal conductivity have attracted tremendous attention. It has been demonstrated that the formation of a nanoparticle assembly inside the polymer matrix provides a continuous pathway for efficient heat transfer, and thus it is essential for achieving high thermal conductivity. In this work, we explored the ability to direct the self-assembly of gold nanorods (AuNRs) via patterned block copolymer (BCP) thin films. Selective sequestration of AuNRs with various aspect ratios in one block domain was achieved, with over 30% of the surface covered by an ordered AuNR assembly orienting parallel to the geometric confinement. The final nanostructure resulting from the directed self-assembly process is determined by the competition between thermodynamic consideration and kinetic factors. The coalescence and sintering of the AuNR assembly was accomplished by both furnace thermal annealing and rapid thermal annealing at low temperatures. The mechanism through which efficient sintering occurred is investigated with scanning electron microscopy. It is found that the sintering process initially takes place locally, resulting in small AuNR aggregates. Eventually the aggregates grow into a globally continuous, percolating network structure. In addition, the overall heat transfer coefficient was measured in an environmental scanning electron microscope by following droplet growth over time. The present study opens up new opportunities to accomplish controlled assembly of nanoparticles with high concentration for different nanorod-based applications as well as

  9. 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.

  10. 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.

  11. New Poly(dimethylsiloxane)/Poly(perfluorooctylethyl acrylate) Block Copolymers: Structure and Order Across Multiple Length Scales in Thin Films

    SciTech Connect

    E Martinelli; G Galli; S Krishnan; M Paik; C Ober; D Fischer

    2011-12-31

    Three sets of a new class of low surface tension block copolymers were synthesized consisting of a poly(dimethylsiloxane) (PDMS) block and a poly(perfluorooctylethyl acrylate) (AF8) block. The polymers were prepared using a bromo-terminated PDMS macroinitiator, to which was attached an AF8 block grown using atom transfer radical polymerization (ATRP) in such a designed way that the molecular weight and composition of the two polymer blocks were regularly varied. The interplay of both the phase separated microstructure and the mesomorphic character of the fluorinated domains with their effect on surface structure was evaluated using a suite of analytical tools. Surfaces of spin-coated and thermally annealed films were assessed using a combination of X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) studies. Both atomic force microscopy (AFM) measurements and grazing incidence small angle X-ray scattering (GISAXS) studies were carried out to evaluate the microstructure of the thin films. Even in block copolymers in which the PDMS block was the majority component, a significant presence of the lower surface energy AF8 block was detected at the film surface. Moreover, the perfluorooctyl helices of the AF8 repeat units were highly oriented at the surface in an ordered, tilted smectic structure, which was compared with those of the bulk powder samples using wide-angle X-ray powder diffraction (WAXD) studies.

  12. Controlling the morphology of side chain liquid crystalline block copolymer thin films through variations in liquid crystalline content.

    PubMed

    Verploegen, Eric; Zhang, Tejia; Jung, Yeon Sik; Ross, Caroline; Hammond, Paula T

    2008-10-01

    In this paper, we describe methods for manipulating the morphology of side-chain liquid crystalline block copolymers through variations in the liquid crystalline content. By systematically controlling the covalent attachment of side chain liquid crystals to a block copolymer (BCP) backbone, the morphology of both the liquid crystalline (LC) mesophase and the phase-segregated BCP microstructures can be precisely manipulated. Increases in LC functionalization lead to stronger preferences for the anchoring of the LC mesophase relative to the substrate and the intermaterial dividing surface. By manipulating the strength of these interactions, the arrangement and ordering of the ultrathin film block copolymer nanostructures can be controlled, yielding a range of morphologies that includes perpendicular and parallel cylinders, as well as both perpendicular and parallel lamellae. Additionally, we demonstrate the utilization of selective etching to create a nanoporous liquid crystalline polymer thin film. The unique control over the orientation and order of the self-assembled morphologies with respect to the substrate will allow for the custom design of thin films for specific nanopatterning applications without manipulation of the surface chemistry or the application of external fields.

  13. Directed self-assembly of block copolymers in thin films on surfaces patterned by electro-oxidation nanolithography

    NASA Astrophysics Data System (ADS)

    Xu, Ji

    We have studied the wetting and self-assembly behavior of block copolymer thin films on chemical patterns in various geometries. Carboxylic-terminated, mesh-like patterns were generated on OTS modified silicon wafers by AFM electro-oxidation lithography. The films were pinned on the carboxylic regions due to the strong interaction of the minor component block with the surface which was also found to suppress film dewetting over the unpatterned methyl regions. We have found that the cylindrical microdomains orient normal to the methyl-terminated patterns and remain laterally confined within them. Defect-free, hexagonally packed cylindrical microdomains could be obtained thanks to the "corralling" action of the patterns. Domain deformation or point defects arose when the dimensions or shapes of the patterns were not commensurate with the natural packing of the copolymers. Tetragonal packing of microdomains was observed when a square-shaped confinement geometry, with dimension comparable to 2L 0 (natural period), was used. The stretching or compression of polymer chains was found to accomendate the incommensurable confinement imposed by chemical patterns, and a free energy model was applied for interpretation. Solvent annealing was conbined with chemical dot patterns to direct the self-assembly of block copolymers in thin films, and silicon oxide nanodots were fabricated through a tone-reversal process.

  14. Deconvoluting the mechanism of microwave annealing of block copolymer thin films.

    PubMed

    Jin, Cong; Murphy, Jeffrey N; Harris, Kenneth D; Buriak, Jillian M

    2014-04-22

    The self-assembly of block copolymer (BCP) thin films is a versatile method for producing periodic nanoscale patterns with a variety of shapes. The key to attaining a desired pattern or structure is the annealing step undertaken to facilitate the reorganization of nanoscale phase-segregated domains of the BCP on a surface. Annealing BCPs on silicon substrates using a microwave oven has been shown to be very fast (seconds to minutes), both with and without contributions from solvent vapor. The mechanism of the microwave annealing process remains, however, unclear. This work endeavors to uncover the key steps that take place during microwave annealing, which enable the self-assembly process to proceed. Through the use of in situ temperature monitoring with a fiber optic temperature probe in direct contact with the sample, we have demonstrated that the silicon substrate on which the BCP film is cast is the dominant source of heating if the doping of the silicon wafer is sufficiently low. Surface temperatures as high as 240 °C are reached in under 1 min for lightly doped, high resistivity silicon wafers (n- or p-type). The influence of doping, sample size, and BCP composition was analyzed to rule out other possible mechanisms. In situ temperature monitoring of various polymer samples (PS, P2VP, PMMA, and the BCPs used here) showed that the polymers do not heat to any significant extent on their own with microwave irradiation of this frequency (2.45 GHz) and power (∼600 W). It was demonstrated that BCP annealing can be effectively carried out in 60 s on non-microwave-responsive substrates, such as highly doped silicon, indium tin oxide (ITO)-coated glass, glass, and Kapton, by placing a piece of high resistivity silicon wafer in contact with the sample-in this configuration, the silicon wafer is termed the heating element. Annealing and self-assembly of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) and polystyrene-block-poly(methyl methacrylate) (PS

  15. Azobenzene photoswitching as a tool for controlling block copolymer self-assembly in dip-coated thin films

    NASA Astrophysics Data System (ADS)

    Vapaavuori, Jaana; Grosrenaud, Josué; Borozenko, Kateryna; Pellerin, Christian; Bazuin, Geraldine; Department of Chemistry, University of Montreal Team

    Understanding how to control the characteristics of microphase-separated block copolymer thin films is of crucial importance for developing nanotechnological applications, such as producing nanoscale lithography templates for the electronics industry. The supramolecular complexation of small molecules selectively to one of the blocks in suitable block copolymers enables modulating the block volume fractions and thereby controlling the type of surface morphology obtained in thin films. In this contribution, we show that the morphology of dip-coated polystyrene-b-poly(4-vinylpyridine) polymer films containing a hydrogen-bonding azobenzene guest can be further controlled using light as an external in situ stimulus during the dip-coating procedure. A change from spherical to cylindrical morphology was demonstrated when the geometry of the azobenzene units was switched by illumination at 365 nm. Film thickness measurements revealed that the thickness of the films can also be tailored by light, since films prepared under irradiation are significantly thicker than non-irradiated ones. The photochemical requirements to guide the choice of azobenzene molecule and the nature of the solvent used will be discussed in view of an optimal material combination for easily directable systems.

  16. Minimal Topographic Surfaces for Directed Self-assembly of Cylinder-forming Block Copolymer Thin films with Lateral Order

    NASA Astrophysics Data System (ADS)

    Choi, Jaewon; Carter, Kenneth; Russell, Thomas

    2015-03-01

    Controlling the orientation of cylinder-forming block copolymer microdomains in thin films is important for block copolymer applications such as lithographic masks and bit patterned media. However, it is still challenging to produce perfectly ordered cylindrical microdomains with perpendicular orientation over very large areas by using topographical surfaces. Here, we investigate the generation of a single hexagonal array of cylindrical poly(styrene-b-ethylene oxide) (PS-b-PEO) microdomains with perpendicular orientation on minimally patterned surfaces over large areas by thermal annealing without a brush layer. Key factors, such as pattern dimension and film thickness, emerge as being critical for inducing a single grain of perpendicular orientation of PS-b-PEO microdomains over large areas. We systematically investigated the effect of pattern dimension on the generation of perpendicular cylindrical PS-b-PEO microdomains. Furthermore, by solvent vapor annealing, we produced a single grain of parallel cylindrical PS-b-PEO microdomains over large areas on the same minimally patterned surfaces. This simple approach can be an alternative route to achieve the desired orientation of cylinder-forming block copolymer microdomains over large areas.

  17. Analysis of Order Formation in Block Copolymer Thin Films UsingResonant Soft X-Ray Scattering

    SciTech Connect

    Virgili, Justin M.; Tao, Yuefei; Kortright, Jeffrey B.; Balsara,Nitash P.; Segalman, Rachel A.

    2006-11-27

    The lateral order of poly(styrene-block-isoprene) copolymer(PS-b-PI) thin films is characterized by the emerging technique ofresonant soft X-ray scattering (RSOXS) at the carbon K edge and comparedto ordering in bulk samples of the same materials measured usingconventional small-angle X-ray scattering. We show resonance using theoryand experiment that the loss of scattering intensity expected with adecrease in sample volume in the case of thin films can be overcome bytuning X-rays to the pi* resonance of PS or PI. Using RSOXS, we study themicrophase ordering of cylinder- and phere-forming PS-b-PI thin films andcompare these results to position space data obtained by atomic forcemicroscopy. Our ability to examine large sample areas (~;9000 mu m2) byRSOXS enables unambiguous identification of the lateral lattice structurein the thin films. In the case of the sphere-forming copolymer thin film,where the spheres are hexagonally arranged, the average sphere-to-spherespacing is between the bulk (body-centered cubic) nearest neighbor andbulk unit cell spacings. In the case of the cylinder-forming copolymerthin film, the cylinder-to-cylinder spacing is within experimental errorof that obtained in the bulk.

  18. 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

  19. Neutral wetting brush layers for block copolymer thin films using homopolymer blends processed at high temperatures.

    PubMed

    Ceresoli, M; Palermo, M; Ferrarese Lupi, F; Seguini, G; Perego, M; Zuccheri, G; Phadatare, S D; Antonioli, D; Gianotti, V; Sparnacci, K; Laus, M

    2015-10-16

    Binary homopolymer blends of two hydroxyl-terminated polystyrene (PS-OH) and polymethylmethacrylate (PMMA-OH) homopolymers (Mn ∼ 16000 g mol(-1)) were grafted on SiO2 substrates by high-temperature (T > 150 °C), short-time (t < 600 s) thermal treatments. The resulting brush layer was tested to screen preferential interactions of the SiO2 substrate with the different symmetric and asymmetric PS-b-PMMA block copolymers deposited on top of the grafted molecules. By properly adjusting the blend composition and the processing parameters, an efficient surface neutralization path was identified, enabling the formation, in the block copolymer film, of homogeneous textures of lamellae or cylinders perpendicularly oriented with respect to the substrate. A critical interplay between the phase segregation of the homopolymer blends and their grafting process on the SiO2 was observed. In fact, the polar SiO2 is preferential for the PMMA-rich phase that forms a homogeneous layer on the substrate, while the PS-rich phase is located at the polymer-air interface. During the thermal treatment, phase segregation and grafting proceed simultaneously. Complete wetting of the PS rich phase on the PMMA rich phase leads to the formation of a PS/PMMA bilayer. In this case, the progressive diffusion of PS chains toward the polymer-SiO2 interface during the thermal treatment allows tuning of the brush layer composition.

  20. 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

  1. Chemical Interactions and Their Role in the Microphase Separation of Block Copolymer Thin Films

    PubMed Central

    Farrell, Richard A.; Fitzgerald, Thomas G.; Borah, Dipu; Holmes, Justin D.; Morris, Michael A.

    2009-01-01

    The thermodynamics of self-assembling systems are discussed in terms of the chemical interactions and the intermolecular forces between species. It is clear that there are both theoretical and practical limitations on the dimensions and the structural regularity of these systems. These considerations are made with reference to the microphase separation that occurs in block copolymer (BCP) systems. BCP systems self-assemble via a thermodynamic driven process where chemical dis-affinity between the blocks driving them part is balanced by a restorative force deriving from the chemical bond between the blocks. These systems are attracting much interest because of their possible role in nanoelectronic fabrication. This form of self-assembly can obtain highly regular nanopatterns in certain circumstances where the orientation and alignment of chemically distinct blocks can be guided through molecular interactions between the polymer and the surrounding interfaces. However, for this to be possible, great care must be taken to properly engineer the interactions between the surfaces and the polymer blocks. The optimum methods of structure directing are chemical pre-patterning (defining regions on the substrate of different chemistry) and graphoepitaxy (topographical alignment) but both centre on generating alignment through favourable chemical interactions. As in all self-assembling systems, the problems of defect formation must be considered and the origin of defects in these systems is explored. It is argued that in these nanostructures equilibrium defects are relatively few and largely originate from kinetic effects arising during film growth. Many defects also arise from the confinement of the systems when they are ‘directed’ by topography. The potential applications of these materials in electronics are discussed. PMID:19865513

  2. Patterning at the 10 nanometer length scale using a strongly segregating block copolymer thin film and vapor phase infiltration of inorganic precursors

    NASA Astrophysics Data System (ADS)

    Choi, Jonathan W.; Li, Zhaodong; Black, Charles T.; Sweat, Daniel P.; Wang, Xudong; Gopalan, Padma

    2016-06-01

    In this work, we demonstrate the use of self-assembled thin films of the cylinder-forming block copolymer poly(4-tert-butylstyrene-block-2-vinylpyridine) to pattern high density features at the 10 nm length scale. This material's large interaction parameter facilitates pattern formation in single-digit nanometer dimensions. This block copolymer's accessible order-disorder transition temperature allows thermal annealing to drive the assembly of ordered 2-vinylpyridine cylinders that can be selectively complexed with the organometallic precursor trimethylaluminum. This unique chemistry converts organic 2-vinylpyridine cylinders into alumina nanowires with diameters ranging from 8 to 11 nm, depending on the copolymer molecular weight. Graphoepitaxy of this block copolymer aligns and registers sub-12 nm diameter nanowires to larger-scale rectangular, curved, and circular features patterned by optical lithography. The alumina nanowires function as a robust hard mask to withstand the conditions required for patterning the underlying silicon by plasma etching. We conclude with a discussion of some of the challenges that arise with using block copolymers for patterning at sub-10 nm feature sizes.In this work, we demonstrate the use of self-assembled thin films of the cylinder-forming block copolymer poly(4-tert-butylstyrene-block-2-vinylpyridine) to pattern high density features at the 10 nm length scale. This material's large interaction parameter facilitates pattern formation in single-digit nanometer dimensions. This block copolymer's accessible order-disorder transition temperature allows thermal annealing to drive the assembly of ordered 2-vinylpyridine cylinders that can be selectively complexed with the organometallic precursor trimethylaluminum. This unique chemistry converts organic 2-vinylpyridine cylinders into alumina nanowires with diameters ranging from 8 to 11 nm, depending on the copolymer molecular weight. Graphoepitaxy of this block copolymer aligns and

  3. Orientation Control in Thin Films of a High-χ Block Copolymer with a Surface Active Embedded Neutral Layer.

    PubMed

    Zhang, Jieqian; Clark, Michael B; Wu, Chunyi; Li, Mingqi; Trefonas, Peter; Hustad, Phillip D

    2016-01-13

    Directed self-assembly (DSA) of block copolymers (BCPs) is an attractive advanced patterning technology being considered for future integrated circuit manufacturing. By controlling interfacial interactions, self-assembled microdomains in thin films of polystyrene-block-poly(methyl methacrylate), PS-b-PMMA, can be oriented perpendicular to surfaces to form line/space or hole patterns. However, its relatively weak Flory interaction parameter, χ, limits its capability to pattern sub-10 nm features. Many BCPs with higher interaction parameters are capable of forming smaller features, but these "high-χ" BCPs typically have an imbalance in surface energy between the respective blocks that make it difficult to achieve the required perpendicular orientation. To address this challenge, we devised a polymeric surface active additive mixed into the BCP solution, referred to as an embedded neutral layer (ENL), which segregates to the top of the BCP film during casting and annealing and balances the surface tensions at the top of the thin film. The additive comprises a second BCP with a "neutral block" designed to provide matched surface tensions with the respective polymers of the main BCP and a "surface anchoring block" with very low surface energy that drives the material to the air interface during spin-casting and annealing. The surface anchoring block allows the film to be annealed above the glass transition temperature of the two materials without intermixing of the two components. DSA was also demonstrated with this embedded neutral top layer formulation on a chemical patterned template using a single step coat and simple thermal annealing. This ENL technology holds promise to enable the use of high-χ BCPs in advanced patterning applications.

  4. Orientation Control in Thin Films of a High-χ Block Copolymer with a Surface Active Embedded Neutral Layer.

    PubMed

    Zhang, Jieqian; Clark, Michael B; Wu, Chunyi; Li, Mingqi; Trefonas, Peter; Hustad, Phillip D

    2016-01-13

    Directed self-assembly (DSA) of block copolymers (BCPs) is an attractive advanced patterning technology being considered for future integrated circuit manufacturing. By controlling interfacial interactions, self-assembled microdomains in thin films of polystyrene-block-poly(methyl methacrylate), PS-b-PMMA, can be oriented perpendicular to surfaces to form line/space or hole patterns. However, its relatively weak Flory interaction parameter, χ, limits its capability to pattern sub-10 nm features. Many BCPs with higher interaction parameters are capable of forming smaller features, but these "high-χ" BCPs typically have an imbalance in surface energy between the respective blocks that make it difficult to achieve the required perpendicular orientation. To address this challenge, we devised a polymeric surface active additive mixed into the BCP solution, referred to as an embedded neutral layer (ENL), which segregates to the top of the BCP film during casting and annealing and balances the surface tensions at the top of the thin film. The additive comprises a second BCP with a "neutral block" designed to provide matched surface tensions with the respective polymers of the main BCP and a "surface anchoring block" with very low surface energy that drives the material to the air interface during spin-casting and annealing. The surface anchoring block allows the film to be annealed above the glass transition temperature of the two materials without intermixing of the two components. DSA was also demonstrated with this embedded neutral top layer formulation on a chemical patterned template using a single step coat and simple thermal annealing. This ENL technology holds promise to enable the use of high-χ BCPs in advanced patterning applications. PMID:26682931

  5. Crystalline Structure in Thin Films of DEH-PPV Homopolymer And PPV-B-PI Rod-Coil Block Copolymers

    SciTech Connect

    Olsen, B.D.; Alcazar, D.; Krikorian, V.; Toney, M.F.; Thomas, E.L.; Segalman, R.A.; /UC, Berkeley /LBL, Berkeley /MIT /SLAC, SSRL

    2009-04-30

    The rod orientation and crystalline packing of a model semiconducting rodlike polymer, poly(2,5-di(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene) (DEH-PPV), is shown to affect the self-assembly of weakly segregated rod-coil block copolymers. The in-plane packing of DEH-PPV rods in lamellar poly(2,5-di(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene-b-isoprene) (DEH-PPV-b-PI) diblock copolymers is nearly identical to that observed in DEH-PPV homopolymers for compositions ranging from 0.42 to 0.82 vol % coil block. The crystal structure of DEH-PPV, characterized by grazing incidence X-ray diffraction and electron diffraction, consists of a tetragonal unit cell having c = 0.665 nm with a = b = 1.348 nm. The polymer chain axis is aligned along the [001] direction, and the nearest neighbor rod-rod spacing along 110 is 1.0 nm. As-cast thin films of DEH-PPV homopolymer demonstrate chain alignment primarily perpendicular to the substrate in 5100 g/mol homopolymer, while for 3500 g/mol homopolymer the chains align both perpendicular and parallel to the substrate. For the DEH-PPV-b-PI block copolymers, a sharper 001 reflection is observed due to the effect of microphase separation, improving alignment and stacking of the rods. The lamellar phases have a smectic A-like packing structure with the rods oriented parallel to the lamellar normal regardless of coil fraction; however, at coil fractions above about 0.8 the crystalline lattice of the rods becomes rapidly disordered as evidenced by loss of all but the two strongest Bragg reflections. This suggests that the constraints of packing into the unit cell outweigh the chain stretching and segment-segment repulsion energies that are predicted to lead to a transition from normal (smectic A) to tilted (smectic C) rod orientation within the lamellae at high coil fraction; increasing coil fraction breaks apart the crystalline lattice rather than distorting it into a tilted polymorph.

  6. 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.

  7. Micellar transitions in solvent-annealed thin films of an amphiphilic block copolymer controlled with tunable surface fields.

    PubMed

    Chang, Chih-Yao; Lee, Yu-Chi; Wu, Pin-Jiun; Liou, Jiun-You; Sun, Ya-Sen; Ko, Bao-Tsan

    2011-12-01

    We investigated the response of symmetric poly(styrene-block-4vinylpyridine) P(S-b-4VP) diblock copolymer micelles to surface fields of variable strength at free surfaces and substrate interfaces when the micelles as spun were subjected to solvent annealing. Free surface interactions were controlled with solvent annealing in solvents of varied selectivity. On exposure to vapors of a solvent strongly selective for PS, the micelles retained their spherical shape but grew into cylindrical micelles or lamellar nanostructures via fusion on exposure to slightly selective or neutral solvent vapors. Giant 2D disks that completely wetted PS-grafted substrates resulted when spherical micelles were exposed to vapors of a highly selective solvent for P4VP. The interfacial interactions were controlled through subjecting them to UV/ozone (UVO) substrates initially coated with an end-grafted layer of short PS chains, with which the grafted PS chains became oxidized, degraded, or totally removed through UVO treatment for a controlled duration. When thin films were annealed in vapors of THF, the structural transition from spherical to cylindrical micelles depended on the interfacial field. On applying selective UVO exposure of optimal duration, we fabricated a substrate with two interfacial chemistries that promoted varied micellar species (spherical and cylindrical micelles) with a sharp boundary developed within thin films through solvent annealing for a controlled duration.

  8. Micrometer-Scale Ordering of Silicon-Containing Block Copolymer Thin Films via High-Temperature Thermal Treatments.

    PubMed

    Giammaria, Tommaso Jacopo; Ferrarese Lupi, Federico; Seguini, Gabriele; Perego, Michele; Vita, Francesco; Francescangeli, Oriano; Wenning, Brandon; Ober, Christopher K; Sparnacci, Katia; Antonioli, Diego; Gianotti, Valentina; Laus, Michele

    2016-04-20

    Block copolymer (BCP) self-assembly is expected to complement conventional optical lithography for the fabrication of next-generation microelectronic devices. In this regard, silicon-containing BCPs with a high Flory-Huggins interaction parameter (χ) are extremely appealing because they form high-resolution nanostructures with characteristic dimensions below 10 nm. However, due to their slow self-assembly kinetics and low thermal stability, these silicon-containing high-χ BCPs are usually processed by solvent vapor annealing or in solvent-rich ambient at a low annealing temperature, significantly increasing the complexity of the facilities and of the procedures. In this work, the self-assembly of cylinder-forming polystyrene-block-poly(dimethylsiloxane-random-vinylmethylsiloxane) (PS-b-P(DMS-r-VMS)) BCP on flat substrates is promoted by means of a simple thermal treatment at high temperatures. Homogeneous PS-b-P(DMS-r-VMS) thin films covering the entire sample surface are obtained without any evidence of dewetting phenomena. The BCP arranges in a single layer of cylindrical P(DMS-r-VMS) nanostructures parallel-oriented with respect to the substrate. By properly adjusting the surface functionalization, the heating rate, the annealing temperature, and the processing time, one can obtain correlation length values larger than 1 μm in a time scale fully compatible with the stringent requirements of the microelectronic industry. PMID:27020526

  9. Polyacrylonitrile block copolymers for the preparation of a thin carbon coating around TiO2 nanorods for advanced lithium-ion batteries.

    PubMed

    Oschmann, Bernd; Bresser, Dominic; Tahir, Muhammad Nawaz; Fischer, Karl; Tremel, Wolfgang; Passerini, Stefano; Zentel, Rudolf

    2013-11-01

    Herein, a new method for the realization of a thin and homogenous carbonaceous particle coating, made by carbonizing RAFT polymerization derived block copolymers anchored on anatase TiO2 nanorods, is presented. These block copolymers consist of a short anchor block (based on dopamine) and a long, easily graphitizable block of polyacrylonitrile. The grafting of such block copolymers to TiO2 nanorods creates a polymer shell, which can be visualized by atomic force microscopy (AFM). Thermal treatment at 700 °C converts the polyacrylonitrile block to partially graphitic structures (as determined by Raman spectroscopy), establishing a thin carbon coating (as determined by transmission electron microscopy, TEM, analysis). The carbon-coated TiO2 nanorods show improved electrochemical performance in terms of achievable specific capacity and, particularly, long-term cycling stability by reducing the average capacity fading per cycle from 0.252 mAh g(-1) to only 0.075 mAh g(-1) .

  10. Polyacrylonitrile block copolymers for the preparation of a thin carbon coating around TiO2 nanorods for advanced lithium-ion batteries.

    PubMed

    Oschmann, Bernd; Bresser, Dominic; Tahir, Muhammad Nawaz; Fischer, Karl; Tremel, Wolfgang; Passerini, Stefano; Zentel, Rudolf

    2013-11-01

    Herein, a new method for the realization of a thin and homogenous carbonaceous particle coating, made by carbonizing RAFT polymerization derived block copolymers anchored on anatase TiO2 nanorods, is presented. These block copolymers consist of a short anchor block (based on dopamine) and a long, easily graphitizable block of polyacrylonitrile. The grafting of such block copolymers to TiO2 nanorods creates a polymer shell, which can be visualized by atomic force microscopy (AFM). Thermal treatment at 700 °C converts the polyacrylonitrile block to partially graphitic structures (as determined by Raman spectroscopy), establishing a thin carbon coating (as determined by transmission electron microscopy, TEM, analysis). The carbon-coated TiO2 nanorods show improved electrochemical performance in terms of achievable specific capacity and, particularly, long-term cycling stability by reducing the average capacity fading per cycle from 0.252 mAh g(-1) to only 0.075 mAh g(-1) . PMID:24115201

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Real-Time Guided Wave Depolarized Light Scattering of Block Copolymer Thin Films during in Situ Annealing

    NASA Astrophysics Data System (ADS)

    Wilbur, Jeffrey; Balsara, Nitash; Fang, Zhuangxi; Newstein, Maurice; Garetz, Bruce

    2007-03-01

    The guided wave depolarized light scattering technique for measuring grain structure in block copolymer thin films has been further developed to enable us to measure scattering in films heated above the glass transition temperature. We previously published work in which we used a prism to couple a plane-polarized beam into and out of the transverse magnetic (TM) mode of a glassy polymer film, measured the extent of depolarized scattering into the transverse electric (TE) mode within the film, and correlated the intensity of the TE signal to grain structure. Through the design and incorporation of a grating coupler system in which the polymer film is deposited onto the coupler itself, we have supplanted the prism coupler and removed the requirement that the measured film be glassy, enabling measurements of grain structure during annealing. Coupled with our recently developed theoretical solution for GWDLS, we are able to analyze the grain structure averaged over a 1 cm cross section of a film as it changes in real time.

  17. Highly enhanced dynamics of microdomains ordering by solvent vapor annealing of thin block copolymer films on polymer network supports

    NASA Astrophysics Data System (ADS)

    Tsarkova, Larisa; Stenbock-Fermor, Anja; Böker, Alexander; Knoll, Armin; IBM Reserach Collaboration; DWI Team

    2014-03-01

    We studied the solvent driven ordering dynamics of block copolymer films supported by a densely cross-linked organic hard mask (HM) designed for lithographic fabrication. We found that the ordering of microphase separated domains on the HM layer proceeds significantly faster as compared to similar films on silicon wafers. This leads to a pronounced enhancement of the dynamics of both the terrace-formation as well as the long-range lateral ordering of the microdomains. The effect is independent on the chemical structure and volume composition of the studied block copolymers (cylinder-/ lamella-forming). Importantly, enhanced ordering is achieved even at a reduced degree of swelling corresponding to an intermediate to strong segregation regime, when similar films on conventional substrate show very limited ordering. In-situ ellipsometric measurements of the swollen films revealed an insignificant increase by 1-3 vol. % in the solvent up-take by HM-supported films. Therefore we attribute the enhanced dynamics to reduced interactions at the block copolymer/HM-support interface. Apart from immediate technological impact in block copolymer-assisted nanolithography, our findings convey novel insight into effects of molecular architecture on polymer-solvent interactions. Forckenbeckstr. 50 52056 Aachen, Germany.

  18. 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 packed PS cylinders at appropriate stoichiometries. The smectic layers and the PS domains are strongly aligned by the application of large (> 2T) magnetic fields in a manner reflective of the positive diamagnetic anisotropy and the planar anchoring of perylene units at the PS interface. We use a combination of SAXS studies in-situ with applied magnetic fields, GISAXS and polarized optical transmission measurements to characterize the system. Magnetic fields thus offer a viable route for directing the self-assembly of functional materials based on rigid chromophores and further, that supramolecular approaches can be complementary to such efforts.

  19. Engineering topochemical polymerizations using block copolymer templates.

    PubMed

    Zhu, Liangliang; Tran, Helen; Beyer, Frederick L; Walck, Scott D; Li, Xin; Agren, Hans; Killops, Kato L; Campos, Luis M

    2014-09-24

    With the aim to achieve rapid and efficient topochemical polymerizations in the solid state, via solution-based processing of thin films, we report the integration of a diphenyldiacetylene monomer and a poly(styrene-b-acrylic acid) block copolymer template for the generation of supramolecular architectural photopolymerizable materials. This strategy takes advantage of non-covalent interactions to template a topochemical photopolymerization that yields a polydiphenyldiacetylene (PDPDA) derivative. In thin films, it was found that hierarchical self-assembly of the diacetylene monomers by microphase segregation of the block copolymer template enhances the topochemical photopolymerization, which is complete within a 20 s exposure to UV light. Moreover, UV-active cross-linkable groups were incorporated within the block copolymer template to create micropatterns of PDPDA by photolithography, in the same step as the polymerization reaction. The materials design and processing may find potential uses in the microfabrication of sensors and other important areas that benefit from solution-based processing of flexible conjugated materials. PMID:25208609

  20. Directed self-assembly of block copolymer thin films: From fundamentals science to applications

    NASA Astrophysics Data System (ADS)

    Teel, George Lewis

    A modern approach to satellite based experimentation has evolved from large, multi-instrumented satellites, to cheaper, smaller, almost disposable yet still reliable small spacecrafts. These small satellites are either sent to the International Space Station (ISS) to be dropped out into low earth orbit (LEO), or dropped off as a secondary payload into various orbits. While it is cheap to have small spacecraft accomplishing these missions, the lifetime expectancy is very short. Currently there are no commercialized propulsion systems that exist to keep them flying for prolonged periods of time. Recently researched at the Micro Propulsion and Nanotechnology Lab (MPNL), at the George Washington University (GWU), have been developments of a variety of Vacuum Arc Thrusters (VAT's) dubbed Micro-Cathode Vacuum Arc Thrusters (muCATs). muCAT's provide an inert electric means of propulsion for small spacecraft. The issue with these muCATs has been their efficiency levels and low amounts of thrust that they provide. The muCATs can provide muN levels of thrust per pulse. While being proficient for small spacecrafts, an increase in thrust is highly sought for, but the improvements must retain a small footprint and low power consumption. The topic of this thesis is the development and characterization of a new type of muCAT. The interest in this new design has been conceptualized based on experiments for plasma coating techniques. By utilizing the physics of evaporation, which has been used to decrease macroparticles (MP's) for thin film deposition, it has been theorized to also be applied to VAT technology. The concept is to increase levels of thrust with the muCAT, and provide higher levels of efficiency. This effect can be created without many additional components nor multiple additional loads to the thruster subsystem. Development of this new mechanic for thruster technology has been investigated through a variety of tests for fundamental proofs of concept. Running in two

  1. On the mechanism of electrical conduction in thin films of some polysulfone-poly(alkylene oxide)-poly(dimethylsiloxane) block copolymers

    NASA Astrophysics Data System (ADS)

    Rusu, G. G.; Airinei, A.; Hamciuc, V.; Rambu, A. P.; Caplanus, I.; Rusu, G. I.

    2014-01-01

    Polysulfone poly(alkylene oxide)-poly(dimethylsiloxane) block copolymers have been prepared by the hydrosilylation reaction of allyl endcapped poly[(ethylene oxide) (propylene oxide)] oligomers with Si-H terminated polydimethylsiloxane in chlorobenzene using an isopropanol solution of hexachloroplatinic (IV) acid as catalyst for hydrosilylation. The temperature dependences of electrical conductivity and thermoelectric power (Seebeck coefficient) of copolymers were studied using thin-film samples deposited from dimethylformamide (spin coating technique) onto glass substrates. Organic films with reproducible electronic transport and optical properties can be obtained if, after deposition, they are submitted to a heat treatment consisting of several successive heating/cooling cycles within temperature range of (295-485) K. Investigated copolymers presents typical semiconducting characteristics. The values of some fundamental parameters (activation energy of electrical conduction, ratio of carrier mobilities, optical energy bandgap) have been determined. The mechanisms of electronic transport are identified in different temperature domains. Transmission and absorption spectra have been recorded and optical energy bandgaps are calculated from the absorption spectra. The thermistor effect of investigated copolymers is also discussed.

  2. 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.

  3. Imide/arylene ether block copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, B. J.; Hergenrother, P. M.; Bass, R. G.

    1991-01-01

    Two series of imide/arylene either block copolymers were prepared using an arylene ether block and either an amorphous or semi-crystalline imide block. The resulting copolymers were characterized and selected physical and mechanical properties were determined. These results, as well as comparisons to the homopolymer properties, are discussed.

  4. Pattern transfer using block copolymers.

    PubMed

    Gu, Xiaodan; Gunkel, Ilja; Russell, Thomas P

    2013-10-13

    To meet the increasing demand for patterning smaller feature sizes, a lithography technique is required with the ability to pattern sub-20 nm features. While top-down photolithography is approaching its limit in the continued drive to meet Moore's law, the use of directed self-assembly (DSA) of block copolymers (BCPs) offers a promising route to meet this challenge in achieving nanometre feature sizes. Recent developments in BCP lithography and in the DSA of BCPs are reviewed. While tremendous advances have been made in this field, there are still hurdles that need to be overcome to realize the full potential of BCPs and their actual use.

  5. 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.

  6. Method for making block siloxane copolymers

    DOEpatents

    Butler, N.L.; Jessop, E.S.; Kolb, J.R.

    1981-02-25

    A method for synthesizing block polysiloxane copolymers is disclosed. Diorganoscyclosiloxanes and an end-blocking compound are interacted in the presence of a ring opening polymerization catalyst, producing a blocked prepolymer. The prepolymer is then interacted with a silanediol, resulting in condensation polymerization of the prepolymers. A second end-blocking compound is subsequently introduced to end-cap the polymers and copolymers formed from the condensation polymerization.

  7. Method for making block siloxane copolymers

    DOEpatents

    Butler, Nora; Jessop, Edward S.; Kolb, John R.

    1982-01-01

    A method for synthesizing block polysiloxane copolymers. Diorganoscyclosiloxanes and an end-blocking compound are interacted in the presence of a ring opening polymerization catalyst, producing a blocked prepolymer. The prepolymer is then interacted with a silanediol, resulting in condensation polymerization of the prepolymers. A second end-blocking compound is subsequently introduced to end-cap the polymers and copolymers formed from the condensation polymerization.

  8. Reordering transitions during annealing of block copolymer cylinder phases

    SciTech Connect

    Majewski, Pawel W.; Yager, Kevin G.

    2015-10-06

    While equilibrium block-copolymer morphologies are dictated by energy-minimization effects, the semi-ordered states observed experimentally often depend on the details of ordering pathways and kinetics. In this study, we explore reordering transitions in thin films of block-copolymer cylinder-forming polystyrene-block-poly(methyl methacrylate). We observe several transient states as films order towards horizontally-aligned cylinders. In particular, there is an early-stage reorganization from randomly-packed cylinders into hexagonally-packed vertically-aligned cylinders; followed by a reorientation transition from vertical to horizontal cylinder states. These transitions are thermally activated. The growth of horizontal grains within an otherwise vertical morphology proceeds anisotropically, resulting in anisotropic grains in the final horizontal state. The size, shape, and anisotropy of grains are influenced by ordering history; for instance, faster heating rates reduce grain anisotropy. These results help elucidate aspects of pathway-dependent ordering in block-copolymer thin films.

  9. Log-rolling block copolymers cylinders

    NASA Astrophysics Data System (ADS)

    Kim, So Youn; Kim, Ye Chan; Kim, Dong Hyup; Kwon, Na Kyung; Register, Richard A.

    Shear has been the most effective method to create long range order of micro- or nano- structures in soft materials. When shear is applied, soft particles or polymers tend to align along the shear direction to minimize the viscous dissipation, thus transverse (so-called ``log-rolling'') alignment is unfavored. In this study, for the first time we report the transverse alignment of cylinder-forming block copolymers. Poly(styrene-b-methyl methacrylate), PS-PMMA, can form a metastable hemicylinder structure when confined in a thin film, and this hemicylinder structure can align either along the shear direction, or transverse to the shear direction (``log-rolling''), depending on the shearing temperature. This unusual ``log-rolling'' behavior is explained by the different chain mobility of the two blocks in PS-PMMA; the rigidity of core cylinder is the critical parameter determining the direction of shear alignment.

  10. 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.

  11. Synthesis and morphology characterization of polydimethylsiloxane-containing block copolymers

    NASA Astrophysics Data System (ADS)

    Wadley, Maurice

    The thin film morphology characteristics of polydimethylsiloxane-containing block copolymers have been investigated. For this investigation, a commercially available hydroxyl terminated PDMS was purchased from Gelest and attached to a carboxylic acid functional reversible addition-fragmentation chain transfer (RAFT) agent by Steglich esterification. This produced macro-RAFT agents to which styrene monomer was polymerized. By using this approach the generation of low polydispersity polystyrene-block-polydimethylsiloxane (PS-block-PDMS) copolymers of various molecular weights spanning a wide volume fraction range in which the PDMS block remained the same in each polymerization. Synthesized block copolymers were characterized by gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. Bulk and thin film characterization of PS-block-PDMS copolymers was done by small-angle x-ray scattering (SAXS), transmission electron microscopy (TEM), contact angle measurements, scanning force microscopy (SFM), and grazing incidence small-angle X-ray scattering (GISAXS). The following observations have been made. For PS-rich PS-block -PDMS copolymer thin films the low surface tension of PDMS caused it to migrate to the film surface regardless of solvent choice. The surface morphology was found to depend strongly on the solubility parameter of the solvent and exhibited SFM images consistent with parallel cylinder, perforated lamellar, and lamellar surface layers with increasing solvent solubility parameter. This behavior was due to the selective swelling of the individual blocks under slightly selective, good solvent conditions. A custom solvent annealing apparatus provided similar results in which order-order transitions in the thin films were observed with increasing solvent solubility parameter. Additionally improvements in the long-range order were observed after 1 h of solvent annealing. PS-rich PS-block-PDMS copolymer thin films also displayed PDMS

  12. Block Copolymer Membranes for Biofuel Purification

    NASA Astrophysics Data System (ADS)

    Evren Ozcam, Ali; Balsara, Nitash

    2012-02-01

    Purification of biofuels such as ethanol is a matter of considerable concern as they are produced in complex multicomponent fermentation broths. Our objective is to design pervaporation membranes for concentrating ethanol from dilute aqueous mixtures. Polystyrene-b-polydimethylsiloxane-b-polystyrene block copolymers were synthesized by anionic polymerization. The polydimethylsiloxane domains provide ethanol-transporting pathways, while the polystyrene domains provide structural integrity for the membrane. The morphology of the membranes is governed by the composition of the block copolymer while the size of the domains is governed by the molecular weight of the block copolymer. Pervaporation data as a function of these two parameters will be presented.

  13. Block copolymer structures in nano-pores

    NASA Astrophysics Data System (ADS)

    Pinna, Marco; Guo, Xiaohu; Zvelindovsky, Andrei

    2010-03-01

    We present results of coarse-grained computer modelling of block copolymer systems in cylindrical and spherical nanopores on Cell Dynamics Simulation. We study both cylindrical and spherical pores and systematically investigate structures formed by lamellar, cylinders and spherical block copolymer systems for various pore radii and affinity of block copolymer blocks to the pore walls. The obtained structures include: standing lamellae and cylinders, ``onions,'' cylinder ``knitting balls,'' ``golf-ball,'' layered spherical, ``virus''-like and mixed morphologies with T-junctions and U-type defects [1]. Kinetics of the structure formation and the differences with planar films are discussed. Our simulations suggest that novel porous nano-containers can be formed by confining block copolymers in pores of different geometries [1,2]. [4pt] [1] M. Pinna, X. Guo, A.V. Zvelindovsky, Polymer 49, 2797 (2008).[0pt] [2] M. Pinna, X. Guo, A.V. Zvelindovsky, J. Chem. Phys. 131, 214902 (2009).

  14. 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.

  15. Chemically enhancing block copolymers for block-selective synthesis of self-assembled metal oxide nanostructures.

    PubMed

    Kamcev, Jovan; Germack, David S; Nykypanchuk, Dmytro; Grubbs, Robert B; Nam, Chang-Yong; Black, Charles T

    2013-01-22

    We report chemical modification of self-assembled block copolymer thin films by ultraviolet light that enhances the block-selective affinity of organometallic precursors otherwise lacking preference for either copolymer block. Sequential precursor loading and reaction facilitate formation of zinc oxide, titanium dioxide, and aluminum oxide nanostructures within the polystyrene domains of both lamellar- and cylindrical-phase modified polystyrene-block-poly(methyl methacrylate) thin film templates. Near-edge X-ray absorption fine structure measurements and Fourier transform infrared spectroscopy show that photo-oxidation by ultraviolet light creates Lewis basic groups within polystyrene, resulting in an increased Lewis base-acid interaction with the organometallic precursors. The approach provides a method for generating both aluminum oxide patterns and their corresponding inverses using the same block copolymer template.

  16. Electrostatic control of block copolymer morphology

    NASA Astrophysics Data System (ADS)

    Sing, Charles E.; Zwanikken, Jos W.; Olvera de La Cruz, Monica

    2014-07-01

    Energy storage is at present one of the foremost issues society faces. However, material challenges now serve as bottlenecks in technological progress. Lithium-ion batteries are the current gold standard to meet energy storage needs; however, they are limited owing to the inherent instability of liquid electrolytes. Block copolymers can self-assemble into nanostructures that simultaneously facilitate ion transport and provide mechanical stability. The ions themselves have a profound, yet previously unpredictable, effect on how these nanostructures assemble and thus the efficiency of ion transport. Here we demonstrate that varying the charge of a block copolymer is a powerful mechanism to predictably tune nanostructures. In particular, we demonstrate that highly asymmetric charge cohesion effects can induce the formation of nanostructures that are inaccessible to conventional uncharged block copolymers, including percolated phases desired for ion transport. This vastly expands the design space for block copolymer materials and is informative for the versatile design of battery electrolyte materials.

  17. 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.

  18. 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

  19. Rapid self-assembly of block copolymers to photonic crystals

    DOEpatents

    Xia, Yan; Sveinbjornsson, Benjamin R; Grubbs, Robert H; Weitekamp, Raymond; Miyake, Garret M; Atwater, Harry A; Piunova, Victoria; Daeffler, Christopher Scot; Hong, Sung Woo; Gu, Weiyin; Russell, Thomas P.

    2016-07-05

    The invention provides a class of copolymers having useful properties, including brush block copolymers, wedge-type block copolymers and hybrid wedge and polymer block copolymers. In an embodiment, for example, block copolymers of the invention incorporate chemically different blocks comprising polymer size chain groups and/or wedge groups that significantly inhibit chain entanglement, thereby enhancing molecular self-assembly processes for generating a range of supramolecular structures, such as periodic nanostructures and microstructures. The present invention also provides useful methods of making and using copolymers, including block copolymers.

  20. 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

  1. Chain exchange in block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Lu, Jie; Bates, Frank; Lodge, Timothy

    2014-03-01

    Block copolymer micelles are aggregates formed by self-assembly of amphiphilic copolymers dispersed in a selective solvent, driven by unfavorable interactions between the solvent and the core-forming block. Due to the relatively long chains being subject to additional thermodynamic and dynamic constraints (e.g., entanglements, crystallinity, vitrification), block copolymer micelles exhibit significantly slower equilibration kinetics than small molecule surfactants. As a result, details of the mechanism(s) of equilibration in block copolymer micelles remain unclear. This present works focuses on the chain exchange kinetics of poly(styrene-b-ethylenepropylene) block copolymers in squalane (C30H62) using time-resolved small angle neutron scattering (TR-SANS). A mixture of h-squalane and d-squalane is chosen so that it contrast matches a mixed 50/50 h/d polystyrene micelle core. When the temperature is appropriate and isotopically labeled chains undergo mixing, the mean core contrast with respect to the solvent decreases, and the scattering intensity is therefore reduced. This strategy allows direct probing of chain exchange rate from the time dependent scattering intensity I(q, t).

  2. Controlled Architecture of Dual-Functional Block Copolymer Brushes on Thin-Film Composite Membranes for Integrated "Defending" and "Attacking" Strategies against Biofouling.

    PubMed

    Ye, Gang; Lee, Jongho; Perreault, François; Elimelech, Menachem

    2015-10-21

    We report a new macromolecular architecture of dual functional block copolymer brushes on commercial thin-film composite (TFC) membranes for integrated "defending" and "attacking" strategies against biofouling. Mussel-inspired catechol chemistry is used for a convenient immobilization of initiator molecules to the membrane surface with the aid of polydopamine (PDA). Zwitterionic polymer brushes with strong hydration capacity and quaternary ammonium salt (QAS) polymer brushes with bactericidal ability are sequentially grafted on TFC membranes via activators regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP), an environmentally benign and controlled polymerization method. Measurement of membrane intrinsic transport properties in reverse osmosis experiments shows that the modified TFC membrane maintains the same water permeability and salt selectivity as the pristine TFC membrane. Chemical force microscopy and protein/bacterial adhesion studies are carried out for a comprehensive evaluation of the biofouling resistance and antimicrobial ability, demonstrating low biofouling propensity and excellent bacterial inactivation for the modified TFC membrane. We conclude that this polymer architecture, with complementary "defending" and "attacking" capabilities, can effectively prevent the attachment of biofoulants and formation of biofilms and thereby significantly mitigate biofouling on TFC membranes. PMID:26378606

  3. Controlled Architecture of Dual-Functional Block Copolymer Brushes on Thin-Film Composite Membranes for Integrated "Defending" and "Attacking" Strategies against Biofouling.

    PubMed

    Ye, Gang; Lee, Jongho; Perreault, François; Elimelech, Menachem

    2015-10-21

    We report a new macromolecular architecture of dual functional block copolymer brushes on commercial thin-film composite (TFC) membranes for integrated "defending" and "attacking" strategies against biofouling. Mussel-inspired catechol chemistry is used for a convenient immobilization of initiator molecules to the membrane surface with the aid of polydopamine (PDA). Zwitterionic polymer brushes with strong hydration capacity and quaternary ammonium salt (QAS) polymer brushes with bactericidal ability are sequentially grafted on TFC membranes via activators regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP), an environmentally benign and controlled polymerization method. Measurement of membrane intrinsic transport properties in reverse osmosis experiments shows that the modified TFC membrane maintains the same water permeability and salt selectivity as the pristine TFC membrane. Chemical force microscopy and protein/bacterial adhesion studies are carried out for a comprehensive evaluation of the biofouling resistance and antimicrobial ability, demonstrating low biofouling propensity and excellent bacterial inactivation for the modified TFC membrane. We conclude that this polymer architecture, with complementary "defending" and "attacking" capabilities, can effectively prevent the attachment of biofoulants and formation of biofilms and thereby significantly mitigate biofouling on TFC membranes.

  4. Formation of Anisotropic Block Copolymer Gels

    NASA Astrophysics Data System (ADS)

    Liaw, Chya Yan; Shull, Kenneth; Henderson, Kevin; Joester, Derk

    2011-03-01

    Anisotropic, fibrillar gels are important in a variety of processes. Biomineralization is one example, where the mineralization process often occurs within a matrix of collagen or chitin fibers that trap the mineral precursors and direct the mineralization process. We wish to replicate this type of behavior within block copolymer gels. Particularly, we are interested in employing gels composed of cylindrical micelles, which are anisotropic and closely mimic biological fibers. Micelle geometry is controlled in our system by manipulating the ratio of molecular weights of the two blocks and by controlling the detailed thermal processing history of the copolymer solutions. Small-Angle X-ray Scattering and Dynamic Light Scattering are used to determine the temperature dependence of the gel formation process. Initial experiments are based on a thermally-reversible alcohol-soluble system, that can be subsequently converted to a water soluble system by hydrolysis of a poly(t-butyl methacrylate) block to a poly (methacrylic acid) block. MRSEC.

  5. Beyond Orientation: The Impact of Electric Fields on Block Copolymers

    SciTech Connect

    Liedel, Clemens; Boker, A.; Pester, Christian; Ruppel, Markus A; Urban, Volker S

    2012-01-01

    Since the first report on electric field-induced alignment of block copolymers (BCPs) in 1991, electric fields have been shown not only to direct the orientation of BCP nanostructures in bulk, solution, and thin films, but also to reversibly induce order-order transitions, affect the order-disorder transition temperature, and control morphologies' dimensions with nanometer precision. Theoretical and experimental results of the past years in this very interesting field of research are summarized and future perspectives are outlined.

  6. Block copolymer compatibilization of cocontinuous polymer blends.

    SciTech Connect

    Galloway, Jeffrey A.; Macosko, Christopher W.; Bell, Joel R.; Jeon, Hyun K.

    2004-12-01

    The effect of block copolymers on the cocontinuous morphology of 50/50 (w/w) polystyrene (PS)/high density polyethylene (HDPE) blends was investigated using symmetric polystyrene-polyethylene block copolymers (PS-PE) with molecular weights varying from 6 to 200 kg/mol. The coarsening rate during annealing was compared to the Doi-Ohta theory. An intermediate molecular weight PS-PE, 40 kg/mol, showed remarkable results in reducing the phase size and stabilizing the blend morphology during annealing. Mixing small amounts of 6, 100 or 200 kg/mol PS-PE in the blend did not reduce the phase size significantly, but did decrease the coarsening rate during annealing. In stabilizing the morphology, 6 kg/mol PS-PE was inferior to 100 and 200 kg/mol. The existence of an optimal molecular weight block copolymer is due to a balance between the ability of the block copolymer to reach the interface and its relative stabilization effect at the interface.

  7. Influence of substrate interaction and confinement on electric-field-induced transition in symmetric block-copolymer thin films.

    PubMed

    Mukherjee, Arnab; Mukherjee, Rajdip; Ankit, Kumar; Bhattacharya, Avisor; Nestler, Britta

    2016-03-01

    In the present work, we study morphologies arising due to competing substrate interaction, electric field, and confinement effects on a symmetric diblock copolymer. We employ a coarse-grained nonlocal Cahn-Hilliard phenomenological model taking into account the appropriate contributions of substrate interaction and electrostatic field. The proposed model couples the Ohta-Kawasaki functional with Maxwell equation of electrostatics, thus alleviating the need for any approximate solution used in previous studies. We calculate the phase diagram in electric-field-substrate strength space for different film thicknesses. In addition to identifying the presence of parallel, perpendicular, and mixed lamellae phases similar to analytical calculations, we also find a region in the phase diagram where hybrid morphologies (combination of two phases) coexist. These hybrid morphologies arise either solely due to substrate affinity and confinement or are induced due to the applied electric field. The dependence of the critical fields for transition between the various phases on substrate strength, film thickness, and dielectric contrast is discussed. Some preliminary 3D results are also presented to corroborate the presence of hybrid morphologies. PMID:27078402

  8. Influence of substrate interaction and confinement on electric-field-induced transition in symmetric block-copolymer thin films

    NASA Astrophysics Data System (ADS)

    Mukherjee, Arnab; Mukherjee, Rajdip; Ankit, Kumar; Bhattacharya, Avisor; Nestler, Britta

    2016-03-01

    In the present work, we study morphologies arising due to competing substrate interaction, electric field, and confinement effects on a symmetric diblock copolymer. We employ a coarse-grained nonlocal Cahn-Hilliard phenomenological model taking into account the appropriate contributions of substrate interaction and electrostatic field. The proposed model couples the Ohta-Kawasaki functional with Maxwell equation of electrostatics, thus alleviating the need for any approximate solution used in previous studies. We calculate the phase diagram in electric-field-substrate strength space for different film thicknesses. In addition to identifying the presence of parallel, perpendicular, and mixed lamellae phases similar to analytical calculations, we also find a region in the phase diagram where hybrid morphologies (combination of two phases) coexist. These hybrid morphologies arise either solely due to substrate affinity and confinement or are induced due to the applied electric field. The dependence of the critical fields for transition between the various phases on substrate strength, film thickness, and dielectric contrast is discussed. Some preliminary 3D results are also presented to corroborate the presence of hybrid morphologies.

  9. Reordering transitions during annealing of block copolymer cylinder phases

    DOE PAGES

    Majewski, Pawel W.; Yager, Kevin G.

    2015-10-06

    While equilibrium block-copolymer morphologies are dictated by energy-minimization effects, the semi-ordered states observed experimentally often depend on the details of ordering pathways and kinetics. In this study, we explore reordering transitions in thin films of block-copolymer cylinder-forming polystyrene-block-poly(methyl methacrylate). We observe several transient states as films order towards horizontally-aligned cylinders. In particular, there is an early-stage reorganization from randomly-packed cylinders into hexagonally-packed vertically-aligned cylinders; followed by a reorientation transition from vertical to horizontal cylinder states. These transitions are thermally activated. The growth of horizontal grains within an otherwise vertical morphology proceeds anisotropically, resulting in anisotropic grains in the final horizontalmore » state. The size, shape, and anisotropy of grains are influenced by ordering history; for instance, faster heating rates reduce grain anisotropy. These results help elucidate aspects of pathway-dependent ordering in block-copolymer thin films.« less

  10. Sub-10 nm features obtained from directed self-assembly of semicrystalline polycarbosilane-based block copolymer thin films.

    PubMed

    Aissou, Karim; Mumtaz, Muhammad; Fleury, Guillaume; Portale, Giuseppe; Navarro, Christophe; Cloutet, Eric; Brochon, Cyril; Ross, Caroline A; Hadziioannou, Georges

    2015-01-14

    Highly-ordered arrays with sub-10 nm features are produced with topographical-directed self-assembly of low-molecular-weight poly(1,1-dimethyl silacyclobutane)-block-poly(methyl methacrylate). This system turns out to be of high interest for lithographic applications since the domain orientation is solely controlled through the polymer layer thickness, while the promotion of the microphase separation is obtained by a short thermal annealing process under mild conditions.

  11. Block copolymers for opto-electronics

    NASA Astrophysics Data System (ADS)

    Sun, Sam-Shajing; Fan, Zhen; Wang, Yiqing; Taft, Charles; Haliburton, James H.; Maaref, Shahin; Ledbetter, Abram J.; Bonner, Carl E.

    2004-05-01

    A D(donor)-B(bridge)-A(acceptor)-B(bridge)-type block copolymer system has been developed and preliminarily examined for potential opto-electronic photovoltaic functions. The unique feature of the device includes a primary DBAB-type block copolymer backbone, where D and A are conjugated donor and acceptor polymer blocks, and B is a non-conjugated and flexible chain, a π orbital stacked and conjugated chain self-assembled and ordered "secondary structure", and a donor/acceptor asymmetric layers sandwiched D/A columnar "tertiary structure". This structure is expected to improve photovoltaic power conversion efficiency significantly in comparison to most existing organic or polymeric donor/acceptor binary photovoltaic systems due to the reduction of "exciton loss", the "carrier loss", as well as the "photon loss" via three-dimensional space and energy level optimizations. Preliminary experimental results revealed better morphology and opto-electronic properties of DBAB vs. D/A blends.

  12. 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.

  13. 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

  14. 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

  15. Rod-Coil Block Polyimide Copolymers

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Kinder, James D. (Inventor)

    2005-01-01

    This invention is a series of rod-coil block polyimide copolymers that are easy to fabricate into mechanically resilient films with acceptable ionic or protonic conductivity at a variety of temperatures. The copolymers consist of short-rigid polyimide rod segments alternating with polyether coil segments. The rods and coil segments can be linear, branched or mixtures of linear and branched segments. The highly incompatible rods and coil segments phase separate, providing nanoscale channels for ion conduction. The polyimide segments provide dimensional and mechanical stability and can be functionalized in a number of ways to provide specialized functions for a given application. These rod-coil black polyimide copolymers are particularly useful in the preparation of ion conductive membranes for use in the manufacture of fuel cells and lithium based polymer batteries.

  16. Monte Carlo simulations of the phase separation of a copolymer blend in a thin film.

    PubMed

    Wang, Zhexiao; Shao, Jing; Pan, Heng; Feng, Xiaoshuang; Chen, Peng; Xia, Ru; Wu, Xiangsong; Qian, Jiasheng

    2015-02-23

    Monte Carlo simulations were carried out to study the phase separation of a copolymer blend comprising an alternating copolymer and/or block copolymer in a thin film, and a phase diagram was constructed with a series of composed recipes. The effects of composition and segregation strength on phase separation were discussed in detail. The chain conformation of the block copolymer and alternating copolymer were investigated with changes of the segregation strength. Our simulations revealed that the segment distribution along the copolymer chain and the segregation strength between coarse-grained beads are two important parameters controlling phase separation and chain conformation in thin films of a copolymer blend. A well-controlled phase separation in the copolymer blend can be used to fabricate novel nanostructures. PMID:25504337

  17. Toughness in block copolymer modified epoxies

    NASA Astrophysics Data System (ADS)

    Declet-Perez, Carmelo

    One of the major shortcomings preventing the widespread use of epoxy resins in engineering applications is the inherent brittleness of these materials. The incorporation of small amounts of amphiphilic block copolymers into the formulation is one of the most promising strategies to toughen epoxies. These molecules are known to form nanostructures in the epoxy resin that can be preserved upon curing. This strategy is very attractive since significant enhancements in toughness can be obtained without detrimental effects on other properties of the matrix. Despite many examples of successful implementation, an in-depth understanding of the factors that lead to toughness in block copolymer modified epoxies is still elusive. The goal of this dissertation is to understand, first, the deformation mechanisms leading to toughness and, second, how different formulation parameters affect these processes. In this work we used two types of block copolymer modifiers, which produced nanostructures with different physical properties. These block copolymers self-assembled into well-dispersed spherical micelles with either rubbery or glassy cores in various epoxy formulations. Both of these modifiers toughened different epoxy formulations, although to different extents. The rubbery core micelles consistently outperformed the glassy core micelles by roughly a factor of two. While the toughening afforded by the rubbery core micelles was consistent with the current understanding of toughening, the results from the glassy core micelles could not be explained with the same reasoning. In order to understand the deformation mechanisms leading to different levels of toughness, we performed small-angle x-ray scattering experiments while simultaneously deforming our material. This combination of techniques, referred to as in-situ SAXS, allowed us to monitor changes in the structure of the block copolymer micelles as a result of the applied load. With this technique, we showed that the rubbery

  18. 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.

  19. Cavitation in block copolymer modified epoxy

    NASA Astrophysics Data System (ADS)

    Declet-Perez, Carmelo; Francis, Lorraine; Bates, Frank

    2013-03-01

    Today, brittleness in epoxy networks limits most commercial applications. Significant toughness can be imparted by adding small amounts of micelle forming block copolymers (BCP) without compromising critical properties such as high use temperature and modulus. Curing the network locks in the self-assembled BCP micellar structures formed in the monomer resin providing control of the resulting morphology. Despite significant research over the last decade, a complete description of the parameters influencing toughness in block copolymer modified epoxies is still lacking. In this presentation we compare the ultimate mechanical behavior of epoxies modified with spherical micelle forming BCP's containing rubbery and glassy cores using real-time in-situ small-angle X-ray scattering (SAXS) performed during tensile deformation. Striking differences in the 2D SAXS patterns were documented for epoxies modified with rubbery (PEP) versus glassy (PS) micelle cores. Rubbery cores dilate by 100% in volume upon specimen yielding, while the glassy micelle cores deform at approximately constant volume. These results provide direct evidence of a cavitation mediated mechanism for toughness in block copolymer modified epoxies. We further interpret characteristic butterfly features in the 2D SAXS patterns in terms of epoxy network deformation. Support was provided by the NSF sponsored MRSEC at the University of Minnesota

  20. Concentration Dependent Structure of Block Copolymer Solutions

    NASA Astrophysics Data System (ADS)

    Choi, Soohyung; Bates, Frank S.; Lodge, Timothy P.

    2015-03-01

    Addition of solvent molecules into block copolymer can induce additional interactions between the solvent and both blocks, and therefore expands the range of accessible self-assembled morphologies. In particular, the distribution of solvent molecules plays a key role in determining the microstructure and its characteristic domain spacing. In this study, concentration dependent structures formed by poly(styrene-b-ethylene-alt-propylene) (PS-PEP) solution in squalane are investigated using small-angle X-ray scattering. This reveals that squalane is essentially completely segregated into the PEP domains. In addition, the conformation of the PS block changes from stretched to nearly fully relaxed (i.e., Gaussian conformation) as amounts of squalane increases. NRF

  1. Responsive block copolymer photonics triggered by protein-polyelectrolyte coacervation.

    PubMed

    Fan, Yin; Tang, Shengchang; Thomas, Edwin L; Olsen, Bradley D

    2014-11-25

    Ionic interactions between proteins and polyelectrolytes are demonstrated as a method to trigger responsive transitions in block copolymer (BCP) photonic gels containing one neutral hydrophobic block and one cationic hydrophilic block. Poly(2-vinylpyridine) (P2VP) blocks in lamellar poly(styrene-b-2-vinylpyridine) block copolymer thin films are quaternized with primary bromides to yield swollen gels that show strong reflectivity peaks in the visible range; exposure to aqueous solutions of various proteins alters the swelling ratios of the quaternized P2VP (QP2VP) gel layers in the PS-QP2VP materials due to the ionic interactions between proteins and the polyelectrolyte. Parameters such as charge density, hydrophobicity, and cross-link density of the QP2VP gel layers as well as the charge and size of the proteins play significant roles on the photonic responses of the BCP gels. Differences in the size and pH-dependent charge of proteins provide a basis for fingerprinting proteins based on their temporal and equilibrium photonic response. The results demonstrate that the BCP gels and their photonic effect provide a robust and visually interpretable method to differentiate different proteins.

  2. Perspective: Evolutionary design of granular media and block copolymer patterns

    NASA Astrophysics Data System (ADS)

    Jaeger, Heinrich M.; de Pablo, Juan J.

    2016-05-01

    The creation of new materials "by design" is a process that starts from desired materials properties and proceeds to identify requirements for the constituent components. Such process is challenging because it inverts the typical modeling approach, which starts from given micro-level components to predict macro-level properties. We describe how to tackle this inverse problem using concepts from evolutionary computation. These concepts have widespread applicability and open up new opportunities for design as well as discovery. Here we apply them to design tasks involving two very different classes of soft materials, shape-optimized granular media and nanopatterned block copolymer thin films.

  3. Structure and Properties of Block Copolymers of Polystyrene and Polybutadiene

    NASA Astrophysics Data System (ADS)

    Askadskii, Andrei A.; Andryushchenko, T. A.; Zubov, P. I.

    1984-08-01

    Recent studies of the structure and properties of block copolymers of polystyrene and polybutadiene are reviewed, with special emphasis on the effect of the structure and of the formation conditions for the samples on the interrelated physico-mechanical properties. Problems associated with the macro- and micro-layering of block copolymer solutions are examined in detail. Work on the analysis of block copolymer structures from measurements of sorption characteristics is reviewed in the light of an assumed relaxation mechanism for the sorption and swelling processes. The prospects of controlling the structure and properties of block copolymers are shown to be good. The bibliography contains 190 references.

  4. 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.

  5. Method of producing nanopatterned articles using surface-reconstructed block copolymer films

    SciTech Connect

    Russell, Thomas P; Park, Soojin; Wang, Jia-Yu; Kim, Bokyung

    2013-08-27

    Nanopatterned surfaces are prepared by a method that includes forming a block copolymer film on a substrate, annealing and surface reconstructing the block copolymer film to create an array of cylindrical voids, depositing a metal on the surface-reconstructed block copolymer film, and heating the metal-coated block copolymer film to redistribute at least some of the metal into the cylindrical voids. When very thin metal layers and low heating temperatures are used, metal nanodots can be formed. When thicker metal layers and higher heating temperatures are used, the resulting metal structure includes nanoring-shaped voids. The nanopatterned surfaces can be transferred to the underlying substrates via etching, or used to prepare nanodot- or nanoring-decorated substrate surfaces.

  6. Synthesis of non-polar/hydrogen bonding block copolymers

    NASA Astrophysics Data System (ADS)

    Montgomery, Steven J.

    Methods for the synthesis of novel block copolymers consisting of a non-polar segment and a hydrogen bonding segment were developed using a combination of living polymerization techniques. A series of well defined block copolymers was synthesized consisting of polybutadiene-block-poly(t-butyldimethylsilyloxystyrene), polybutadiene-block-poly(p-acetoxystyrene) and polybutadiene-block-poly(methyl methacrylate). The block copolymers containing t-butyldimethylsilyloxystyrene and p-acetoxystyrene may be deprotected to yield polybutadiene-block-poly(4-hydroxystyrene). Specifically, non-polar/hydrogen bonding (NP/HB) block copolymers were synthesized via two routes. The first consisted of anionic polymerization. The second involved a mechanistic transformation technique comprised of anionic and atom transfer radical polymerization techniques. The mechanistic transformation route was determined to be the superior method with regard to the molecular weight of the polymers produced, the abundance of compatible monomers, and the facile nature of the reaction technique.

  7. Piezoelectric Properties of Non-Polar Block Copolymers

    SciTech Connect

    Pester, Christian; Ruppel, Markus A; Schoberth, Heiko; Schmidt, K.; Liedel, Clemens; Van Rijn, Patrick; Littrell, Ken; Schindler, Kerstin; Hiltl, Stephanie; Czubak, Thomas; Mays, Jimmy; Urban, Volker S; Boker, Alexander

    2011-01-01

    Piezoelectric properties in non-polar block copolymers are a novelty in the field of electroactive polymers. The piezoelectric susceptibility of poly(styrene-b-isoprene) block copolymer lamellae is found to be up to an order of magnitude higher when compared to classic piezoelectric materials. The electroactive response increases with temperature and is found to be strongest in the disordered phase.

  8. Influence of Architecture on the Behavior of Microphase Separated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Speetjens, Frank W., II

    chemistry and physics of two other block copolymer systems are explored: (1) the self-assembly, thin film template fabrication, and post fabrication-template modification of reactive poly(styrene-b-vinyl dimethylazalactone) block copolymers, and (2) the synthesis and rheological characteristics of amphiphilic poly(vinyl alcohol)-based ABA triblock copolymer hydrogels.

  9. Patchy micelles based on coassembly of block copolymer chains and block copolymer brushes on silica particles.

    PubMed

    Zhu, Shuzhe; Li, Zhan-Wei; Zhao, Hanying

    2015-04-14

    Patchy particles are a type of colloidal particles with one or more well-defined patches on the surfaces. The patchy particles with multiple compositions and functionalities have found wide applications from the fundamental studies to practical uses. In this research patchy micelles with thiol groups in the patches were prepared based on coassembly of free block copolymer chains and block copolymer brushes on silica particles. Thiol-terminated and cyanoisopropyl-capped polystyrene-block-poly(N-isopropylacrylamide) block copolymers (PS-b-PNIPAM-SH and PS-b-PNIPAM-CIP) were synthesized by reversible addition-fragmentation chain transfer polymerization and chemical modifications. Pyridyl disulfide-functionalized silica particles (SiO2-SS-Py) were prepared by four-step surface chemical reactions. PS-b-PNIPAM brushes on silica particles were prepared by thiol-disulfide exchange reaction between PS-b-PNIPAM-SH and SiO2-SS-Py. Surface micelles on silica particles were prepared by coassembly of PS-b-PNIPAM-CIP and block copolymer brushes. Upon cleavage of the surface micelles from silica particles, patchy micelles with thiol groups in the patches were obtained. Dynamic light scattering, transmission electron microscopy, and zeta-potential measurements demonstrate the preparation of patchy micelles. Gold nanoparticles can be anchored onto the patchy micelles through S-Au bonds, and asymmetric hybrid structures are formed. The thiol groups can be oxidized to disulfides, which results in directional assembly of the patchy micelles. The self-assembly behavior of the patchy micelles was studied experimentally and by computer simulation. PMID:25811763

  10. 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.

  11. Block Copolymer Templates for Optical Materials and Devices

    NASA Astrophysics Data System (ADS)

    Urbas, Augustine; Martin, Maldovan; Carter, W. C.; Thomas, E. L.; Fasolka, Michael; Fraser, Cassandra

    2002-03-01

    Block copolymers can act as super-lattices for creating novel optical structures. We have fabricated block copolymer photonic crystals from one, two and three dimensionally periodic systems and have enhanced their dielectric properties towards creating complete 3D band gaps. By using carefully selected blends of linear and star block copolymers, we are able to create hierarchical blends which exhibit precise molecular positioning of fluorescent molecules. We are exploring these unique patterning capabilities of block copolymer systems for the formation of ordered arrays of optically active components within a photonic crystal. Precise location of both fluorescent and nonlinear components within block copolymer photonic crystals affords new opportunities for creating low threshold, upconverting and array lasers as well as optical modulators and other photonic devices.

  12. Electric field induced selective disordering in lamellar block copolymers.

    PubMed

    Ruppel, Markus; Pester, Christian W; Langner, Karol M; Sevink, Geert J A; Schoberth, Heiko G; Schmidt, Kristin; Urban, Volker S; Mays, Jimmy W; Böker, Alexander

    2013-05-28

    External electric fields align nanostructured block copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the order-disorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented parallel to the applied field prevail. The present study adds an additional mechanism to the experimentally corroborated suite of mechanistic pathways, by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the order-disorder transition and well below it. PMID:23573901

  13. Anomalous Micellization of Pluronic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Leonardi, Amanda; Ryu, Chang Y.

    2014-03-01

    Poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) (PEO-PPO-PEO) block copolymers, commercially known as Pluronics, are a unique family of amphiphilic triblock polymers, which self-assemble into micelles in aqueous solution. These copolymers have shown promise in therapeutic, biomedical, cosmetic, and nanotech applications. As-received samples of Pluronics contain low molecular weight impurities (introduced during the manufacturing and processing), that are ignored in most applications. It has been observed, however, that in semi-dilute aqueous solutions, at concentrations above 1 wt%, the temperature dependent micellization behavior of the Pluronics is altered. Anomalous behavior includes a shift of the critical micellization temperature and formation of large aggregates at intermediate temperatures before stable sized micelles form. We attribute this behavior to the low molecular weight impurities that are inherent to the Pluronics which interfere with the micellization process. Through the use of Dynamic Light Scattering and HPLC, we compared the anomalous behavior of different Pluronics of different impurity levels to their purified counterparts.

  14. 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.

  15. Equilibrium and Kinetics of Block Copolymers Micelles

    NASA Astrophysics Data System (ADS)

    Mysona, Joshua; Morse, David

    Both equilibrium properties of micelles, such as the critical micelle concentration (CMC), and dynamical properties such as the micelle lifetime are difficult to study in simulations because of the slow dynamics of the processes by which micelles are created and destroyed. We first discuss a method of precisely identifying the CMC in a simple model of block copolymer micelles in a homopolymer matrix, which makes use of thermodynamic integration to compute the free energy of formation. We then examine the free energy barriers to competing mechanisms for creating and destroying micelles, which could occur predominantly either by a step-wise process involving insertion and extraction of single molecules or by fission and fusion of entire micelles.

  16. Block copolymer adhesion promoters via ring-opening metathesis polymerization

    DOEpatents

    Kent, Michael S.; Saunders, Randall

    1997-01-01

    Coupling agents based on functionalized block copolymers for bonding thermoset polymers to solid materials. These are polymers which possess at least two types of functional groups, one which is able to attach to and react with solid surfaces, and another which can react with a thermoset resin, which are incorporated as pendant groups in monomers distributed in blocks (typically two) along the backbone of the chain. The block copolymers in this invention are synthesized by living ring-opening metathesis polymerization.

  17. 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.

  18. Morphological studies on block copolymer modified PA 6 blends

    NASA Astrophysics Data System (ADS)

    Poindl, M.; Bonten, C.

    2014-05-01

    Recent studies show that compounding polyamide 6 (PA 6) with a PA 6 polyether block copolymers made by reaction injection molding (RIM) or continuous anionic polymerization in a reactive extrusion process (REX) result in blends with high impact strength and high stiffness compared to conventional rubber blends. In this paper, different high impact PA 6 blends were prepared using a twin screw extruder. The different impact modifiers were an ethylene propylene copolymer, a PA PA 6 polyether block copolymer made by reaction injection molding and one made by reactive extrusion. To ensure good particle matrix bonding, the ethylene propylene copolymer was grafted with maleic anhydride (EPR-g-MA). Due to the molecular structure of the two block copolymers, a coupling agent was not necessary. The block copolymers are semi-crystalline and partially cross-linked in contrast to commonly used amorphous rubbers which are usually uncured. The combination of different analysis methods like atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) gave a detailed view in the structure of the blends. Due to the partial cross-linking, the particles of the block copolymers in the blends are not spherical like the ones of ethylene propylene copolymer. The differences in molecular structure, miscibility and grafting of the impact modifiers result in different mechanical properties and different blend morphologies.

  19. Morphological studies on block copolymer modified PA 6 blends

    SciTech Connect

    Poindl, M. E-mail: christian.bonten@ikt.uni-stuttgart.de; Bonten, C. E-mail: christian.bonten@ikt.uni-stuttgart.de

    2014-05-15

    Recent studies show that compounding polyamide 6 (PA 6) with a PA 6 polyether block copolymers made by reaction injection molding (RIM) or continuous anionic polymerization in a reactive extrusion process (REX) result in blends with high impact strength and high stiffness compared to conventional rubber blends. In this paper, different high impact PA 6 blends were prepared using a twin screw extruder. The different impact modifiers were an ethylene propylene copolymer, a PA PA 6 polyether block copolymer made by reaction injection molding and one made by reactive extrusion. To ensure good particle matrix bonding, the ethylene propylene copolymer was grafted with maleic anhydride (EPR-g-MA). Due to the molecular structure of the two block copolymers, a coupling agent was not necessary. The block copolymers are semi-crystalline and partially cross-linked in contrast to commonly used amorphous rubbers which are usually uncured. The combination of different analysis methods like atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) gave a detailed view in the structure of the blends. Due to the partial cross-linking, the particles of the block copolymers in the blends are not spherical like the ones of ethylene propylene copolymer. The differences in molecular structure, miscibility and grafting of the impact modifiers result in different mechanical properties and different blend morphologies.

  20. Nanopatterning of recombinant proteins and viruses using block copolymer templates

    NASA Astrophysics Data System (ADS)

    Cresce, Arthur Von Wald

    The study of interfaces is important in understanding biological interactions, including cellular signaling and virus infection. This thesis is an original effort to examine the interaction between a block copolymer and both a protein and a virus. Block copolymers intrinsically form nanometer-scale structures over large areas without expensive processing, making them ideal for the synthesis of the nanopatterned surfaces used in this study. The geometry of these nanostructures can be easily tuned for different applications by altering the block ratio and composition of the block copolymer. Block copolymers can be used for controlled uptake of metal ions, where one block selectively binds metal ions while the other does not. 5-norbornene-2,3-dicarboxylic acid is synthesized through ring-opening metathesis polymerization. It formed spherical domains with spheres approximately 30 nm in diameter, and these spheres were then subsequently loaded with nickel ion. This norbornene block copolymer was tested for its ability to bind histidine-tagged green fluorescent protein (hisGFP), and it was found that the nickel-loaded copolymer was able to retain hisGFP through chelation between the histidine tag and the metal-containing portions of the copolymer surface. Poly(styrene-b-4-vinylpyridine) (PS/P4VP) was also loaded with nickel, forming a cylindrical microstructure. The binding of Tobacco mosaic virus and Tobacco necrosis virus was tested through Tween 20 detergent washes. Electron microscopy allowed for observation of both block copolymer nanostructures and virus particles. Results showed that Tween washes could not remove bound Tobacco mosaic virus from the surface of PS/P4VP. It was also seen that the size and tunability of block copolymers and the lack of processing needed to attain different structures makes them attractive for many applications, including microfluidic devices, surfaces to influence cellular signaling and growth, and as a nanopatterning surface for

  1. Hollow ZIF-8 Nanoworms from Block Copolymer Templates.

    PubMed

    Yu, Haizhou; Qiu, Xiaoyan; Neelakanda, Pradeep; Deng, Lin; Khashab, Niveen M; Nunes, Suzana P; Peinemann, Klaus-Viktor

    2015-01-01

    Recently two quite different types of "nano-containers" have been recognized as attractive potential drug carriers; these are wormlike filamenteous micelles ("filomicelles") on the one hand and metal organic frameworks on the other hand. In this work we combine these two concepts. We report for the first time the manufacturing of metal organic framework nanotubes with a hollow core. These worm-like tubes are about 200 nm thick and several μm long. The preparation is simple: we first produce long and flexible filament-shaped micelles by block copolymer self-assembly. These filomicelles serve as templates to grow a very thin layer of interconnected ZIF-8 crystals on their surface. Finally the block copolymer is removed by solvent extraction and the hollow ZIF-8 nanotubes remain. These ZIF-NTs are surprisingly stable and withstand purification by centrifugation. The synthesis method is straightforward and can easily be applied for other metal organic framework materials. The ZIF-8 NTs exhibit high loading capacity for the model anti cancer drug doxorubicin (DOX) with a pH-triggered release. Hence, a prolonged circulation in the blood stream and a targeted drug release behavior can be expected.

  2. Hollow ZIF-8 Nanoworms from Block Copolymer Templates

    PubMed Central

    Yu, Haizhou; Qiu, Xiaoyan; Neelakanda, Pradeep; Deng, Lin; Khashab, Niveen M.; Nunes, Suzana P.; Peinemann, Klaus-Viktor

    2015-01-01

    Recently two quite different types of “nano-containers” have been recognized as attractive potential drug carriers; these are wormlike filamenteous micelles (“filomicelles”) on the one hand and metal organic frameworks on the other hand. In this work we combine these two concepts. We report for the first time the manufacturing of metal organic framework nanotubes with a hollow core. These worm-like tubes are about 200 nm thick and several μm long. The preparation is simple: we first produce long and flexible filament-shaped micelles by block copolymer self-assembly. These filomicelles serve as templates to grow a very thin layer of interconnected ZIF-8 crystals on their surface. Finally the block copolymer is removed by solvent extraction and the hollow ZIF-8 nanotubes remain. These ZIF-NTs are surprisingly stable and withstand purification by centrifugation. The synthesis method is straightforward and can easily be applied for other metal organic framework materials. The ZIF-8 NTs exhibit high loading capacity for the model anti cancer drug doxorubicin (DOX) with a pH-triggered release. Hence, a prolonged circulation in the blood stream and a targeted drug release behavior can be expected. PMID:26471862

  3. Nanopatterned barium titanate on block copolymers

    NASA Astrophysics Data System (ADS)

    Lee, Tu

    This dissertation describes the synthesis, the characterization and the modeling of a triblock copolymer of polystyrene(PS)-polybutadiene(PB)-polystyrene(PS) monolayer thin film patterned with nanometer sized cubic BaTiO3 crystals, with a focus on the influence of length scales and the hierarchical structure on the ferroelectric properties of BaTiO3. BaTiO3, a dielectric and a ferroelectric, is used extensively in multilayer capacitors, thermistors and electrooptic devices. Its ferroelectric properties are known to be size dependent in the nanometer scale. To gain further insight into the fundamental characteristics of BaTiO3 in the nanometer scale, BaTiO3 is crystallized, for the first time, in a confined environment hosted by a PS-PB-PS triblock copolymer monolayer thin film with nanodomains of tunable geometry and size. The engineering of the PS-PB-PS triblock copolymer monolayer thin film includes fractionation, elimination of interfacial interaction, control of film thickness and minimization of pinholes. The resulting monolayer contains cylindrical PS nanodomains embedded in a PB matrix. The film thickness, the diameter of the PS domain and the domain center-to-domain center distance are 31 nm, 15 nm and 31 nm respectively. Cubic BaTiO3 nanoparticles having a narrow size distribution of 10 nm are formed and located predominantly within the PB matrices by three steps: epoxidation-hydroxylation, barium titanation and vapor-phase hydrothermal process. The volume fraction of BaTiO3 phase is 0.0113. The effective dielectric constant of the BaTiO3/PS-PB-PS composite monolayer is 5.5 +/- 2.5. With the assistance of dielectric mixing rules, the dielectric constant of the cubic BaTiO3 phase is determined to be 160. The relative low dielectric constant of the BaTiO3 phase is usually explained by the critical size above which BaTiO3 particles are tetragonal and ferroelectric and below which particles are cubic and non-ferroelectric. But, the inconsistency of the

  4. Microemulsions of ABA Amphiphilic Block Copolymers and Surfactants

    NASA Astrophysics Data System (ADS)

    Braun-Shmueli, Liora; Netanel, Ortal; Regev, Oren; Gottlieb, Moshe

    2001-03-01

    The system composed of oil (decane), water and an ABA amphiphilic block copolymer is capable of exhibiting an extremely rich phase and rheological behavior. In this paper we describe the rheological properties of a synthetic amphiphilic block copolymer dissolved in a water-in-oil microemulsion with and without the stabilizing effect of small molecular weight surfactant molecules. The block copolymer is an ABA type copolymer composed of poly(oxyethylene) (PEO) as the hydrophilic A block and poly(dimethyl siloxane) (PDMS) as the hydrophobic center B block. The resulting copolymer is insoluble in water and hardly soluble in decane (good solvent for the PDMS). In the presence of water in oil microemulsion stabilized by the small molecular weight surfactant AOT a one-phase region is maintained when the copolymer is added. Yet, peculiar rheological behavior is observed. For constant water-microemulsion concentration (φ) addition of polymer increases the system viscosity as expected. Yet, the lower φ the higher the viscosity and at high φ the effect of polymer addition is quite low. Furthermore, the insoluble block copolymer in oil turns into a gel-like one phase system upon addition of small amounts of either water or water and surfactant solution. Experiments show that a maximum in elasticity or viscosity is attained at a droplet concentration equivalent to about 80 polymer chains per drop. Small angle x-ray and neutron scattering experiments were carried out to elucidate the system morphology.

  5. High-Tg Polynorbornene-Based Block and Random Copolymers for Butanol Pervaporation Membranes

    NASA Astrophysics Data System (ADS)

    Register, Richard A.; Kim, Dong-Gyun; Takigawa, Tamami; Kashino, Tomomasa; Burtovyy, Oleksandr; Bell, Andrew

    Vinyl addition polymers of substituted norbornene (NB) monomers possess desirably high glass transition temperatures (Tg); however, until very recently, the lack of an applicable living polymerization chemistry has precluded the synthesis of such polymers with controlled architecture, or copolymers with controlled sequence distribution. We have recently synthesized block and random copolymers of NB monomers bearing hydroxyhexafluoroisopropyl and n-butyl substituents (HFANB and BuNB) via living vinyl addition polymerization with Pd-based catalysts. Both series of polymers were cast into the selective skin layers of thin film composite (TFC) membranes, and these organophilic membranes investigated for the isolation of n-butanol from dilute aqueous solution (model fermentation broth) via pervaporation. The block copolymers show well-defined microphase-separated morphologies, both in bulk and as the selective skin layers on TFC membranes, while the random copolymers are homogeneous. Both block and random vinyl addition copolymers are effective as n-butanol pervaporation membranes, with the block copolymers showing a better flux-selectivity balance. While polyHFANB has much higher permeability and n-butanol selectivity than polyBuNB, incorporating BuNB units into the polymer (in either a block or random sequence) limits the swelling of the polyHFANB and thereby improves the n-butanol pervaporation selectivity.

  6. Structure of Block Copolymer Hydrogel Formed by Complex Coacervate Process

    NASA Astrophysics Data System (ADS)

    Choi, Soohyung; Ortony, Julia; Krogstad, Daniel; Spruell, Jason; Lynd, Nathaniel; Han, Songi; Kramer, Edward

    2012-02-01

    Complex coacervation occurs when oppositely charged polyelectrolytes associate in solution, forming dense micron-sized droplets. Hydrogels with coacervate block domains were formed by mixing two ABA and A'BA' triblock copolymer solutions in water where the A and A' blocks are oppositely charged. Small-angle neutron scattering (SANS) was used to investigate the structure of hydrogels formed by ABA triblock copolymers (A block: poly(allyl glycidyl ether) functionalized with guanidinium (A) or sulfonate (A'), B block: poly(ethylene oxide)). By using an appropriate fitting model, structural information such as coacervate core block radius and water volume fraction w can be extracted from SANS data. The results reveal that w in the coacervate core block was significantly higher than in conventional triblock copolymer hydrogels where microphase separation is driven by the hydrophobicity of the core-forming blocks.

  7. 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.

  8. Synthetic Cell Elements from Block Copolymers. Dynamic Aspects

    NASA Astrophysics Data System (ADS)

    Discher, Dennis

    2003-03-01

    Amphiphilic block copolymers can self-assemble in water into various stable morphologies which resemble key cell structures, notably filaments and membranes. Filamentous worms of copolymer, microns-long, will be introduced, and related dynamics of copolymer vesicle polymersomes will be detailed. Fluorescence visualization of single worms stretched under flow demonstrates their stability as well as a means to control flexibility. Polymersome membranes have been more thoroughly studied, especially copolymer molecular weight effects. We summarize results suggestive of a transition from Rouse-like behavior to entangled chains. Viewed together, the results ask the question: what physics are needed next to mimic cell activities such as crawling?

  9. Correlative infrared nanospectroscopic and nanomechanical imaging of block copolymer microdomains.

    PubMed

    Pollard, Benjamin; Raschke, Markus B

    2016-01-01

    Intermolecular interactions and nanoscale phase separation govern the properties of many molecular soft-matter systems. Here, we combine infrared vibrational scattering scanning near-field optical microscopy (IR s-SNOM) with force-distance spectroscopy for simultaneous characterization of both nanoscale optical and nanomechanical molecular properties through hybrid imaging. The resulting multichannel images and correlative analysis of chemical composition, spectral IR line shape, modulus, adhesion, deformation, and dissipation acquired for a thin film of a nanophase separated block copolymer (PS-b-PMMA) reveal complex structural variations, in particular at domain interfaces, not resolved in any individual signal channel alone. These variations suggest that regions of multicomponent chemical composition, such as the interfacial mixing regions between microdomains, are correlated with high spatial heterogeneity in nanoscale material properties. PMID:27335750

  10. Correlative infrared nanospectroscopic and nanomechanical imaging of block copolymer microdomains.

    PubMed

    Pollard, Benjamin; Raschke, Markus B

    2016-01-01

    Intermolecular interactions and nanoscale phase separation govern the properties of many molecular soft-matter systems. Here, we combine infrared vibrational scattering scanning near-field optical microscopy (IR s-SNOM) with force-distance spectroscopy for simultaneous characterization of both nanoscale optical and nanomechanical molecular properties through hybrid imaging. The resulting multichannel images and correlative analysis of chemical composition, spectral IR line shape, modulus, adhesion, deformation, and dissipation acquired for a thin film of a nanophase separated block copolymer (PS-b-PMMA) reveal complex structural variations, in particular at domain interfaces, not resolved in any individual signal channel alone. These variations suggest that regions of multicomponent chemical composition, such as the interfacial mixing regions between microdomains, are correlated with high spatial heterogeneity in nanoscale material properties.

  11. Correlative infrared nanospectroscopic and nanomechanical imaging of block copolymer microdomains

    PubMed Central

    Pollard, Benjamin

    2016-01-01

    Summary Intermolecular interactions and nanoscale phase separation govern the properties of many molecular soft-matter systems. Here, we combine infrared vibrational scattering scanning near-field optical microscopy (IR s-SNOM) with force–distance spectroscopy for simultaneous characterization of both nanoscale optical and nanomechanical molecular properties through hybrid imaging. The resulting multichannel images and correlative analysis of chemical composition, spectral IR line shape, modulus, adhesion, deformation, and dissipation acquired for a thin film of a nanophase separated block copolymer (PS-b-PMMA) reveal complex structural variations, in particular at domain interfaces, not resolved in any individual signal channel alone. These variations suggest that regions of multicomponent chemical composition, such as the interfacial mixing regions between microdomains, are correlated with high spatial heterogeneity in nanoscale material properties. PMID:27335750

  12. 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.

  13. New adhesive systems based on functionalized block copolymers

    SciTech Connect

    Kent, M.; Saunders, R.; Hurst, M.; Small, J.; Emerson, J.; Zamora, D.

    1997-05-01

    The goal of this work was to evaluate chemically-functionalized block copolymers as adhesion promoters for metal/thermoset resin interfaces. Novel block copolymers were synthesized which contain pendant functional groups reactive toward copper and epoxy resins. In particular, imidazole and triazole functionalities that chelate with copper were incorporated onto one block, while secondary amines were incorporated onto the second block. These copolymers were found to self-assemble from solution onto copper surfaces to form monolayers. The structure of the adsorbed monolayers were studied in detail by neutron reflection and time-of-flight secondary ion mass spectrometry. The monolayer structure was found to vary markedly with the solution conditions and adsorption protocol. Appropriate conditions were found for which the two blocks form separate layers on the surface with the amine functionalized block exposed at the air surface. Adhesion testing of block copolymer-coated copper with epoxy resins was performed in both lap shear and peel modes. Modest enhancements in bond strengths were observed with the block copolymer applied to the native oxide. However, it was discovered that the native oxide is the weak link, and that by simply removing the native oxide, and then applying an epoxy resin before the native oxide can reform, excellent bond strength in the as-prepared state as well as excellent retention of bond strength after exposure to solder in ambient conditions are obtained. It is recommended that long term aging studies be performed with and without the block copolymer. In addition, the functionalized block copolymer method should be evaluated for another system that has inherently poor bonding, such as the nickel/silicone interface, and for systems involving metals and alloys which form oxides very rapidly, such as aluminum and stainless steel, where bonding strategies involve stabilizing the native oxide.

  14. Self-doped microphase separated block copolymer electrolyte

    DOEpatents

    Mayes, Anne M.; Sadoway, Donald R.; Banerjee, Pallab; Soo, Philip; Huang, Biying

    2002-01-01

    A polymer electrolyte includes a self-doped microphase separated block copolymer including at least one ionically conductive block and at least one second block that is immiscible in the ionically conductive block, an anion immobilized on the polymer electrolyte and a cationic species. The ionically conductive block provides a continuous ionically conductive pathway through the electrolyte. The electrolyte may be used as an electrolyte in an electrochemical cell.

  15. 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.

  16. Oligoaniline-containing supramolecular block copolymer nanodielectric materials.

    PubMed

    Hardy, Christopher G; Islam, Md Sayful; Gonzalez-Delozier, Dioni; Ploehn, Harry J; Tang, Chuanbing

    2012-05-14

    We report a new generation of nanodielectric energy storage materials based on supramolecular block copolymers. In our approach, highly polarizable, conducting nanodomains are embedded within an insulating matrix through block copolymer microphase separation. An applied electric field leads to electronic polarization of the conducting domains. The high interfacial area of microphase-separated domains amplifies the polarization, leading to high dielectric permittivity. Specifically, reversible addition fragmentation transfer (RAFT) polymerization was used to prepare block copolymers with poly(methyl acrylate) (PMA) as the insulating segment and a strongly acidic dopant moiety, poly-(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA), as the basis for the conducting segment. The PAMPSA block was complexed with an oligoaniline trimer to form a dopant-conjugated moiety complex that is electronically conductive after oxidation. For the undoped neat block copolymers, the increase of the PMA block length leads to a transition in dielectric properties from ionic conductor to dielectric capacitor with polarization resulting from migration of protons within the isolated PAMPSA domains. The oligoaniline-doped copolymers show remarkably different dielectric properties. At frequencies above 200 kHz, they exhibit characteristics of dielectric capacitors with much higher permittivity and lower dielectric loss than the corresponding undoped copolymers. PMID:22331602

  17. Oligoaniline-containing supramolecular block copolymer nanodielectric materials.

    PubMed

    Hardy, Christopher G; Islam, Md Sayful; Gonzalez-Delozier, Dioni; Ploehn, Harry J; Tang, Chuanbing

    2012-05-14

    We report a new generation of nanodielectric energy storage materials based on supramolecular block copolymers. In our approach, highly polarizable, conducting nanodomains are embedded within an insulating matrix through block copolymer microphase separation. An applied electric field leads to electronic polarization of the conducting domains. The high interfacial area of microphase-separated domains amplifies the polarization, leading to high dielectric permittivity. Specifically, reversible addition fragmentation transfer (RAFT) polymerization was used to prepare block copolymers with poly(methyl acrylate) (PMA) as the insulating segment and a strongly acidic dopant moiety, poly-(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA), as the basis for the conducting segment. The PAMPSA block was complexed with an oligoaniline trimer to form a dopant-conjugated moiety complex that is electronically conductive after oxidation. For the undoped neat block copolymers, the increase of the PMA block length leads to a transition in dielectric properties from ionic conductor to dielectric capacitor with polarization resulting from migration of protons within the isolated PAMPSA domains. The oligoaniline-doped copolymers show remarkably different dielectric properties. At frequencies above 200 kHz, they exhibit characteristics of dielectric capacitors with much higher permittivity and lower dielectric loss than the corresponding undoped copolymers.

  18. Electrically conductive doped block copolymer of polyacetylene and polyisoprene

    DOEpatents

    Aldissi, Mahmoud

    1985-01-01

    An electrically conductive block copolymer of polyisoprene and polyacetyl and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I.sub.2 to give it an electrical conductivity in the metallic regime.

  19. 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.

  20. Continuous concentric lamellar block copolymer nanofibers with long range order.

    PubMed

    Ma, Minglin; Titievsky, Kirill; Thomas, Edwin L; Rutledge, Gregory C

    2009-04-01

    Fibers with long-range ordered internal structures have applications in various areas such as photonic band gap fibers, optical waveguides, wearable power, sensors, and sustained drug release. Up to now, such fibers have been formed by melt extrusion or drawing from a macroscopic preformed rod and were typically limited to diameters >10 microm with internal features >1 microm (Abouraddy, A. F.; et al. Nat. Mater. 2007, 6, 336). We describe a new class of continuous fibers and fibrous membranes with long-range ordered concentric lamellar structure that have fiber diameters and feature sizes 2-3 orders of magnitude smaller than those made by conventional methods. These fibers are created through confined self-assembly of block copolymers within core-shell electrospun filaments. In contrast to the copolymer in bulk or thin films, the domains of the concentric lamellar structure are shown here to vary quantitatively with (radial) position and to exhibit a novel dislocation that accommodates variations in fiber diameter robustly, permitting for the first time the realization of long-range order in technologically meaningful, continuous fibers with approximately 300 nm diameter and 50 nm radial period. PMID:19351195

  1. Millisecond ordering of block-copolymer films via photo-thermal gradients

    SciTech Connect

    Majewski, Pawel W.; Yager, Kevin G.

    2015-03-12

    For the promise of self-assembly to be realized, processing techniques must be developed that simultaneously enable control of the nanoscale morphology, rapid assembly, and, ideally, the ability to pattern the nanostructure. Here, we demonstrate how photo-thermal gradients can be used to control the ordering of block-copolymer thin films. Highly localized laser heating leads to intense thermal gradients, which induce a thermophoretic force on morphological defects. This increases the ordering kinetics by at least 3 orders-of-magnitude, compared to conventional oven annealing. By simultaneously exploiting the thermal gradients to induce shear fields, we demonstrate uniaxial alignment of a block-copolymer film in less than a second. Finally, we provide examples of how control of the incident light-field can be used to generate prescribed configurations of block-copolymer nanoscale patterns.

  2. Millisecond ordering of block-copolymer films via photo-thermal gradients

    DOE PAGES

    Majewski, Pawel W.; Yager, Kevin G.

    2015-03-12

    For the promise of self-assembly to be realized, processing techniques must be developed that simultaneously enable control of the nanoscale morphology, rapid assembly, and, ideally, the ability to pattern the nanostructure. Here, we demonstrate how photo-thermal gradients can be used to control the ordering of block-copolymer thin films. Highly localized laser heating leads to intense thermal gradients, which induce a thermophoretic force on morphological defects. This increases the ordering kinetics by at least 3 orders-of-magnitude, compared to conventional oven annealing. By simultaneously exploiting the thermal gradients to induce shear fields, we demonstrate uniaxial alignment of a block-copolymer film in lessmore » than a second. Finally, we provide examples of how control of the incident light-field can be used to generate prescribed configurations of block-copolymer nanoscale patterns.« less

  3. 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.

  4. Patterned silica films using microphase separation of a block copolymer

    NASA Astrophysics Data System (ADS)

    Kataoka, Sho; Takeuchi, Yasutaka; Endo, Akira

    2014-11-01

    Block copolymers exhibit various nanoscale ordered morphologies induced by microphase separation. Here, we present a method for providing two types of patterned silica films on Si wafer substrates simply by shifting the phase equilibrium of a block copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-P4VP). In this method, siloxane is adsorbed onto poly(4-vinylpyridine) blocks of PS-P4VP whose structure varies with solvent polarity and is calcined to remove the block copolymer. Siloxane is in a dispersed phase with toluene as a solvent resulting in silica nanoparticle arrays, while siloxane is in a continuous phase with N, N-dimethylformamide (DMF) resulting in silica films with ordered mesopores. Since the pore size of silica films prepared in DMF is approximately 20 nm, the film has the ability to serve as a support for enzymes such as laccase.

  5. Reversible Switching of Block Copolymer Nanopatterns by Orthogonal Electric Fields.

    PubMed

    Liedel, Clemens; Lewin, Christian; Tsarkova, Larisa; Böker, Alexander

    2015-12-01

    It is demonstrated that the orientation of striped patterns can be reversibly switched between two perpendicular in-plane orientations upon exposure to electric fields. The results on thin films of symmetric polystyrene-block-poly(2-vinyl pyridine) polymer in the intermediate segregation regime disclose two types of reorientation mechanisms from perpendicular to parallel relative to the electric field orientation. Domains orient via grain rotation and via formation of defects such as stretched undulations and temporal phase transitions. The contribution of additional fields to the structural evolution is also addressed to elucidate the generality of the observed phenomena. In particular solvent effects are considered. This study reveals the stabilization of the meta-stable in-plane oriented lamella due to sequential swelling and quenching of the film. Further, the reorientation behavior of lamella domains blended with selective nanoparticles is addressed, which affect the interfacial tensions of the blocks and hence introduce another internal field to the studied system. Switching the orientation of aligned block copolymer patterns between two orthogonal directions may open new applications of nanomaterials as switchable electric nanowires or optical gratings. PMID:26449286

  6. Fluorinated polyphenylenevinylene (PPV) block co-polymers for nanophotonics

    NASA Astrophysics Data System (ADS)

    Sun, Sam-Shajing; Nguyen, Thuong; Brooks, Jaleesa

    2013-09-01

    Polymer based optoelectronic materials and thin film devices exhibit great potential in future space applications due to their flexibility, light weight, large light absorption coefficient, and promising radiation tolerance in space environment as compared to their inorganic semiconductor counterparts. Since carbon-fluorine (C-F) chemical bonds are much stronger than the carbon-hydrogen (C-H) bonds, fluorinated polymer films offer great potential for space applications due their expected resistance to oxidation, thermal stability, excellent wear properties, and low coefficients of friction. Their use in a space environment is extremely attractive since they are expected to retain their lubricating characteristics in vacuum, unlike many solid lubricants. Current existing polymer photovoltaic materials and devices suffer low photoelectric power conversion efficiencies due to a number factors including poor morphologies at nano scale that hinder the charge separation and transport. This paper reports our recent work on a fluorinated DBfA type block copolymer system where the donor (D) block contains a donor substituted and hydrocarbon based polyphenylenevinylene (PPV), acceptor (fA) block contains a fluorinated and a sulfone acceptor substituted polyphenylenevinylene (f-PPV), and B is a non-conjugated and flexible bridge unit. Preliminary studies reveal DBfA exhibits better nano phase morphologies and over 100 times more efficient optoelectronic conversion efficiencies as compared to D/fA blend.

  7. Functional block copolymers for applications in advanced materials, energy storage, and lithography

    NASA Astrophysics Data System (ADS)

    Hardy, Christopher George

    Block copolymers spontaneously self-assembly into a wide variety of ordered nanostructures on the length scale of 5 - 100 nm due to the thermodynamic immiscibility between the covalently linked, chemically distinct polymer chains. Incorporating desirable functional groups into block copolymer systems can lead to confinement of the functional group to a specific domain upon microphase separation of the block copolymer. The resulting materials display desirable characteristics of the functional group in a well-ordered nanostructure. Such systems have been utilized in a wide variety of applications including catalysis, ceramic materials, and membranes. This dissertation is focused on the synthesis, characterization, self-assembly and materials processing of various functionalized block copolymer systems. An assortment of monomers functionalized with specific groups were prepared and polymerized by a variety of polymerization techniques including atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization, and ring-opening metathesis polymerization. Self-assembly of the functionalized block copolymers led to well defined nanostructures in bulk and thin films. Depending upon the functional group incorporated, the ordered materials were utilized in various applications including ordered catalysts, energy storage, and templates for nanolithography..

  8. 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

  9. Proteins detection by polymer optical fibers sensitised with overlayers of block and random copolymers

    NASA Astrophysics Data System (ADS)

    El Sachat, Alexandros; Meristoudi, Anastasia; Markos, Christos; Pispas, Stergios; Riziotis, Christos

    2014-03-01

    A low cost and low complexity optical detection method of proteins is presented by employing a detection scheme based on electrostatic interactions, and implemented by sensitization of a polymer optical fibers' (POF) surface by thin overlayers of properly designed sensitive copolymer materials with predesigned charges. This method enables the fast detection of proteins having opposite charge to the overlayer, and also the effective discrimination of differently charged proteins like lysozyme (LYS) and bovine serum albumin (BSA). As sensitive materials the block and the random copolymers of the same monomers were employed, namely the block copolymer poly(styrene-b-2vinylpyridine) (PS-b- P2VP) and the corresponding random copolymer poly(styrene-r-2vinylpyridine) (PS-r-P2VP), of similar composition and molecular weights. Results show systematically different response between the block and the random copolymers, although of the same order of magnitude, drawing thus important conclusions on their applications' techno-economic aspects given that they have significantly different associated manufacturing method and costs. The use of the POF platform, in combination with those adaptable copolymer sensing materials could lead to efficient low cost bio-detection schemes.

  10. Ion Transport in Nanostructured Block Copolymer/Ionic Liquid Membranes

    NASA Astrophysics Data System (ADS)

    Hoarfrost, Megan Lane

    Incorporating an ionic liquid into one block copolymer microphase provides a platform for combining the outstanding electrochemical properties of ionic liquids with a number of favorable attributes provided by block copolymers. In particular, block copolymers thermodynamically self-assemble into well-ordered nanostructures, which can be engineered to provide a durable mechanical scaffold and template the ionic liquid into continuous ion-conducting nanochannels. Understanding how the addition of an ionic liquid affects the thermodynamic self-assembly of block copolymers, and how the confinement of ionic liquids to block copolymer nanodomains affects their ion-conducting properties is essential for predictable structure-property control. The lyotropic phase behavior of block copolymer/ionic liquid mixtures is shown to be reminiscent of mixtures of block copolymers with selective molecular solvents. A variety of ordered microstructures corresponding to lamellae, hexagonally close-packed cylinders, body-centered cubic, and face-centered cubic oriented micelles are observed in a model system composed of mixtures of imidazolium bis(trifluoromethylsulfonyl)imide ([Im][TFSI]) and poly(styrene- b-2-vinyl pyridine) (PS-b-P2VP). In contrast to block copolymer/molecular solvent mixtures, the interfacial area occupied by each PS-b-P2VP chain decreases upon the addition of [Im][TFSI], indicating a considerable increase in the effective segregation strength of the PS-b-P2VP copolymer with ionic liquid addition. The relationship between membrane structure and ionic conductivity is illuminated through the development of scaling relationships that describe the ionic conductivity of block copolymer/ionic liquid mixtures as a function of membrane composition and temperature. It is shown that the dominant variable influencing conductivity is the overall volume fraction of ionic liquid in the mixture, which means there

  11. Block Copolymer Nanocomposites in Electric Fields: Kinetics of Alignment

    SciTech Connect

    Liedel, Clemens; Pester, Christian; Ruppel, Markus A; Lewin, Christian; Pavan, Mariela J.; Urban, Volker S; Shenhar, Roy; Bosecke, Peter; Boker, Alexander

    2013-01-01

    We investigate the kinetics of block copolymer/nanoparticle composite alignment in an electric field using in situ transmission small-angle X-ray scattering. As a model system, we employ a lamellae forming polystyrene-block-poly(2-vinyl pyridine) block copolymer with different contents of gold nanoparticles in thick films under solvent vapor annealing. While the alignment improves with increasing nanoparticle fraction, the kinetics slows down. This is explained by changes in the degree of phase separation and viscosity. Our findings provide extended insights into the basics of nanocomposite alignment.

  12. Block copolymer adhesion promoters via ring-opening metathesis polymerization

    DOEpatents

    Kent, M.S.; Saunders, R.

    1997-02-18

    Coupling agents are disclosed based on functionalized block copolymers for bonding thermoset polymers to solid materials. These are polymers which possess at least two types of functional groups, one which is able to attach to and react with solid surfaces, and another which can react with a thermoset resin, which are incorporated as pendant groups in monomers distributed in blocks (typically two) along the backbone of the chain. The block copolymers in this invention are synthesized by living ring-opening metathesis polymerization. 18 figs.

  13. Method of forming oriented block copolymer line patterns, block copolymer line patterns formed thereby, and their use to form patterned articles

    SciTech Connect

    Russell, Thomas P.; Hong, Sung Woo; Lee, Doug Hyun; Park, Soojin; Xu, Ting

    2015-10-13

    A block copolymer film having a line pattern with a high degree of long-range order is formed by a method that includes forming a block copolymer film on a substrate surface with parallel facets, and annealing the block copolymer film to form an annealed block copolymer film having linear microdomains parallel to the substrate surface and orthogonal to the parallel facets of the substrate. The line-patterned block copolymer films are useful for the fabrication of magnetic storage media, polarizing devices, and arrays of nanowires.

  14. 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.

  15. 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.

  16. Single- and Multilayered Nanostructures via Laser-Induced Block Copolymer Self-Assembly

    NASA Astrophysics Data System (ADS)

    Majewski, Pawel; Yager, Kevin; Rahman, Atikur; Black, Charles

    We present a novel method of accelerated self-assembly of block copolymer thin films utilizing laser light, called Laser Zone Annealing (LZA). In our approach, steep temperature transients are induced in block copolymer films by rastering narrowly focused laser line over the light-absorbing substrate. Extremely steep temperature gradients accelerate the process of self-assembly by several orders-of-magnitude compared to conventional oven annealing, and, when coupled to photo-thermal shearing, lead to global alignment of block copolymer domains assessed by GISXAS diffraction studies and real-space SEM imaging. We demonstrate monolithic alignment of various block-copolymer thin films including PS-b-PMMA, PS-b-PEO, PS-b-P2VP, PS-b-PI and observe different responsiveness to the shearing rate depending on the characteristic relaxation timescale of the particular material. Subsequently, we use the aligned polymeric films as templates for synthesis of single- and multi-layered arrays of inorganic, metallic or semiconducting nanowires and nanomeshes and investigate their anisotropic electro-optical properties. Research carried out in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

  17. Host-Guest Self-assembly in Block Copolymer Blends

    PubMed Central

    Park, Woon Ik; Kim, YongJoo; Jeong, Jae Won; Kim, Kyungho; Yoo, Jung-Keun; Hur, Yoon Hyung; Kim, Jong Min; Thomas, Edwin L.; Alexander-Katz, Alfredo; Jung, Yeon Sik

    2013-01-01

    Ultrafine, uniform nanostructures with excellent functionalities can be formed by self-assembly of block copolymer (BCP) thin films. However, extension of their geometric variability is not straightforward due to their limited thin film morphologies. Here, we report that unusual and spontaneous positioning between host and guest BCP microdomains, even in the absence of H-bond linkages, can create hybridized morphologies that cannot be formed from a neat BCP. Our self-consistent field theory (SCFT) simulation results theoretically support that the precise registration of a spherical BCP microdomain (guest, B-b-C) at the center of a perforated lamellar BCP nanostructure (host, A-b-B) can energetically stabilize the blended morphology. As an exemplary application of the hybrid nanotemplate, a nanoring-type Ge2Sb2Te5 (GST) phase-change memory device with an extremely low switching current is demonstrated. These results suggest the possibility of a new pathway to construct more diverse and complex nanostructures using controlled blending of various BCPs. PMID:24217036

  18. 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.

  19. Self-Assembled Asymmetric Block Copolymer Membranes: Bridging the Gap from Ultra- to Nanofiltration.

    PubMed

    Yu, Haizhou; Qiu, Xiaoyan; Moreno, Nicolas; Ma, Zengwei; Calo, Victor Manuel; Nunes, Suzana P; Peinemann, Klaus-Viktor

    2015-11-16

    The self-assembly of block copolymers is an emerging strategy to produce isoporous ultrafiltration membranes. However, thus far, it has not been possible to bridge the gap from ultra- to nanofiltration and decrease the pore size of self-assembled block copolymer membranes to below 5 nm without post-treatment. It is now reported that the self-assembly of blends of two chemically interacting copolymers can lead to highly porous membranes with pore diameters as small as 1.5 nm. The membrane containing an ultraporous, 60 nm thin separation layer can fully reject solutes with molecular weights of 600 g mol(-1) in aqueous solutions with a water flux that is more than one order of magnitude higher than the permeance of commercial nanofiltration membranes. Simulations of the membrane formation process by dissipative particle dynamics (DPD) were used to explain the dramatic observed pore size reduction combined with an increase in water flux. PMID:26388216

  20. Liquid-crystalline ordering helps block copolymer self-assembly.

    PubMed

    Yu, Haifeng; Kobayashi, Takaomi; Yang, Huai

    2011-08-01

    Interaction between liquid-crystalline elastic deformation and microphase separation in liquid-crystalline block copolymers enables them to supramolecularly assemble into ordered nanostructures with high regularity. With the help of liquid-crystalline alignment, parallel and perpendicular patterning of nanostructures is fabricated with excellent reproducibility and mass production, which provides nanotemplates and nanofabrication processes for preparing varieties of nanomaterials. Furthermore, nanoscale microphase separation improves the optical performance of block-copolymer fi lms by eliminating the scattering of visible light, leading to advanced applications in optical devices and actuators. Recent progress in liquid-crystalline block copolymers, including their phase diagram, structure-property relationship, nanostructure control and nanotemplate applications, is reviewed. PMID:21910267

  1. Characterization of Lithium Polysulfide Salts in Homopolymers and Block Copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Dunyang; Wujcik, Kevin; Balsara, Nitash

    Ion-conducting polymers are important for solid-state batteries due to the promise of better safety and the potential to produce higher energy density batteries. Nanostructured block copolymer electrolytes can provide high ionic conductivity and mechanical strength through microphase separation. One of the potential use of block copolymer electrolytes is in lithium-sulfur batteries, a system that has high theoretical energy density wherein the reduction of sulfur leads to the formation of lithium polysulfide intermediates. In this study we investigate the effect of block copolymer morphology on the speciation and transport properties of the polysulfides. The morphology and conductivities of polystyrene-b-poly(ethylene oxide) (SEO) containing lithium polysulfides were studies using small-angle X-ray scattering and ac impedance spectroscopy. UV-vis spectroscopy is being used to determine nature of the polysulfide species in poly(ethylene oxide) and SEO. Department of Energy, Soft Matter Electron Microscopy Program and Battery Materials Research Program.

  2. Controlling block copolymer phase behavior using ionic surfactant

    NASA Astrophysics Data System (ADS)

    Ray, D.; Aswal, V. K.

    2016-05-01

    The phase behavior of poly(ethylene oxide)-poly(propylene oxide-poly(ethylene oxide) PEO-PPO-PEO triblock copolymer [P85 (EO26PO39EO26)] in presence of anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution as a function of temperature has been studied using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations (1 wt%) of block copolymer and surfactants. Each of the individual components (block copolymer and surfactant) and the nanoparticle-surfactant mixed system have been examined at varying temperature. The block copolymer P85 forms spherical micelles at room temperature whereas shows sphere-to-rod like micelle transition at higher temperatures. On the other hand, SDS surfactant forms ellipsoidal micelles over a wide temperature range. Interestingly, it is found that phase behavior of mixed micellar system (P85 + SDS) as a function of temperature is drastically different from that of P85, giving the control over the temperature-dependent phase behavior of block copolymers.

  3. Photovoltaic enhancement of organic solar cells by a bridged donor-acceptor block copolymer approach

    NASA Astrophysics Data System (ADS)

    Sun, Sam-Shajing; Zhang, Cheng; Ledbetter, Abram; Choi, Soobum; Seo, Kang; Bonner, Carl E.; Drees, Martin; Sariciftci, Niyazi Serdar

    2007-01-01

    The authors show that a photovoltaic device composed of a -donor-bridge-acceptor-bridge- type block copolymer thin film exhibits a significant performance improvement over its corresponding donor/acceptor blend (Voc increased from 0.14to1.10V and Jsc increased from 0.017 to 0.058mA/cm2) under identical conditions, where donor is an alkyl derivatized poly-p-phenylenevinylene (PPV) conjugated block, acceptor is a sulfone-alkyl derivatized PPV conjugated block, and bridge is a nonconjugated and flexible unit. The authors attribute such improvement to the block copolymer intrinsic nanophase separation and molecular self-assembly that results in the reduction of the exciton and carrier losses.

  4. Quasi-Block Copolymers Based on a General Polymeric Chain Stopper.

    PubMed

    Sanguramath, Rajashekharayya A; Nealey, Paul F; Shenhar, Roy

    2016-07-11

    Quasi-block copolymers (q-BCPs) are block copolymers consisting of conventional and supramolecular blocks, in which the conventional block is end-terminated by a functionality that interacts with the supramolecular monomer (a "chain stopper" functionality). A new design of q-BCPs based on a general polymeric chain stopper, which consists of polystyrene end-terminated with a sulfonate group (PS-SO3 Li), is described. Through viscosity measurements and a detailed diffusion-ordered NMR spectroscopy study, it is shown that PS-SO3 Li can effectively cap two types of model supramolecular monomers to form q-BCPs in solution. Furthermore, differential scanning calorimetry data and structural characterization of thin films by scanning force microscopy suggests the existence of the q-BCP architecture in the melt. The new design considerably simplifies the synthesis of polymeric chain stoppers; thus promoting the utilization of q-BCPs as smart, nanostructured materials. PMID:27276387

  5. Quasi-Block Copolymers Based on a General Polymeric Chain Stopper.

    PubMed

    Sanguramath, Rajashekharayya A; Nealey, Paul F; Shenhar, Roy

    2016-07-11

    Quasi-block copolymers (q-BCPs) are block copolymers consisting of conventional and supramolecular blocks, in which the conventional block is end-terminated by a functionality that interacts with the supramolecular monomer (a "chain stopper" functionality). A new design of q-BCPs based on a general polymeric chain stopper, which consists of polystyrene end-terminated with a sulfonate group (PS-SO3 Li), is described. Through viscosity measurements and a detailed diffusion-ordered NMR spectroscopy study, it is shown that PS-SO3 Li can effectively cap two types of model supramolecular monomers to form q-BCPs in solution. Furthermore, differential scanning calorimetry data and structural characterization of thin films by scanning force microscopy suggests the existence of the q-BCP architecture in the melt. The new design considerably simplifies the synthesis of polymeric chain stoppers; thus promoting the utilization of q-BCPs as smart, nanostructured materials.

  6. 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

  7. 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.

  8. Regular and Irregular Mixing in Hydrocarbon Block Copolymers

    NASA Astrophysics Data System (ADS)

    Register, Richard; Beckingham, Bryan

    2014-03-01

    Since hydrocarbon polymers interact through relatively simple (dispersive) interactions, one might expect them to be described by simple models of mixing energetics, such as regular mixing. However, the pioneering work of Graessley on saturated hydrocarbon polymer blends showed that while regular mixing is obeyed in some cases, both positive and negative deviations (in the magnitude of the mixing enthalpy) from regular mixing are observed in other cases. Here, we describe the mixing energetics for two series of hydrocarbon polymers wherein the interaction strengths may be continuously tuned, and which can be readily incorporated into block copolymers. Random copolymers of styrene and medium-vinyl isoprene, in which either the isoprene or both the isoprene and styrene units have been saturated, obey regular mixing over the entire composition range and for both hydrogenated derivatives. Well-defined block copolymers with arbitrarily small interblock interaction strengths can be constructed from these units, permitting the interdomain spacing to be made arbitrarily large while holding the order-disorder transition temperature constant. However, block copolymers of hydrogenated polybutadiene with such random copolymers show very strong positive deviations from regular mixing when the styrene aromaticity is preserved, and sizable negative deviations when the styrene units are saturated to vinylcyclohexane. Both of these cases can be quantitatively described by a ternary mixing model.

  9. Yield Stress Enhancement in Glassy-Polyethylene Block Copolymers

    NASA Astrophysics Data System (ADS)

    Mulhearn, William; Register, Richard

    Polyethylene (PE) has the highest annual production volume of all synthetic polymers worldwide, and is valuable across many applications due to its low cost, toughness, processability, and chemical resistance. However, PE is not well suited to certain applications due to its modest yield stress and Young's modulus (approximately 30 MPa and 1 GPa, respectively for linear, high-density PE). Irreversible deformation of PE results from dislocation of crystal stems and eventual crystal fragmentation under applied stress. The liquid-like amorphous fraction provides no useful mechanical support to the crystal fold surface in a PE homopolymer, so the only method to enhance the force required for crystal slip, and hence the yield stress, is crystal thickening via thermal treatment. An alternative route towards modifying the mechanical properties of PE involves copolymerization of a minority high-glass transition temperature block into a majority-PE block copolymer. In this work, we investigate a system of glassy/linear-PE block copolymers prepared via ring-opening metathesis polymerization of cyclopentene and substituted norbornene monomers followed by hydrogenation. We demonstrate that a large change in mechanical properties can be achieved with the addition of a short glassy block (e.g. a doubling of the yield stress and Young's modulus versus PE homopolymer with the addition of 25 percent glassy block). Furthermore, owing to the low interaction energy between PE and the substituted polynorbornene blocks employed, these high-yield PE block copolymers can exhibit single-phase melts for ease of processability.

  10. Block Copolymer Membranes for Efficient Capture of a Chemotherapy Drug

    PubMed Central

    2016-01-01

    We introduce the use of block copolymer membranes for an emerging application, “drug capture”. The polymer is incorporated in a new class of biomedical devices, referred to as ChemoFilter, which is an image-guided temporarily deployable endovascular device designed to increase the efficacy of chemotherapy-based cancer treatment. We show that block copolymer membranes consisting of functional sulfonated polystyrene end blocks and a structural polyethylene middle block (S-SES) are capable of capturing doxorubicin, a chemotherapy drug. We focus on the relationship between morphology of the membrane in the ChemoFilter device and efficacy of doxorubicin capture measured in vitro. Using small-angle X-ray scattering and cryogenic scanning transmission electron microscopy, we discovered that rapid doxorubicin capture is associated with the presence of water-rich channels in the lamellar-forming S-SES membranes in aqueous environment. PMID:27547493

  11. Hierarchical pattern formation through photo-induced disorder in block copolymer/additive composite films

    NASA Astrophysics Data System (ADS)

    Yao, Li; Watkins, James

    2013-03-01

    Segregation strength in hybrid materials can be increased through selective hydrogen bonding between organic or nanoparticle additives and one block of weakly segregated block copolymers to generate well ordered hybrid materials. Here, we report the use of enantiopure tartaric acid as the additive to dramatically improve ordering in poly(ethylene oxide-block-tert-butyl acrylate) (PEO-b-PtBA) copolymers. Phase behavior and morphologies within both bulk and thin films were studied by TEM, AFM and X-ray scattering. Suppression of PEO crystallization by the interaction between tartaric acid and the PEO block enables the formation of well ordered smooth thin films. With the addition of a photo acid generator, photo-induced disorder in PEO-b-PtBA/tartaric acid composite system can be achieved upon UV exposure to deprotect PtBA block to yield poly(acrylic acid) (PAA), which is phase-miscible with PEO. Due to the strong interaction of tartaric acid with both blocks, the system undergoes a disordering transition within seconds during a post-exposure baking. With the assistance of trace-amounts of base quencher, high resolution, hierarchical patterns of sub-micron regions of ordered and disordered domains were achieved in thin films through area-selective UV exposure using a photo-mask. Funding from Center for Hierarchical Manufacturing (CHM); Facility support from Materials Research Science and Engineering Center at UMass Amherst and Cornell High Energy Synchrotron Source

  12. Fluctuation Dynamics of Block Copolymer Vesicles

    SciTech Connect

    Falus, P.; Borthwick, M.A.; Mochrie, S.G.J.

    2010-07-13

    X-ray photon correlation spectroscopy was used to characterize the wave-vector- and temperature-dependent dynamics of spontaneous thermal fluctuations in a vesicle (L4) phase that occurs in a blend of a symmetric poly(styrene-ethylene/butylene-styrene) triblock copolymer with a polystyrene homopolymer. Measurements of the intermediate scattering function reveal stretched-exponential behavior versus time, with a stretching exponent slightly larger than 2/3. The corresponding relaxation rates show an approximate q{sup 3} dependence versus wave vector. Overall, the experimental measurements are well described by theories that treat the dynamics of independent membrane plaquettes.

  13. Directed Self-assembly of Block Copolymer with Sub-15 nm Domain Spacing Using Nanoimprinted Photoresist Templates

    NASA Astrophysics Data System (ADS)

    Sun, Zhiwei; Chen, Zhenbin; Zhang, Wenxu; Coughlin, E. Bryan; Xiao, Shuaigang; Russell, Thomas

    There has been increasing interest in preparing block copolymer thin films with ultra-small domain spacings for use as etching masks for ultra-high resolution nanolithography. One method to prepare block copolymer materials with small feature sizes is salt doping, increasing the Flory-Huggins interaction and allowing microphase separation to be maintained at lower molecular weights. Lamellae-forming P2VP- b-PS- b-P2VP block copolymer with various molecular weight was synthesized using RAFT polymerization with a dual functional chain transfer agent. Copper (II) Chloride or Gold (III) chloride was found to be selectively associated with P2VP block and increase the unfavorable interactions between PS and P2VP blocks, driving the disordered block copolymer into the ordered state. A 14 nm lamellar spacing of P2VP- b-PS- b-P2VP thin film was prepared using copper (II) Chloride doping after acetone vapor annealing on neutral brushes. Metallic nano-wire arrays were prepared after selective infiltration of platinum salt into the P2VP domain and oxygen plasma treatment. The directed self-assembly of salt doped P2VP- b-PS- b-P2VP triblock copolymer having long-rang lateral order on nanoimprinted photoresist templates with shallow trenches was also studied.

  14. Block-copolymer-induced structure formation in microemulsions

    SciTech Connect

    Hilfiker, R.; Eicke, H.F.; Steeb, C.; Hofmeier, U. )

    1991-02-07

    Transient electric birefringence measurements were performed on water/AOT (sodium bis(2-ethylhexyl) sulfosuccinate)/isooctane microemulsions with various amounts of block-copoly(oxyethylene/isoprene/oxyethylene) added. The authors could show that addition of the copolymer leads to a formation of nanodroplet (ND)-copolymer-aggregates. The contributions of NDs and aggregates to the induced birefringence could easily be separated because the NDs exhibited a negative and the aggregates a positive induced birefringence and because the time scales corresponding to the two processes were different.

  15. Formation and Characterization of Anisotropic Block Copolymer Gels

    NASA Astrophysics Data System (ADS)

    Liaw, Chya Yan; Joester, Derk; Burghardt, Wesley; Shull, Kenneth

    2012-02-01

    Cylindrical micelles formed from block copolymer solutions closely mimic biological fibers that are presumed to guide mineral formation during biosynthesis of hard tissues like bone. The goal of our work is to use acrylic block copolymers as oriented templates for studying mineral formation reactions in model systems where the structure of the underlying template is well characterized and reproducible. Self-consistent mean field theory is first applied to investigate the thermodynamically stable micellar morphologies as a function of temperature and block copolymer composition. Small-angle x-ray scattering, optical birefringence and shear rheometry are used to study the morphology development during thermal processing. Initial experiments are based on a thermally-reversible alcohol-soluble system that can be converted to an aqueous gel by hydrolysis of a poly(t-butyl methacrylate) block to a poly(methacrylic acid) block. Aligned cylindrical domains are formed in the alcohol-based system when shear is applied in an appropriate temperature regime, which is below the critical micelle temperature but above the temperature at which the relaxation time of the gels becomes too large. Processing strategies for producing the desired cylindrical morphologies are being developed that account for both thermodynamic and kinetic effects.

  16. Nonionic block copolymers assemble on the surface of protein bionanoparticle.

    PubMed

    Liu, Zhi; Gu, Jingxia; Wu, Man; Jiang, Shidong; Wu, Dayong; Wang, Qian; Niu, Zhongwei; Huang, Yong

    2012-08-21

    Efficient delivery of therapeutic proteins to a target site remains a challenge due to rapid clearance from the body. Here, we selected tobacco mosaic virus (TMV) as a model protein system to investigate the interactions between the protein and a nonionic block copolymer as a possible protecting agent for the protein. By varying the temperature, we were able to obtain core-shell structures based on hydrophobic interactions among PO blocks and noncovalent interactions between TMV and EO blocks. The protein-polymer interactions were characterized by dynamic light scattering and isothermal titration calorimetry. This study establishes principles for the possible design of clinically useful protein delivery systems.

  17. Self-Assembly of Rod-Coil Block Copolymers and Their Application in Electroluminescent Devices

    SciTech Connect

    Tao, Yuefei; Ma, Biwu; Segalman, Rachel A.

    2008-11-18

    The formation of alternating electron transporting and hole transporting 15 nm lamellae within the active layer of an organic light-emitting diode (OLED) is demonstrated to improve device performance. A new multifunctional bipolar rod-coil block copolymer containing a poly(alkoxy phenylenevinylene) (PPV) rod-shaped block as the hole transporting and emitting material and a poly(vinyloxadiazole) coil-shaped electron transporting block is synthesized. This new block copolymer is the active material of a self-assembling multicomponent electroluminescent device that can be deposited in a single step. In the thin film, grazing incidence X-ray scattering and transmission electron microscopy demonstrate that the layers form grains which are oriented bimodally: parallel and perpendicular from the anode. In this mixed orientation, the device demonstrates better performance than those with either pure PPV or a blend of the two analogous homopolymers as the active materials, i.e., higher external quantum efficiency (EQE) and brightness. This improved device performance is mainly attributed to the bipolar functionality and microphase separation of the block copolymer, which provide highly efficient hole and electron recombination at the nanodomain interfaces.

  18. Self-Assembly of Rod-Coil Block Copolymers And Their Application in Electroluminescent Devices

    SciTech Connect

    Tao, Y.; Ma, B.; Segalman, R.A.

    2009-05-26

    The formation of alternating electron transporting and hole transporting 15 nm lamellae within the active layer of an organic light-emitting diode (OLED) is demonstrated to improve device performance. A new multifunctional bipolar rod-coil block copolymer containing a poly(alkoxy phenylenevinylene) (PPV) rod-shaped block as the hole transporting and emitting material and a poly(vinyloxadiazole) coil-shaped electron transporting block is synthesized. This new block copolymer is the active material of a self-assembling multicomponent electroluminescent device that can be deposited in a single step. In the thin film, grazing incidence X-ray scattering and transmission electron microscopy demonstrate that the layers form grains which are oriented bimodally: parallel and perpendicular from the anode. In this mixed orientation, the device demonstrates better performance than those with either pure PPV or a blend of the two analogous homopolymers as the active materials, i.e., higher external quantum efficiency (EQE) and brightness. This improved device performance is mainly attributed to the bipolar functionality and microphase separation of the block copolymer, which provide highly efficient hole and electron recombination at the nanodomain interfaces.

  19. 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.

  20. Periodic nanostructures from self assembled wedge-type block-copolymers

    DOEpatents

    Xia, Yan; Sveinbjornsson, Benjamin R.; Grubbs, Robert H.; Weitekamp, Raymond; Miyake, Garret M.; Piunova, Victoria; Daeffler, Christopher Scot

    2015-06-02

    The invention provides a class of wedge-type block copolymers having a plurality of chemically different blocks, at least a portion of which incorporates a wedge group-containing block providing useful properties. For example, use of one or more wedge group-containing blocks in some block copolymers of the invention significantly inhibits chain entanglement and, thus, the present block copolymers materials provide a class of polymer materials capable of efficient molecular self-assembly to generate a range of structures, such as periodic nanostructures and microstructures. Materials of the present invention include copolymers having one or more wedge group-containing blocks, and optionally for some applications copolymers also incorporating one or more polymer side group-containing blocks. The present invention also provides useful methods of making and using wedge-type block copolymers.

  1. The influence of block copolymers on silica-filled polyisoprene

    NASA Astrophysics Data System (ADS)

    Gurovich, Daniel

    2001-10-01

    In the present work, precipitated silica, liquid polyisoprene, and poly(dimethyl siloxane-co-isoprene) block copolymer (PDMS-PI) are mixed in different formulations. The dynamic rheological properties of the resulting uncured materials are measured and used to assess filler-filler networking. In small-amplitude tests, composites containing PDMS-PI exhibit lower values of the dynamic storage modulus (G') than those observed in control samples prepared without copolymer additives. The control samples remain stable during several months of storage, while most of the samples containing low molecular weight block copolymers show evidence of an aging process. The only sample that showed no evidence of aging contained PDMS-PI of the highest molecular weight used in the study (42 kg/mol). The rheological manifestations of the aging process include a pronounced decrease in small-amplitude G' with time, accompanied by weakening amplitude dependence of both G' and G ″. These suggest a progressive reduction of filler-filler interactions, presumably caused by the development of a block copolymer layer at the filler-polymer interface. The make-up of that interfacial region is investigated by means of magic-angle spinning solid-state proton NMR experiments carried out on bound polymer fractions that survive extraction in a good solvent. Spin-spin relaxation times and the intensities of the relaxation modes associated with these characteristic times are used to identify the proportion of both PDMS and polyisoprene among the segments strongly immobilized by close contact with the silica surface and among the rest of the bound (un-extracted) interfacial layer. The changes in mechanical properties are correlated not with the overall composition of the bound polymer fraction, but with the increase in PDMS segments in close contact with the filler surface. At low block copolymer concentrations the rate of segregation of PDMS segments towards the silica surface is determined by the

  2. Fabrication of nanoporous block copolymer films using highly selective solvents and non-solvent extraction

    NASA Astrophysics Data System (ADS)

    Ye, Changhuai; Vogt, Bryan

    Nanoporous polymeric films with high porosity are necessary for some applications, such as anti-reflective coating. A simple and relatively environmental benign method is developed to fabricate nanoporous block copolymer thin film with tunable porosity up to 69% based on selective solvent swelling of the majority phase and subsequent rapid extraction with a miscible non-solvent (water). Poly(butylnorbornene)-block-poly(hydroxyhexafluoroisopropyl norbornene) (BuHFA) is used to generate these porous thin films due to its high Tg (>300 °C) and the selectivity of primary alcohols towards HFA. The porosity of these nanoporous films is highly dependent on the solvent quality for HFA. The modulus of the as-prepared nanoporous BuHFA thin films with the porosity from 0% to 69% was investigated by surface wrinkling and a scaling law of modulus versus density was obtained. These nanoporous thin films act as anti-reflective coatings and an increase in transmittance from approximately 92% to 99.1% (average for the full range of visible light) was obtained for double-side coated glass slides. This methodology is simple and highly tunable; extension to other block copolymer systems is likely possible if sufficient solubility contrast between segments exists.

  3. DNA block copolymers: functional materials for nanoscience and biomedicine.

    PubMed

    Schnitzler, Tobias; Herrmann, Andreas

    2012-09-18

    We live in a world full of synthetic materials, and the development of new technologies builds on the design and synthesis of new chemical structures, such as polymers. Synthetic macromolecules have changed the world and currently play a major role in all aspects of daily life. Due to their tailorable properties, these materials have fueled the invention of new techniques and goods, from the yogurt cup to the car seat belts. To fulfill the requirements of modern life, polymers and their composites have become increasingly complex. One strategy for altering polymer properties is to combine different polymer segments within one polymer, known as block copolymers. The microphase separation of the individual polymer components and the resulting formation of well defined nanosized domains provide a broad range of new materials with various properties. Block copolymers facilitated the development of innovative concepts in the fields of drug delivery, nanomedicine, organic electronics, and nanoscience. Block copolymers consist exclusively of organic polymers, but researchers are increasingly interested in materials that combine synthetic materials and biomacromolecules. Although many researchers have explored the combination of proteins with organic polymers, far fewer investigations have explored nucleic acid/polymer hybrids, known as DNA block copolymers (DBCs). DNA as a polymer block provides several advantages over other biopolymers. The availability of automated synthesis offers DNA segments with nucleotide precision, which facilitates the fabrication of hybrid materials with monodisperse biopolymer blocks. The directed functionalization of modified single-stranded DNA by Watson-Crick base-pairing is another key feature of DNA block copolymers. Furthermore, the appropriate selection of DNA sequence and organic polymer gives control over the material properties and their self-assembly into supramolecular structures. The introduction of a hydrophobic polymer into DBCs

  4. Magnetic alignment of block copolymer microdomains by intrinsic chain anisotropy

    SciTech Connect

    Rokhlenko, Yekaterina; Yager, Kevin G.; Gopinadhan, Manesh; Osuji, Chinedum O.; Zhang, Kai; O'Hern, Corey S.; Larson, Steven R.; Gopalan, Padma; Majewski, Pawel W.

    2015-12-18

    We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, Δχ, that drives alignment and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding Δχ ≈ 2×10–8. From field-dependent scattering data, we estimate that grains of ≈ 1.2 μm are present during alignment. Furthermore, these results demonstrate that intrinsic anisotropy is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.

  5. Magnetic alignment of block copolymer microdomains by intrinsic chain anisotropy

    DOE PAGES

    Rokhlenko, Yekaterina; Yager, Kevin G.; Gopinadhan, Manesh; Osuji, Chinedum O.; Zhang, Kai; O'Hern, Corey S.; Larson, Steven R.; Gopalan, Padma; Majewski, Pawel W.

    2015-12-18

    We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, Δχ, that drives alignment and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding Δχ ≈ 2×10–8. From field-dependent scattering data, we estimate that grains of ≈ 1.2 μm are present during alignment. Furthermore, these results demonstrate that intrinsic anisotropymore » is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.« less

  6. Magnetic Alignment of Block Copolymer Microdomains by Intrinsic Chain Anisotropy

    NASA Astrophysics Data System (ADS)

    Rokhlenko, Yekaterina; Gopinadhan, Manesh; Osuji, Chinedum O.; Zhang, Kai; O'Hern, Corey S.; Larson, Steven R.; Gopalan, Padma; Majewski, Paweł W.; Yager, Kevin G.

    2015-12-01

    We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, Δ χ , that drives alignment and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding Δ χ ≈2 ×1 0-8. From field-dependent scattering data, we estimate that grains of ≈1.2 μ m are present during alignment. These results demonstrate that intrinsic anisotropy is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.

  7. 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

  8. Proton Transport in Nanostructured Block Copolymer/Ionic Liquid Membranes

    NASA Astrophysics Data System (ADS)

    Hoarfrost, Megan; Tyagi, Madhu; Reimer, Jeffrey; Segalman, Rachel

    2011-03-01

    Nanostructured block copolymer/ionic liquid mixtures are of interest for creating membranes having high proton conductivity coupled with high thermal stability. In these mixtures, it is anticipated that nanoconfinement to block copolymer domains will affect ionic liquid proton transport properties. Using pulsed-field gradient NMR and quasi-elastic neutron scattering, this relationship has been investigated for mixtures of poly(styrene-b- 2-vinylpyridine) (S2VP) with ionic liquids composed of imidazole and bis(trifluoromethane)sulfonimide (HTFSI), where the ionic liquids selectively reside in the P2VP domains of the block copolymer. Proton mobility is highest in the neat ionic liquids when there is an excess of imidazole compared to HTFSI due to proton hopping between hydrogen-bonded imidazoles. As predicted, the amount of proton hopping can be tuned by nanoconfinement, as evidenced by the finding that a lamellar mixture of an imidazole- excess ionic liquid with S2VP has greater proton mobility than a corresponding disordered mixture of the ionic liquid with P2VP homopolymer.

  9. Stereocomplex Formation in Incompatible Racemic Chiral Polylactide Block Copolymers

    NASA Astrophysics Data System (ADS)

    Sun, Lu; Zhu, Lei

    2006-03-01

    Stereocomplexes in incompatible racemic chiral polylactide (PLA) block copolymers have not been widely studied. In this work, we synthesized PLLA and PDLA containing block copolymers by ring opening polymerization of L- and D-lactides from hydroxyl-terminated hydrophilic [poly(ethylene oxide) (PEO)] and hydrophobic [poly(ethylene-co-1,2-butylene) (PEB)] oligomers, respectively. Two samples PEO-b-PLLA (2,000-5,400) and PEB-b-PDLA (4,200-5,400) were chosen. The stereocomplexes were cast from equal molar blends of above two block copolymers in chloroform solution, followed by two different thermal treatments before stereocomplex formation; The blend was either heated to 250 C and quickly quench to 160 C or heated to 250 C for 15 min and quench to 160 C for stereocomplex crystal growth. Before the formation of stereocomplexes, lamellar and cylindrical morphologies were observed in blends for the first and second thermal treatments, respectively, as evidenced by small-angle X-ray scattering (SAXS). After complete crystal growth, the 100% stereocomplexes was confirmed by differential scanning calorimetry and wide-angle X-ray diffraction (WAXD). The morphologies of stereocomplexes grown from these two pre-existing microphases (lamellar vs. cylindrical) were studied by time-resolved SAXS and transmission electron microscopy (TEM).

  10. Electrically Tunable Soft-Solid Block Copolymer Structural Color.

    PubMed

    Park, Tae Joon; Hwang, Sun Kak; Park, Sungmin; Cho, Sung Hwan; Park, Tae Hyun; Jeong, Beomjin; Kang, Han Sol; Ryu, Du Yeol; Huh, June; Thomas, Edwin L; Park, Cheolmin

    2015-12-22

    One-dimensional photonic crystals based on the periodic stacking of two different dielectric layers have been widely studied, but the fabrication of mechanically flexible polymer structural color (SC) films, with electro-active color switching, remains challenging. Here, we demonstrate free-standing electric field tunable ionic liquid (IL) swollen block copolymer (BCP) films. Placement of a polymer/ionic liquid film-reservoir adjacent to a self-assembled poly(styrene-block-quaternized 2-vinylpyridine) (PS-b-QP2VP) copolymer SC film allowed the development of red (R), green (G), and blue (B) full-color SC block copolymer films by swelling of the QP2VP domains by the ionic liquid associated with water molecules. The IL-polymer/BCP SC film is mechanically flexible with excellent color stability over several days at ambient conditions. The selective swelling of the QP2VP domains could be controlled by both the ratio of the IL to a polymer in the gel-like IL reservoir layer and by an applied voltage in the range of -3 to +6 V using a metal/IL reservoir/SC film/IL reservoir/metal capacitor type device.

  11. Flow Controlled Solvent Vapor Annealing of Block Copolymers for Lithographic Applications

    NASA Astrophysics Data System (ADS)

    Gotrik, Kevin Willy

    Self-assembly of block copolymer thin-films may provide an inexpensive alternative to patterning lithographic features below the resolution limits of traditional optical methods. Block copolymers (BCPs) are polymers made of two or more distinct monomer /block units that are covalently bonded. Due to their differences in surface energy, the different blocks tend to phase segregate like oil and water; but because of the covalent linkage, this segregation is practically limited to size scales ranging from only a few nm to ≈ 100 nm. A thin film of a BCP can be used in much the same way as a photoresist in the lithographic process, whereas a desired pattern morphology can be obtained by etching one block away and leaving behind a self-assembled hard mask for the underlying substrate. After a thin film of BCP is coated onto a given substrate, the BCP must be given an annealing step, where the disordered entangled polymer networks can be allowed to diffuse and equilibrate into lower free energy configurations which result in periodic patterns of micelles with different morphologies such as spheres, in/out of plane cylinders, etc. This work explored the technique of solvent vapor annealing, where organic solvents were allowed to interact with BCP thin films to facilitate annealing and act as surrogates for the different BCP polymer blocks. This allowed for a wide range of control over the BCP self-assembly (morphology, periodicity, etc.) for a given molecular weight BCP. Additionally, by adding heat at critical times during the self-assembly, time scales for solvent vapor enhanced self-assembly could be reduced from hours to seconds making the prospects for this technology to become industrially applicable more promising. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs mit.edu)

  12. Effect of water uptake on morphology of polymerized ionic liquid block copolymers and random copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Tsen-Shan; Ye, Yuesheng; Elabd, Yossef; Winey, Karen

    2012-02-01

    Dynamic studies of polymer morphology probe how the physical properties of polymerized ionic liquids are affected by the environment, such as temperature or moisture. For a series of poly(methyl methacrylate-b-1-[2-(methacryloyloxy)ethyl]-3-Butylimidazolium X^-) block and random copolymers with hydrophilic counterions (X^- = Br^-, HCO3^-, OH^-), the introduction of water vapor to the system can swell the ionic liquid block, causing enlarged hydrophilic domains and swollen channels for ion conduction. This expected expansion of ionic liquid domains in humid environments can be used to intelligently design these copolymers for use in technological applications. The effect of water vapor exposure in these imidazolium-based acrylate polymers is studied by small-angle X-ray scattering. These morphology results will be discussed alongside complementary studies of water uptake and ion conductivity.

  13. High χ block copolymers based on chemical modification of poly(t-butyl acrylate) containing block copolymers

    NASA Astrophysics Data System (ADS)

    Park, Sungmin; Jo, Seongjun; Lee, Yonghoon; Ryu, Chang Y.; Ryu, Du Yeol; Chun, Jun Sung

    2016-03-01

    We report the synthesis and characterization of novel block copolymer (BCP) materials for the directed self-assembly (DSA) nanolithography applications. Specifically, the poly(t-butyl acrylate) (PtBA) block in the styrenic block copolymers have been chemically modified to a fluorinated block for the enhancement of the BCP χ-parameters. dPSb- PtBA had been first synthesized by anionic polymerization to prepare a well-defined BCP precursor with narrow polydispersity for the fluorination of PtBA block. Then, the precursor BCP was chemically modified by transalcoholysis of the PtBA-block with 2,2,2-trifluoroethanol. This strategy offers the advantage of flexibility and controllability to tailor the χ-parameter, while maintaining the narrow molecular weight distribution of the BCP materials for the advanced lithography applications. The transmission electron microscopy/small angle x-ray scattering (TEM/SAXS) characterization results of the modified BCP consisting of poly(fluoroalkylate) and PS supported the development of highly ordered lamellar domains in bulk.

  14. 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

  15. Biodegradable PELA block copolymers: in vitro degradation and tissue reaction.

    PubMed

    Younes, H; Nataf, P R; Cohn, D; Appelbaum, Y J; Pizov, G; Uretzky, G

    1988-01-01

    Degradation of, and tissue reaction elicited by a series of polyethylene oxide (PEO)/polylactic acid (PLA) PELA block copolymers were studied in vitro and in vivo. In particular, the effect of pH, temperature and enzymatic activity was addressed. The mass loss was faster, the more basic the media, while, expectedly, PELA copolymers degraded faster with the higher temperature. The addition of an enzyme (carboxylic ester hydrolase) had no effect. The degradation process strongly affected the mechanical properties of the materials under investigation, the elongation at break dropping drastically after two days of degradation. After seven days, only gross observation of the extensively degraded samples was possible. The in vivo studies compared the tissue reaction elicited by various PELA copolymers to that evoked by PLA. Evaluation of tissue reaction observed with a PELA sample after sterilization with gamma radiation showed acute inflammation with considerable dispersion of the material, 12 days after implantation. The granulomatous reaction observed with PELA copolymers after ethylene oxide sterilization was identical to the reaction observed with PLA. PMID:3064826

  16. Contrast enhanced diffusion NMR: quantifying impurities in block copolymers for DSA

    NASA Astrophysics Data System (ADS)

    Wojtecki, Rudy; Porath, Ellie; Vora, Ankit; Nelson, Alshakim; Sanders, Daniel

    2016-03-01

    Block-copolymers (BCPs) offer the potential to meet the demands of next generation lithographic materials as they can self-assemble into scalable and tailorable nanometer scale patterns. In order for these materials to find wide spread adoption many challenges remain, including reproducible thin film morphology, for which the purity of block copolymers is critical. One of the sources of impurities are reaction conditions used to synthesize block copolymers that may result in the formation of homopolymer as a side product, which can impact the quality and the morphology of self-assembled features. Detection and characterization of these homopolymer impurities can be challenging by traditional methods of polymer characterization. We will discuss an alternate NMR-based method for the detection of homopolymer impurities in block copolymers - contrast enhanced diffusion ordered spectroscopy (CEDOSY). This experimental technique measures the diffusion coefficient of polymeric materials in the solution allowing for the `virtual' or spectroscopic separation of BCPs that contain homopolymer impurities. Furthermore, the contrast between the diffusion coefficient of mixtures containing BCPs and homopolymer impurities can be enhanced by taking advantage of the chemical mismatch of the two blocks to effectively increase the size of the BCP (and diffusion coefficient) through the formation of micelles using a cosolvent, while the size and diffusion coefficient of homopolymer impurities remain unchanged. This enables the spectroscopic separation of even small amounts of homopolymer impurities that are similar in size to BCPs. Herein, we present the results using the CEDOSY technique with both first generation BCP system, poly(styrene)-b-poly(methyl methacrylate), as well as a second generation high-χ system.

  17. Combinatorial Block Copolymer Ordering on Tunable Rough Substrates

    SciTech Connect

    Kulkarni, Manish M.; Yager, Kevin G.; Sharma, Ashutosh; Karim, Alamgir

    2012-10-25

    Morphology control of block copolymer (BCP) thin films through substrate interaction via controlled roughness parameters is of significant interest for numerous high-tech applications ranging from solar cells to high-density storage media. While effects of substrate surface energy (SE) and roughness (R) on BCP morphology have been individually investigated, their synergistic effects have not been explored in any systematic manner. Interestingly, orientation response of BCP to changes in SE can be similar to what can be accomplished with variations in R. Here we present a novel approach for orienting lamellar BCP films of poly(styrene)-block-poly(methyl methacrylate) (PS-PMMA) on spin-coated xerogel (a dried gel of silica nanoparticle network) substrate with simultaneously tunable surface energy, {gamma}{sub s} {approx} 29-53 mJ/m{sup 2}, by UVO exposure and roughness, R{sub rms} {approx} 0.5-30 nm, by sol-gel processing steps of regulating the catalyst concentration and sol aging time. As in previous BCP orientation studies on 20 nm diameter monodisperse silica nanoparticle coated surface, we find a similar but broadened oscillatory BCP orientation behavior with film thickness due to the random rather than periodic rough surfaces. We also find that higher random roughness amplitude is not the necessary criteria for obtaining a vertical orientation of BCP lamellae. Rather, a high surface fractal dimension (D{sub f} > 2.4) of the rough substrate in conjunction with an optimal substrate surface energy {gamma}{sub s} {approx} 29 mJ/m{sup 2} results in 100% vertically oriented lamellar microdomains. The AFM measured film surface microstructure correlates well with the internal 3D BCP film structure probed by grazing incidence small-angle X-ray scattering (GISAXS) and rotational small-angle neutron scattering (SANS). In contrast to tunable self-assembled monolayer (SAM)-coated substrates, the xerogel films are very durable and retain their chemical properties over period

  18. 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

  19. Long-Range Ordering of Block Copolymers on Well-Controlled Patterned Substrates

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Eun; Kim, Nam-Kyun; Park, Jina; Lee, Donghyun

    2015-03-01

    In this study, we achieved long-range ordering of block copolymers (BCPs) by combining solvent-annealing process and well-controlled patterned substrates. Nano-lines of poly(tetrafluoro ethylene) (PTFE) were firstly fabricated in large area as a PTFE bar was rubbed on Si substrates at 340 °C. The amplitude and pitch distance of PTFE nanolines were around 17 nm and 150 nm, respectively. Then, asymmetric polystyrene-block-poly(2-vinylpyridine) copolymers (PS- b-P2VP) were subsequently spin-coated on the patterned substrates after a thin layer of poly(vinyl alcohol) (PVA) was prepared on the PTFE patterned substrates to enhance the wettability of BCP thin films. As BCP thin films were solvent-annealed in vapor of organic solvents, highly ordered BCP nanostructures oriented either parallel or perpendicular to the surface were generated in large area. In addition, the nanopatterns were successfully transferred to the underlying PVA layer or Si substrate by dry etching. Thus, the resulting nanopatterns were utilized as templates to synthesize inorganic nanofeatures. The ordering behavior of BCP thin films on the patterned substrates was characterized by using AFM, SEM and GI-SAXS.

  20. 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

  1. Metal Nanoparticle/Block Copolymer Composite Assembly and Disassembly.

    PubMed

    Li, Zihui; Sai, Hiroaki; Warren, Scott C; Kamperman, Marleen; Arora, Hitesh; Gruner, Sol M; Wiesner, Ulrich

    2009-01-01

    Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-3-mercaptopropyl-N-3-methylammonium chloride as the ligand, which provided high solubility of NPs in various solvents as well as high affinity to PDMAEMA. From NP synthesis, existence of sub-1 nm Pt NPs was confirmed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. Estimations of the Pt NP ligand head group density based on HAADF-STEM images and thermogravimetric analysis (TGA) data yielded results comparable to what has been found for alkanethiol self-assembled monolayers (SAMs) on flat Pt {111} surfaces. Changing the volume fraction of Pt NPs in block copolymer-NP composites yielded hybrids with spherical micellar, wormlike micellar, lamellar and inverse hexagonal morphologies. Disassembly of hybrids with spherical, wormlike micellar, and lamellar morphologies generated isolated metal-NP based nano-spheres, cylinders and sheets, respectively. Results suggest the existence of powerful design criteria for the formation of metal-based nanostructures from designer blocked macromolecules.

  2. Metal Nanoparticle/Block Copolymer Composite Assembly and Disassembly

    PubMed Central

    Li, Zihui; Sai, Hiroaki; Warren, Scott C.; Kamperman, Marleen; Arora, Hitesh; Gruner, Sol M.; Wiesner, Ulrich

    2010-01-01

    Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-3-mercaptopropyl-N-3-methylammonium chloride as the ligand, which provided high solubility of NPs in various solvents as well as high affinity to PDMAEMA. From NP synthesis, existence of sub-1 nm Pt NPs was confirmed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. Estimations of the Pt NP ligand head group density based on HAADF-STEM images and thermogravimetric analysis (TGA) data yielded results comparable to what has been found for alkanethiol self-assembled monolayers (SAMs) on flat Pt {111} surfaces. Changing the volume fraction of Pt NPs in block copolymer-NP composites yielded hybrids with spherical micellar, wormlike micellar, lamellar and inverse hexagonal morphologies. Disassembly of hybrids with spherical, wormlike micellar, and lamellar morphologies generated isolated metal-NP based nano-spheres, cylinders and sheets, respectively. Results suggest the existence of powerful design criteria for the formation of metal-based nanostructures from designer blocked macromolecules. PMID:21103025

  3. Sequential Block Copolymer Self-Assemblies Controlled by Metal-Ligand Stoichiometry.

    PubMed

    Yin, Liyuan; Wu, Hongwei; Zhu, Mingjie; Zou, Qi; Yan, Qiang; Zhu, Liangliang

    2016-06-28

    While numerous efforts have been devoted to developing easy-to-use probes based on block copolymers for detecting analytes due to their advantages in the fields of self-assembly and sensing, a progressive response on block copolymers in response to a continuing chemical event is not readily achievable. Herein, we report the self-assembly of a 4-piperazinyl-1,8-naphthalimide based functional block copolymer (PS-b-PN), whose self-assembly and photophysics can be controlled by the stoichiometry-dependent metal-ligand interaction upon the side chain. The work takes advantages of (1) stoichiometry-controlled coordination-structural transformation of the piperazinyl moiety on PS-b-PN toward Fe(3+) ions, thereby resulting in a shrinkage-expansion conversion of the self-assembled nanostructures in solution as well as in thin film, and (2) stoichiometry-controlled competition between photoinduced electron transfer and spin-orbital coupling process upon naphthalimide fluorophore leading to a boost-decline emission change of the system. Except Fe(3+) ions, such a stoichiometry-dependent returnable property cannot be observed in the presence of other transition ions. The strategy for realizing the dual-channel sequential response on the basis of the progressively alterable nanomorphologies and emissions might provide deeper insights for the further development of advanced polymeric sensors.

  4. Sequential Block Copolymer Self-Assemblies Controlled by Metal-Ligand Stoichiometry.

    PubMed

    Yin, Liyuan; Wu, Hongwei; Zhu, Mingjie; Zou, Qi; Yan, Qiang; Zhu, Liangliang

    2016-06-28

    While numerous efforts have been devoted to developing easy-to-use probes based on block copolymers for detecting analytes due to their advantages in the fields of self-assembly and sensing, a progressive response on block copolymers in response to a continuing chemical event is not readily achievable. Herein, we report the self-assembly of a 4-piperazinyl-1,8-naphthalimide based functional block copolymer (PS-b-PN), whose self-assembly and photophysics can be controlled by the stoichiometry-dependent metal-ligand interaction upon the side chain. The work takes advantages of (1) stoichiometry-controlled coordination-structural transformation of the piperazinyl moiety on PS-b-PN toward Fe(3+) ions, thereby resulting in a shrinkage-expansion conversion of the self-assembled nanostructures in solution as well as in thin film, and (2) stoichiometry-controlled competition between photoinduced electron transfer and spin-orbital coupling process upon naphthalimide fluorophore leading to a boost-decline emission change of the system. Except Fe(3+) ions, such a stoichiometry-dependent returnable property cannot be observed in the presence of other transition ions. The strategy for realizing the dual-channel sequential response on the basis of the progressively alterable nanomorphologies and emissions might provide deeper insights for the further development of advanced polymeric sensors. PMID:27275516

  5. Thermally-induced transition of lamellae orientation in block-copolymer films on ‘neutral’ nanoparticle-coated substrates

    DOE PAGES

    Yager, Kevin G.; Forrey, Christopher; Singh, Gurpreet; Satija, Sushil K.; Page, Kirt A.; Patton, Derek L.; Jones, Ronald L.; Karin, Alamgir; Douglas, Jack F.

    2015-06-01

    Block-copolymer orientation in thin films is controlled by the complex balance between interfacial free energies, including the inter-block segregation strength, the surface tensions of the blocks, and the relative substrate interactions. While block-copolymer lamellae orient horizontally when there is any preferential affinity of one block for the substrate, we recently described how nanoparticle-roughened substrates can be used to modify substrate interactions. We demonstrate how such ‘neutral’ substrates can be combined with control of annealing temperature to generate vertical lamellae orientations throughout a sample, at all thicknesses. We observe an orientational transition from vertical to horizontal lamellae upon heating, as confirmedmore » using a combination of atomic force microscopy (AFM), neutron reflectometry (NR) and rotational small-angle neutron scattering (RSANS). Using molecular dynamics (MD) simulations, we identify substrate-localized distortions to the lamellar morphology as the physical basis of the novel behavior. In particular, under strong segregation conditions, bending of horizontal lamellae induce a large energetic cost. At higher temperatures, the energetic cost of conformal deformations of lamellae over the rough substrate is reduced, returning lamellae to the typical horizontal orientation. Thus, we find that both surface interactions and temperature play a crucial role in dictating block-copolymer lamellae orientation. As a result, our combined experimental and simulation findings suggest that controlling substrate roughness should provide a useful and robust platform for controlling block-copolymer orientation in applications of these materials.« less

  6. Thermally-induced transition of lamellae orientation in block-copolymer films on ‘neutral’ nanoparticle-coated substrates

    SciTech Connect

    Yager, Kevin G.; Forrey, Christopher; Singh, Gurpreet; Satija, Sushil K.; Page, Kirt A.; Patton, Derek L.; Jones, Ronald L.; Karin, Alamgir; Douglas, Jack F.

    2015-06-01

    Block-copolymer orientation in thin films is controlled by the complex balance between interfacial free energies, including the inter-block segregation strength, the surface tensions of the blocks, and the relative substrate interactions. While block-copolymer lamellae orient horizontally when there is any preferential affinity of one block for the substrate, we recently described how nanoparticle-roughened substrates can be used to modify substrate interactions. We demonstrate how such ‘neutral’ substrates can be combined with control of annealing temperature to generate vertical lamellae orientations throughout a sample, at all thicknesses. We observe an orientational transition from vertical to horizontal lamellae upon heating, as confirmed using a combination of atomic force microscopy (AFM), neutron reflectometry (NR) and rotational small-angle neutron scattering (RSANS). Using molecular dynamics (MD) simulations, we identify substrate-localized distortions to the lamellar morphology as the physical basis of the novel behavior. In particular, under strong segregation conditions, bending of horizontal lamellae induce a large energetic cost. At higher temperatures, the energetic cost of conformal deformations of lamellae over the rough substrate is reduced, returning lamellae to the typical horizontal orientation. Thus, we find that both surface interactions and temperature play a crucial role in dictating block-copolymer lamellae orientation. As a result, our combined experimental and simulation findings suggest that controlling substrate roughness should provide a useful and robust platform for controlling block-copolymer orientation in applications of these materials.

  7. Complex microstructures of ABC triblock copolymer thin films directed by polymer brushes based on self-consistent field theory.

    PubMed

    Jiang, Zhibin; Xu, Chang; Qiu, Yu Dong; Wang, Xiaoliang; Zhou, Dongshan; Xue, Gi

    2014-01-01

    The morphology and the phase diagram of ABC triblock copolymer thin film directed by polymer brushes are investigated by the self-consistent field theory in three dimensions. The polymer brushes coated on the substrate can be used as a good soft template to tailor the morphology of the block copolymer thin films compared with those on the hard substrates. The polymer brush is identical with the middle block B. By continuously changing the composition of the block copolymer, the phase diagrams are constructed for three cases with the fixed film thickness and the brush density: identical interaction parameters, frustrated and non-frustrated cases. Some ordered complex morphologies are observed: parallel lamellar phase with hexagonally packed pores at surfaces (LAM3 (ll) -HFs), perpendicular lamellar phase with cylinders at the interface (LAM(⊥)-CI), and perpendicular hexagonally packed cylinders phase with rings at the interface (C2 (⊥)-RI). A desired direction (perpendicular or parallel to the coated surfaces) of lamellar phases or cylindrical phases can be obtained by varying the composition and the interactions between different blocks. The phase diagram of ABC triblock copolymer thin film wetted between the polymer brush-coated surfaces is very useful in designing the directed pattern of ABC triblock copolymer thin film. PMID:25114650

  8. John H. Dillon Medal Lecture: Molecular Heterogeneity in Block Copolymer Self-Assembly

    NASA Astrophysics Data System (ADS)

    Mahanthappa, Mahesh

    2013-03-01

    Narrow molecular weight dispersity in block copolymers has long been considered necessary for well-defined, periodic structure formation, by analogy to various crystallization processes. Consequently, much attention has focused on narrow dispersity copolymers derived from controlled and ``living'' polymerization techniques. However, these methods restrict the palette of functional monomers amenable to block copolymerization, thus constraining the physical and chemical properties of the resulting materials. New polymer syntheses enable access to a ``Pandora's Box'' of block copolymers with unusual chemical functionalities and useful physical properties, at the expense of introducing significant segmental dispersities into the resulting copolymers. The development and use of these functional materials requires basic understanding of the physical implications of continuous segmental dispersity on block copolymer phase behavior. Our work aims to understand the physical principles underlying polydisperse ABA-type triblock copolymer self-assembly, in order to transform segmental dispersity into a predictable and useful tool for manipulating block copolymer morphology. We have systematically demonstrated that mid-segment dispersity in ABA triblock copolymers does not preclude the formation of classical, structurally periodic, microphase separated morphologies. Mid-segment dispersity instead shifts the locations of the composition-dependent phase windows, dilates the microdomains, and unexpectedly stabilizes the microphase separated ABA triblock copolymer melts. Studies of three different polydisperse copolymer systems have provided general insights into the consequences of chain length heterogeneity on block copolymer self-assembly.

  9. Effect of Sequence Features on Assembly of Spider Silk Block Copolymers

    PubMed Central

    Tokareva, Olena S.; Lin, Shangchao; Jacobsen, Matthew M.; Huang, Wenwen; Rizzo, Daniel; Li, David; Simon, Marc; Staii, Cristian; Cebe, Peggy; Wong, Joyce Y.; Buehler, Markus J.; Kaplan, David L.

    2014-01-01

    Bioengineered spider silk block copolymers were studied to understand the effect of protein chain length and sequence chemistry on the formation of secondary structure and materials assembly. Using a combination of in vitro protein design and assembly studies, we demonstrate that silk block copolymers possessing multiple repetitive units self-assemble into lamellar microstructures. Additionally, the study provides insights into the assembly behavior of spider silk block copolymers in concentrated salt solutions. PMID:24613991

  10. Periodic nanoscale patterning of polyelectrolytes over square centimeter areas using block copolymer templates.

    PubMed

    Oded, Meirav; Kelly, Stephen T; Gilles, Mary K; Müller, Axel H E; Shenhar, Roy

    2016-05-18

    Nano-patterned materials are beneficial for applications such as solar cells, opto-electronics, and sensing owing to their periodic structure and high interfacial area. Here, we present a non-lithographic approach for assembling polyelectrolytes into periodic nanoscale patterns over cm(2)-scale areas. Chemically modified block copolymer thin films featuring alternating charged and neutral domains are used as patterned substrates for electrostatic self-assembly. In-depth characterization of the deposition process using spectroscopy and microscopy techniques, including the state-of-the-art scanning transmission X-ray microscopy (STXM), reveals both the selective deposition of the polyelectrolyte on the charged copolymer domains as well as gradual changes in the film topography that arise from further penetration of the solvent molecules and possibly also the polyelectrolyte into these domains. Our results demonstrate the feasibility of creating nano-patterned polyelectrolyte layers, which opens up new opportunities for structured functional coating fabrication.

  11. Cross-linked block copolymer templated assembly of nanoparticle arrays with high density and position selectivity

    NASA Astrophysics Data System (ADS)

    Liu, Zhicheng; Chang, Tongxin; Huang, Haiying; Bai, Lu

    2016-10-01

    Patterning ordered nanoparticle arrays is crucial for the fascinating collective properties of nanoparticles. Block copolymer template provides us a platform for the simple and efficient assembly of nanoparticle arrays. In this work, cylinder-forming poly(styrene-block-2-vinylpyridine) thin film was firstly plasma-etched to expose poly(2-vinylpyridine) cylinders. Then the templates were cross-linked by small molecules so as to access gold nanoparticle arrays with both high density and excellent position selectivity. The cross-linking process significantly restrains the unfavorable surface reconstruction of the thin film. It is demonstrated that the quality of the nanoparticle array was affected by the degree of the cross-linking and the immersion time in nanoparticle solution. The highly ordered gold nanoparticle arrays are promising in several fields such as optics and surface enhanced Raman scattering (SERS).

  12. Gamma radiation induced degradation in PE-PP block copolymer

    SciTech Connect

    Ravi, H. R.; Sreepad, H. R.; Ahmed, Khaleel; Govindaiah, T. N.

    2012-06-05

    In the present investigation, effect of gamma irradiation on the PP-PE block copolymer has been studied. The polymer has been subjected to gamma irradiation from 100 to 500 Mrad dosages. Characterization of the polymer using XRD and FTIR was done both before irradiation and after irradiation in each step. Effect of irradiation on the electrical properties of the material has also been studied. FTIR study shows that the sample loses C - C stretching mode of vibration but gains C=C stretching mode of vibration after irradiation. Present investigation clearly indicates that though the electrical conductivity increases in the material, it undergoes degradation and shows brittleness due to irradiation.

  13. Surfaces of Fluorinated Pyridinium Block Copolymers with Enhanced Antibacterial Activity

    SciTech Connect

    Krishnan,S.; Ward, R.; Hexemer, A.; Sohn, K.; Lee, K.; Angert, E.; Fischer, D.; Kramer, E.; Ober, C.

    2006-01-01

    Polystyrene-b-poly(4-vinylpyridine) copolymers were quaternized with 1-bromohexane and 6-perfluorooctyl-1-bromohexane. Surfaces prepared from these polymers were characterized by contact angle measurements, near-edge X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy. The fluorinated pyridinium surfaces showed enhanced antibacterial activity compared to their nonfluorinated counterparts. Even a polymer with a relatively low molecular weight pyridinium block showed high antimicrobial activity. The bactericidal effect was found to be related to the molecular composition and organization in the top 2-3 nm of the surface and increased with increasing hydrophilicity and pyridinium concentration of the surface.

  14. 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.

  15. Gamma radiation induced degradation in PE-PP block copolymer

    NASA Astrophysics Data System (ADS)

    Ravi, H. R.; Sreepad, H. R.; Ahmed, Khaleel; Govindaiah, T. N.

    2012-06-01

    In the present investigation, effect of gamma irradiation on the PP-PE block copolymer has been studied. The polymer has been subjected to gamma irradiation from 100 to 500 Mrad dosages. Characterization of the polymer using XRD and FTIR was done both before irradiation and after irradiation in each step. Effect of irradiation on the electrical properties of the material has also been studied. FTIR study shows that the sample loses C - C stretching mode of vibration but gains C=C stretching mode of vibration after irradiation. Present investigation clearly indicates that though the electrical conductivity increases in the material, it undergoes degradation and shows brittleness due to irradiation.

  16. 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.

  17. (Electro)Mechanical Properties of Olefinic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Spontak, Richard

    2014-03-01

    Conventional styrenic triblock copolymers (SBCs) swollen with a midblock-selective oil have been previously shown to exhibit excellent electromechanical properties as dielectric elastomers. In this class of electroactive polymers, compliant electrodes applied as active areas to opposing surfaces of an elastomer attract each other, and thus compress the elastomer due to the onset of a Maxwell stress, upon application of an external electric field. This isochoric process is accompanied by an increase in lateral area, which yields the electroactuation strain (measuring beyond 300% in SBC systems). Performance parameters such as the Maxwell stress, transverse strain, dielectric breakdown, energy density and electromechanical efficiency are determined directly from the applied electric field and resulting electroactuation strain. In this study, the same principle used to evaluate SBC systems is extended to olefinic block copolymers (OBCs), which can be described as randomly-coupled multiblock copolymers that consist of crystallizable polyethylene hard segments and rubbery poly(ethylene-co-octene) soft segments. Considerations governing the development of a methodology to fabricate electroresponsive OBC systems are first discussed for several OBCs differing in composition and bulk properties. Evidence of electroactuation in selectively-solvated OBC systems is presented and performance metrics measured therefrom are quantitatively compared with dielectric elastomers derived from SBC and related materials.

  18. 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.

  19. Melt-Miscibility in Block Copolymers Containing Polyethylene and Substituted Polynorbornene Blocks

    NASA Astrophysics Data System (ADS)

    Mulhearn, William; Register, Richard

    2015-03-01

    Block copolymers containing a crystallizable block, such as polyethylene (PE), and a high-Tg amorphous block are potentially interesting materials since the rigid glassy block can mitigate the poor yield strength of the PE crystals. However, chemical incompatibility between blocks, quantified by the Flory interaction parameter χ or the interaction energy density X, drives microphase separation at low temperatures or high chain lengths. To prepare a high molecular weight PE-containing block copolymer that is easy to process (i.e. with a disordered low-viscosity melt) it is necessary to select amorphous blocks that have low mixing energies with PE. The only suitable polymers currently known are chemically similar to PE and therefore have similarly low glass transition temperatures. We investigate a series of both low- and high-Tg polymers based on substituted norbornene monomers, polymerized via ring-opening metathesis polymerization (ROMP). Several ROMP polymers of this type exhibit high Tg and low interaction energy against PE. For example, hydrogenated poly(cyclohexyl norbornene) has Tg = 88 oC and has interaction energy density XhPCyN - PE ~ 0.8 MPa, comparable to the interaction energy density between PE and hydrogenated polyisoprene. The miscibility of an amorphous block can be further tuned by statistical copolymerization of norbornene units with aromatic side-groups (high Hildebrand solubility parameter) and norbornene units with aliphatic side-groups (low Hildebrand solubility parameter).

  20. Silver-enhanced block copolymer membranes with biocidal activity.

    PubMed

    Madhavan, Poornima; Hong, Pei-Ying; Sougrat, Rachid; Nunes, Suzana P

    2014-01-01

    Silver nanoparticles were deposited on the surface and pore walls of block copolymer membranes with highly ordered pore structure. Pyridine blocks constitute the pore surfaces, complexing silver ions and promoting a homogeneous distribution. Nanoparticles were then formed by reduction with sodium borohydride. The morphology varied with the preparation conditions (pH and silver ion concentration), as confirmed by field emission scanning and transmission electron microscopy. Silver has a strong biocide activity, which for membranes can bring the advantage of minimizing the growth of bacteria and formation of biofilm. The membranes with nanoparticles prepared under different pH values and ion concentrations were incubated with Pseudomonas aeruginosa and compared with the control. The strongest biocidal activity was achieved with membranes containing membranes prepared under pH 9. Under these conditions, the best distribution with small particle size was observed by microscopy.

  1. Transport of Water in Semicrystalline Block Copolymer Membranes

    NASA Astrophysics Data System (ADS)

    Hallinan, Daniel; Oparaji, Onyekachi

    Poly(styrene)-block-poly(ethylene oxide) (PS- b-PEO) is a semicrystalline block copolymer (BCP) with interesting properties. It is mechanically tough, amphiphilic, and has a polar phase. The mechanical toughness is due to the crystallinity of PEO and the high glass transition temperature of PS, as well as the morphological structure of the BCP. The polymer has high CO2, water, and salt solubility that derive from the polar PEO component. Potential applications include CO2 separation, water purification, and lithium air batteries. In all of the aforementioned applications, water transport is an important parameter. The presence of water can also affect thermal and mechanical properties. Water transport and thermal and mechanical properties of a lamellar PS- b-PEO copolymer have been measured as a function of water activity. Water transport can be affected by the heterogeneous nature of a semicrystalline BCP. Therefore, Fourier transform infrared - attenuated total reflectance (FTIR-ATR) spectroscopy has been employed, because water transport and polymer swelling can be measured simultaneously. The effect of BCP structure on transport has been investigated by comparing water transport in PS- b-PEO to a PEO homopolymer. The crystalline content of the PEO and the presence of glassy PS lamellae will be used to explain the transport results.

  2. 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

  3. Single Helix to Double Gyroid in Chiral Block Copolymers

    SciTech Connect

    C Chen; H Hsueh; Y Chiang; R Ho; S Akasaka; H Hasegawa

    2011-12-31

    An order-order phase transition of chiral block copolymers (BCPs*) from single helix to double gyroid (H* {yields} G) through a nucleation and growth process was demonstrated. The H* and G phases can be obtained by solution casting from fast and slow solvent evaporation, respectively, suggesting that the H* phase is a metastable phase. Consequently, the coexistence of H* and G phases can be found in the solution-cast samples from intermediate solvent evaporation. To truly examine the transition mechanism of the H* {yields} G, electron tomography was carried out to directly visualize the morphological evolution in real space, in particular, the transition zone at interface. Unlike the mechanisms for the transitions of block copolymers (BCPs) by considering the interdomain spacing matching, a significant mismatch in the lattices for the H* {yields} G was found. Consequently, the transition may require an adjustment on the geometric dimensions to justify corresponding lattice mismatch. As a result, the morphological observations from electron tomography offer new insights into BCP phase transitions.

  4. Synthesis and antibacterial activity of nisin-containing block copolymers.

    PubMed

    Joshi, Pranav R; McGuire, Joseph; Neff, Jennifer A

    2009-10-01

    Nisin, an antibacterial peptide proven to be an effective inhibitor of Gram-positive bacteria, was incorporated into novel block copolymer constructs and tested for retained antibacterial activity. Covalent coupling was achieved by chemical modification of the N-terminal isoleucine to introduce a thiol group. Thiolated-nisin derivatives were then linked to poly[ethylene oxide]-poly[propylene oxide]-poly[ethylene oxide] (PEO-PPO-PEO) triblocks that had been end-activated such that terminal hydroxyl groups of the PEO chains were replaced with pyridyl disulfide moieties. The nisin-containing block copolymers were separated from free nisin by dialysis and showed antimicrobial activity against the Gram-positive indicator strain Pediococcus pentosaceus. The contribution to antimicrobial activity from nisin that was covalently linked was not distinguished from the contribution of nisin that had associated with the PEO-PPO-PEO triblocks through noncovalent interactions. However, nisin that was covalently linked showed activity upon reduction of the disulfide bond and release from the end-activated PEO. PMID:19358262

  5. 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.

  6. Morphological evolution of lamellar forming polystyrene-block-poly(4-vinylpyridine) copolymers under solvent annealing.

    PubMed

    Ghoshal, Tandra; Chaudhari, Atul; Cummins, Cian; Shaw, Matthew T; Holmes, Justin D; Morris, Michael A

    2016-06-28

    In this work, we are reporting a very simple and efficient method to form lamellar structures of symmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymer thin films with vertically (to the surface plane) orientated lamellae using a solvent annealing approach. The methodology does not require any brush chemistry to engineer a neutral surface and it is the block neutral nature of the film-solvent vapour interface that defines the orientation of the lamellae. The microphase separated structure of two different molecular weight lamellar forming PS-block-P4VP copolymers formed under solvent vapour annealing was monitored using atomic force microscopy (AFM) so as to understand the morphological changes of the films upon different solvent exposure. In particular, the morphology changes from micellar structures to well-defined microphase separated arrangements. The choice of solvent/s (single and dual solvent exposure) and the solvent annealing conditions (temperature, time etc.) has important effects on structural transitions of the films and it was found that a block neutral solvent was required to realize vertically aligned P4VP lamellae. The results of the structural variation of the phase separated nanostructured films through the exposure to ethanol are also described.

  7. Morphological evolution of lamellar forming polystyrene-block-poly(4-vinylpyridine) copolymers under solvent annealing.

    PubMed

    Ghoshal, Tandra; Chaudhari, Atul; Cummins, Cian; Shaw, Matthew T; Holmes, Justin D; Morris, Michael A

    2016-06-28

    In this work, we are reporting a very simple and efficient method to form lamellar structures of symmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymer thin films with vertically (to the surface plane) orientated lamellae using a solvent annealing approach. The methodology does not require any brush chemistry to engineer a neutral surface and it is the block neutral nature of the film-solvent vapour interface that defines the orientation of the lamellae. The microphase separated structure of two different molecular weight lamellar forming PS-block-P4VP copolymers formed under solvent vapour annealing was monitored using atomic force microscopy (AFM) so as to understand the morphological changes of the films upon different solvent exposure. In particular, the morphology changes from micellar structures to well-defined microphase separated arrangements. The choice of solvent/s (single and dual solvent exposure) and the solvent annealing conditions (temperature, time etc.) has important effects on structural transitions of the films and it was found that a block neutral solvent was required to realize vertically aligned P4VP lamellae. The results of the structural variation of the phase separated nanostructured films through the exposure to ethanol are also described. PMID:27240904

  8. A generalized method for alignment of block copolymer films: solvent vapor annealing with soft shear.

    PubMed

    Qiang, Zhe; Zhang, Yuanzhong; Groff, Jesse A; Cavicchi, Kevin A; Vogt, Bryan D

    2014-08-28

    One of the key issues associated with the utilization of block copolymer (BCP) thin films in nanoscience and nanotechnology is control of their alignment and orientation over macroscopic dimensions. We have recently reported a method, solvent vapor annealing with soft shear (SVA-SS), for fabricating unidirectional alignment of cylindrical nanostructures. This method is a simple extension of the common SVA process by adhering a flat, crosslinked poly(dimethylsiloxane) (PDMS) pad to the BCP thin film. The impact of processing parameters, including annealing time, solvent removal rate and the physical properties of the PDMS pad, on the quality of alignment quantified by the Herman's orientational factor (S) is systematically examined for a model system of polystyrene-block-polyisoprene-block-polystyrene (SIS). As annealing time increases, the SIS morphology transitions from isotropic rods to highly aligned cylinders. Decreasing the rate of solvent removal, which impacts the shear rate imposed by the contraction of the PDMS, improves the orientation factor of the cylindrical domains; this suggests the nanostructure alignment is primarily induced by contraction of PDMS during solvent removal. Moreover, the physical properties of the PDMS controlled by the crosslink density impact the orientation factor by tuning its swelling extent during SVA-SS and elastic modulus. Decreasing the PDMS crosslink density increases S; this effect appears to be primarily driven by the changes in the solubility of the SVA-SS solvent in the PDMS. With this understanding of the critical processing parameters, SVA-SS has been successfully applied to align a wide variety of BCPs including polystyrene-block-polybutadiene-block-polystyrene (SBS), polystyrene-block-poly(N,N-dimethyl-n-octadecylammonium p-styrenesulfonate) (PS-b-PSS-DMODA), polystyrene-block-polydimethylsiloxane (PS-b-PDMS) and polystyrene-block-poly(2-vinlypyridine) (PS-b-P2VP). These results suggest that SVA-SS is a generalizable

  9. 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

  10. 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

  11. 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.

  12. Self-Assembly of Magnetic Nanoparticles at the Surface and Within Block Copolymer Films

    NASA Astrophysics Data System (ADS)

    Xu, Chen; Ohno, Kohji; Composto, Russell

    2007-03-01

    We investigate the self-assembly of magnetic Fe3O4 nanoparticles in thin films of a symmetric block copolymer of poly(styrene-b-methyl methacrylate), PS-b-PMMA (75 kg/mol). The Fe3O4 nanoparticles (4nm) are grafted by poly(methyl methacrylate) (PMMA) (2.7 kg/mol) brushes to improve their compatibility. The weight percent of Fe3O4 in PS-b-PMMA is 1, 4 and 10. The Fe3O4 reside at the intermaterial dividing surface and also form small disk-like aggregates within the PMMA phase. The addition of Fe3O4 slows down the transition from perpendicular to parallel lamellae morphology at the surface and slowing down increases as weight percent Fe3O4 increases. Using cross-sectional TEM, nanoparticles are found to be rejected from the parallel lamellae and gather preferentially within the perpendicular lamellae. These studies demonstrate that the Fe3O4 particles influence thin film morphology and visa versa. Because of widespread interest in nanodevices, this study shows that arrays of functional nanoparticles can be formed using block copolymer templates.

  13. Master curve captures the effect of domain morphology on ethanol pervaporation through block copolymer membranes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report on the effect of changing nanoscale morphology on pervaporation of ethanol/water mixtures through block copolymer membranes. Experiments were conducted using polystyrene-b-polybutadiene-b-polystyrene (SBS) copolymers with polybutadiene (PB) as the ethanol transporting block, using an 8 wt%...

  14. Hierarchical Manipulation of Block Copolymer Patterns on 3D Topographic Substrates: Beyond Graphoepitaxy.

    PubMed

    Park, Sungjune; Cheng, Xiao; Böker, Alexander; Tsarkova, Larisa

    2016-08-01

    Templates of complex nanopatterns in a form of hierarchically sequenced dots and stripes can be generated in block copolymer films on lithography-free 3D topographic substrates. The approach exploits thickness- and swelling-responsive morphological behavior of block copolymers, and demonstrates novel possibilities of topography-guided registration of nanopatterns due to periodic confinement and spontaneous orthogonal flow-fields. PMID:27270877

  15. Morphological study of biodegradable PEO/PLA block copolymers.

    PubMed

    Younes, H; Cohn, D

    1987-11-01

    A series of PEO/PLA copolymers, covering a wide range of compositions and segmental lengths, was synthesized, and their morphology was investigated by means of DSC and IR studies. For matrices comprising PEO chains with molecular weights below 3400, no soft-segment crystallinity was detected. When long hard segments were present, essentially monophasic, semicrystalline polymers were obtained, with PLA blocks melting around 130 degrees C. Polymers containing longer soft segments (PEO 6000) exhibited a two-phase matrix, with both components being able to crystallize. The relative degree of crystallinity of PEO and PLA blocks was also determined. The thermal history of the sample strongly affected the morphology of the matrix, especially when both blocks were long enough to crystallize. To further explore these polymers, solvent cast films were prepared and their morphology assessed. Casting from acetone, which is an excellent solvent for PLA, resulted in hard blocks exhibiting lower degrees of crystallinity, while methanol had a similar effect on PEO soft segments. PMID:3680315

  16. Multifunctional Poly(N-vinylcarbazole)-Based Block Copolymers and their Nanofabrication and Photosensitizing Properties.

    PubMed

    Tam, Wing Yan; Mak, Chris S K; Ng, Alan Man Ching; Djurišić, Aleksandra B; Chan, Wai Kin

    2009-04-20

    The synthesis of poly(N-vinylcarbazole)-based block copolymers functionalized with rhenium diimine complexes or pendant terpyridine ligands is reported. The copolymers are synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, and they exhibit interesting morphological properties as a result of the phase separation between different blocks. The rhenium complex polymer block may function as a photosensitizer, while the terpyridine-containing polymer block can be used as the template for nanofabrication by selective deposition of zinc complexes.

  17. Phase behavior of multi-arm star-shaped polystyrene-block-poly(methyl methacrylate) copolymer

    NASA Astrophysics Data System (ADS)

    Jang, Sangshin; Moon, Hong Chul; Bae, Dusik; Kwak, Jonghen; Kim, Jin Kon

    2013-03-01

    We synthesized star-shaped polystyrene-block-poly(methyl methacrylate) copolymer (PS- b-PMMA) by utilizing α-cyclodextrin (α-CD) as a core of the star-shaped block copolymer. Eighteen hydroxyl groups on α-CD were transformed to bromine by the reaction with α-bromoisobutyryl bromide. We found that the number of bromine substituted arms per one α-CD was higher than 16, which was determined by nuclear magnetic resonance and Matrix-assisted laser desorption/ionization. We could control molecular weight of block copolymers by changing polymerization times. The block copolymers were characterized by gel permeation chromatography and nuclear magnetic resonance. Phase behaviors of these star-shaped block copolymers were investigated by small angle X-ray scattering and transmission electron microscopy.

  18. 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.

  19. Physical Continuity and Vertical Alignment of Block Copolymer Domains by Kinetically Controlled Electrospray Deposition.

    PubMed

    Hu, Hanqiong; Choo, Youngwoo; Feng, Xunda; Osuji, Chinedum O

    2015-07-01

    The fabrication of block copolymer (BCP) thin films is reported with vertically aligned cylindrical domains using continuous electrospray deposition onto bare wafer surfaces. The out-of-plane orientation of hexagonally packed styrene cylinders is achieved in the "fast-wet" deposition regime in which rapid evaporation of the solvent in deposited droplets of polymer solution drives the vertical alignment of the self-assembled structure. Thermally activated crosslinking of the polybutadiene matrix provides kinetic control of the morphology, freezing the vertical alignment and preventing relaxation of the system to its preferred parallel orientation on the nontreated substrate. Physically continuous vertically oriented domains can be achieved over several micrometers of film thickness. The ability of electrospray deposition to fabricate well-ordered and aligned BCP films on nontreated substrates, the low amount of material used relative to spin-coating, and the continuous nature of the deposition may open up new opportunities for BCP thin films. PMID:25959572

  20. Self-assembly of miktoarm star-like ABn block copolymers: from wet to dry brushes.

    PubMed

    Xu, Yuci; Wang, Chao; Zhong, Shuo; Li, Weihua; Lin, Zhiqun

    2015-03-10

    Self-assembly of miktoarm star-like ABn block copolymer in both selective solvent (A- or B-selective) and miscible homopolymer matrix (A or B homopolymer), that is, formation of micelles, was for the first time investigated by theoretical calculations based on self-consistent mean field theory. Interestingly, the calculation revealed that the size of micelles in solvent was smaller than that in homopolymer under the same conditions. In B-selective solvent, with increasing number of B blocks n in miktoarm star-like ABn block copolymer at a fixed volume fraction of A block, the micellar size decreased gradually. In stark contrast, when miktoarm star-like ABn block copolymer dissolved in B homopolymer matrix at molecular weight ratio of B homopolymer to ABn block copolymer fH = 0.30, the overall micellar size decreased nonmonotonically as the number of B blocks n in ABn block copolymer increased. The largest micelle was formed in AB2 (i.e., n = 2). This intriguing finding can be attributed to a wet-to-dry brush transition that occurred from n = 1 to n = 2 in the micellization of miktoarm star-like ABn block copolymer. Moreover, the micellization behaviors of miktoarm star-like ABn block copolymer in A-selective solvent and A homopolymer matrix were also explored, where the overall micellar size in both scenarios was found to decrease monotonically as n in ABn block copolymer increased. These self-assembled nanostructures composed of miktoarm star-like ABn block copolymers may promise a wide range of applications in size-dependent drug delivery and bionanotechnology.

  1. Anion conductive aromatic block copolymers containing diphenyl ether or sulfide groups for application to alkaline fuel cells.

    PubMed

    Yokota, Naoki; Ono, Hideaki; Miyake, Junpei; Nishino, Eriko; Asazawa, Koichiro; Watanabe, Masahiro; Miyatake, Kenji

    2014-10-01

    A novel series of aromatic block copolymers composed of fluorinated phenylene and biphenylene groups and diphenyl ether (QPE-bl-5) or diphenyl sulfide (QPE-bl-6) groups as a scaffold for quaternized ammonium groups is reported. The block copolymers were synthesized via aromatic nucleophilic substitution polycondensation, chloromethylation, quaternization, and ion exchange reactions. The block copolymers were soluble in organic solvents and provided thin and bendable membranes by solution casting. The membranes exhibited well-developed phase-separated morphology based on the hydrophilic/hydrophobic block copolymer structure. The membranes exhibited mechanical stability as confirmed by DMA (dynamic mechanical analyses) and low gas and hydrazine permeability. The QPE-bl-5 membrane with the highest ion exchange capacity (IEC = 2.1 mequiv g(-1)) exhibited high hydroxide ion conductivity (62 mS cm(-1)) in water at 80 °C. A noble metal-free fuel cell was fabricated with the QPE-bl-5 as the membrane and electrode binder. The fuel cell operated with hydrazine as a fuel exhibited a maximum power density of 176 mW cm(-2) at a current density of 451 mA cm(-2).

  2. Sprayable Elastic Conductors Based on Block Copolymer Silver Nanoparticle Composites

    PubMed Central

    2015-01-01

    Block copolymer silver nanoparticle composite elastic conductors were fabricated through solution blow spinning and subsequent nanoparticle nucleation. The reported technique allows for conformal deposition onto nonplanar substrates. We additionally demonstrated the ability to tune the strain dependence of the electrical properties by adjusting nanoparticle precursor concentration or localized nanoparticle nucleation. The stretchable fiber mats were able to display electrical conductivity values as high as 2000 ± 200 S/cm with only a 12% increase in resistance after 400 cycles of 150% strain. Stretchable elastic conductors with similar and higher bulk conductivity have not achieved comparable stability of electrical properties. These unique electromechanical characteristics are primarily the result of structural changes during mechanical deformation. The versatility of this approach was demonstrated by constructing a stretchable light emitting diode circuit and a strain sensor on planar and nonplanar substrates. PMID:25491507

  3. Structure-property relationships in multilayered polymeric system and olefinic block copolymers

    NASA Astrophysics Data System (ADS)

    Khariwala, Devang

    diffusion. Subsequently, the oxygen permeability was directly related to the composition profile in each layer and changed as the interdiffusion proceeded. This methodology enabled the extraction of the mutual diffusion co-efficient, D, for the Nylon-6/EVOH system. The effect of comonomer content in EVOH on the mutual diffusion coefficient was also studied by comparing the kinetics of interdiffusion of Nylon-6 with two EVOHs containing 24 and 44 mole % ethylene. Chapter 3. Exciting new developments in polyolefin synthesis give rise to olefinic block copolymers with properties typical of thermoplastic elastomers. The block copolymers synthesized by chain shuttling technology consist of crystallizable ethylene-octene blocks with low comonomer content and high melting temperature (hard blocks), alternating with amorphous ethylene-octene blocks with high comonomer content and low glass transition temperature (soft blocks). This study describes the material science of these unique polymers as characterized by thermal analysis, X-ray diffraction, microscopy, and tensile deformation. The crystallizable blocks are long enough to form well-organized lamellar crystals with the orthorhombic unit cell and high melting temperature. The lamellae are organized into space-filling spherulites in all compositions even in copolymers with only 18 wt% hard block. The morphology is consistent with crystallization from a miscible melt. Crystallization of the hard blocks forces segregation of the noncrystallizable soft blocks into the interlamellar regions. Good separation of hard and soft blocks in the solid state is confirmed by distinct and separate beta- and alpha-relaxations in all the block copolymers. Compared to statistical ethylene-octene copolymers, the blocky architecture imparts a substantially higher crystallization temperature, a higher melting temperature and a better organized crystalline morphology, while maintaining a lower glass transition temperature. The differences between

  4. 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.

  5. Directed Nanorod Assembly Using Block Copolymer-Based Supramolecules

    NASA Astrophysics Data System (ADS)

    Thorkelsson, Kari; Mastroianni, Alexander; Ercius, Peter; Xu, Ting

    2013-03-01

    Nanorods display many unique electrical, mechanical, and optical properties unavailable in traditional bulk materials, and are attractive building blocks toward functional materials. The collective properties of anisotropic building blocks often depend strongly on their spatial arrangements, interparticle ordering, and macroscopic alignment. We have systematically investigated the phase behavior of nanocomposites composed of nanorods and block copolymer (BCP)-based supramolecules forming spherical, cylindrical and lamellar morphologies. Initial exploration showed that the nanorods can be readily dispersed in polymeric matrix and the overall morphology of nanorod-containing supramolecular nanocomposite depends on the nanorod-polymer interactions, inter-rod interactions and entropy associated with polymer chain deformation. The energetic contributions from the components of the system can be tailored to disperse nanorods with control over inter-rod ordering and the alignment of nanorods within BCP microdomains. By varying the supramolecular morphology and composition, arrays, sheets, and interconnected networks of nanorods are demonstrated that may prove useful for fabrication of optically and electrically active nanodevices.

  6. 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.

  7. 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.

  8. Fullerene-grafted block copolymers used as compatibilizer in P3HT/PCBM bulk heterojunctions: morphology and photovoltaic performances

    NASA Astrophysics Data System (ADS)

    Gernigon, V.; Lévêque, P.; Brochon, C.; Audinot, J.-N.; Leclerc, N.; Bechara, R.; Richard, F.; Heiser, T.; Hadziioannou, G.

    2011-12-01

    The nanostructure of the active layer in polymer/fullerene bulk heterojunction solar cells is known to have a strong impact on the device performances. Controlling the polymer/fullerene blend morphology is therefore particularly important. In this work, a rod-coil block copolymer, based on a regioregular poly(3-hexylthiophene) electron-donor rod block and a C60-grafted coil block, is used as compatibilizer and its influences on the thin film morphology as well as the photovoltaic performances are investigated. It is shown that a small fraction of compatibilizer can enhance the device performances in an otherwise non-optimized process. At higher fractions or long annealing times however, the fullerene-grafted copolymer is found to behave as a nucleation center and triggers the formation of fullerene crystals.

  9. Tough Block Copolymer Organogels and Elastomers as Short Fiber Composites

    NASA Astrophysics Data System (ADS)

    Kramer, Edward J.

    2012-02-01

    The origins of the exceptional toughness and elastomeric properties of gels and elastomers from block copolymers with semicrystalline syndiotactic polypropylene blocks will be discussed. Using synchrotron X-radiation small angle (SAXS) and wide angle X-ray scattering (WAXS) experiments were simultaneously performed during step cycle tensile deformation of these elastomers and gels. From these results the toughness can be attributed to the formation, orientation and elongation of the crystalline fibrils along the tensile direction. The true stress and true strain ɛH during each cycle were recorded, including the true strain at zero load ɛH,p after each cycle that resulted from the plastic deformation of the sPP crystals in the gel or elastomer. The initial Young's modulus Einit and maximum tangent modulus Emax in each cycle undergo dramatic changes as a function of ɛH,p, with Einit decreasing for ɛH,p <= 0.1 and then increasing slowly as ɛH,p increases to 1 while Emax increases rapidly over the entire range of ɛH,p resulting in a ratio of Emax/Einit > 100 to 1000 at the highest maximum (nominal) strain. Based on SAXS patterns from the deformed and relaxed gels, as well as on previous results on deformation of semicrystalline random copolymers by Strobl and coworkers, we propose that the initial decrease in Einit and increase in Emax with ɛH,p are due to a breakup of the network of the original sPP crystal lamellae and the conversion of the sPP lamellae into fibrils whose aspect ratio increases with further plastic deformation, respectively. The gel elastic properties can be understood quantitatively as those of a short fiber composite with a highly deformable matrix. At zero stress the random copolymer midblock chains that connect the fibrils cause these to make all angles to the tensile axis (low Einit), while at the maximum strain the stiff, crystalline sPP fibrils align with the tensile axis producing a strong, relatively stiff gel. The evolution of the

  10. Thermodynamics of Surfactants, Block Copolymers and Their Mixtures in Water: The Role of the Isothermal Calorimetry

    PubMed Central

    De Lisi, Rosario; Milioto, Stefania; Muratore, Nicola

    2009-01-01

    The thermodynamics of conventional surfactants, block copolymers and their mixtures in water was described to the light of the enthalpy function. The two methodologies, i.e. the van’t Hoff approach and the isothermal calorimetry, used to determine the enthalpy of micellization of pure surfactants and block copolymers were described. The van’t Hoff method was critically discussed. The aqueous copolymer+surfactant mixtures were analyzed by means of the isothermal titration calorimetry and the enthalpy of transfer of the copolymer from the water to the aqueous surfactant solutions. Thermodynamic models were presented to show the procedure to extract straightforward molecular insights from the bulk properties. PMID:19742173

  11. Poly(lactide)-block-poly([epsilon]-caprolactone-co-[epsilon]-decalactone)-block-poly(lactide) copolymer elastomers

    SciTech Connect

    Schneiderman, Deborah K.; Hill, Erin M.; Martello, Mark T.; Hillmyer, Marc A.

    2015-08-28

    Batch ring opening transesterification copolymerization of ε-caprolactone and ε-decalactone was used to generate statistical copolymers over a wide range of compositions and molar masses. Reactivity ratios determined for this monomer pair, rCL = 5.9 and rDL = 0.03, reveal ε-caprolactone is added preferentially regardless of the propagating chain end. Relative to poly(ε-caprolactone) the crystallinity and melting point of these statistical copolymers were depressed by the addition of ε-decalactone; copolymers containing greater than 31 mol% (46 wt%) ε-decalactone were amorphous. Poly(lactide)-block-poly(ε-caprolactone-co-ε-decalactone)-block-poly(lactide) triblock polymers were also prepared and used to explore the influence of midblock composition on the temperature dependent Flory-Huggins interaction parameter (χ). In addition, uniaxial extension tests were used to determine the effects of midblock composition, poly(lactide) content, and molar mass on the mechanical properties of these new elastomeric triblocks.

  12. 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

  13. 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.

  14. How to Place Block Copolymer Molecules at the Interface of a Binary Blend

    NASA Astrophysics Data System (ADS)

    Chen, Zhong-Ren; Xu, Yuci; Zhong, Shuo

    2015-03-01

    Block copolymers have been used to reduce the domain size of immiscible polymer blends and thus improve the mechanical and other properties. The effectiveness of this method, however, depends on the percentage of these polymeric surfactants residing at the interface of the blend. In fact, theoretical as well as experimental work indicate that a large percentage of block copolymers form micelles in the bulk of one or both of the component polymers. These micelles may serve as weak spots initiating crack propagation. Previous work have been focused on the design of molecular architecture and synthesis of new block copolymers to address this problem. In this presentation, a simple mixing strategy is applied to make each block copolymer molecule stay at the interface. As one example, when this strategy is used to mix natural rubber (NR) with butadiene rubber (BR), a small amount of low molecular weight block copolymer (LIR) improves both processing characteristics such as melt viscosity and mechanical properties of cured samples, such as crack resistance. AFM micrographs show the much smaller domain size; and an original real-time monitoring system reveals the lowest crack growth rate. Using a model A/B/A-B binary blend, we have witnessed by microscopy that all block copolymer molecules form micelles at the first mixing step, and all of these micelles are disappeared and all block copolymer molecules stay at the interface after the second mixing step.

  15. 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

  16. 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.

  17. Bicontinuous ceramics with high surface area from block copolymer templates.

    PubMed

    Hsueh, Han-Yu; Ho, Rong-Ming

    2012-06-01

    Mesoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-b-poly(L-lactide) (PS-PLLA), followed by hydrolysis of PLLA block. Well-defined polymer/ceramic nanohybrid materials with inorganic gyroid nanostructures in a PS matrix can be obtained by using the mesoporous PS as a template for sol-gel reaction. Titanium tetraisopropoxide (TTIP) is used as a precursor to give a model system for the fabrication of metal oxide nanostructures from reactive transition metal alkoxides. By controlling the rates of capillary-driven pore filling and sol-gel reaction, the templated synthesis can be well-developed. Also, by taking advantage of calcination, bicontinuous TiO(2) with controlled crystalline phase (i.e., anatase phase) can be fabricated after removal of the PS template and crystallization of TiO(2) by calcination leading to high photocatalytic efficiency. This new approach provides an easy way to fabricate high-surface-area and high-porosity ceramics with self-supporting structure and controlled crystalline phase for practical applications. As a result, a platform technology to fabricate precisely controlled polymer/ceramic nanohybrids and mesoporous ceramic materials can be established. PMID:22530553

  18. 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.

  19. Surface Modification of Block Copolymer Through Sulfur Containing Plasma Treatment.

    PubMed

    Choi, Sang Wook; Shin, Jae Hee; Jeon, Min Hwan; Mun, Jeong Ho; Kim, Sang Ouk; Yeom, Geun Young; Kim, Kyong Nam

    2015-10-01

    Some of the important issues of block copolymer (BCP) as an application to the potential low cost next generation lithography are thermal stability and deformation during pattern transfer process in addition to defect density, line edge/width roughness, etc. In this study, sulfur containing plasma treatment was used to modify the BCP and the effects of the plasma on the properties of plasma treated BCP were investigated. The polystyrene hole pattern obtained from polystyrene polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) was initially degraded when the polystyrene hole was annealed at 190 °C for 15 min. However, when the hole pattern was treated using sulfur containing plasmas using H2S or SF6 up to 2 min, possibly due to the sulfurization of the polystyrene hole surface, no change in the hole pattern was observed after the annealing even though there is a slight change in hole shapes during the plasma treatment. The optimized plasma treated polystyrene pattern showed the superior characteristics as the mask layer by showing better thermal stability, higher chemical inertness, and higher etch selectivity during plasma etching. PMID:26726468

  20. Enhanced Lateral Ordering in Cylinder Forming PS-b-PMMA Block Copolymers Exploiting the Entrapped Solvent.

    PubMed

    Seguini, Gabriele; Zanenga, Fabio; Giammaria, Tommaso J; Ceresoli, Monica; Sparnacci, Katia; Antonioli, Diego; Gianotti, Valentina; Laus, Michele; Perego, Michele

    2016-03-01

    The self-assembly of block copolymer (BCP) thin films produces dense and ordered nanostructures. Their exploitation as templates for nanolithography requires the capability to control the lateral order of the nanodomains. Among a multiplicity of polymers, the widely studied all-organic polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) BCP can easily form nanodomains perpendicularly oriented with respect to the substrate, since the weakly unbalanced surface interactions are effectively neutralized by grafting to the substrate an appropriate poly(styrene-random-methyl methacrylate) P(S-r-MMA) random copolymer (RCP). This benefit along with the selective etching of the PMMA component and the chemical similarity with the standard photoresist materials deserved for PS-b-PMMA the role of BCP of choice for the technological implementation in nanolithography. This work demonstrates that the synergic effect of thermal annealing with the initial solvent naturally trapped in the basic RCP + BCP system after the deposition process can be exploited to enhance the lateral order. The solvent content embedded in the total RCP + BCP system can be tuned by changing the molecular weight and thus the thickness of the grafted RCP brush layer, without introducing external reservoirs or dedicated setup and/or systems. The appropriate supply of solvent supports a grain coarsening kinetics following a power law with a 1/3 growth exponent for standing hexagonally ordered cylinders. PMID:26959626

  1. A bio-inspired microstructure induced by slow injection moulding of cylindrical block copolymers.

    PubMed

    Stasiak, Joanna; Brubert, Jacob; Serrani, Marta; Nair, Sukumaran; de Gaetano, Francesco; Costantino, Maria Laura; Moggridge, Geoff D

    2014-08-28

    It is well known that block copolymers with cylindrical morphology show alignment with shear, resulting in anisotropic mechanical properties. Here we show that well-ordered bi-directional orientation can be achieved in such materials by slow injection moulding. This results in a microstructure, and anisotropic mechanical properties, similar to many natural tissues, making this method attractive for engineering prosthetic fibrous tissues. An application of particular interest to us is prosthetic polymeric heart valve leaflets, mimicking the shape, microstructure and hence performance of the native valve. Anisotropic layers have been observed for cylinder-forming block copolymers centrally injected into thin circular discs. The skin layers exhibit orientation parallel to the flow direction, whilst the core layer shows perpendicularly oriented domains; the balance of skin to core layers can be controlled by processing parameters such as temperature and injection rate. Heart valve leaflets with a similar layered structure have been prepared by injection moulding. Numerical modelling demonstrates that such complex orientation can be explained and predicted by the balance of shear and extensional flow.

  2. Patterns with PS-b-PMMA block copolymer on various substrates and their applications

    NASA Astrophysics Data System (ADS)

    Alam, Md. Mahbub; Lee, Yu-Rim; Jung, Woo-Gwang

    2011-01-01

    High density arrays of nanostructures over large area can be formed by self-assembly of block copolymers on a variety of substrates such as silica deposited silicon wafer, glass, GaN, PET etc. This block copolymer thin film, such that the domains are oriented perpendicularly to the substrate, is particularly useful for the formation of templates for patterns. The degradation and elimination of the minor component transforms the material into an array of nanopores to form some patterned template that offer potential benefits in a number of applications. The morphology of the polymer surface is strongly dependent on the thickness of the polymer layer. Moreover it is necessary to control the size and shape in order to get the desired properties. Spin coating fallowed by baking the polymer solution onto the substrate self assembles the components of the polymer. PS and PMMA have significantly different photodegradation properties. Exposure to ultraviolet radiation degrades the PMMA (polymethyl methacrylate) chain that can be removed by rinsing in acetic acid giving patterned holes. Sonicating the samples in different solutions in different steps gives fingerprint pattern or sometimes patterns with PS cylindrical domains with large interstitial spaces. Moreover the interstitial space depends on the composition of the polymer solution. All these controlled patterns made on GaN, Glass can be applied to make photonic crystal

  3. Electric-Field-Induced Alignment of Block Copolymer/Nanoparticle Blends

    SciTech Connect

    Liedel, Clemens; Schindler, Kerstin; Pavan, Mariela J.; Lewin, Christian; Pester, Christian W; Ruppel, Markus A; Urban, Volker S; Shenhar, Roy; Boker, Alexander

    2013-01-01

    External electric fi elds readily align birefringent block-copolymer mesophases. In this study the effect of gold nanoparticles on the electric-fi eld-induced alignment of a lamellae-forming polystyrene- block -poly(2-vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric-fi eldassisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such fi lms under benign experimental conditions.

  4. Electric-field-induced alignment of block copolymer/nanoparticle blends.

    PubMed

    Liedel, Clemens; Schindler, Kerstin A; Pavan, Mariela J; Lewin, Christian; Pester, Christian W; Ruppel, Markus; Urban, Volker S; Shenhar, Roy; Böker, Alexander

    2013-10-11

    External electric fields readily align birefringent block-copolymer mesophases. In this study the effect of gold nanoparticles on the electric-field-induced alignment of a lamellae-forming polystyrene-block-poly(2-vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric-field-assisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such films under benign experimental conditions. PMID:23495246

  5. Non-immunogenic, hydrophilic/cationic block copolymers and uses thereof

    DOEpatents

    Scales, Charles W.; Huang, Faqing; McCormick, Charles L.

    2010-05-18

    The present invention provides novel non-immunogenic, hydrophilic/cationic block copolymers comprising a neutral-hydrophilic polymer and a cationic polymer, wherein both polymers have well-defined chain-end functionality. A representative example of such a block copolymer comprises poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) and poly(N-[3-(dimethylamino)propyl]methacrylamide) (PDMAPMA). Also provided is a synthesis method thereof in aqueous media via reversible addition fragmentation chain transfer (RAFT) polymerization. Further provided are uses of these block copolymers as drug delivery vehicles and protection agents.

  6. Anti-Biofouling Effect of PEG-Grafted Block Copolymer Synthesized by RAFT Polymerization.

    PubMed

    Kim, Seon-Mi; Han, Sang Suk; Kim, A Young; Choi, Beom-Jin; Paik, Hyun-Jong; Lee, Inwon; Park, Hyun; Chun, Ho Hwan; Cho, Youngjin; Hwang, Do-Hoon

    2015-10-01

    Poly(glycidyl methadrylate-block-styrene) (PGMA-b-PS), a block copolymer consisting of glycidyl methacrylate and styrene, was synthesized via reversible addition-fragmentation chain transfer living polymerization. The synthesized PGMA-b-PS was then grafted with low-molecular-weight polyethylene glycol (PEG) via epoxy ring opening to give PGMA-g-PEG-b-PS, which was evaluated as an anti-biofouling coating material. As a preliminary test for the anti-biofouling effect, a protein adsorption experiment was performed on the synthesized block copolymer surface. The block copolymers were spin-coated onto silicon wafers, and protein adsorption experiments were carried out using fluorescein isothiocyanate conjugate-labeled bovine serum albumin. The fluorescence intensity of the protein adsorbed on the block copolymer surface was compared with that of a polystyrene film as a reference. The synthesized PGMA-g-PEG-b-PS film showed much lower fluorescence intensity than that of the PS film.

  7. A strategy to explore stable and metastable ordered phases of block copolymers.

    PubMed

    Xu, Weiquan; Jiang, Kai; Zhang, Pingwen; Shi, An-Chang

    2013-05-01

    Block copolymers with their rich phase behavior and ordering transitions have become a paradigm for the study of structured soft materials. A major challenge in the study of the phase behavior of block copolymers is to obtain different stable and metastable phases of the system. A strategy to discover complex ordered phases of block copolymers within the self-consistent field theory framework is developed by a combination of fast algorithms and novel initialization procedures. This strategy allows the generation of a large number of candidate structures, which can then be used to construct phase diagrams. Application of the strategy is illustrated using ABC star triblock copolymers as an example. A large number of candidate structures, including many three-dimensionally ordered phases, of the system are obtained and categorized. A phase diagram is constructed for symmetrically interacting ABC star triblock copolymers. PMID:23551204

  8. 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.

  9. Surface-induced ordering for confined random block copolymers

    NASA Astrophysics Data System (ADS)

    Gutman, Lorin; Chakraborty, Arup K.

    1994-12-01

    Motivated by practical issues that pertain to polymer adhesion, we consider the equilibrium behavior of a dilute solution of ideal A-B random block copolymers confined between two solid surfaces. We develop a general theory for the situation wherein the A-A, B-B, and A-B intersegment interactions are different, and furthermore, the A and B segments interact differently with the solid surfaces. Random block copolymers constitute a class of materials wherein a quenched disorder (the sequence distribution) is carried by the fluid whose statistical properties are of interest. In our theory, we perform quenched disorder averages using the replica trick. The nonlocal terms in our action functional are decoupled by introducing a set of random fields. The resulting equations for the propagator are analyzed within the framework of eigenfunction expansions. Since we consider long chains in confined geometries, we invoke the ground state approximation. We also carry out the functional integrals over the random fields using saddle points. Our theory does not treat the segment-surface interactions within a mean field approximation. Our analysis leads to a set of nonlinear self-consistent-field equations. We have solved our general equations numerically for a particular problem. In order to isolate and highlight the effects of dissimilar segment-surface interactions, we consider a case wherein the intersegment interactions are all alike (of the excluded volume type), while the A segments are attracted to the solid surfaces and the B units are repelled. For this specific problem we find that, above a threshold value of the fraction of attractive segments, significant microphase ordering is induced by the surface. This leads to damped oscillations in the composition profile. This onset of significant surface-induced composition fluctuations is accompanied by an ``adsorption-desorption transition'' which corresponds to a qualitative change in the shape of the total segment density

  10. Crystallization and Microphase Separation in Chiral Block Copolymers

    NASA Astrophysics Data System (ADS)

    Ho, Rong-Ming

    2012-02-01

    Block copolymers composed of chiral entities, denoted as chiral block copolymers (BCP*s), were designed to fabricate helical architectures from self-assembly. A helical phase (denoted H*) was discovered in the self-assembly of poly(styrene)-b-poly(L-lactide) (PS-PLLA) BCPs*. To examine the phase behavior of the PS-PLLA, self-assembled superstructures resulting from the competition between crystallization and microphase separation of the PS-PLLA in solution were examined. A kinetically controlled process by changing non-solvent addition rate was utilized to control the BCP* self-assembly. Single-crystal lozenge lamellae were obtained by the slow self-assembly (i.e., slow non-solvent addition rate) of PS-PLLA whereas amorphous helical ribbon superstructures were obtained from the fast self-assembly (i.e., fast non-solvent addition rate). As a result, the formation of helical architectures from the self-assembly of the PS-PLLA reflects the impact of chirality on microphase separation, but the chiral effect might be overwhelmed by crystallization. Consequently, various crystalline PS-PLLA nanostructures in bulk were obtained by controlling the crystallization temperature of PLLA (Tc,PLLA) at which crystalline helices and crystalline cylinders occur while Tc,PLLA=x Tg,PS, respectively. Anisotropic arrangement of the PLLA crystallites grown within the microdomains was identified. The formation of this exclusive crystalline growth is attributed to the spatial confinement effect for crystallization. While Tc,PLLA=x Tg,PS, the preferential growth may modulate the curvature of microdomains by shifting the molecular chains to access the fast path for crystalline growth due to the increase in chain mobility. As a result, a spring-like behavior of the helical nanostructure

  11. 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.

  12. Synthesis and Characterization of Stimuli Responsive Block Copolymers, Self-Assembly Behavior and Applications

    SciTech Connect

    Determan, Michael Duane

    2005-12-17

    The central theme of this thesis work is to develop new block copolymer materials for biomedical applications. While there are many reports of stimuli-responsive amphiphilic [19-21] and crosslinked hydrogel materials [22], the development of an in situ gel forming, pH responsive pentablock copolymer is a novel contribution to the field, Figure 1.1 is a sketch of an ABCBA pentablock copolymer. The A blocks are cationic tertiary amine methacrylates blocked to a central Pluronic F127 triblock copolymer. In addition to the prerequisite synthetic and macromolecular characterization of these new materials, the self-assembled supramolecular structures formed by the pentablock were experimentally evaluated. This synthesis and characterization process serves to elucidate the important structure property relationships of these novel materials, The pH and temperature responsive behavior of the pentablock copolymer were explored especially with consideration towards injectable drug delivery applications. Future synthesis work will focus on enhancing and tuning the cell specific targeting of DNA/pentablock copolymer polyplexes. The specific goals of this research are: (1) Develop a synthetic route for gel forming pentablock block copolymers with pH and temperature sensitive properties. Synthesis of these novel copolymers is accomplished with ATRP, yielding low polydispersity and control of the block copolymer architecture. Well defined macromolecular characteristics are required to tailor the phase behavior of these materials. (2) Characterize relationship between the size and shape of pentablock copolymer micelles and gel structure and the pH and temperature of the copolymer solutions with SAXS, SANS and CryoTEM. (3) Evaluate the temperature and pH induced phase separation and macroscopic self-assembly phenomenon of the pentablock copolymer. (4) Utilize the knowledge gained from first three goals to design and formulate drug delivery formulations based on the multi

  13. Fluorosilicone multi-block copolymers tethering quaternary ammonium salt groups for antimicrobial purpose

    NASA Astrophysics Data System (ADS)

    Zhou, Fang; Qin, Xiaoshuai; Li, Yancai; Ren, Lixia; Zhao, Yunhui; Yuan, Xiaoyan

    2015-08-01

    Symmetrically structured fluorosilicone multi-block copolymers containing poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(hexafluorobutyl methacrylate) (PHFBMA) were sequentially synthesized via reversible addition-fragmentation chain transfer polymerization, using a polydimethylsiloxane (PDMS) chain transfer agent with dithiocarbonate groups at both ends. Then, the CBABC-type block copolymers were quaternized with n-octyliodide to tether quaternary ammonium salt (QAS) groups in the PDMAEMA blocks for the antimicrobial use. The obtained fluorosilicone copolymers showed clear variations in the C-N+ composition and surface morphology on their films depending on the content of the PHFBMA blocks, which were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The results indicated that the symmetrical CBABC structure favored PDMS and QAS tethered blocks migrating to the film surface. With the mass percentage of the PHFBMA increased from 0 to 32.5%, the surface roughness of the copolymer film decreased gradually with a tendency to form a smooth surface. Owing to the surface properties, fluorosilicone multi-block copolymers containing a certain amount of PHFBMA with higher C-N+ content and relatively smooth morphology demonstrated obvious antimicrobial activity against Gram-positive bacteria, Bacillus subtilis and Gram-negative bacteria, Escherichia coli. The functionalized multi-block copolymers based on fluorosilicone and QAS groups would have potential applications in antimicrobial coatings.

  14. Nanostructured Colloidal Particles by Confined Self-Assembly of Block Copolymers in Evaporative Droplets

    NASA Astrophysics Data System (ADS)

    Kim, Minsoo; Yi, Gi-Ra

    2015-06-01

    Block copolymers (BCPs) can create various morphology by self-assembly in bulk or film. Recently, using BCPs in confined geometries such as thin film (one-dimension), cylindrical template (two-dimension), or emulsion droplet (three-dimension), nanostructured BCP particles have been prepared, in which unique nanostructures of the BCP are formed via solvent annealing process and can be controlled depending on molecular weight ratio and interaction parameter of the BCPs, and droplet size. Moreover, by tuning interfacial property of the BCP particles, anisotropic particles with unique nanostructures have been prepared. Furthermore, for practical application such as drug delivery system, sensor, self-healing, metamaterial, and optoelectronic device, functional nanoparticles can be incorporated inside BCP particles. In this article, we summarize recent progress on the production of structured BCP particles and composite particles with metallic nanoparticles.

  15. Surface Dynamics of Block Copolymer Films by X-ray Photon Correlation Spectroscopy

    SciTech Connect

    Song, Sanghoon; Cha, Wonsuk; Lee, Heeju; Li, Xiaolong; Kim, Hyunjung; Jiang, Zhang; Narayanan, Suresh; Ruehm, Adrian; Sinha, S. K.

    2009-04-19

    We investigated the structure and dynamics of supported block copolymer films of poly(styrene)-b-poly(dimethylsiloxane)(PS-b-PDMS) in the spherical phase by x-ray photon correlation spectroscopy (XPCS) in grazing angle geometry. The temperature range studied was between 160 deg. and 210 deg. C, much higher than glass transition temperature (Tg), with thickness from 40 nm to 600 nm. Using x-ray reflectivity and x-ray photoelectron spectroscopy (XPS), we found that the PDMS-rich layer near the surface appeared at a temperature higher than Tg. Universal scaling of the dynamics, even with the bilayer model, was observed. From the fitting with the bilayer model, viscosities from both layers were obtained. The results from the surface dynamics are compared with the theory of overdamped thermal capillary waves on thin films.

  16. Mimicking Conjugated Polymer Thin Film Photophysics with a Well-Defined Triblock Copolymer in Solution

    SciTech Connect

    Brazard, Johanna; Ono, Robert J.; Bielawski, Christopher W.; Barbara, Paul F.; Vanden Bout, David A.

    2013-04-25

    Conjugated polymers (CPs) are promising materials for use in electronic applications, such as low-cost, easily processed organic photovoltaic (OPV) devices. Improving OPV efficiencies is hindered by a lack of a fundamental understanding of the photophysics in CP-based thin films that is complicated by their heterogeneous nanoscale morphologies. Here, we report on a poly(3-hexylthiophene)-block-poly(tert-butyl acrylate)-block-poly(3-hexylthiophene) rod–coil–rod triblock copolymer. In good solvents, this polymer resembles solutions of P3HT; however, upon the addition of a poor solvent, the two P3HT chains within the triblock copolymer collapse, affording a material with electronic spectra identical to those of a thin film of P3HT. Using this new system as a model for thin films of P3HT, we can attribute the low fluorescence quantum yield of films to the presence of a charge-transfer state, providing fundamental insights into the condensed phase photophysics that will help to guide the development of the next generation of materials for OPVs.

  17. Phase Behavior of Star-shaped polystyrene-block-poly(methyl methacrylate) Copolymers

    NASA Astrophysics Data System (ADS)

    Jang, Sangshin; Moon, Hongchul; Lee, Youngmin; Kim, Jin Kon

    2012-02-01

    Star-shaped polystyrene-block-poly(methyl methacrylate) copolymer (PS-b-PMMA) was synthesized by utilizing α-cyclodextrin (α-CD) as a junction point of the star-shaped block copolymer. Eighteen hydroxyl groups on α-CD were substituted with bromine by the reaction with α-bromoisobutyryl bromide for atom transfer radical polymerization. We found that the number of bromine substituted arms per one α-CD was higher than 16 measured by nuclear magnetic resonance and Matrix-assisted laser desorption/ionization. We could control molecular weight of this unusual kind of block copolymer depending on polymerization times. Those polymers were characterized by gel permeation chromatography and nuclear magnetic resonance. Phase behavior of these star-shaped block copolymers were investigated.

  18. Theoretical and Experimental Investigations of Contact Hole Shrink using PS-PMMA Block Copolymers

    NASA Astrophysics Data System (ADS)

    Ginzburg, Valeriy; Hustad, Phillip; Weinhold, Jeffrey; Sharma, Rahul; Chuang, Vivian; Trefonas, Peter

    2012-02-01

    One possible application of block copolymer directed self-assembly (DSA) involves rectification or ``shrink'' of contact holes in a polarity switched photoresist (see, e.g., J. Cheng et al., ACS Nano 8, 4815 [2010]). The block copolymer (e.g., PS-PMMA) undergoes ordering inside the cylindrical hole; the central (PMMA) domain is then etched out so that the hole diameter is effectively reduced. We utilize strong segregation theory (SST) and numerical self-consistent field theory (SCFT) to calculate the phase behavior of the block copolymers as function of their molecular weight and composition, as well as the contact hole diameter and the surface chemistry of the walls. The model predictions were compared with experimental data, and a good agreement was found. The results illustrate how modeling can serve to guide block copolymer selection for DSA contact hole rectification application.

  19. Arrangement of C60 via the self-assembly of post-functionalizable polyisocyanate block copolymer.

    PubMed

    Min, Joonkeun; Shah, Priyank N; Chae, Chang-Geun; Lee, Jae-Suk

    2012-12-13

    Poly(furfuryl isocyanate) (PFIC), which includes the reactive furan group, was synthesized by anionic polymerization using a sodium benzhydroxide (Na-BH), self-assembly initiator. We determined the optimum polymerization conditions by varying both the reaction time and the molar ratio of the monomer to the initiator. Block copolymer, poly(furfuryl isocyanate)-b-poly(n-hexyl isocyanate), was synthesized under optimized polymerization conditions. The PFIC was modified by Diels-Alder reactions with C60 for functionalization. Transmission electron microscopy (TEM) was used to study the self-assembly of block copolymers and modified block copolymer with C60. C60 formed highly ordered aggregates on the PFIC domains via self-assembly of the block copolymer.

  20. Complexation-tailored morphology of asymmetric block copolymer membranes.

    PubMed

    Madhavan, Poornima; Peinemann, Klaus-Viktor; Nunes, Suzana P

    2013-08-14

    Hydrogen-bond formation between polystyrene-b-poly (4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) and -OH/-COOH functionalized organic molecules was used to tune morphology of asymmetric nanoporous membranes prepared by simultaneous self-assembly and nonsolvent induced phase separation. The morphologies were characterized by field emmision scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Hydrogen bonds were confirmed by infrared (IR), and the results were correlated to rheology characterization. The OH-functionalized organic molecules direct the morphology into hexagonal order. COOH-functionalized molecules led to both lamellar and hexagonal structures. Micelle formation in solutions and their sizes were determined using dynamic light scattering (DLS) measurements and water fluxes of 600-3200 L/m(2)·h·bar were obtained. The pore size of the plain BCP membrane was smaller than with additives. The following series of additives led to pores with hexagonal order with increasing pore size: terephthalic acid (COOH-bifunctionalized) < rutin (OH-multifunctionalized) < 9-anthracenemethanol (OH-monofunctionalized) < 3,5-dihydroxybenzyl alcohol (OH-trifunctionalized).

  1. Direct Nanorod Assembly Using Block Copolymer-Based Supramolecules

    NASA Astrophysics Data System (ADS)

    Thorkelsson, Kari; Mastroianni, Alexander; Ercius, Peter; Xu, Ting

    2012-02-01

    One-dimensional nanomaterials with high aspect ratios, such as nanorods, exhibit unique and useful anisotropic optical, magnetic, and electrical properties. The collective properties of 1-D nanomaterials depend on their spatial arrangements, interparticle ordering, and macroscopic alignment. Developing routes to control their organization with high precision is critical to generate functional materials. We have investigated the co-assemblies of nanorods and block copolymer (BCP)-based supramolecules that self-assemble into spherical, lamellar and cylindrical morphologies. By varying energetic contributions from the rod-rod interactions and the deformation of the supramolecule, a wide library of nanorod assemblies including highly aligned arrays, continuous networks, and clusters can be readily accessed. Since macroscopic alignment of BCP microdomains can be obtained by application of external fields, present studies open up a new route to manipulate macroscopic alignments of nanorods. Fundamentally, these studies have demonstrated that in these blends, the energetic contributions from the polymer chain deformation and rod-rod interactions are comparable and can be tailored to disperse nanorods with control over inter-rod ordering and their relative alignment.

  2. Multilayer block copolymer meshes by orthogonal self-assembly

    PubMed Central

    Tavakkoli K. G., Amir; Nicaise, Samuel M.; Gadelrab, Karim R.; Alexander-Katz, Alfredo; Ross, Caroline A.; Berggren, Karl K.

    2016-01-01

    Continued scaling-down of lithographic-pattern feature sizes has brought templated self-assembly of block copolymers (BCPs) into the forefront of nanofabrication research. Technologies now exist that facilitate significant control over otherwise unorganized assembly of BCP microdomains to form both long-range and locally complex monolayer patterns. In contrast, the extension of this control into multilayers or 3D structures of BCP microdomains remains limited, despite the possible technological applications in next-generation devices. Here, we develop and analyse an orthogonal self-assembly method in which multiple layers of distinct-molecular-weight BCPs naturally produce nanomesh structures of cylindrical microdomains without requiring layer-by-layer alignment or high-resolution lithographic templating. The mechanisms for orthogonal self-assembly are investigated with both experiment and simulation, and we determine that the control over height and chemical preference of templates are critical process parameters. The method is employed to produce nanomeshes with the shapes of circles and Y-intersections, and is extended to produce three layers of orthogonally oriented cylinders. PMID:26796218

  3. Ultraslow dynamics in asymmetric block copolymers with nanospherical domains.

    PubMed

    Mandare, Prashant; Winter, H Henning

    2006-01-01

    Low shear rate and low frequency measurements focused on the extremely slow dynamics of a three-dimensional body-centered cubic (BCC) structure of an asymmetric block copolymer under nanophase-separated conditions. The material studied was poly(styrene-b-ethylene-co-butylene-b-styrene) swollen in a hydrocarbon oil selective for the midblock. Transient viscosities during start-up of shear flow at extremely low shear rates are governed by very long relaxation times and by a modulus that is nearly the same as the plateau modulus obtained from oscillatory shear experiments. Only at extremely low shear rates a zero shear viscosity could be attained. Its very high value is close to the viscosity calculated from stress relaxation experiments. The steady shear viscosity decreases by several orders of magnitude when increasing the shear rate. SAXS experiments on samples sheared even at very low rates indicated loss of the BCC order that was present in the annealed samples before shearing. The SAXS profile recorded on such a sample showed a first-order maximum followed by a broad shoulder indicating a liquid-like short-range order of PS nanospheres in the swollen EB matrix.

  4. Non-crosslinked, amorphous, block copolymer electrolyte for batteries

    DOEpatents

    Mayes, Anne M.; Ceder, Gerbrand; Chiang, Yet-Ming; Sadoway, Donald R.; Aydinol, Mehmet K.; Soo, Philip P.; Jang, Young-Il; Huang, Biying

    2006-04-11

    Solid battery components are provided. A block copolymeric electrolyte is non-crosslinked and non-glassy through the entire range of typical battery service temperatures, that is, through the entire range of at least from about 0.degree. C. to about 70.degree. C. The chains of which the copolymer is made each include at least one ionically-conductive block and at least one second block immiscible with the ionically-conductive block. The chains form an amorphous association and are arranged in an ordered nanostructure including a continuous matrix of amorphous ionically-conductive domains and amorphous second domains that are immiscible with the ionically-conductive domains. A compound is provided that has a formula of Li.sub.xM.sub.yN.sub.zO.sub.2. M and N are each metal atoms or a main group elements, and x, y and z are each numbers from about 0 to about 1. y and z are chosen such that a formal charge on the M.sub.yN.sub.z portion of the compound is (4-x). In certain embodiments, these compounds are used in the cathodes of rechargeable batteries. The present invention also includes methods of predicting the potential utility of metal dichalgogenide compounds for use in lithium intercalation compounds. It also provides methods for processing lithium intercalation oxides with the structure and compositional homogeneity necessary to realize the increased formation energies of said compounds. An article is made of a dimensionally-stable, interpenetrating microstructure of a first phase including a first component and a second phase, immiscible with the first phase, including a second component. The first and second phases define interphase boundaries between them, and at least one particle is positioned between a first phase and a second phase at an interphase boundary. When the first and second phases are electronically-conductive and ionically-conductive polymers, respectively, and the particles are ion host particles, the arrangement is an electrode of a battery.

  5. The packing of soft materials: Molecular asymmetry, geometric frustration and optimal lattices in block copolymer melts

    NASA Astrophysics Data System (ADS)

    Grason, Gregory M.

    Melts of block copolymers provide an ideal route to engineering well-controlled structures on nanometer length scales. Through the control of only a few thermodynamic parameters, these systems can be tuned to self-assemble into periodic structures of an astounding variety. It is known that geometry plays a particularly important role in determining equilibrium structure since phase behavior of copolymer melts is generically insensitive to detail at the monomeric scale. Here, we explore a particular way in which the geometry of packing objects in three dimensions frustrates the internal configurations of segregated block copolymer domains. In particular, we find that lattices of spherical micelles are sensitive to the periodic structure of the lattice arrangement because these micelles are forced to occupy the non-ideal, polyhedral unit cells of the lattice. By analyzing the energetics of block copolymer melts in the limit of strongly-segregated domains, we find that the interfaces which separate unlike polymer domains tend to adopt the polyhedral shape of the lattice unit cell, and this tendency is entirely controlled by the specific copolymer architecture. Furthermore, in the limit where interfaces are perfectly polyhedral, a remarkable simplicity emerges, and the relative stability of competing lattice arrangements of micelles can be assessed purely in terms of geometric measures of the two-dimensional lattice unit cell. From this analysis we predict the stability of a novel cubic arrangement spherical micelles in block copolymer melts, the A15 lattice. To corroborate our geometric arguments we develop and implement a numerical self-consistent field theory for melts of highly asymmetric block copolymers. This field theory allows us to systematically and efficiently explore the equilibrium phase behavior of asymmetric copolymer melts as a function of molecular architecture. These numerical results bear out the predictions of our geometric analysis and confirm that

  6. 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

  7. 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.

  8. Electrically conductive doped block copolymer of polyacetylene and polyisoprene. [Soluble in organic solvents

    DOEpatents

    Aldissi, M.

    1984-06-27

    An electrically conductive block copolymer of polyisoprene and polyacetylene and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I/sub 2/ to give it an electrical conductivity in the metallic regime.

  9. Key roles for chain flexibility in block copolymer membranes that contain pores or make tubes.

    PubMed

    Srinivas, Goundla; Discher, Dennis E; Klein, Michael L

    2005-12-01

    Block copolymer amphiphiles that self-assemble into membranes present robust and functionalizable alternatives to biological assemblies. Coarse-grained molecular dynamics shows that thick bilayers of A-B copolymers accommodate protein-like channels and also tend to regulate transport. This occurs as flexible, hydrophilic A chains insert into the pore and obstruct water entry. A-B-A triblocks that exploit "hairpin" and "straight" conformations also show assembly into novel nanotubules and further highlight the key roles for chain flexibility in biomimetic block copolymer assemblies.

  10. Facile synthesis and characterization of novel biodegradable amphiphilic block copolymers bearing pendant hydroxyl groups.

    PubMed

    Hu, Gaicen; Fan, Xiaoshan; Xu, Bingcan; Zhang, Delong; Hu, Zhiguo

    2014-10-01

    Novel amphiphilic block copolymers bearing pendant hydroxyl groups polylactide-b-poly(3,3-bis(Hydroxymethyl-triazolylmethyl) oxetane)-b-polylactide (PLA-b-PHMTYO-b-PLA) were synthesized via a facile and efficient method. First, the block copolymer intermediates polylactide-b-poly(3,3-Diazidomethyloxetane)-b-polylactide (PLA-b-PBAMO-b-PLA) were synthesized through ring-opening polymerization of lactide using PBAMO as a macroinitiator. Following "Click" reaction of PLA-b-PBAMO-b-PLA with propargyl alcohol provided the targeted amphiphilic block copolymers PLA-b-PHMTYO-b-PLA with pendant hydroxyl groups. The composition and structure of prepared copolymers were characterized by (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy, Fourier transform infrared (FT-IR) and gel permeation chromatography (GPC). The self-assembly behavior of the copolymers in water was investigated by transmission electron microscope (TEM), dynamic light scattering (DLS) and static light scattering (SLS). The results showed that the novel copolymers PLA-b-PHMTYO-b-PLA self-assembled into spherical micelles with diameters ranging from 100 nm to 200 nm in aqueous solution. These copolymers also exhibited low critical micellar concentrations (CMC: 6.9 × 10(-4)mg/mL and 3.9 × 10(-5)mg/mL, respectively). In addition, the in vitro cytotoxicity of these copolymers was determined in the presence of L929 cells. The results showed that the block copolymers PLA-b-PHMTYO-b-PLA exhibited better biocompatibility. Therefore, these well-defined copolymers are expected to find some applications in drug delivery or tissue engineering. PMID:25175206

  11. Facile synthesis and characterization of novel biodegradable amphiphilic block copolymers bearing pendant hydroxyl groups.

    PubMed

    Hu, Gaicen; Fan, Xiaoshan; Xu, Bingcan; Zhang, Delong; Hu, Zhiguo

    2014-10-01

    Novel amphiphilic block copolymers bearing pendant hydroxyl groups polylactide-b-poly(3,3-bis(Hydroxymethyl-triazolylmethyl) oxetane)-b-polylactide (PLA-b-PHMTYO-b-PLA) were synthesized via a facile and efficient method. First, the block copolymer intermediates polylactide-b-poly(3,3-Diazidomethyloxetane)-b-polylactide (PLA-b-PBAMO-b-PLA) were synthesized through ring-opening polymerization of lactide using PBAMO as a macroinitiator. Following "Click" reaction of PLA-b-PBAMO-b-PLA with propargyl alcohol provided the targeted amphiphilic block copolymers PLA-b-PHMTYO-b-PLA with pendant hydroxyl groups. The composition and structure of prepared copolymers were characterized by (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy, Fourier transform infrared (FT-IR) and gel permeation chromatography (GPC). The self-assembly behavior of the copolymers in water was investigated by transmission electron microscope (TEM), dynamic light scattering (DLS) and static light scattering (SLS). The results showed that the novel copolymers PLA-b-PHMTYO-b-PLA self-assembled into spherical micelles with diameters ranging from 100 nm to 200 nm in aqueous solution. These copolymers also exhibited low critical micellar concentrations (CMC: 6.9 × 10(-4)mg/mL and 3.9 × 10(-5)mg/mL, respectively). In addition, the in vitro cytotoxicity of these copolymers was determined in the presence of L929 cells. The results showed that the block copolymers PLA-b-PHMTYO-b-PLA exhibited better biocompatibility. Therefore, these well-defined copolymers are expected to find some applications in drug delivery or tissue engineering.

  12. Plasmonic nanostructures based on block copolymer templates for efficient organic solar cells

    NASA Astrophysics Data System (ADS)

    Go, Seung Jae; Lee, Dong-Eun; Lee, Dong Hyun; Chin, Byung Doo

    2016-01-01

    Plasmonic nanostructures fabricated from self-assembled patterns of block copolymers (BCPs) were applied for organic solar cells (OSCs). A thin film of a cylinder-forming polystrene- block-poly(2-vinylpyridine) copolymer (PS- b-P2VP) was spin-coated on the transparent electrode of the OSCs, where nanostructures such as dot, dot with mixed line, and line patterns emerged during different solvent annealing processes. Selective conversion of hydrogen tetrachloroaurate (III) (HAuCl4) in P2VP blocks yielded gold (Au) nanostructures, which were used to trigger the localized surface plasmonic resonance (LSPR) effect at the OSCs. Plasmonic nanostructures with almost similar scales of BCP patterns were formed at the anode/buffer interface at the OSC, showing no-table enhancements of the short circuit current ( J sc) and the power conversion efficiency (3.57% for the reference compared to 4.35% for the optimum LSPR-OSC) as the size and the anisotropy of Au patterns changed from a simple dot through an integrated dot-line pattern to a line pattern. Based on the experimental analyses of the light absorption, photoluminescence, and exciton lifetime of OSC, such an enhancement would be mainly attributed to size-dependent LSPR-induced scattering and absorption at the OSC's active layer, which is not in intimate contact with the Au nanostructures. Up to a 26% increase in the power conversion efficiency could be observed at the plasmonic structures from BCP template, providing an accurately tuning and powerful tailoring of the LSPR-enhancing patterns for the OSCs.

  13. Tunable Encapsulation Structure of Block Copolymer Coated Single-Walled Carbon Nanotubes in Aqueous Solution

    DOE PAGES

    Han, Youngkyu; Ahn, Suk-Kyun; Zhang, Zhe; Smith, Gregory Scott; Do, Changwoo

    2015-05-15

    The nano-sized and shape-tunable molecular building blocks can provide great opportunities for the fabrication of precisely controlled nanostructures. In this work, we have fabricated a molecular building block of single-walled carbon nanotubes (SWNTs) coated by PPO-PEO-PPO block copolymers whose encapsulation structure can be controlled via temperature or addition of small molecules. The structure and optical properties of SWNT-block copolymers have been investigated by small angle neutron scattering (SANS), ultraviolet-visible (UV-vis) spectroscopy, atomic force microscopy (AFM), and molecular dynamics (MD) simulation. The structure of the hydrated block copolymer layer surrounding SWNT can be controlled reversibly by varying temperature as well asmore » by irreversibly adding 5-methylsalicylic acid (5MS). Increasing hydrophobicity of the polymers with temperature and strong tendency of 5MS to interact with both block copolymers and orbitals of the SWNTs are likely to be responsible for the significant structural change of the block copolymer encapsulation layer, from loose corona shell to tightly encapsulating compact shell. These result shows an efficient and simple way to fabricate and manipulate carbon-based nano building blocks in aqueous systems with tunable structure.« less

  14. Tunable Encapsulation Structure of Block Copolymer Coated Single-Walled Carbon Nanotubes in Aqueous Solution

    SciTech Connect

    Han, Youngkyu; Ahn, Suk-Kyun; Zhang, Zhe; Smith, Gregory Scott; Do, Changwoo

    2015-05-15

    The nano-sized and shape-tunable molecular building blocks can provide great opportunities for the fabrication of precisely controlled nanostructures. In this work, we have fabricated a molecular building block of single-walled carbon nanotubes (SWNTs) coated by PPO-PEO-PPO block copolymers whose encapsulation structure can be controlled via temperature or addition of small molecules. The structure and optical properties of SWNT-block copolymers have been investigated by small angle neutron scattering (SANS), ultraviolet-visible (UV-vis) spectroscopy, atomic force microscopy (AFM), and molecular dynamics (MD) simulation. The structure of the hydrated block copolymer layer surrounding SWNT can be controlled reversibly by varying temperature as well as by irreversibly adding 5-methylsalicylic acid (5MS). Increasing hydrophobicity of the polymers with temperature and strong tendency of 5MS to interact with both block copolymers and orbitals of the SWNTs are likely to be responsible for the significant structural change of the block copolymer encapsulation layer, from loose corona shell to tightly encapsulating compact shell. These result shows an efficient and simple way to fabricate and manipulate carbon-based nano building blocks in aqueous systems with tunable structure.

  15. Synthesis of carboxylic block copolymers via reversible addition fragmentation transfer polymerization for tooth erosion prevention.

    PubMed

    Lei, Y; Wang, T; Mitchell, J W; Qiu, J; Kilpatrick-Liverman, L

    2014-12-01

    Dental professionals are seeing a growing population of patients with visible signs of dental erosion. The approach currently being used to address the problem typically leverages the enamel protection benefits of fluoride. In this report, an alternative new block copolymer with a hydrophilic polyacrylic acid (PAA) block and a hydrophobic poly(methyl methacrylate) (PMMA) block was developed to similarly reduce the mineral loss from enamel under acidic conditions. This series of PMMA-b-PAA block copolymers was synthesized by reversible addition fragmentation transfer (RAFT) polymerization. Their structures were characterized by gel permeation chromatography (GPC) and (1)H nuclear magnetic resonance (NMR) spectra. The molar fractions of acrylic acid (AA) in the final block copolymer were finely controlled from 0.25 to 0.94, and the molecular weight (Mn) of PMMA-b-PAA was controlled from 10 kDa to 90 kDa. The binding capability of the block copolymer with hydroxyapatite (HAP) was investigated by ultraviolet-visible spectroscopy (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy. FTIR spectra confirmed that the PMMA-b-PAA block copolymer could bind to HAP via bridging bidentate bonds. Both UV-Vis and FTIR spectra additionally indicated that a high polymer concentration and low solution pH favored the polymer binding to HAP. The erosion-preventing efficacy of the PMMA-b-PAA block copolymer in inhibiting HAP mineral loss was quantitatively evaluated by atomic absorption spectroscopy (AAS). Based on the results, polymer treatment reduced the amount of calcium released by 27% to 30% in comparison with the unprotected samples. Scanning electron microscope (SEM) observations indicated that PMMA-b-PAA polymer treatment protected enamel from acid erosion. This new amphiphilic block copolymer has significant potential to be integrated into dentifrices or mouthrinses as an alternative non-fluoride ingredient to reduce tooth erosion.

  16. Synthesis of Carboxylic Block Copolymers via Reversible Addition Fragmentation Transfer Polymerization for Tooth Erosion Prevention

    PubMed Central

    Lei, Y.; Wang, T.; Mitchell, J.W.; Qiu, J.; Kilpatrick-Liverman, L.

    2014-01-01

    Dental professionals are seeing a growing population of patients with visible signs of dental erosion. The approach currently being used to address the problem typically leverages the enamel protection benefits of fluoride. In this report, an alternative new block copolymer with a hydrophilic polyacrylic acid (PAA) block and a hydrophobic poly(methyl methacrylate) (PMMA) block was developed to similarly reduce the mineral loss from enamel under acidic conditions. This series of PMMA-b-PAA block copolymers was synthesized by reversible addition fragmentation transfer (RAFT) polymerization. Their structures were characterized by gel permeation chromatography (GPC) and 1H nuclear magnetic resonance (NMR) spectra. The molar fractions of acrylic acid (AA) in the final block copolymer were finely controlled from 0.25 to 0.94, and the molecular weight (Mn) of PMMA-b-PAA was controlled from 10 kDa to 90 kDa. The binding capability of the block copolymer with hydroxyapatite (HAP) was investigated by ultraviolet–visible spectroscopy (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy. FTIR spectra confirmed that the PMMA-b-PAA block copolymer could bind to HAP via bridging bidentate bonds. Both UV-Vis and FTIR spectra additionally indicated that a high polymer concentration and low solution pH favored the polymer binding to HAP. The erosion-preventing efficacy of the PMMA-b-PAA block copolymer in inhibiting HAP mineral loss was quantitatively evaluated by atomic absorption spectroscopy (AAS). Based on the results, polymer treatment reduced the amount of calcium released by 27% to 30% in comparison with the unprotected samples. Scanning electron microscope (SEM) observations indicated that PMMA-b-PAA polymer treatment protected enamel from acid erosion. This new amphiphilic block copolymer has significant potential to be integrated into dentifrices or mouthrinses as an alternative non-fluoride ingredient to reduce tooth erosion. PMID:25248611

  17. Perpendicularly oriented sub-10-nm block copolymer lamellae by atmospheric thermal annealing for one minute

    PubMed Central

    Seshimo, Takehiro; Maeda, Rina; Odashima, Rin; Takenaka, Yutaka; Kawana, Daisuke; Ohmori, Katsumi; Hayakawa, Teruaki

    2016-01-01

    The directed self-assembly (DSA) of block co-polymers (BCPs) can realize next-generation lithography for semiconductors and a variety of soft materials. It is imperative to simultaneously achieve many requirements such as a high resolution, orientation control of micro-domains, etch selectivity, rapid and mild annealing, a low cost, and compatibility with manufacturing for developing suitable BCPs. Here, we describe a new design for modified polysiloxane-based BCPs targeted for sub-10-nm-wide lines, which are able to form perpendicularly oriented lamellar structures in thin films. The hydroxyl groups in the side chains introduced in the polysiloxane block provide a good balance with the polystyrene surface free energy, thereby leading to the perpendicular orientation. Moreover, this orientation can be completed in only one minute at 130 °C in an air atmosphere. Oxygen plasma etching for the thin films results in the achievement of a line width of 8.5 nm. PMID:26782329

  18. Perpendicularly oriented sub-10-nm block copolymer lamellae by atmospheric thermal annealing for one minute.

    PubMed

    Seshimo, Takehiro; Maeda, Rina; Odashima, Rin; Takenaka, Yutaka; Kawana, Daisuke; Ohmori, Katsumi; Hayakawa, Teruaki

    2016-01-01

    The directed self-assembly (DSA) of block co-polymers (BCPs) can realize next-generation lithography for semiconductors and a variety of soft materials. It is imperative to simultaneously achieve many requirements such as a high resolution, orientation control of micro-domains, etch selectivity, rapid and mild annealing, a low cost, and compatibility with manufacturing for developing suitable BCPs. Here, we describe a new design for modified polysiloxane-based BCPs targeted for sub-10-nm-wide lines, which are able to form perpendicularly oriented lamellar structures in thin films. The hydroxyl groups in the side chains introduced in the polysiloxane block provide a good balance with the polystyrene surface free energy, thereby leading to the perpendicular orientation. Moreover, this orientation can be completed in only one minute at 130 °C in an air atmosphere. Oxygen plasma etching for the thin films results in the achievement of a line width of 8.5 nm. PMID:26782329

  19. Mechanism of titania deposition into cylindrical poly(styrene-block-4 vinyl pyridine) block copolymer templates.

    PubMed

    Lou, Qin; Chinthamanipeta, Pavan S; Shipp, Devon A

    2011-12-20

    A simple and effective way for TiO(2) to be deposited on silicon or indium tin oxide (ITO) substrates has been achieved by using a poly(styrene-block-4-vinyl pyridine) (PS-b-P4VP) block copolymer template. In particular, a mechanism for the formation of TiO(2) within the P4VP phase was developed. Within this model, the TiO(2) deposition occurs by swelling of the protonated P4VP segments followed by transport of Ti precursor, probably protonated Ti(OH)(4) given the low pH conditions used, into the swollen P4VP followed by condensation into TiO(2) during the heating/plasma etch processes. TiO(2) nanostructure morphology is affected by pH and deposition temperatures, because these parameters affect the degree of protonation of P4VP segments and diffusion of the titanium(IV) bis(ammonium lactato)dihydroxide (TALH) precursor into the film. A pH range of 2.1-2.5 for silicon substrates and pH = 2.1 for ITO substrates gave the narrower TiO(2) nanostructures distributions, and deposition at 70 °C gave TiO(2) nanostructures with more regular arrangements and smoother surface than those deposited at room temperature. The use of 1,4-diiodobutane as a P4VP cross-linking compound is demonstrated to be a critical parameter for maintaining good cylindrical surface morphology for both the block copolymer template and the TiO(2) nanostructures.

  20. Tuning of Polymeric Nanoparticles by Coassembly of Thermoresponsive Polymers and a Double Hydrophilic Thermoresponsive Block Copolymer.

    PubMed

    Zhang, Qilu; Voorhaar, Lenny; Filippov, Sergey K; Yeşil, Berin Fatma; Hoogenboom, Richard

    2016-05-26

    The coassembly behavior of thermoresponsive statistical copolymers and a double hydrophilic block copolymer having a permanently hydrophilic block and a thermoresponsive block is investigated. By adjusting the hydrophilicity of the thermoresponsive statistical copolymers, hybrid nanoparticles are obtained with various ratios of the two species. Importantly, the size of these nanoparticles can be controlled in between 40 and 250 nm dependent on the TCP and the amount of statistical copolymers in the solution. Simultaneous analysis of static and dynamic light scattering data indicates that the possible structure of nanoparticles varies from hard sphere to less compact architecture and most probably depends on a difference between cloud point temperatures of individual components. This developed coassembly method provides a simple platform for the preparation of defined polymeric nanoparticles. PMID:27144970

  1. Preparation of Pickering Double Emulsions Using Block Copolymer Worms

    PubMed Central

    2015-01-01

    The rational formulation of Pickering double emulsions is described using a judicious combination of hydrophilic and hydrophobic block copolymer worms as highly anisotropic emulsifiers. More specifically, RAFT dispersion polymerization was utilized to prepare poly(lauryl methacrylate)–poly(benzyl methacrylate) worms at 20% w/w solids in n-dodecane and poly(glycerol monomethacrylate)–poly(2-hydroxypropyl methacrylate)–poly(benzyl methacrylate) worms at 13% w/w solids in water by polymerization-induced self-assembly (PISA). Water-in-oil-in-water (w/o/w) double emulsions can be readily prepared with mean droplet diameters ranging from 30 to 80 μm using a two-stage approach. First, a w/o precursor emulsion comprising 25 μm aqueous droplets is prepared using the hydrophobic worms, followed by encapsulation within oil droplets stabilized by the hydrophilic worms. The double emulsion droplet diameter and number of encapsulated water droplets can be readily varied by adjusting the stirring rate employed during the second stage. For each stage, the droplet volume fraction is relatively high at 0.50. The double emulsion nature of the final formulation was confirmed by optical and fluorescence microscopy studies. Such double emulsions are highly stable to coalescence, with little or no change in droplet diameter being detected over storage at 20 °C for 10 weeks as judged by laser diffraction. Preliminary experiments indicate that the complementary o/w/o emulsions can also be prepared using the same pair of worms by changing the order of homogenization, although somewhat lower droplet volume fractions were required in this case. Finally, we demonstrate that triple and even quadruple emulsions can be formulated using these new highly anisotropic Pickering emulsifiers. PMID:25834923

  2. Preparation of Pickering double emulsions using block copolymer worms.

    PubMed

    Thompson, Kate L; Mable, Charlotte J; Lane, Jacob A; Derry, Mathew J; Fielding, Lee A; Armes, Steven P

    2015-04-14

    The rational formulation of Pickering double emulsions is described using a judicious combination of hydrophilic and hydrophobic block copolymer worms as highly anisotropic emulsifiers. More specifically, RAFT dispersion polymerization was utilized to prepare poly(lauryl methacrylate)-poly(benzyl methacrylate) worms at 20% w/w solids in n-dodecane and poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate)-poly(benzyl methacrylate) worms at 13% w/w solids in water by polymerization-induced self-assembly (PISA). Water-in-oil-in-water (w/o/w) double emulsions can be readily prepared with mean droplet diameters ranging from 30 to 80 μm using a two-stage approach. First, a w/o precursor emulsion comprising 25 μm aqueous droplets is prepared using the hydrophobic worms, followed by encapsulation within oil droplets stabilized by the hydrophilic worms. The double emulsion droplet diameter and number of encapsulated water droplets can be readily varied by adjusting the stirring rate employed during the second stage. For each stage, the droplet volume fraction is relatively high at 0.50. The double emulsion nature of the final formulation was confirmed by optical and fluorescence microscopy studies. Such double emulsions are highly stable to coalescence, with little or no change in droplet diameter being detected over storage at 20 °C for 10 weeks as judged by laser diffraction. Preliminary experiments indicate that the complementary o/w/o emulsions can also be prepared using the same pair of worms by changing the order of homogenization, although somewhat lower droplet volume fractions were required in this case. Finally, we demonstrate that triple and even quadruple emulsions can be formulated using these new highly anisotropic Pickering emulsifiers.

  3. Poly(vinylidene fluoride)/nickel nanocomposites from semicrystalline block copolymer precursors.

    PubMed

    Voet, Vincent S D; Tichelaar, Martijn; Tanase, Stefania; Mittelmeijer-Hazeleger, Marjo C; ten Brinke, Gerrit; Loos, Katja

    2013-01-01

    The fabrication of nanoporous poly(vinylidene fluoride) (PVDF) and PVDF/nickel nanocomposites from semicrystalline block copolymer precursors is reported. Polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PS-b-PVDF-b-PS) is prepared through functional benzoyl peroxide initiated polymerization of VDF, followed by atom transfer radical polymerization (ATRP) of styrene. The crystallization of PVDF plays a dominant role in the formation of the block copolymer structure, resulting in a spherulitic superstructure with an internal crystalline-amorphous lamellar nanostructure. The block copolymer promotes the formation of the ferroelectric β-polymorph of PVDF. Selective etching of the amorphous regions with nitric acid leads to nanoporous PVDF, which functions as a template for the generation of PVDF/Ni nanocomposites. The lamellar nanostructure and the β-crystalline phase are conserved during the etching procedure and electroless nickel deposition. PMID:23138962

  4. Interactions between plasma and block copolymers used in directed self-assembly patterning

    NASA Astrophysics Data System (ADS)

    Sirard, Stephen; Azarnouche, Laurent; Gurer, Emir; Durand, William; Maher, Michael; Mori, Kazunori; Blachut, Gregory; Janes, Dustin; Asano, Yusuke; Someya, Yasunobu; Hymes, Diane; Graves, David; Ellison, Christopher J.; Willson, C. Grant

    2016-03-01

    The directed self-assembly (DSA) of block copolymers offers a promising route for scaling feature sizes below 20 nm. At these small dimensions, plasmas are often used to define the initial patterns. It is imperative to understand how plasmas interact with each block in order to design processes with sufficient etch contrast and pattern fidelity. Symmetric lamella forming block copolymers including, polystyrene-b-poly(methyl methacrylate) and several high-χ silicon-containing and tin-containing block copolymers were synthesized, along with homopolymers of each block, and exposed to various oxidizing, reducing, and fluorine-based plasma processes. Etch rate kinetics were measured, and plasma modifications of the materials were characterized using XPS, AES, and FTIR. Mechanisms for achieving etch contrast were elucidated and were highly dependent on the block copolymer architecture. For several of the polymers, plasma photoemissions were observed to play an important role in modifying the materials and forming etch-resistant protective layers. Furthermore, it was observed for the silicon- and tin-containing polymers that an initial transient state exists, where the polymers exhibit an enhanced etch rate, prior to the formation of the etch-resistant protective layer. Plasma developed patterns were demonstrated for the differing block copolymer materials with feature sizes ranging from 20 nm down to approximately 5 nm.

  5. Low-Temperature Processable Block Copolymers That Preserve the Function of Blended Proteins.

    PubMed

    Iwasaki, Yasuhiko; Takemoto, Kyohei; Tanaka, Shinya; Taniguchi, Ikuo

    2016-07-11

    Low-temperature processable polymers have attracted increasing interest as ecological materials because of their reduced energy consumption during processing and suitability for making composites with heat-sensitive biomolecules at ambient temperature. In the current study, low-temperature processable biodegradable block copolymers were synthesized by ring-opening polymerization of l-lactide (LLA) using polyphosphoester as a macroinitiator. The polymer films could be processed under a hydraulic pressure of 35 MPa. The block copolymer films swelled in water because the polyphosphoester block was partially hydrated. Interestingly, the swelling ratio of the films changed with temperature. The pressure-induced order-to-disorder transition of the block copolymers was characterized by small-angle X-ray scattering; a crystallinity reduction in the block copolymers was observed after application of pressure. The crystallinity of the block copolymers was recovered after removing the applied pressure. The Young's modulus of the block copolymer films increased as the LLA unit content increased. Moreover, the modulus did not change after multiple processing cycles and the recyclability of the block copolymers was also confirmed. Finally, polymer films with embedded proteinase K as a model protein were prepared. The activity of catalase loaded into the polymer films was evaluated after processing at different temperatures. The activity of catalase was preserved when the polymer films were processed at room temperature but was significantly reduced after high-temperature processing. The suitability of low-temperature processable biodegradable polymers for making biofunctional composites without reducing protein activity was clarified. These materials will be useful for biomedical and therapeutic applications. PMID:27280847

  6. Controlled self-assembly of conjugated rod-coil block copolymers for applications in organic optoelectronics

    NASA Astrophysics Data System (ADS)

    Tao, Yuefei

    Organic electronics are of great interest in manufacturing light weight, mechanical flexible, and inexpensive large area devices. While significant improvements have been made over the last several years and it is now clear that morphology on the lengthscale of exciton diffusion (10nm) is of crucial importance, a clear relationship between structure and device properties has not emerged. This lack of understanding largely emerges from an inability to control morphology on this lengthscale. This thesis will center around an approach, based on block copolymer self-assembly, to generate equilibrium nanostructures on the 10 nm lengthscale of exciton diffusion and study their effects on device performance. Self-assembly of semiconducting block copolymers is complicated by the non-classical chain shape of conjugated polymers. Unlike classical polymers, the chains do not assume a Gaussian coil shape which is stretched near block copolymer interfaces, instead the chains are elongated and liquid crystalline. Previous work has demonstrated how these new molecular interactions and shapes control the phase diagram of so-called rod-coil block copolymers. Here, we will focus on controlling domain size, orientation, and chemical structure. While domain size can be controlled directly through molecular weight, this requires significant additional synthesis of domain size is to be varied. Here, the domain size is controlled by blending homopolymers into a self-assembling rod-coil block copolymer. When coil-like blocks are incorporated, the domains swell, as expected. When rod-like blocks are incorporated, they interdigitate with the rods of the block copolymers. This results in an increase in interfacial area which forces the coils to rearrange and an overall decrease in domain size with increasing rod content. Control over lamellar orientation is crucial in order to design and control charge transport pathways and exciton recombination or separation interfaces. While numerous

  7. Solvent vapor induced morphology variation in thin films of PS-b-PLA copolymers

    NASA Astrophysics Data System (ADS)

    Foote, Lauren; Heres, Maximilian; Kinsey, Thomas; Sangoro, Joshua

    Molecular dynamics in thin films of PS-b-PLA copolymers annealed by solvent vapor annealing is investigated using broadband dielectric spectroscopy, atomic force microscopy and ellipsometry. Impact of morphology changes on molecular dynamics are analyzed. The results of this study are discussed within the framework of current understanding of morphology control of copolymer thin films.

  8. Poly(vinylidene fluoride)/nickel nanocomposites from semicrystalline block copolymer precursors

    NASA Astrophysics Data System (ADS)

    Voet, Vincent S. D.; Tichelaar, Martijn; Tanase, Stefania; Mittelmeijer-Hazeleger, Marjo C.; ten Brinke, Gerrit; Loos, Katja

    2012-12-01

    The fabrication of nanoporous poly(vinylidene fluoride) (PVDF) and PVDF/nickel nanocomposites from semicrystalline block copolymer precursors is reported. Polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PS-b-PVDF-b-PS) is prepared through functional benzoyl peroxide initiated polymerization of VDF, followed by atom transfer radical polymerization (ATRP) of styrene. The crystallization of PVDF plays a dominant role in the formation of the block copolymer structure, resulting in a spherulitic superstructure with an internal crystalline-amorphous lamellar nanostructure. The block copolymer promotes the formation of the ferroelectric β-polymorph of PVDF. Selective etching of the amorphous regions with nitric acid leads to nanoporous PVDF, which functions as a template for the generation of PVDF/Ni nanocomposites. The lamellar nanostructure and the β-crystalline phase are conserved during the etching procedure and electroless nickel deposition.The fabrication of nanoporous poly(vinylidene fluoride) (PVDF) and PVDF/nickel nanocomposites from semicrystalline block copolymer precursors is reported. Polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PS-b-PVDF-b-PS) is prepared through functional benzoyl peroxide initiated polymerization of VDF, followed by atom transfer radical polymerization (ATRP) of styrene. The crystallization of PVDF plays a dominant role in the formation of the block copolymer structure, resulting in a spherulitic superstructure with an internal crystalline-amorphous lamellar nanostructure. The block copolymer promotes the formation of the ferroelectric β-polymorph of PVDF. Selective etching of the amorphous regions with nitric acid leads to nanoporous PVDF, which functions as a template for the generation of PVDF/Ni nanocomposites. The lamellar nanostructure and the β-crystalline phase are conserved during the etching procedure and electroless nickel deposition. Electronic supplementary information (ESI) available

  9. Design and Synthesis of Novel Block Copolymers for Efficient Opto-Electronic Applications

    NASA Technical Reports Server (NTRS)

    Sun, Sam-Shajing; Fan, Zhen; Wang, Yiqing; Taft, Charles; Haliburton, James; Maaref, Shahin

    2002-01-01

    It has been predicted that nano-phase separated block copolymer systems containing electron rich donor blocks and electron deficient acceptor blocks may facilitate the charge carrier separation and migration in organic photovoltaic devices due to improved morphology in comparison to polymer blend system. This paper presents preliminary data describing the design and synthesis of a novel Donor-Bridge-Acceptor (D-B-A) block copolymer system for potential high efficient organic optoelectronic applications. Specifically, the donor block contains an electron donating alkyloxy derivatized polyphenylenevinylene (PPV), the acceptor block contains an electron withdrawing alkyl-sulfone derivatized polyphenylenevinylene (PPV), and the bridge block contains an electronically neutral non-conjugated aliphatic hydrocarbon chain. The key synthetic strategy includes the synthesis of each individual block first, then couple the blocks together. While the donor block stabilizes and facilitates the transport of the holes, the acceptor block stabilizes and facilitates the transport of the electrons, the bridge block is designed to hinder the probability of electron-hole recombination. Thus, improved charge separation and stability are expected with this system. In addition, charge migration toward electrodes may also be facilitated due to the potential nano-phase separated and highly ordered block copolymer ultra-structure.

  10. 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.

  11. Rheology, Morphology and Phase Behavior in Amphiphilic Block Copolymer/microemulsion Systems

    NASA Astrophysics Data System (ADS)

    Gottlieb, Moshe; Braun, Liora; Zhang, Zeng-Rong

    2000-03-01

    Joining together by means of covalent bonds hydrophobic and hydrophilic entities on the same molecule gives rise to materials with interesting properties in aqueous systems or in the presence of mixed solvents such as water/oil microemulsions. In this paper we describe the rheological properties of a synthetic amphiphilic block copolymer dissolved in a water-in-oil microemulsion. The block copolymer is an ABA type copolymer composed of poly(oxyethylene) (PEO) as the hydrophilic A block and poly(dimethyl siloxane) (PDMS) as the hydrophobic center B block. Different polymers have been prepared with a B block of D_p=160 and three different sizes of the A blocks with D_p= 10, 45, and 120 respectively. The resulting copolymer is insoluble in water and hardly soluble in decane (good solvent for the PDMS). In the presence of water in oil microemulsion stabilized by the small molecular weight surfactant AOT a one-phase region is maintained when the copolymer is added. Yet, peculiar rheological behavior is observed. For constant water-microemulsion concentration (φ) addition of polymer increases the system viscosity as expected. Yet, the lower φ the higher the viscosity and at high φ the effect of polymer addition is quite low.

  12. 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.

  13. 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.

  14. 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

  15. ABC triblock surface active block copolymer with grafted ethoxylated fluoroalkyl amphiphilic side chains for marine antifouling/fouling-release applications.

    PubMed

    Weinman, Craig J; Finlay, John A; Park, Daewon; Paik, Marvin Y; Krishnan, Sitaraman; Sundaram, Harihara S; Dimitriou, Michael; Sohn, Karen E; Callow, Maureen E; Callow, James A; Handlin, Dale L; Willis, Carl L; Kramer, Edward J; Ober, Christopher K

    2009-10-20

    An amphiphilic triblock surface-active block copolymer (SABC) possessing ethoxylated fluoroalkyl side chains was synthesized through the chemical modification of a polystyrene-block-poly(ethylene-ran-butylene)-block-polyisoprene polymer precursor. Bilayer coatings on glass slides consisting of a thin layer of the amphiphilic SABC spray coated on a thick layer of a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) thermoplastic elastomer were prepared for biofouling assays with the green alga Ulva and the diatom Navicula. Dynamic water contact angle analysis and X-ray photoelectron spectroscopy (XPS) were used to characterize the surfaces. Additionally, the effect of the Young's modulus of the coating on the release properties of sporelings (young plants) of the green alga Ulva was examined through the use of two different SEBS thermoplastic elastomers possessing modulus values of an order of magnitude in difference. The amphiphilic SABC was found to reduce the settlement density of zoospores of Ulva as well as the strength of attachment of sporelings. The attachment strength of the sporelings was further reduced for the amphiphilic SABC on the "low"-modulus SEBS base layer. The weaker adhesion of diatoms, relative to a PDMS standard, further highlights the antifouling potential of this amphiphilic triblock hybrid copolymer.

  16. Block copolymers via living transition metal initiated polymerizations; Change of mechanism and bimetallic initiator approaches

    SciTech Connect

    Novak, B.M.; Deming, T.J.

    1993-12-31

    The authors have been interested in the development of transition metal catalysts for use in living polymerizations to form polymers with well-defined secondary structures, and to precisely incorporate these regular structures into di- and tri-block copolymers. Much of this work has focused on the development of rodlike helical polyisocyanate and polyisocyanide chains that are known to form liquid crystalline, and/or highly regular crystalline phases. The compound [({eta}{sup 3}C{sub 3}H{sub 5})Ni(OC(O)CF{sub 3})]{sub 2} (I), which has been used extensively as a butadiene polymerization catalyst, has been successfully used in the preparation of polyisocyanide - polybutadiene block copolymers. These blocks have been characterized by using gel permeation chromotography, differential scanning calorimetry, {sup 13}C NMR and scanning electron microscopy. Since both monomer polymerizations are living, this block copolymer synthesis is highly versatile with respect to polymer segment chain lengths and the types of monomers used.

  17. Hemocompatibility of styrenic block copolymers for use in prosthetic heart valves.

    PubMed

    Brubert, Jacob; Krajewski, Stefanie; Wendel, Hans Peter; Nair, Sukumaran; Stasiak, Joanna; Moggridge, Geoff D

    2016-02-01

    Certain styrenic thermoplastic block copolymer elastomers can be processed to exhibit anisotropic mechanical properties which may be desirable for imitating biological tissues. The ex-vivo hemocompatibility of four triblock (hard-soft-hard) copolymers with polystyrene hard blocks and polyethylene, polypropylene, polyisoprene, polybutadiene or polyisobutylene soft blocks are tested using the modified Chandler loop method using fresh human blood and direct contact cell proliferation of fibroblasts upon the materials. The hemocompatibility and durability performance of a heparin coating is also evaluated. Measures of platelet and coagulation cascade activation indicate that the test materials are superior to polyester but inferior to expanded polytetrafluoroethylene and bovine pericardium reference materials. Against inflammatory measures the test materials are superior to polyester and bovine pericardium. The addition of a heparin coating results in reduced protein adsorption and ex-vivo hemocompatibility performance superior to all reference materials, in all measures. The tested styrenic thermoplastic block copolymers demonstrate adequate performance for blood contacting applications. PMID:26704549

  18. Multi-block sulfonated poly(phenylene) copolymer proton exchange membranes

    DOEpatents

    Fujimoto, Cy H.; Hibbs, Michael; Ambrosini, Andrea

    2012-02-07

    Improved multi-block sulfonated poly(phenylene) copolymer compositions, methods of making the same, and their use as proton exchange membranes (PEM) in hydrogen fuel cells, direct methanol fuel cells, in electrode casting solutions and electrodes. The multi-block architecture has defined, controllable hydrophobic and hydrophilic segments. These improved membranes have better ion transport (proton conductivity) and water swelling properties.

  19. 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.

  20. Organic solar cell optimizations in both space and energy regimes: large open circuit voltage from a -DBAB- type block copolymer

    NASA Astrophysics Data System (ADS)

    Sun, S.; Zhang, C.; Haliburton, J.; Ledbetter, A.; Bonner, C.; Drees, M.; Sariciftci, N.

    2005-10-01

    Organic/polymeric solar cells can be optimized in both space (morphology) and energy regimes to minimize the 'photon loss', the 'exciton loss' and the 'carrier loss'. In spatial regime optimization, for instance, a set of thin film solar cell devices fabricated from a -donor-bridge-acceptor-bridge- (-DBAB-) type block copolymer containing polyphenylenevinylene (PPV) conjugated donor and acceptor segments exhibited open circuit voltages (Voc) up to 1.1 volt, which is very impressive for organic/polymeric photovoltaics, though the photoelectric quantum and power conversion efficiencies are still very low due to energy gap mismatch and very small and not yet optimized short circuit current (in micro Amps regime).

  1. Block copolymer mixtures as antimicrobial hydrogels for biofilm eradication.

    PubMed

    Lee, Ashlynn L Z; Ng, Victor W L; Wang, Weixin; Hedrick, James L; Yang, Yi Yan

    2013-12-01

    Current antimicrobial strategies have mostly been developed to manage infections due to planktonic cells. However, microbes in their nature state will tend to exist by attaching to and growing on living and inanimate surfaces that result in the formation of biofilms. Conventional therapies for treating biofilm-related infections are likely to be insufficient due to the lower susceptibility of microbes that are embedded in the biofilm matrix. In this study, we report the development of biodegradable hydrogels from vitamin E-functionalized polycarbonates for antimicrobial applications. These hydrogels were formed by incorporating positively-charged polycarbonates containing propyl and benzyl side chains with vitamin E moiety into physically cross-linked networks of "ABA"-type polycarbonate and poly(ethylene glycol) triblock copolymers. Investigations of the mechanical properties of the hydrogels showed that the G' values ranged from 1400 to 1600 Pa and the presence of cationic polycarbonate did not affect the stiffness of the hydrogels. Shear-thinning behavior was observed as the hydrogels displayed high viscosity at low shear rates that dramatically decreased as the shear rate increased. In vitro antimicrobial studies revealed that the more hydrophobic VE/BnCl(1:30)-loaded hydrogels generally exhibited better antimicrobial/antifungal effects compared to the VE/PrBr(1:30) counterpart as lower minimum biocidal concentrations (MBC) were observed in Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative) and Candida albicans (fungus) (156.2, 312.5, 312.5 mg/L for VE/BnCl(1:30) and 312.5, 2500 and 625 mg/L for VE/PrBr(1:30) respectively). Similar trends were observed for the treatment of biofilms where VE/BnCl(1:30)-loaded hydrogels displayed better efficiency with regards to eradication of biomass and reduction of microbe viability of the biofilms. Furthermore, a high degree of synergistic antimicrobial effects was also observed through the co

  2. 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

  3. Morphological Characterization of Elastin-Mimetic Block Copolymers Utilizing Cryo- and Cryoetch-HRSEM

    NASA Astrophysics Data System (ADS)

    Wright, Elizabeth R.; Conticello, Vincent P.; Apkarian, Robert P.

    2003-06-01

    Elastin-mimetic block copolymers were produced by genetic engineering. Genetically driven synthesis permitted control of the final physiochemical characteristics of the block copolymers. We designed BB and BAB block copolymers in which the A-block was hydrophilic and the B-block was hydrophobic. By designing the copolymers in this manner, it was proposed that they would self-assemble into micellar aggregates that, at high concentration, would form thermoreversible hydrogels. To analyze the three-dimensional fine surface morphology of the copolymers, to the resolution level of a few nanometers, we employed cryo-HRSEM. This method provided vast expanses of the specimen in its frozen hydrated state for survey. In our initial cryo-HRSEM studies, we observed the protein filaments and micelles surrounded by lakes of vitreous ice. Upon examination at low and intermediate magnifications, there was an extensive honeycomb-like filamentous network. To delineate the fine morphology of the hydrogel network at high magnification and to greater depths, we cryoetched away unbound water from the sample surface, in high vacuum, prior to chromium deposition. By using this technique, we were able to visualize for characterization purposes the fine fibril networks formed from the micellar aggregates over the surface of the hydrogel.

  4. Brownian dynamics simulation of amphiphilic block copolymers with different tail lengths, comparison with theory and comicelles.

    PubMed

    Hafezi, Mohammad-Javad; Sharif, Farhad

    2015-11-01

    Study on the effect of amphiphilic copolymers structure on their self assembly is an interesting subject, with important applications in the area of drug delivery and biological system treatments. Brownian dynamics simulations were performed to study self-assembly of the linear amphiphilic block copolymers with the same hydrophilic head, but hydrophobic tails of different lengths. Critical micelle concentration (CMC), gyration radius distribution, micelle size distribution, density profiles of micelles, shape anisotropy, and dynamics of micellization were investigated as a function of tail length. Simulation results were compared with predictions from theory and simulation for mixed systems of block copolymers with long and short hydrophobic tail, reported in our previous work. Interestingly, the equilibrium structural and dynamic parameters of pure and mixed block copolymers were similarly dependant on the intrinsic/apparent hydrophobic block length. Log (CMC) was, however; proportional to the tail length and had a different behavior compared to the mixed system. The power law scaling relation of equilibrium structural parameters for amphiphilic block copolymers predicts the same dependence for similar hydrophobic tail lengths, but the power law prediction of CMC is different, which is due to its simplifying assumptions as discussed here.

  5. Synthesis of manganese oxide supported on mesoporous titanium oxide: Influence of the block copolymer

    SciTech Connect

    Schmit, F.; Bois, L.; Chiriac, R.; Toche, F.; Chassagneux, F.; Besson, M.; Descorme, C.; Khrouz, L.

    2015-01-15

    Manganese oxides supported on mesoporous titanium oxides were synthesized via a sol–gel route using block copolymer self-assembly. The oxides were characterized by X-ray diffraction, infrared spectroscopy, thermal analyses, nitrogen adsorption/desorption, electron microscopy and electronic paramagnetic resonance. A mesoporous anatase containing amorphous manganese oxide particles could be obtained with a 0.2 Mn:Ti molar ratio. At higher manganese loading (0.5 Mn:Ti molar ratio), segregation of crystalline manganese oxide occurred. The influence of block copolymer and manganese salt on the oxide structure was discussed. The evolution of the textural and structural characteristics of the materials upon hydrothermal treatment was also investigated. - Graphical abstract: One-pot amorphous MnO{sub 2} supported on mesoporous anataseTiO{sub 2}. - Highlights: • Mesoporous manganese titanium oxides were synthesized using block copolymer. • Block copolymers form complexes with Mn{sup 2+} from MnCl{sub 2}. • With block copolymer, manganese oxide can be dispersed around the titania crystallites. • With Mn(acac){sub 2}, manganese is dispersed inside titania. • MnOOH crystallizes outside mesoporous titania during hydrothermal treatment.

  6. Thermosensitive PNIPAM-b-HTPB block copolymer micelles: molecular architectures and camptothecin drug release.

    PubMed

    Luo, Yan-Ling; Yang, Xiao-Li; Xu, Feng; Chen, Ya-Shao; Zhang, Bin

    2014-02-01

    Two kinds of thermo-sensitive poly(N-isoproplacrylamide) (PNIPAM) block copolymers, AB4 four-armed star multiblock and linear triblock copolymers, were synthesized by ATRP with hydroxyl-terminated polybutadiene (HTPB) as central blocks, and characterization was performed by (1)H NMR, FT-IR and SEC. The multiblock copolymers could spontaneously assemble into more regular spherical core-shell nanoscale micelles than the linear triblock copolymer. The physicochemical properties were detected by a surface tension technique, nano particle analyzer, TEM, DLS and UV-vis measurements. The multiblock copolymer micelles had lower critical micelle concentration than the linear counterpart, TEM size from 100 to 120 nm and the hydrodynamic diameters below 150 nm. The micelles exhibited thermo-dependent size change, with low critical solution temperature about 33-35 °C. The characteristic parameters were affected by the composition ratios, length of PNIPAM blocks and molecular architectures. The camptothecin release demonstrated that the drug release was thermo-responsive, accompanied by the temperature-induced structural changes of the micelles. MTT assays were performed to evaluate the biocompatibility or cytotoxicity of the prepared copolymer micelles. PMID:24184534

  7. Structure and ionic conductivity of block copolymer electrolytes over a wide salt concentration range

    NASA Astrophysics Data System (ADS)

    Chintapalli, Mahati; Le, Thao; Venkatesan, Naveen; Thelen, Jacob; Rojas, Adriana; Balsara, Nitash

    Block copolymer electrolytes are promising materials for safe, long-lasting lithium batteries because of their favorable mechanical and ion transport properties. The morphology, phase behavior, and ionic conductivity of a block copolymer electrolyte, SEO mixed with LiTFSI was studied over a wide, previously unexplored salt concentration range using small angle X-ray scattering, differential scanning calorimetry and ac impedance spectroscopy, respectively. SEO exhibits a maximum in ionic conductivity at twice the salt concentration that PEO, the homopolymer analog of the ion-containing block, does. This finding is contrary to prior studies that examined a more limited range of salt concentrations. In SEO, the phase behavior of the PEO block and LiTFSI closely resembles the phase behavior of homopolymer PEO and LiTFSI. The grain size of the block copolymer morphology was found to decrease with increasing salt concentration, and the ionic conductivity of SEO correlates with decreasing grain size. Structural effects impact the ionic conductivity-salt concentration relationship in block copolymer electrolytes. SEO: polystyrene-block-poly(ethylene oxide); also PS-PEO LiTFSI: lithium bis(trifluoromethanesulfonyl imide

  8. Kinetic control of block copolymer self-assembly into multicompartment and novel geometry nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Yingchao; Wang, Xiaojun; Zhang, Ke; Wooley, Karen; Mays, Jimmy; Percec, Virgil; Pochan, Darrin

    2012-02-01

    Micelles with the segregation of hydrophobic blocks trapped in the same nanoparticle core have been produced through co-self-assembly of two block copolymers in THF/water dilute solution. The dissolution of two block copolymer sharing the same polyacrylic acid PAA blocks in THF undergoes consequent aggregation and phase separation through either slow water titration or quick water addition that triggers the micellar formation. The combination and comparison of the two water addition kinetic pathways are the keys of forming multicompartment structures at high water content. Importantly, the addition of organic diamine provides for acid-base complexation with the PAA side chains which, in turn, plays the key role of trapping unlike hydrophobic blocks from different block copolymers into one nanoparticle core. The kinetic control of solution assembly can be applied to other molecular systems such as dendrimers as well as other block copolymer molecules. Transmission electron microscopy, cryogenic transmission electron microscopy, light scattering have been applied to characterize the micelle structures.

  9. Vertical Continuity and Alignment of Block Copolymer Domains by Kinetically Controlled Electrospray Deposition

    NASA Astrophysics Data System (ADS)

    Hu, Hanqiong; Woo, Youngwoo; Feng, Xunda; Osuji, Chinedum; Osuji Lab Team

    2015-03-01

    We report the fabrication of vertically aligned cylindrical block copolymer (BCP) domains using continuous electrospray deposition (ESD) onto bare wafer surfaces. The out-of-plane orientation of hexagonally packed styrene cylinders was achieved in a ``fast-wet'' deposition regime where rapid evaporation of solvent in droplets of polymer solution drove the vertical alignment of SBS domains. The deposition conditions were optimized such that thermally activated crosslinking of the polybutadiene matrix provided kinetic control of the morphology, locking in the vertical alignment and preventing relaxation of the system to its preferred parallel orientation on the non-treated substrate. Physically continuous and vertically oriented domains is achieved over several microns of film thickness. We describe the effects of flow rate, collection distance and substrate temperature on thin film morphology and demonstrate selective etching capabilities. The ability of ESD to fabricate well-ordered and aligned BCP films on non-treated substrates, the low utilization of material relative to spin-coating and the continuous nature of the deposition may open up new opportunities for BCP thin films. We are exploring ESD as a new platform for sequential deposition of BCPs with different functionalities.

  10. Coarse-grained molecular dynamics modeling of the kinetics of lamellar block copolymer defect annealing

    NASA Astrophysics Data System (ADS)

    Peters, Andrew J.; Lawson, Richard A.; Nation, Benjamin D.; Ludovice, Peter J.; Henderson, Clifford L.

    2016-01-01

    State-of-the-art block copolymer (BCP)-directed self-assembly (DSA) methods still yield defect densities orders of magnitude higher than is necessary in semiconductor fabrication despite free-energy calculations that suggest equilibrium defect densities are much lower than is necessary for economic fabrication. This disparity suggests that the main problem may lie in the kinetics of defect removal. This work uses a coarse-grained model to study the rates, pathways, and dependencies of healing a common defect to give insight into the fundamental processes that control defect healing and give guidance on optimal process conditions for BCP-DSA. It is found that bulk simulations yield an exponential drop in defect heal rate above χN˜30. Thin films show no change in rate associated with the energy barrier below χN˜50, significantly higher than the χN values found previously for self-consistent field theory studies that neglect fluctuations. Above χN˜50, the simulations show an increase in energy barrier scaling with 1/2 to 1/3 of the bulk systems. This is because thin films always begin healing at the free interface or the BCP-underlayer interface, where the increased A-B contact area associated with the transition state is minimized, while the infinitely thick films cannot begin healing at an interface.

  11. Aqueous self-assembly of giant bottlebrush block copolymer surfactants as shape-tunable building blocks.

    PubMed

    Fenyves, Ryan; Schmutz, Marc; Horner, Ian J; Bright, Frank V; Rzayev, Javid

    2014-05-28

    Programmed self-assembly of well-defined molecular building blocks enables the fabrication of precisely structured nanomaterials. In this work, we explore a new class of giant polymeric surfactants (Mn = (0.7-4.4) × 10(6) g/mol) with bottlebrush architecture and show that their persistent molecular shape leads to the formation of uniform aggregates in a predictable manner. Amphiphilic bottlebrush block copolymers containing polylactide (PLA) and poly(ethylene oxide) (PEO) side chains were synthesized by a grafting-from method, and their self-assembly in aqueous environment was studied by cryogenic transmission electron microscopy. The produced micelle structures with varying interfacial curvatures and core radii (19-55 nm) boasted rod-like hydrophilic PEO brushes protruding from the hydrophobic PLA cores normal to the interface. Highly uniform spherical micelles with low dispersities were obtained from bottlebrush amphiphiles with packing parameters of ∼0.3, estimated from the polymer structural data. Long cylindrical micelles and other nonspherical aggregates were observed for the first time for compositionally less asymmetric bottlebrush surfactants. Critical micelle concentration values of 1 nM, measured for PEO-rich bottlebrush amphiphiles, indicated an enhanced thermodynamic stability of the produced micelle aggregates. Shape-dependent assembly of bottlebrush surfactants allows for the rational fabrication of a range of micelle structures in narrow morphological windows.

  12. Polythiophene-block-poly(γ-benzyl L-glutamate): Synthesis and study of a new rod-rod block copolymer

    SciTech Connect

    Wu, Zong-Quan; Ono, Robert J.; Chen, Zheng; Li, Zicheng; Bielawski, Christopher W.

    2011-01-01

    Coupling of ethynyl terminated poly(3-hexylthiophene) with azide terminated poly(γ-benzyl L-glutamate) afforded the respective block copolymer in good yield and high purity; this material was found to self assemble into hierarchal structures in solution and in the solid state.

  13. Polybenzimidazole block copolymers for fuel cell: synthesis and studies of block length effects on nanophase separation, mechanical properties, and proton conductivity of PEM.

    PubMed

    Maity, Sudhangshu; Jana, Tushar

    2014-05-14

    A series of meta-polybenzimidazole-block-para-polybenzimidazole (m-PBI-b-p-PBI), segmented block copolymers of PBI, were synthesized with various structural motifs and block lengths by condensing the diamine terminated meta-PBI (m-PBI-Am) and acid terminated para-PBI (p-PBI-Ac) oligomers. NMR studies and existence of two distinct glass transition temperatures (Tg), obtained from dynamical mechanical analysis (DMA) results, unequivocally confirmed the formation of block copolymer structure through the current polymerization methodology. Appropriate and careful selection of oligomers chain length enabled us to tailor the block length of block copolymers and also to make varieties of structural motifs. Increasingly distinct Tg peaks with higher block length of segmented block structure attributed the decrease in phase mixing between the meta-PBI and para-PBI blocks, which in turn resulted into nanophase segregated domains. The proton conductivities of proton exchange membrane (PEM) developed from phosphoric acid (PA) doped block copolymer membranes were found to be increasing substantially with increasing block length of copolymers even though PA loading of these membranes did not alter appreciably with varying block length. For example when molecular weight (Mn) of blocks were increased from 1000 to 5500 then the proton conductivities at 160 °C of resulting copolymers increased from 0.05 to 0.11 S/cm. Higher block length induced nanophase separation between the blocks by creating less morphological barrier within the block which facilitated the movement of the proton in the block and hence resulting higher proton conductivity of the PEM. The structural varieties also influenced the phase separation and proton conductivity. In comparison to meta-para random copolymers reported earlier, the current meta-para segmented block copolymers were found to be more suitable for PBI-based PEM.

  14. Aqueous-Based Fabrication of Low-VOC Nanostructured Block Copolymer Films as Potential Marine Antifouling Coatings.

    PubMed

    Kim, Kris S; Gunari, Nikhil; MacNeil, Drew; Finlay, John; Callow, Maureen; Callow, James; Walker, Gilbert C

    2016-08-10

    The ability to fabricate nanostructured films by exploiting the phenomenon of microphase separation has made block copolymers an invaluable tool for a wide array of coating applications. Standard approaches to engineering nanodomains commonly involve the application of organic solvents, either through dissolution or annealing protocols, resulting in the release of volatile organic compounds (VOCs). In this paper, an aqueous-based method of fabricating low-VOC nanostructured block copolymer films is presented. The reported procedure allows for the phase transfer of water insoluble triblock copolymer, poly(styrene-block-2 vinylpyridine-block-ethylene oxide) (PS-b-P2VP-b-PEO), from a water immiscible phase to an aqueous environment with the assistance of a diblock copolymeric phase transfer agent, poly(styrene-block-ethylene oxide) (PS-b-PEO). Phase transfer into the aqueous phase results in self-assembly of PS-b-P2VP-b-PEO into core-shell-corona micelles, which are characterized by dynamic light scattering techniques. The films that result from coating the micellar solution onto Si/SiO2 surfaces exhibit nanoscale features that disrupt the ability of a model foulant, a zoospore of Ulva linza, to settle. The multilayered architecture consists of a pH-responsive P2VP-"shell" which can be stimulated to control the size of these features. The ability of these nanostructured thin films to resist protein adsorption and serve as potential marine antifouling coatings is supported through atomic force microscopy (AFM) and analysis of the settlement of Ulva linza zoospore. Field trials of the surfaces in a natural environment show the inhibition of macrofoulants for 1 month. PMID:27388921

  15. 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

  16. 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

  17. Three-dimensional inverse design of nanopatterns with block copolymers and homopolymers

    NASA Astrophysics Data System (ADS)

    Xu, Dan; Liu, Hong; Zhu, You-Liang; Lu, Zhong-Yuan

    2016-02-01

    We propose a facile inverse design strategy to generate three-dimensional (3D) nanopatterns by using either block copolymers or a binary homopolymer blend via dissipative particle dynamics simulations. We find that the composition window of block copolymers to form a specific 3D morphology can be expanded when the self-assembly of block copolymers is directed by templates. We also find that a binary homopolymer blend can serve as a better candidate in the inverse templating design, since they have similar performances on recovering the target pattern, with much lower cost. This strategy is proved efficient for fabricating templates with desired topographical configuration, and the inverse design idea sheds lights on better control and design of materials with complex nanopatterns.

  18. Three-dimensional inverse design of nanopatterns with block copolymers and homopolymers.

    PubMed

    Xu, Dan; Liu, Hong; Zhu, You-Liang; Lu, Zhong-Yuan

    2016-03-01

    We propose a facile inverse design strategy to generate three-dimensional (3D) nanopatterns by using either block copolymers or a binary homopolymer blend via dissipative particle dynamics simulations. We find that the composition window of block copolymers to form a specific 3D morphology can be expanded when the self-assembly of block copolymers is directed by templates. We also find that a binary homopolymer blend can serve as a better candidate in the inverse templating design, since they have similar performances on recovering the target pattern, with much lower cost. This strategy is proved efficient for fabricating templates with desired topographical configuration, and the inverse design idea sheds lights on better control and design of materials with complex nanopatterns. PMID:26880143

  19. Efficient Synthesis of Cyclic Block Copolymers by Rotaxane Protocol by Linear/Cyclic Topology Transformation.

    PubMed

    Valentina, Stephanie; Ogawa, Takahiro; Nakazono, Kazuko; Aoki, Daisuke; Takata, Toshikazu

    2016-06-20

    High-yielding synthesis of cyclic block copolymer (CBC) using the rotaxane protocol by linear-cyclic polymer topology transformation was first demonstrated. Initial complexation of OH-terminated sec-ammonium salt and a crown ether was followed by the successive living ring-opening polymerizations of two lactones to a linear block copolymer having a rotaxane structure by the final capping of the propagation end. CBC was obtained in a high yield by an exploitation of the mechanical linkage through the translational movement of the rotaxane component to transform polymer structure from linear to cyclic. Furthermore, the change of the polymer topology was translated into a macroscopic change in crystallinity of the block copolymer. PMID:27037975

  20. Charge transfer in the low-temperature radiolysis of styrene-butadiene block copolymers

    SciTech Connect

    Khatipov, S.A.; Edrisov, A.T.; Milinchuk, V.K.

    1995-05-01

    Radiation-induced conductivity of polystyrene, polybutadiene, and styrene-butadiene block copolymers, resulting from irradiation of the samples with fast electrons of 75 keV energy under vacuum at 100 K, was studied. A negative deviation of the radiation-induced conductivity constant A{sub m} from the corresponding additive values was detected upon varying the composition of block copolymers. It is concluded that the interfacial charge transfer from polystyrene to polybutadiene microdomains occurs in the block copolymers. This conclusion is confirmed by the results of investigations of drift mobility of the charge carriers and effects of donor-acceptor admixtures on the radiation-induced conductivity of the polymers studied.

  1. Amphiphilic block copolymers in oil-water-surfactant mixtures: efficiency boosting, structure, phase behaviour and mechanism

    NASA Astrophysics Data System (ADS)

    Gompper, G.; Richter, D.; Strey, R.

    2001-10-01

    The effect of amphiphilic block copolymers on the phase behaviour and structure of ternary microemulsions in water, oil and non-ionic surfactant mixtures is reviewed. Recent experiments have revealed that the addition of small amounts of polyethylenepropylene-polyethyleneoxide block copolymer to the ternary systems leads to a dramatic increase in the volumes of oil and water solubilized into a bicontinuous microemulsion for a given surfactant volume fraction. While phase diagrams directly show the power of the amphiphilic block copolymers as efficiency boosters, the theoretical analysis in terms of bending energy discloses the mechanism for the efficiency boosting as due to the variation of the surfactant film curvature elasticity by tethered polymers in the form of mushrooms at the interface. Neutron scattering experiments employing a high-precision two-dimensional contrast variation technique confirm this picture and demonstrate that the polymer molecules uniformly decorate the surfactant film.

  2. Selective directed self-assembly of coexisting morphologies using block copolymer blends

    NASA Astrophysics Data System (ADS)

    Stein, A.; Wright, G.; Yager, K. G.; Doerk, G. S.; Black, C. T.

    2016-08-01

    Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. Here we expand on traditional DSA chemical patterning. A blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This is in contrast to the typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist.

  3. Efficient Synthesis of Cyclic Block Copolymers by Rotaxane Protocol by Linear/Cyclic Topology Transformation.

    PubMed

    Valentina, Stephanie; Ogawa, Takahiro; Nakazono, Kazuko; Aoki, Daisuke; Takata, Toshikazu

    2016-06-20

    High-yielding synthesis of cyclic block copolymer (CBC) using the rotaxane protocol by linear-cyclic polymer topology transformation was first demonstrated. Initial complexation of OH-terminated sec-ammonium salt and a crown ether was followed by the successive living ring-opening polymerizations of two lactones to a linear block copolymer having a rotaxane structure by the final capping of the propagation end. CBC was obtained in a high yield by an exploitation of the mechanical linkage through the translational movement of the rotaxane component to transform polymer structure from linear to cyclic. Furthermore, the change of the polymer topology was translated into a macroscopic change in crystallinity of the block copolymer.

  4. Ordered porous mesostructured materials from nanoparticle-block copolymer self-assembly

    DOEpatents

    Warren, Scott; Wiesner, Ulrich; DiSalvo, Jr., Francis J

    2013-10-29

    The invention provides mesostructured materials and methods of preparing mesostructured materials including metal-rich mesostructured nanoparticle-block copolymer hybrids, porous metal-nonmetal nanocomposite mesostructures, and ordered metal mesostructures with uniform pores. The nanoparticles can be metal, metal alloy, metal mixture, intermetallic, metal-carbon, metal-ceramic, semiconductor-carbon, semiconductor-ceramic, insulator-carbon or insulator-ceramic nanoparticles, or combinations thereof. A block copolymer/ligand-stabilized nanoparticle solution is cast, resulting in the formation of a metal-rich (or semiconductor-rich or insulator-rich) mesostructured nanoparticle-block copolymer hybrid. The hybrid is heated to an elevated temperature, resulting in the formation of an ordered porous nanocomposite mesostructure. A nonmetal component (e.g., carbon or ceramic) is then removed to produce an ordered mesostructure with ordered and large uniform pores.

  5. Functional Nanomaterials based on Nanoporous Block Copolymer Templates

    NASA Astrophysics Data System (ADS)

    Kim, Jin Kon

    2011-03-01

    Nanoporous templates have been widely used for the development of new functional nanostructured materials suitable for electronics, optics, magnetism, and energy storage materials. We have prepared nanoporous templates by using thin films of mixtures of polystyrene-block-poly(methyl methacrylate) (PS- b -PMMA) and PMMA homopolymers. These nanoporous films were found to be very effective for the separation of human Rhinovirus type 14, major pathogen of a common cold in humans. We found that when the pore size was effectively controlled down to 6 nm, a long-term constant in vitro release of BSA and hGH was achieved without their denaturation up to 2 months. The long-term constant delivery based on this membrane for protein drugs within the therapeutic range can be highly appreciated for the patients with hormone-deficiency. Work done in collaboration with Seung Yun Yang, Pohang University of Science and Technology. This work was supported by the National Creative Research Initiative Program supported by NRF.

  6. 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

  7. Collapse transitions in thermosensitive multi-block copolymers: a Monte Carlo study.

    PubMed

    Rissanou, Anastassia N; Tzeli, Despoina S; Anastasiadis, Spiros H; Bitsanis, Ioannis A

    2014-05-28

    Monte Carlo simulations are performed on a simple cubic lattice to investigate the behavior of a single linear multiblock copolymer chain of various lengths N. The chain of type (AnBn)m consists of alternating A and B blocks, where A are solvophilic and B are solvophobic and N = 2nm. The conformations are classified in five cases of globule formation by the solvophobic blocks of the chain. The dependence of globule characteristics on the molecular weight and on the number of blocks, which participate in their formation, is examined. The focus is on relative high molecular weight blocks (i.e., N in the range of 500-5000 units) and very differing energetic conditions for the two blocks (very good-almost athermal solvent for A and bad solvent for B). A rich phase behavior is observed as a result of the alternating architecture of the multiblock copolymer chain. We trust that thermodynamic equilibrium has been reached for chains of N up to 2000 units; however, for longer chains kinetic entrapments are observed. The comparison among equivalent globules consisting of different number of B-blocks shows that the more the solvophobic blocks constituting the globule the bigger its radius of gyration and the looser its structure. Comparisons between globules formed by the solvophobic blocks of the multiblock copolymer chain and their homopolymer analogs highlight the important role of the solvophilic A-blocks. PMID:24880322

  8. Collapse transitions in thermosensitive multi-block copolymers: A Monte Carlo study

    SciTech Connect

    Rissanou, Anastassia N.; Tzeli, Despoina S.; Anastasiadis, Spiros H.; Bitsanis, Ioannis A.

    2014-05-28

    Monte Carlo simulations are performed on a simple cubic lattice to investigate the behavior of a single linear multiblock copolymer chain of various lengths N. The chain of type (A{sub n}B{sub n}){sub m} consists of alternating A and B blocks, where A are solvophilic and B are solvophobic and N = 2nm. The conformations are classified in five cases of globule formation by the solvophobic blocks of the chain. The dependence of globule characteristics on the molecular weight and on the number of blocks, which participate in their formation, is examined. The focus is on relative high molecular weight blocks (i.e., N in the range of 500–5000 units) and very differing energetic conditions for the two blocks (very good—almost athermal solvent for A and bad solvent for B). A rich phase behavior is observed as a result of the alternating architecture of the multiblock copolymer chain. We trust that thermodynamic equilibrium has been reached for chains of N up to 2000 units; however, for longer chains kinetic entrapments are observed. The comparison among equivalent globules consisting of different number of B-blocks shows that the more the solvophobic blocks constituting the globule the bigger its radius of gyration and the looser its structure. Comparisons between globules formed by the solvophobic blocks of the multiblock copolymer chain and their homopolymer analogs highlight the important role of the solvophilic A-blocks.

  9. Micelles and polymersomes obtained by self-assembly of dextran and polystyrene based block copolymers.

    PubMed

    Houga, Clément; Giermanska, Joanna; Lecommandoux, Sébastien; Borsali, Redouane; Taton, Daniel; Gnanou, Yves; Le Meins, Jean-François

    2009-01-12

    The self-assembly of dextran-block-polystyrene (dex-b-PS) block copolymers was investigated in solution. The hydrophobic PS weight fraction in these block copolymers ranges from 7 to 92% w/w, whereas the average number molar mass of dextran was kept constant at 6600 gmol(-1). Self-assembly by direct dissolution in water could be performed only for block copolymers with a low hydrophobic content (7% w/w), whereas mixtures of tetrahydrofuran and dimethylsulfoxide were required for higher PS content, before transferring the structures into water. Core-shell micelles, ovoïds, and vesicles could be identified upon characterization by light and neutrons scattering, atomic force microscopy, and transmission electron microscopy. Most of the morphologies observed were not expected considering the chemical composition of the block copolymers. Finally, the size and shape of these nanoparticles were fixed upon cross-linking the dextran block through reaction of the hydroxyl groups with divinylsulfone. The role of the dextran conformation on the self-assembly process is discussed.

  10. Formation of Nonclassical Ordered Phases of A B -Type Multiarm Block Copolymers

    NASA Astrophysics Data System (ADS)

    Gao, Ya; Deng, Hanlin; Li, Weihua; Qiu, Feng; Shi, An-Chang

    2016-02-01

    The formation of ordered phases from block copolymers is driven by a delicate balance between the monomer-monomer interaction and chain configurational entropy. The configurational entropy can be regulated by designed chain architecture, resulting in a new entropy-driven mechanism to control the self-assembly of ordered phases from block copolymers. An effective routine to regulate the configurational entropy is to utilize multiarm architecture, in which the entropic contribution to the free energy could be qualitatively controlled by the fraction of bridging configurations. As an illustration of this mechanism, the phase behavior of two A B -type multiarm block copolymers, B0-(Bi-Ai) m and (B1-Ai-B2) m where the minority A blocks form cylindrical or spherical domains, are examined using the self-consistent field theory (SCFT). The SCFT results demonstrate that the packing symmetry of the cylinders or spheres can be controlled by the length of the bridging B blocks. Several nonclassical ordered phases, including a novel square array cylinder with p 4 m m symmetry, are predicted to form from the A B -type multiarm block copolymers.

  11. 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

  12. 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).

  13. Emission quenching and charge separation in bridged donor-acceptor block copolymers

    NASA Astrophysics Data System (ADS)

    Bonner, Carl E., Jr.; Sun, Sam-Shajing; Wang, Meina; Vick, Shameika; Winston, Kizzy M.; Ledbetter, Abram J.; Douglas, Lawrence

    2004-11-01

    The optical properties of previously synthesized sulfone and methoxy substituted block co-polymers of poly-phenlyenevinylene (PPV) have been examined. An internal space charge field is formed which has been used to quench the luminescence intensity in these materials by separating optically generated excitons and electron-hole pairs. The absorption and emission spectra and the time dependence of the emission of donor and acceptor derivatized block co-polymers was measured and the quenching of the luminescence was observed and quantified. PPV materials with this internal field have potential applications as solar energy converters and photodetectors.

  14. Azidated Ether-Butadiene-Ether Block Copolymers as Binders for Solid Propellants

    NASA Astrophysics Data System (ADS)

    Cappello, Miriam; Lamia, Pietro; Mura, Claudio; Polacco, Giovanni; Filippi, Sara

    2016-07-01

    Polymeric binders for solid propellants are usually based on hydroxyl-terminated polybutadiene (HTPB), which does not contribute to the overall energy output. Azidic polyethers represent an interesting alternative but may have poorer mechanical properties. Polybutadiene-polyether copolymers may combine the advantages of both. Four different ether-butadiene-ether triblock copolymers were prepared and azidated starting from halogenated and/or tosylated monomers using HTPB as initiator. The presence of the butadiene block complicates the azidation step and reduces the storage stability of the azidic polymer. Nevertheless, the procedure allows modifying the binder properties by varying the type and lengths of the energetic blocks.

  15. Data on macrophage mediated muscle transfection upon delivery of naked plasmid DNA with block copolymers.

    PubMed

    Mahajan, Vivek; Gaymalov, Zagit; Alakhova, Daria; Gupta, Richa; Zucker, Irving H; Kabanov, Alexander V

    2016-06-01

    The data contains 14 figures supporting the research article "Horizontal gene transfer from macrophages to ischemic muscles upon delivery of naked DNA with Pluronic block copolymers" [1]. The data explains the surgical procedure and histological characterization of Murine Hind Limb Ischemia. The data also shows the kinetics of luciferase gene expression, spread of GFP expression through muscle and the colocalization of GFP with cellular markers in ischemic muscles injected with pDNA alone or pDNA/Pluronic. Finally the data shows the effect of Pluronic Block Copolymer to enhance total gene expression (cmv-promoter driven luciferase gene) in coculture of DNA transfected MØs with muscle cells. PMID:27222845

  16. Crystalline Oligo(ethylene sulfide) Domains Define Highly Stable Supramolecular Block Copolymer Assemblies.

    PubMed

    Brubaker, Carrie E; Velluto, Diana; Demurtas, Davide; Phelps, Edward A; Hubbell, Jeffrey A

    2015-07-28

    With proper control over copolymer design and solvation conditions, self-assembled materials display impressive morphological variety that encompasses nanoscale colloids as well as bulk three-dimensional architectures. Here we take advantage of both hydrophobicity and crystallinity to mediate supramolecular self-assembly of spherical micellar, linear fibrillar, or hydrogel structures by a family of highly asymmetric poly(ethylene glycol)-b-oligo(ethylene sulfide) (PEG-OES) copolymers. Assembly structural polymorphism was achieved with modification of PEG-OES topology (linear versus multiarm) and with precise, monomer-by-monomer control of OES length. Notably, all three morphologies were accessed utilizing OES oligomers with degrees of polymerization as short as three. These exceptionally small assembly forming blocks represent the first application of ethylene sulfide oligomers in supramolecular materials. While the assemblies demonstrated robust aqueous stability over time, oxidation by hydrogen peroxide progressively converted ethylene sulfide residues to increasingly hydrophilic and amorphous sulfoxides and sulfones, causing morphological changes and permanent disassembly. We utilized complementary microscopic and spectroscopic techniques to confirm this chemical stimulus-responsive behavior in self-assembled PEG-OES colloidal dispersions and physical gels. In addition to inherent stimulus-responsive behavior, fibrillar assemblies demonstrated biologically relevant molecular delivery, as confirmed by the dose-dependent activation of murine bone marrow-derived dendritic cells following fibril-mediated delivery of the immunological adjuvant monophosphoryl lipid A. In physical gels composed of either linear or multiarm PEG-OES precursors, rheologic analysis also identified mechanical stimulus-responsive shear thinning behavior. Thanks to the facile preparation, user-defined morphology, aqueous stability, carrier functionality, and stimuli-responsive behaviors of

  17. Structured nanoporous surfaces from hybrid block copolymer micelle films with metal ions

    NASA Astrophysics Data System (ADS)

    Kim, Minsoo P.; Kim, Hyeong Jun; Kim, Bumjoon J.; Yi, Gi-Ra

    2015-03-01

    We present a novel method for producing structured nanoporous thin films using block copolymer (BCP) micelles loaded with metallic ions. The BCP micellar thin films containing gold (Au) ions were prepared by spin-coating poly(styrene-block-4-vinylpyridine) (PS-b-P4VP) micelle solutions in which Au precursors (AuCl4-) were selectively loaded onto the P4VP core. When the micellar films were exposed to cetyltrimethylammonium bromide (CTAB) solutions, the Au precursors were selectively extracted from the P4VP domains due to their strong electrostatic interaction with CTAB, leading to the formation of pores in the micelles. Consequently, regularly patterned nanoporous surfaces were formed. By controlling the molecular weight (Mn) of PS-b-P4VP and the amount of Au precursors (λ) that were loaded in the P4VP domains, the pore size and depth could be tuned precisely. In particular, when a sufficient amount of Au precursors was loaded (λ ≥ 0.3), the porous surface nanostructure was well developed. In addition, the pore size and depth of the nanostructure increased as the λ value increased. For instance, when the λ value increased from 0.3 to 1.0, the pore size increased from 22.8 nm to 28.8 nm, and the pore depth increased from 2.1 nm to 3.2 nm. Interestingly, the transition from the nonporous structures to the porous structures in the micellar film could be reversibly controlled by adding and removing the Au precursors in the film. Moreover, our method for the preparation of nanoporous films can be extended to micellar film by incorporating other metal ions such as silver (Ag) and iron (Fe).

  18. 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

  19. Biodegradable DNA-Brush Block Copolymer Spherical Nucleic Acids Enable Transfection Agent-Free Intracellular Gene Regulation.

    PubMed

    Zhang, Chuan; Hao, Liangliang; Calabrese, Colin M; Zhou, Yu; Choi, Chung Hang J; Xing, Hang; Mirkin, Chad A

    2015-10-28

    By grafting multiple DNA strands onto one terminus of a polyester chain, a DNA-brush block copolymer that can assemble into micelle structure is constructed. These micelle spherical nucleic acids have a density of nucleic acids that is substantively higher than linear DNA block copolymer structures, which makes them effective cellular transfection and intracellular gene regulation agents.

  20. Mesoporous monoliths of inverse bicontinuous cubic phases of block copolymer bilayers

    NASA Astrophysics Data System (ADS)

    Park, Chiyoung; La, Yunju; An, Tae Hyun; Jeong, Hu Young; Kang, Sebyung; Joo, Sang Hoon; Ahn, Hyungju; Shin, Tae Joo; Kim, Kyoung Taek

    2015-03-01

    Solution self-assembly of block copolymers into inverse bicontinuous cubic mesophases is a promising new approach for creating porous polymer films and monoliths with highly organized bicontinuous mesoporous networks. Here we report the direct self-assembly of block copolymers with branched hydrophilic blocks into large monoliths consisting of the inverse bicontinuous cubic structures of the block copolymer bilayer. We suggest a facile and scalable method of solution self-assembly by diffusion of water to the block copolymer solution, which results in the unperturbed formation of mesoporous monoliths with large-pore (>25 nm diameter) networks weaved in crystalline lattices. The surface functional groups of the internal large-pore networks are freely accessible for large guest molecules such as protein complexes of which the molecular weight exceeded 100 kDa. The internal double-diamond (Pn3m) networks of large pores within the mesoporous monoliths could be replicated to self-supporting three-dimensional skeletal structures of crystalline titania and mesoporous silica.

  1. 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.

  2. Block copolymer alignment by shear induced during solvent vapor annealing with a crosslinked elastomer capping layer

    NASA Astrophysics Data System (ADS)

    Vogt, Bryan

    2014-03-01

    The long range alignment of block copolymers (BCPs) is generally accomplished through application of a gradient shear force or by topographical or chemical cues patterned into the substrate. These techniques require lithographic patterning, specialty substrates or custom built equipment to achieve the alignment, which limits the broad academic application of aligned BCPs. One technique to improve the large range ordering of BCPs is solvent vapor annealing (SVA), which exposes the BCP film to a controlled atmosphere of solvent vapor to swell the BCP and provide significant enhancements in the chain mobility. Here, we discuss a minor modification of the SVA process; a thin piece of crosslinked poly(dimethyl siloxane) (PDMS) is placed on top of the BCP film before SVA. Exposure to organic solvent vapors causes the PDMS to swell, while the solvent also plasticizes the BCP film. Removal of the solvent induces a shear to the BCP film as the PDMS shrinks back to its initial dimensions. The shape of the PDMS cap determines the anisotropy in the stress applied on deswelling that aligns and orients the BCP domains. Polystyrene-block-polyisoprene-block-polystyrene (SIS) is utilized as a model system to illustrate how the processing parameters impact the orientation as determined by both grazing incidence small angle x-ray scattering (GISAXS) and atomic force microscopy (AFM). Quantification of the alignment by Herman's orientational parameter (S) illustrates high degree of alignment (S =0.95) is possible through appropriate selection of processing conditions. This SVA-based alignment method provides a relatively simple method to orient BCP films within general SVA processing protocols.

  3. Selective separation of similarly sized proteins with tunable nanoporous block copolymer membranes.

    PubMed

    Qiu, Xiaoyan; Yu, Haizhou; Karunakaran, Madhavan; Pradeep, Neelakanda; Nunes, Suzana P; Peinemann, Klaus-Viktor

    2013-01-22

    An integral asymmetric membrane was fabricated in a fast and one-step process by combining the self-assembly of an amphiphilic block copolymer (PS-b-P4VP) with nonsolvent-induced phase separation. The structure was found to be composed of a thin layer of densely packed highly ordered cylindrical channels with uniform pore sizes perpendicular to the surface on top of a nonordered sponge-like layer. The as-assembled membrane obtained a water flux of more than 3200 L m(-2) h(-1) bar(-1), which was at least an order of magnitude higher than the water fluxes of commercially available membranes with comparable pore sizes, making this membrane particularly well suited to size-selective and charge-based separation of biomolecules. To test the performance of the membrane, we conducted diffusion experiments at the physiological pH of 7.4 using bovine serum albumin (BSA) and globulin-γ, two proteins with different diameters but too close in size (2-fold difference in molecular mass) to be efficiently separated via conventional dialysis membrane processes. The diffusion rate differed by a factor of 87, the highest value reported to date. We also analyzed charge-based diffusive transport and separation of two proteins of similar molecular weight (BSA and bovine hemoglobin (BHb)) through the membrane as a function of external pH. The membrane achieved a selectivity of about 10 at pH 4.7, the isoelectric point (pI) of BSA. We then positively charged the membrane to improve the separation selectivity. With the modified membrane BSA was completely blocked when the pH was 7.0, the pI of BHb, while BHb was completely blocked at pH 4.7. Our results demonstrate the potential of our asymmetric membrane to efficiently separate biological substances/pharmaceuticals in bioscience, biotechnology, and biomedicine applications.

  4. Selective separation of similarly sized proteins with tunable nanoporous block copolymer membranes.

    PubMed

    Qiu, Xiaoyan; Yu, Haizhou; Karunakaran, Madhavan; Pradeep, Neelakanda; Nunes, Suzana P; Peinemann, Klaus-Viktor

    2013-01-22

    An integral asymmetric membrane was fabricated in a fast and one-step process by combining the self-assembly of an amphiphilic block copolymer (PS-b-P4VP) with nonsolvent-induced phase separation. The structure was found to be composed of a thin layer of densely packed highly ordered cylindrical channels with uniform pore sizes perpendicular to the surface on top of a nonordered sponge-like layer. The as-assembled membrane obtained a water flux of more than 3200 L m(-2) h(-1) bar(-1), which was at least an order of magnitude higher than the water fluxes of commercially available membranes with comparable pore sizes, making this membrane particularly well suited to size-selective and charge-based separation of biomolecules. To test the performance of the membrane, we conducted diffusion experiments at the physiological pH of 7.4 using bovine serum albumin (BSA) and globulin-γ, two proteins with different diameters but too close in size (2-fold difference in molecular mass) to be efficiently separated via conventional dialysis membrane processes. The diffusion rate differed by a factor of 87, the highest value reported to date. We also analyzed charge-based diffusive transport and separation of two proteins of similar molecular weight (BSA and bovine hemoglobin (BHb)) through the membrane as a function of external pH. The membrane achieved a selectivity of about 10 at pH 4.7, the isoelectric point (pI) of BSA. We then positively charged the membrane to improve the separation selectivity. With the modified membrane BSA was completely blocked when the pH was 7.0, the pI of BHb, while BHb was completely blocked at pH 4.7. Our results demonstrate the potential of our asymmetric membrane to efficiently separate biological substances/pharmaceuticals in bioscience, biotechnology, and biomedicine applications. PMID:23252799

  5. Supramolecular block copolymers by kinetically controlled co-self-assembly of planar and core-twisted perylene bisimides

    NASA Astrophysics Data System (ADS)

    Görl, Daniel; Zhang, Xin; Stepanenko, Vladimir; Würthner, Frank

    2015-05-01

    New synthetic methodologies for the formation of block copolymers have revolutionized polymer science within the last two decades. However, the formation of supramolecular block copolymers composed of alternating sequences of larger block segments has not been realized yet. Here we show by transmission electron microscopy (TEM), 2D NMR and optical spectroscopy that two different perylene bisimide dyes bearing either a flat (A) or a twisted (B) core self-assemble in water into supramolecular block copolymers with an alternating sequence of (AmBB)n. The highly defined ultralong nanowire structure of these supramolecular copolymers is entirely different from those formed upon self-assembly of the individual counterparts, that is, stiff nanorods (A) and irregular nanoworms (B), respectively. Our studies further reveal that the as-formed supramolecular block copolymer constitutes a kinetic self-assembly product that transforms into thermodynamically more stable self-sorted homopolymers upon heating.

  6. Supramolecular block copolymers by kinetically controlled co-self-assembly of planar and core-twisted perylene bisimides

    PubMed Central

    Görl, Daniel; Zhang, Xin; Stepanenko, Vladimir; Würthner, Frank

    2015-01-01

    New synthetic methodologies for the formation of block copolymers have revolutionized polymer science within the last two decades. However, the formation of supramolecular block copolymers composed of alternating sequences of larger block segments has not been realized yet. Here we show by transmission electron microscopy (TEM), 2D NMR and optical spectroscopy that two different perylene bisimide dyes bearing either a flat (A) or a twisted (B) core self-assemble in water into supramolecular block copolymers with an alternating sequence of (AmBB)n. The highly defined ultralong nanowire structure of these supramolecular copolymers is entirely different from those formed upon self-assembly of the individual counterparts, that is, stiff nanorods (A) and irregular nanoworms (B), respectively. Our studies further reveal that the as-formed supramolecular block copolymer constitutes a kinetic self-assembly product that transforms into thermodynamically more stable self-sorted homopolymers upon heating. PMID:25959777

  7. Block Copolymer Electrolytes: Thermodynamics, Ion Transport, and Use in Solid- State Lithium/Sulfur Cells

    NASA Astrophysics Data System (ADS)

    Teran, Alexander Andrew

    Nanostructured block copolymer electrolytes containing an ion-conducting block and a modulus-strengthening block are of interest for applications in solid-state lithium metal batteries. These materials can self-assemble into well-defined microstructures, creating conducting channels that facilitate ion transport. The overall objective of this dissertation is to gain a better understanding of the behavior of salt-containing block copolymers, and evaluate their potential for use in solid-state lithium/sulfur batteries. Anionically synthesized polystyrene-b-poly(ethylene oxide) (SEO) copolymers doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt were used as a model system. This thesis investigates the model system on several levels: from fundamental thermodynamic studies to bulk characterization and finally device assembly and testing. First, the thermodynamics of neat and salt-containing block copolymers was studied. The addition of salt to these materials is necessary to make them conductive, however even small amounts of salt can have significant effects on their phase behavior, and consequently their iontransport and mechanical properties. As a result, the effect of salt addition on block copolymer thermodynamics has been the subject of significant interest over the last decade. A comprehensive study of the thermodynamics of block copolymer/salt mixtures over a wide range of molecular weights, compositions, salt concentrations and temperatures was conducted. Next, the effect of molecular weight on ion transport in both homopolymer and copolymer electrolytes were studied over a wide range of chain lengths. Homopolymer electrolytes show an inverse relationship between conductivity and chain length, with a plateau in the infinite molecular weight limit. This is due to the presence of two mechanisms of ion conduction in homopolymers; the first mechanism is a result of the segmental motion of the chains surrounding the salt ions, 2 creating a liquid

  8. Nanomechanical properties of solvent cast polystyrene and poly(methyl methacrylate) polymer blends and self-assembled block copolymers

    NASA Astrophysics Data System (ADS)

    Lorenzoni, Matteo; Evangelio, Laura; Nicolet, Célia; Navarro, Christophe; San Paulo, Alvaro; Rius, Gemma; Pérez-Murano, Francesc

    2015-07-01

    The nanomechanical properties of solvent-cast polymer thin films have been investigated using PeakForce™ Quantitative Nanomechanical Mapping. The samples consisted of films of polystyrene (PS) and poly(methyl methacrylate) (PMMA) obtained after the dewetting of toluene solution on a polymeric brush layer. Additionally, we have probed the mechanical properties of poly(styrene-b-methyl methacrylate) block copolymers (BCP) as randomly oriented thin films. The probed films have a critical thickness <50 nm and present features to be resolved <42 nm. The Young's modulus values obtained through several nanoindentation experiments present a good agreement with previous literature, suggesting that the PeakForce™ technique could be crucial for BCP investigations, e.g., as a predictor of the mechanical stability of the different phases.

  9. Stability of the fcc structure in block copolymer systems.

    PubMed

    Nonomura, Makiko

    2008-11-19

    The stability of the face-centered cubic (fcc) structure in microphase separated copolymers is investigated by a coarse-grained approach. Direct simulations of the equation for the microphase separation in three dimensions indicate that there is a narrow area above a certain degree of segregation in the phase diagram, where the fcc structure is the most stable structure. By employing the mode expansion, we have confirmed that the fcc structure can form as a metastable structure even in the weak segregation regime.

  10. Resistive switching in high-density nanodevices fabricated by block copolymer self-assembly.

    PubMed

    Frascaroli, Jacopo; Brivio, Stefano; Ferrarese Lupi, Federico; Seguini, Gabriele; Boarino, Luca; Perego, Michele; Spiga, Sabina

    2015-03-24

    Bipolar resistive switching memories based on metal oxides offer a great potential in terms of simple process integration, memory performance, and scalability. In view of ultrahigh density memory applications, a reduced device size is not the only requirement, as the distance between different devices is a key parameter. By exploiting a bottom-up fabrication approach based on block copolymer self-assembling, we obtained the parallel production of bilayer Pt/Ti top electrodes arranged in periodic arrays over the HfO2/TiN surface, building memory devices with a diameter of 28 nm and a density of 5 × 10(10) devices/cm(2). For an electrical characterization, the sharp conducting tip of an atomic force microscope was adopted for a selective addressing of the nanodevices. The presence of devices showing high conductance in the initial state was directly connected with scattered leakage current paths in the bare oxide film, while with bipolar voltage operations we obtained reversible set/reset transitions irrespective of the conductance variability in the initial state. Finally, we disclosed a scalability limit for ultrahigh density memory arrays based on continuous HfO2 thin films, in which a cross-talk between distinct nanodevices can occur during both set and reset transitions. PMID:25743480

  11. Ultrasmooth, Polydopamine Modified Surfaces for Block Copolymer Nanopatterning on Inert and Flexible Substrates

    NASA Astrophysics Data System (ADS)

    Katsumata, Reika; Cho, Joon Hee; Zhou, Sunshine; Kim, Chae Bin; Dulaney, Austin; Janes, Dustin; Ellison, Christopher

    Nature has engineered universal, catechol-containing adhesives that can be synthetically mimicked in the form of polydopamine (PDA). We exploited PDA to enable block copolymer (BCP) nanopatterning on a variety of soft material surfaces in a way that can potentially be applied to flexible electrical devices. Applying BCP nanopatterning to soft substrates is challenging because soft substrates are often chemically inert and possess incompatible low surface energies. In this study, we exploited PDA to enable the formation of BCP nanopatterns on a variety of surfaces such as Teflon, poly(ethylene terephthalate) (PET), and Kapton. While previous studies produced a PDA coating layer too rough for BCP nanopatterning, we succeeded in fabricating conformal and ultra-smooth surfaces of PDA by engineering the PDA coating process and post-sonication procedure. This chemically functionalized, biomimetic thin film (3 nm thick) served as a reactive platform for subsequently grafting a surface treatment to perpendicularly orient a lamellae-forming BCP layer. Furthermore, we demonstrated that a perfectly nanopatterned PDA-PET substrate can be bent without distorting or damaging the nanopattern in conditions that far exceeds typical bending curvatures in roll-to-roll manufacturing.

  12. Toughening of Epoxies: Novel Self-Assembling Block Copolymers Versus Traditional Telechelic Oligomers

    NASA Astrophysics Data System (ADS)

    Bacigalupo, Lauren N.

    Epoxy resins are commonly utilized because of their adhesive capacity and high strength. However, epoxies are inherently brittle; so much research has been dedicated to improving their fracture toughness. This study will focus on a comparing a traditional telechelic oligomer, CTBN, and a novel self-assembling block copolymer, SBM, as it relates to improving the fracture toughness of a lightly crosslinked epoxy system. After characterizing the modified systems for fracture toughness, mechanical and thermal properties, namely yield stress and the glass transition, will be determined in order to discern the impact these modifiers have on the overall properties of the blend. TEM, SEM and TOM techniques will be utilized for characterizing morphology, fractography and subsurface damage, respectively. Once this was accomplished, it was deduced that the toughening mechanisms of CTBN and SBM-modified epoxies are very similar. The main difference between the two is that the inherent structure of SBM allows the SBM-modified epoxy to retain its compressive yield strength. This, consequently, makes SBM ideal for thin bondline applications in the industrial adhesive and/or electronics industry.

  13. Magnetically Directed Two-Dimensional Crystallization of OmpF Membrane Proteins in Block Copolymers.

    PubMed

    Klara, Steven S; Saboe, Patrick O; Sines, Ian T; Babaei, Mahnoush; Chiu, Po-Lin; DeZorzi, Rita; Dayal, Kaushik; Walz, Thomas; Kumar, Manish; Mauter, Meagan S

    2016-01-13

    Two-dimensional (2D) alignment and crystallization of membrane proteins (MPs) is increasingly important in characterizing their three-dimensional (3D) structure, in designing pharmacological agents, and in leveraging MPs for biomimetic devices. Large, highly ordered MP 2D crystals in block copolymer (BCP) matrices are challenging to fabricate, but a facile and scalable technique for aligning and crystallizing MPs in thin-film geometries would rapidly translate into applications. This work introduces a novel method to grow larger and potentially better ordered 2D crystals by performing the crystallization process in the presence of a strong magnetic field. We demonstrate the efficacy of this approach using a β-barrel MP, outer membrane protein F (OmpF), in short-chain polybutadiene-poly(ethylene oxide) (PB-PEO) membranes. Crystals grown in a magnetic field were up to 5 times larger than conventionally grown crystals, and a signal-to-noise (SNR) analysis of diffraction peaks in Fourier transforms of specimens imaged by negative-stain electron microscopy (EM) and cryo-EM showed twice as many high-SNR diffraction peaks, indicating that the magnetic field also improves crystal order. PMID:26677866

  14. Orientational control of block copolymer microdomains by sub-tesla magnetic fields

    NASA Astrophysics Data System (ADS)

    Gopinadhan, Manesh; Choo, Youngwoo; Feng, Xunda; Kawabata, Kohsuke; di, Xiaojun; Osuji, Chinedum

    Magnetic fields offer a versatile approach to controlling the orientation of block copolymer (BCP) microdomains during self-assembly. To date however, such control has required the imposition of large magnetic fields (>3T), necessitating the use of complex magnet systems - either superconducting or very large conventional resistive magnets. Here we demonstrate the ability to direct BCP self-assembly using considerably smaller fields (<1T) which are accessible using simple rare-earth permanent magnets. The low field alignment is enabled by the presence of small quantities of mesogenic species that are blended into, and co-assemble with the liquid crystalline (LC) mesophase of the side-chain LC BCP under study. In situ SAXS experiments reveal a pronounced dependence of the critical alignment field strength on the stoichiometry of the blend, and the ability to generate aligned microdomains with orientational distribution coefficients exceeding 0.95 at sub-1 T fields for appropriate stoichiometries. The alignment response overall can be rationalized in terms of increased mobility and grain size due to the presence of the mesogenic additive. We use a permanent magnet to fabricate films with aligned nanopores, and the utility of this approach to generate complex BCP microdomain patterns in thin films by local field screening are highlighted. NSF DMR-1410568 and DMR-0847534.

  15. Vertically Aligned Nanoplate Particles Directed by Block Copolymer Domains for Anisotropic Properties

    NASA Astrophysics Data System (ADS)

    Krook, Nadia; Meth, Jeffrey; Murray, Christopher; Riggleman, Robert; Composto, Russell

    During common processing methods, anisotropic fillers in polymer nanocomposites align in the direction of flow, parallel to the surfaces, thus enhancing properties in the plane of the substrate. This research aims to create thin film nanocomposites with perpendicularly aligned anisotropic particles to improve properties in the out-of-plane direction. The demonstrated work explores vertical orientation of rare-earth fluoride nanoplates in lamellar-forming poly(styrene- b-methyl methacrylate) to establish a platform that controls the alignment of any planar particle. Currently, gadolinium fluoride (GdF3) rhombus nanoplates with the longest and shortest diagonal dimensions of ~30 nm and ~25 nm, respectively, have been specially synthesized with the potential to intercalate the block copolymer (BCP) domains. By employing a ternary brush blend layer to neutralize silicon substrates to both BCP domains, vertical lamellae orientation has been enabled with an optimum film thickness of ~110 nm. The GdF3 surfaces are chemically modified to drive the plates to a specific BCP domain. After surface modification, the dispersion of GdF3 in homopolymer will first be shown followed by morphology results from integrating GdF3 into the BCP using scanning and transmission electron microscopy.

  16. Anionic polymerization and polyhomologation: an ideal combination to synthesize polyethylene-based block copolymers.

    PubMed

    Zhang, Hefeng; Alkayal, Nazeeha; Gnanou, Yves; Hadjichristidis, Nikos

    2013-10-11

    A novel one-pot methodology combining anionic polymerization and polyhomologation, through a "bridge" molecule (BF3OEt2), was developed for the synthesis of polyethylene (PE)-based block copolymers. The anionically synthesized macroanion reacts with the "bridge" molecule to afford a 3-arm star (trimacromolecular borane) which serves as an initiator for the polyhomologation. PMID:23963373

  17. Interaction of very cold neutrons with a polystyrene-polybutadiene-polystyrene block copolymer

    SciTech Connect

    Antonov, A.V.; Gerasimov, V.I.; Isakov, A.I.; Kuznetsov, S.P.; Meshkov, I.V.; Perekrestenko, A.D.; Tarasov, S.G.

    1985-03-10

    The total interaction cross sections have been studied as a function of the wavelength of very cold neutrons (summation/sub t/(lambda)) in a very-cold-neutron spectrometer (A. V. Antonov et al., Kratk. Soobshch. Fiz. 10, 10 (1977)) with a polystyrene-polybutadiene-polystyrene block copolymer at room temperature and at 99 K.

  18. Multiscale Control of Hierarchical Structure in Crystalline Block Copolymer Nanoparticles Using Microfluidics.

    PubMed

    Bains, Aman; Cao, Yimeng; Moffitt, Matthew G

    2015-11-01

    Hierarchical semicrystalline block copolymer nanoparticles are produced in a segmented gas-liquid microfluidic reactor with top-down control of multiscale structural features, including nanoparticle morphologies, sizes, and internal crystallinities. Control of multiscale structure on disparate length scales by a single control variable (flow rate) enables tailoring of drug delivery nanoparticle function including release rates.

  19. Understanding the Dynamics of Magnetic Field Alignment for Rod-Coil Block Copolymers

    NASA Astrophysics Data System (ADS)

    McCulloch, Bryan; Portale, Giuseppe; Bras, Wim; Hexemer, Alexander; Segalman, Rachel A.

    2012-02-01

    Alignment of semiconducting block copolymer nanostructures is crucial to optimize charge transport in these materials. Magnetic fields can act on the liquid crystalline conjugated polymers, inducing alignment in rod-coil block copolymers. By using a combination of small angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) we have studied the magnetic field alignment of poly(alkoxy phenylene vinylene-b-isoprene) (PPV-PI) rod-coil block copolymers. In situ measurements have also shown the magnetic field leads to a stabilization of the ordered phase. Furthermore, there appear to be two distinct timescales for alignment: at short times the alignment of these materials is fast likely caused by preferential growth of aligned domains, and at long times alignment increases by the very slow process of defect annihilation. Further, there is an optimum temperature where the kinetics and thermodynamic driving forces for alignment are balanced, producing very highly aligned samples. Understanding the mechanisms by which alignment occurs has lead to knowledge helping to rationally optimize the magnetic alignment of rod-coil block copolymers.

  20. Asymmetrical Self-assembly From Fluorinated and Sulfonated Block Copolymers in Aqueous Media

    SciTech Connect

    Wang, Xiaojun; Hong, Kunlun; Baskaran, Durairaj; Goswami, Monojoy; Sumpter, Bobby G; Mays, Jimmy

    2011-01-01

    Block copolymers of fluorinated isoprene and partially sulfonated styrene form novel tapered rods and ribbon-like micelles in aqueous media due to a distribution of sulfonation sites and a large Flory-Huggins interaction parameter. A combination of microscopy, light scattering, and simulation demonstrates the presence of these unique nanostructures. This study sheds light on the micellization behavior of amphiphilic block polymers by revealing a new mechanism of self-assembly.

  1. Phase behavior of ABC-type triple-hydrophilic block copolymers in aqueous solutions.

    PubMed

    Zheng, Lingfei; Wu, Jianqi; Wang, Zheng; Yin, Yuhua; Jiang, Run; Li, Baohui

    2016-07-01

    The phase behavior of symmetric ABC triple-hydrophilic triblock copolymers in concentrated aqueous solutions is investigated using a simulated annealing technique. Two typical cases, in which the hydrophilicity of the middle B-block is either stronger or weaker than that of the end A- and C-blocks, are studied. In these two cases, a variety of phase diagrams are constructed as a function of the volume fraction of the B-block and the copolymer concentration ([Formula: see text] for both non-frustrated and frustrated copolymers. Structures, such as two-color alternatingly packed cylinders or gyroid, and lamellae-in-lamellae etc. that do not occur in the melt system, are obtained in solutions. Rich phase transition sequences, especially re-entrant phase transitions involving complex continuous networks of alternating gyroid and alternating diamond are observed for a given copolymer with decreasing [Formula: see text] . The difference in hydrophilicity among different blocks can result in inhomogeneous distribution of solvent molecules in the morphology, and with the decrease of [Formula: see text] , the distribution of solvent molecules presents a non-monotonic variation. This results in a non-monotonic variation of the effective volume fraction of each domain with the decrease of [Formula: see text] , which induces the re-entrant phase transitions. The presence of a good solvent for all the blocks can cause changes in the effective segregation strengths between different blocks and also in chain conformations, hence can alter the bulk phases and results in the occurrence of new structures and phase transitions. Especially, structures having A-C interfaces or A-C mixed domains can be obtained even in the non-frustrated copolymer systems, and structures obtained in the frustrated systems may be similar to those obtained in the non-frustrated systems. The window of the alternating gyroid structures may occupy a large part of the phase diagram for non

  2. Antimicrobial films obtained from latex particles functionalized with quaternized block copolymers.

    PubMed

    Alvarez-Paino, Marta; Juan-Rodríguez, Rafael; Cuervo-Rodríguez, Rocío; Tejero, Rubén; López, Daniel; López-Fabal, Fátima; Gómez-Garcés, José L; Muñoz-Bonilla, Alexandra; Fernández-García, Marta

    2016-04-01

    New amphiphilic block copolymers with antimicrobial properties were obtained by atom transfer radical polymerization (ATRP) and copper catalyzed cycloaddition following two approaches, a simultaneous strategy or a two-step synthesis, which were proven to be very effective methods. These copolymers were subsequently quaternized using two alkyl chains, methyl and butyl, to amplify their antimicrobial properties and to investigate the effect of alkyl length. Antimicrobial experiments in solution were performed with three types of bacteria, two gram-positive and one gram-negative, and a fungus. Those copolymers quaternized with methyl iodide showed better selectivities on gram-positive bacteria, Staphylococcus aureus and Staphylococcus epidermidis, against red blood cells, demonstrating the importance of the quaternizing agent chosen. Once the solution studies were performed, we prepared poly(butyl methacrylate) latex particles functionalized with the antimicrobial copolymers by emulsion polymerization of butyl methacrylate using such copolymers as surfactants. The characterization by various techniques served to test their effectiveness as surfactants. Finally, films were prepared from these emulsions, and their antimicrobial activity was studied against the gram-positive bacteria. The results indicate that the antimicrobial efficiency of the films depends not only on the copolymer activity but also on other factors such as the surface segregation of the antimicrobial agent to the interface. PMID:26741269

  3. Hierarchical self-assembly of spider silk-like block copolymers

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    Block copolymers provide an attractive venue to study well-defined nano-structures that self-assemble to generate functionalized nano- and mesoporous materials. In the present study, a novel family of spider silk-like block copolymers was designed, bioengineered and characterized to study the impact of sequence chemistry, secondary structure and block length on assembled morphology. Genetic variants of native spider dragline silk (major ampullate spidroin I, Nephila clavipes) were used as polymer building blocks. Characterization by FTIR revealed increased ?-sheet content with increasing hydrophobic A blocks; SEM revealed spheres, rod-like structures, bowl-shaped and giant compound micelles. Langmuir Blodgett monolayers were prepared at the air-water interface at different surface pressures and monolayer films analyzed by AFM revealed oblate to prolate structures. Circular micelles, rod-like, densely packed circular structures were observed for HBA6 at increasing surface pressure. Exploiting hierarchical assembly provide a promising approach to rationale designs of protein block copolymer systems, allowing comparison to traditional synthetic systems.

  4. Controlling Miscibility in Polyethylene-Polynorbornene Block Copolymers via Side-Group Chemistry

    NASA Astrophysics Data System (ADS)

    Mulhearn, William; Register, Richard

    Block copolymers containing a crystallizable block, such as polyethylene (PE), and an amorphous block with high glass transition temperature (Tg) are an interesting class of materials since the rigid glassy block can improve the mechanical response of the article under strain by reinforcing the crystal fold surface. However, to prepare an easily processable PE-containing block copolymer it is necessary to avoid microphase separation in the melt by selection of amorphous blocks with weak repulsive interactions against PE (low Flory interaction parameter χ or interaction energy density X) . Most such low- χ polymers are chemically similar to PE, such as copolymers of ethylene and a small amount of an α-olefin, and therefore exhibit similarly low glass transition temperatures. This work investigates a series of low- and high-Tg polymers based on substituted norbornene monomers, polymerized via ring-opening metathesis polymerization (ROMP). Hydrogenated polynorbornene derivatives possess a wide range of glass transition temperatures, and miscibility with PE can be readily tuned by the choice of substituents on the monomers (e.g. aromatic vs. aliphatic groups). Two species investigated, hydrogenated poly(cyclohexyl norbornene) and hydrogenated poly(norbornyl norbornene), have high Tg and also remain miscible with polyethylene to high molecular weight. Furthermore, we develop a set of mixing rules to qualitatively predict the solubility behavior of substituted ROMP polynorbornenes as a function of their side-groups.

  5. Theory for dynamical self arrest and gelation in microemulsions and the block copolymer systems

    SciTech Connect

    Wu, Sangwook

    2005-01-01

    The main purpose of this work is to investigate the glassy behavior of microemulsions and block copolymers. The origin of glassy behavior in microemulsions and block copolymers is frustration due to a competition between short-range interaction and long range interaction. According to the charge frustrated Ising model, the competition between ferromagnetic interaction and antiferromagnetic interaction is the origin of frustration in microemulsions. The competition between entropic effects and stoichiometric constraints responsible for the formation of micelles in microemulsions can lead to the emergence of a self generated glassy behavior in these systems. In the block copolymer, the competition between the repulsive short range interaction between monomers in polymer chains and the long range interaction by chemical bonds can lead to the emergence of a self generated glassy behavior. The criteria for the fluctuation induced first order transition and our microemulsion and block copolymer glasses are essentially the same. Both are a consequence of the large phase space of low energy excitations (14) (62) (all states with momenta q which fulfill |q| = qm) and are of at the most a moderate supercooling of the liquid state is required. This is strongly supported by the observation in Ref. (14) that the metastable states which are first to appear at a fluctuation induced first order transition are the ones build by a superposition of large amplitude waves of wavenumber qm, but with random orientations and phases, i.e. just the ones which form the metastable states of our microemulsion and block copolymer glass. (38)

  6. Characterization of a Poly(styrene-block-methylacrylate-random-octadecylacrylate-block-styrene) Shape Memory ABA Triblock Copolymer

    NASA Astrophysics Data System (ADS)

    Fei, Pengzhan; Cavicchi, Kevin

    2011-03-01

    A new ABA triblock copolymer of poly(styrene-block- methylacrylate-random-octadecylacrylate-block-styrene) (PS-b- PMA-r-PODA-b-PS) was synthesized by reversible addition fragmentation chain transfer polymerization. The triblock copolymer can generate a three-dimensional, physically crosslinked network by self-assembly, where the glassy PS domains physically crosslink the midblock chains. The side chain crystallization of the polyoctadecylacrylare (PODA) side chain generates a second reversible network enabling shape memory properties. Shape memory tests by uniaxial deformation and recovery of molded dog-bone shape samples demonstrate that shape fixities above 96% and shape recoveries above 98% were obtained for extensional strains up to 300%. An outstanding advantage of this shape memory material is that it can be very easily shaped and remolded by elevating the temperature to 140circ; C, and after remolding the initial shape memory properties are totally recovered by eliminating the defects introduced by the previous deformation cycling.

  7. Synthesis, Characterization and Preliminary Biological Evaluation of P(HPMA)-b-P(LLA) Copolymers: A New Type of Functional Biocompatible Block Copolymer.

    PubMed

    Barz, Matthias; Wolf, Florian K; Canal, Fabiana; Koynov, Kaloian; Vicent, Maria J; Frey, Holger; Zentel, Rudolf

    2010-09-01

    We describe a synthetic pathway to functional P(HPMA)-b-P(LLA) block copolymers. The synthesis relies on a combination of ring-opening polymerization of L-lactide, conversion into a chain transfer agent (CTA) for the RAFT polymerization of pentafluorophenyl methacrylate. A series of block copolymers was prepared that exhibited molecular weights $\\overline M _{\\rm n}$ ranging from 7 600 to 34 300 g · mol(-1) , with moderate PDI between 1.3 and 1.45. These reactive precursor polymers have been transformed into biocompatible P(HPMA)-b-P(LLA) copolymers and their fluorescently labeled derivatives by facile replacement of the pentafluorophenyl groups. The fluorescence label attached to this new type of a partially degradable amphiphilic block copolymer was used to study cellular uptake in human cervix adenocarcinoma (HeLa) cells as well as aggregation behavior by fluorescence correlation spectroscopy (FCS).

  8. The structure of nanochannels formed by block copolymer solutions confined in nanotubes.

    PubMed

    Chen, Houyang; Ruckenstein, Eli

    2009-09-21

    Monte Carlo simulations are employed to obtain information about the radius and the roughness of the inner surface of the channels, which are generated by a family of block copolymer solutions confined in nanotubes. The fluctuations of the above quantities also have been calculated. The simulations have been carried out by varying the interactions between various kinds of segments and those between segments and the wall of the nanotubes, as well as the chemical structure of the copolymer and the nanotube diameter. The present simulations provide insight regarding the structure of ionic and water channels formed by protein in the phospholipid bilayers of the cell membrane.

  9. Chimeric lipid/block copolymer nanovesicles: Physico-chemical and bio-compatibility evaluation.

    PubMed

    Pippa, Natassa; Stellas, Dimitris; Skandalis, Athanasios; Pispas, Stergios; Demetzos, Costas; Libera, Marcin; Marcinkowski, Andrzej; Trzebicka, Barbara

    2016-10-01

    Chimeric systems are mixed nanovectors composed by different in nature materials and exhibit new functionalities and properties. The particular chimeric nanovectors, formed by the co-assembly of low and high molecular weight amphiphiles, have the potential to be utilized as drug delivery platforms. We have utilized two lipids, l-α-phosphatidylcholine, hydrogenated (Soy)(HSPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and a poly(oligoethylene glycol acrylate)-b-poly(lauryl acrylate) (POEGA-PLA) block copolymer, at different molar ratios, in aqueous media. Light scattering, differential scanning calorimetry (DSC) and imaging techniques (cryo-TEM, AFM) were employed in order to elucidate the structure and properties of the nanostructures, as well as the cooperativity between the components. DSC experiments showed considerable interaction of the block copolymer with the lipid bilayers and suggested an inhomogeneous distribution of the copolymer chains and lateral phase separation of the components. Vesicle formation was observed in most cases by cryo-TEM with a chimeric membrane exhibiting kinks, in accordance with DSC data. A series of biocompatibility experiments indicated good in vitro biological stability and low cytotoxicity in vivo of the novel nanocarriers. Finally, ibuprofen (IBU) was used as model drug in order to study the loading and the release properties of the prepared chimeric lipid/block copolymer vesicles.

  10. Chimeric lipid/block copolymer nanovesicles: Physico-chemical and bio-compatibility evaluation.

    PubMed

    Pippa, Natassa; Stellas, Dimitris; Skandalis, Athanasios; Pispas, Stergios; Demetzos, Costas; Libera, Marcin; Marcinkowski, Andrzej; Trzebicka, Barbara

    2016-10-01

    Chimeric systems are mixed nanovectors composed by different in nature materials and exhibit new functionalities and properties. The particular chimeric nanovectors, formed by the co-assembly of low and high molecular weight amphiphiles, have the potential to be utilized as drug delivery platforms. We have utilized two lipids, l-α-phosphatidylcholine, hydrogenated (Soy)(HSPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and a poly(oligoethylene glycol acrylate)-b-poly(lauryl acrylate) (POEGA-PLA) block copolymer, at different molar ratios, in aqueous media. Light scattering, differential scanning calorimetry (DSC) and imaging techniques (cryo-TEM, AFM) were employed in order to elucidate the structure and properties of the nanostructures, as well as the cooperativity between the components. DSC experiments showed considerable interaction of the block copolymer with the lipid bilayers and suggested an inhomogeneous distribution of the copolymer chains and lateral phase separation of the components. Vesicle formation was observed in most cases by cryo-TEM with a chimeric membrane exhibiting kinks, in accordance with DSC data. A series of biocompatibility experiments indicated good in vitro biological stability and low cytotoxicity in vivo of the novel nanocarriers. Finally, ibuprofen (IBU) was used as model drug in order to study the loading and the release properties of the prepared chimeric lipid/block copolymer vesicles. PMID:27519828

  11. The orientation of microdomains and the progression of shear alignment in block copolymer films: The roles of key material, film, and process parameters

    NASA Astrophysics Data System (ADS)

    Davis, Raleigh Lloyd

    Block copolymers provide attractive templates for nanopatterning at size scales inaccessible to conventional fabrication techniques. To serve effectively for most applications, however, the need to impart well-defined orientational and/or positional order to these microdomains is paramount. Shear alignment, has the powerful ability to macroscopically align microdomains in the direction of the applied shear simply by applying a stress at the film's surface. The primary goal of this dissertation is to investigate the influence of key material, film, and process parameters on the ease and quality of alignment in sheared block copolymer films. One important parameter which influences block copolymer thin film morphology is film thickness. To probe this effect rapidly and systematically, a film casting technique known as flowcoating was utilized. Previously, the quantitative relationship between the film thickness profile and the flowcoating process parameters was unclear. We illuminate this process by comparing experimental film thicknesses with a model based on a Landau-Levich treatment; the model thus provides a design approach which allows a user to produce polymer thin films of virtually any desired thickness profile. Via flowcoating, the influence of film thickness on block copolymer thin film morphology was then investigated using a series of polystyrene-poly(n-hexyl methacrylate) (PS-PHMA) diblocks varying in composition and molecular weight. The influence of additional material, film, and process parameters was then investigated using the same series of PS-PHMAs. To quantitatively compare the alignment process across the different block copolymer films, a melting-recrystallization model was fit to the data, which allowed for the determination of two key alignment parameters: the critical stress needed for alignment, and an orientation rate constant. Collectively, these results provide useful scaling rules which enable predictions of the level of alignment which

  12. Synthesis and Characterization of Smart Block Copolymers for Biomineralization and Biomedical Applications

    SciTech Connect

    Kanapathipillai, Mathumai

    2008-01-01

    Self-assembly is a powerful tool in forming structures with nanoscale dimensions. Self-assembly of macromolecules provides an efficient and rapid pathway for the formation of structures from the nanometer to micrometer range that are difficult, if not impossible to obtain by conventional lithographic techniques [1]. Depending on the morphologies obtained (size, shape, periodicity, etc.) these self-assembled systems have already been applied or shown to be useful for a number of applications in nanotechnology [2], biomineralization [3, 4], drug delivery [5, 6] and gene therapy [7]. In this respect, amphiphilic block copolymers that self-organize in solution have been found to be very versatile [1]. In recent years, polymer-micellar systems have been designed that are adaptable to their environment and able to respond in a controlled manner to external stimuli. In short, synthesis of 'nanoscale objects' that exhibit 'stimulus-responsive' properties is a topic gathering momentum, because their behavior is reminiscent of that exhibited by proteins [8]. By integrating environmentally sensitive homopolymers into amphiphilic block copolymers, smart block copolymers with self assembled supramolecular structures that exhibit stimuli or environmentally responsive properties can be obtained [1]. Several synthetic polymers are known to have environmentally responsive properties. Changes in the physical, chemical or biochemical environment of these polymers results in modulation of the solubility or chain conformation of the polymer [9]. There are many common schemes of engineering stimuli responsive properties into materials [8, 9]. Polymers exhibiting lower critical solution temperature (LCST) are soluble in solvent below a specific temperature and phase separate from solvent above that temperature while polymers exhibiting upper critical solution temperatures (UCST) phase separate below a certain temperature. The solubility of polymers with ionizable moieties depends on the

  13. Disk-cylinder and disk-sphere nanoparticles from block copolymer blend solution construction

    SciTech Connect

    Zhu, Jiahua; Zhang, Shiyi; Zhang, Ke; Wang, Xiaojun; Mays, Jimmy; Wooley, Karen L; Pochan, Darrin

    2013-01-01

    Researchers strive to produce nanoparticles with complexity in composition and structure. Although traditional spherical, cylindrical and membranous, or planar, nanostructures are ubiquitous, scientists seek more complicated geometries for potential functionality. Here we report the simple solution construction of multigeometry nanoparticles, disk-sphere and diskcylinder, through a straightforward, molecular-level, blending strategy with binary mixtures of block copolymers. The multigeometry nanoparticles contain disk geometry in the core with either spherical patches along the disk periphery in the case of disk-sphere particles or cylindrical edges and handles in the case of the disk-cylinder particles. The portions of different geometry in the same nanoparticles contain different core block chemistry, thus also defining multicompartments in the nanoparticles. Although the block copolymers chosen for the blends are important for the definition of the final hybrid particles, the control of the kinetic pathway of assembly is critical for successful multigeometry particle construction.

  14. Liquid Crystalline Block Copolymers with Brush Type Architecture: Toward Functional Membranes by Magnetic Field Alignment

    NASA Astrophysics Data System (ADS)

    Choo, Youngwoo; Gopinadhan, Manesh; Mahajan, Lalit; Kasi, Rajeswari; Osuji, Chinedum

    2015-03-01

    We introduce a novel liquid crystalline block copolymer with brush type architecture for membrane applications by magnetic field directed self-assembly. Ring-opening metathesis of n-alkyloxy cyanobiphenyl and polylactide (PLA) functionalized norbornene monomers provides efficient polymerization yielding low polydispersity block copolymers. The molecular weight of the PLA side chains, spacer length of the cyanobiphenyl mesogens are systematically varied to form well-ordered BCP morphologies at varying volume fractions. Interestingly, the system features morphology dependent anchoring condition where mesogens adopt planar anchoring on cylindrical interface while homeotropic anchoring was preferred on a planar block interface. The minority PLA domains from highly aligned materials can be readily degraded by hydrolysis to produce vertically aligned nanoporous polymer films which exhibit reversible thermal switching behavior. The polymers introduced here provide a versatile platform for scalable fabrication of aligned membranes and further functional materials based on such templates. This work was supported by NSF(CCMI-1246804).

  15. Reconstitution of the membrane protein OmpF into biomimetic block copolymer-phospholipid hybrid membranes.

    PubMed

    Bieligmeyer, Matthias; Artukovic, Franjo; Nussberger, Stephan; Hirth, Thomas; Schiestel, Thomas; Müller, Michaela

    2016-01-01

    Structure and function of many transmembrane proteins are affected by their environment. In this respect, reconstitution of a membrane protein into a biomimetic polymer membrane can alter its function. To overcome this problem we used membranes formed by poly(1,4-isoprene-block-ethylene oxide) block copolymers blended with 1,2-diphytanoyl-sn-glycero-3-phosphocholine. By reconstituting the outer membrane protein OmpF from Escherichia coli into these membranes, we demonstrate functionality of this protein in biomimetic lipopolymer membranes, independent of the molecular weight of the block copolymers. At low voltages, the channel conductance of OmpF in 1 M KCl was around 2.3 nS. In line with these experiments, integration of OmpF was also revealed by impedance spectroscopy. Our results indicate that blending synthetic polymer membranes with phospholipids allows for the reconstitution of transmembrane proteins under preservation of protein function, independent of the membrane thickness. PMID:27547605

  16. SYNTHESIS AND CHARACTERIZATION OF SUBSTITUTED POLY(STYRENE)-b-POLY(ACRYLIC ACID) BLOCK COPOLYMER MICELLES

    SciTech Connect

    Pickel, Deanna L; Pickel, Joseph M; Devenyi, Jozsef; Britt, Phillip F

    2009-01-01

    Block copolymer micelle synthesis and characterization has been extensively studied. In particular, most studies have focused on the properties of the hydrophilic corona due to the micelle corona structure s impact on the biodistribution and biocompatibility. Unfortunately, less attention has been given to the effect of the core block on the micelle stability, morphology, and the rate of diffusion of small molecules from the core. This investigation is focused on the synthesis of block copolymers composed of meta-substituted styrenes and acrylic acid by Atom Transfer Radical Polymerization. Micelles with cores composed of substituted styrenes having Tgs ranging from -30 to 100 oC have been prepared and the size and shape of these micelles were characterized by Static and Dynamic Light Scattering and TEM. In addition, the critical micelle concentration and rate of diffusion of small molecules from the core were determined by fluorimetry using pyrene as the probe.

  17. Molecular transport into and out of ionic-liquid filled block copolymer vesicles in water

    NASA Astrophysics Data System (ADS)

    Lodge, Timothy; Yao, Letitia; So, Soonyong

    We have developed a method to prepare stable, size-controlled block copolymer vesicles that contain ionic liquid in the interior, but that are dispersed in water. Such nanoemulsions are of interest as nanoreactors, because the mass transfer and cost limitations of ionic liquids are circumvented. However, a crucial question is whether target molecules (e . g ., reagents and products) can enter and leave the vesicles, respectively, on a useful time scale (i . e ., seconds or shorter). In this talk we will briefly describe methods to prepare such vesicles with narrow size distributions, using poly(styrene)-block-poly(ethylene oxide) and poly(butadiene)-block-poly(ethylene oxide) copolymers of various compositions. We will then present results of pulsed-field gradient NMR measurements of probe diffusion that yield independent measurements of the entry and escape rates for selected small molecules, as a function of membrane thickness and temperature.

  18. Reduction-responsive cholesterol-based block copolymer vesicles for drug delivery.

    PubMed

    Jia, Lin; Cui, Di; Bignon, Jérôme; Di Cicco, Aurelie; Wdzieczak-Bakala, Joanna; Liu, Jianmiao; Li, Min-Hui

    2014-06-01

    We developed a new robust reduction-responsive polymersome based on the amphiphilic block copolymer PEG-SS-PAChol. The stability and robustness were achieved by the smectic physical cross-linking of cholesterol-containing liquid crystal polymer PAChol in the hydrophobic layer. The reduction-sensitivity was introduced by the disulfide bridge (-S-S-) that links the hydrophilic PEG block and the hydrophobic PAChol block. We used a versatile synthetic strategy based on atom transfer radical polymerization (ATRP) to synthesize the reduction-responsive amphiphilic block copolymers. The reductive cleavage of the disulfide bridge in the block copolymers was first evidenced in organic solution. The partial destruction of PEG-SS-PAChol polymersomes in the presence of a reducing agent was then demonstrated by cryo-electron microscopy. Finally, the calcein release from PEG-SS-PAChol polymersomes triggered by glutathione (GSH) was observed both in PBS suspension and in vitro inside the macrophage cells. High GSH concentrations (≥35 mM in PBS or artificially enhanced in macrophage cells by GSH-OEt pretreatment) and long incubation time (in the order of hours) were, however, necessary to get significant calcein release. These polymersomes could be used as drug carriers with very long circulation profiles and slow release kinetics. PMID:24801808

  19. Stable nanoemulsions prepared via interfacial solidification of amphiphilic polyether-polyester block copolymers.

    PubMed

    Kim, Trang Huyen Le; Jun, Hwiseok; Kim, Jee Seon; Nam, Yoon Sung

    2015-04-01

    Oil-in-water (O/W) emulsions are generally stabilized by water-soluble surfactants, which anchor to the surface of oil droplets dispersed in an aqueous solution. Our recent work introduced a new approach to stabilize nanoemulsions through the formation of a semi-solid interphase at the O/W interface using a water-insoluble amphiphilic block copolymer, methoxy poly(ethylene glycol)-block-poly(ɛ-caprolactone). However, the approach is not applicable to relatively non-polar oils due to the quick precipitation of the hydrophobic PCL block within the oil phase. Here we report on successful stabilization of non-polar liquid paraffin nanoemulsions using an amphiphilic copolymers having a new hydrophobic block comprising ɛ-caprolactone and L-lactide. The new block copolymer was reorganized at the O/W interface of liquid paraffin, generating stable nano-sized emulsions via the formation of a robust semi-solid polymeric barrier. The prepared nanoemulsions show excellent dispersion stability even under a high level of mechanical stresses during freeze/thaw cycles.

  20. Stable nanoemulsions prepared via interfacial solidification of amphiphilic polyether-polyester block copolymers.

    PubMed

    Kim, Trang Huyen Le; Jun, Hwiseok; Kim, Jee Seon; Nam, Yoon Sung

    2015-04-01

    Oil-in-water (O/W) emulsions are generally stabilized by water-soluble surfactants, which anchor to the surface of oil droplets dispersed in an aqueous solution. Our recent work introduced a new approach to stabilize nanoemulsions through the formation of a semi-solid interphase at the O/W interface using a water-insoluble amphiphilic block copolymer, methoxy poly(ethylene glycol)-block-poly(ɛ-caprolactone). However, the approach is not applicable to relatively non-polar oils due to the quick precipitation of the hydrophobic PCL block within the oil phase. Here we report on successful stabilization of non-polar liquid paraffin nanoemulsions using an amphiphilic copolymers having a new hydrophobic block comprising ɛ-caprolactone and L-lactide. The new block copolymer was reorganized at the O/W interface of liquid paraffin, generating stable nano-sized emulsions via the formation of a robust semi-solid polymeric barrier. The prepared nanoemulsions show excellent dispersion stability even under a high level of mechanical stresses during freeze/thaw cycles. PMID:25585162

  1. Morphology And Local Mechanical Properties Of A Block Copolymer Cell Substrate

    NASA Astrophysics Data System (ADS)

    Wall, Craig; Yermolenko, Ivan; Krishnan, G. Rajesh; Sarkar, Debanjan; Alexander, John

    2014-03-01

    Atomic force microscopy (AFM) was applied for the characterization of morphology and mechanical properties of a block copolymer coating designed for biomaterials applications. The material is a block-copolymer with poly(ethylene glycol) as one block and a peptide as second block, which are connected through urethane bonds. The AFM images obtained in amplitude modulation mode revealed the morphology is characterized by micron-scale sheaf-like structures embedded in a more homogeneous and, presumably, amorphous matrix. The self-assembly of the peptide segments is responsible for the formation of the ordered sheaf structures and this phenomenon was common for different variations of the components. Maps of elastic modulus and work of adhesion of the block copolymer, which also differentiate the matrix and ordered regions, were obtained with Hybrid mode at different tip-force levels. The quantitative estimates show that elastic modulus varies in the MPa range and work of adhesion in the hundreds of mJ/m2 range. These data are compared with AFM-based nanoindentation that was performed at higher tip-force level. The results indicate that material surface is more complicated and they suggest in-depth morphology variations. A tentative model of the structural organization is proposed.

  2. Morphological studies on supramolecular hybrids comprising a block copolymer and semiconductor nanoparticles

    NASA Astrophysics Data System (ADS)

    Noro, Atsushi; Higuchi, Kota; Sageshima, Yoshio; Matsushita, Yushu

    2013-03-01

    Well-ordered periodic nanostructures have been attaining much attention due to their high potential for nano-applications. Nanophase-separated structures of block copolymer/inorganic nanoparticle hybrids are one of good candidates for such applications. Here we report a systematic study on preparation and morphological observation of hybrids composed of a block copolymer and hydroxy-capped cadmium selenide nanoparticles (h-CdSe) via hydrogen bonding. Three polystyrene- b-poly(4-vinylpyridine) (PS-P4VP) block copolymers with the same PS chain length but with different P4VP chain length were synthesized for hybrid preparation. Each PS-P4VP was mixed with h-CdSe by varying a weight ratio of PS-P4VP:h-CdSe. A hybrid composed of h-CdSe and PS-P4VP bearing long P4VP blocks represents a single nanophase-separated structure, where domain spacing expansion and morphology transition induced by addition of h-CdSe were observed. On the other hand, macrophase separation accompanied by overflow of h-CdSe from nanophase-separated domains was observed in hybrids which contain PS-P4VP bearing short P4VP blocks. These results are attributed to hydrogen-bonding formation and the stoichiometric balance of functional groups. This work was financially supported by JSPS through KAKENHI Grants (no. 22245038 (Y.M.), no. 23655123 (A.N.), and no. 24685035 (A.N.)).

  3. Comparison of surface properties of random, block, and graft copolymers having perfluoroalkyl and silicone-containing side chains.

    PubMed

    Kim, Dong-Kwon; Lee, Soo-Bok

    2002-03-15

    Fluorosilicone copolymers of random, block, and graft with both perfluoroalkyl and silicone-containing side chains were synthesized, and their surface properties and surface modification effects on PVC film were compared. It can be confirmed that the fluorosilicone copolymers of random, block, and graft exhibit very low surface free energies of 9-13 dyn/cm, depending on the perfluoroalkyl group content and their molecular structure. The inherent surface free energies of the fluorosilicone copolymers are significantly influenced by their molecular structure and perfluoroalkyl group content. It can also be found that the fluorosilicone copolymers are very effective for lowering surface free energy. The surface free energy of a copolymer/PVC blend strongly varies with perfluoroalkyl group content as well as molecular structure. The molecular structure of a fluorosilicone copolymer is as important as the perfluoroalkyl group content for their inherent surface free energies and surface modification of other polymers.

  4. Block and Random Copolymers Bearing Cholic Acid and Oligo(ethylene glycol) Pendant Groups: Aggregation, Thermosensitivity, and Drug Loading

    PubMed Central

    2015-01-01

    A series of block and random copolymers consisting of oligo(ethylene glycol) and cholic acid pendant groups were synthesized via ring-opening metathesis polymerization of their norbornene derivatives. These block and random copolymers were designed to have similar molecular weights and comonomer ratios; both types of copolymers showed thermosensitivity in aqueous solutions with similar cloud points. The copolymers self-assembled into micelles in water as shown by dynamic light scattering and transmission electron microscopy. The hydrodynamic diameter of the micelles formed by the block copolymer is much larger and exhibited a broad and gradual shrinkage from 20 to 54 °C below its cloud point, while the micelles formed by the random copolymers are smaller in size but exhibited some swelling in the same temperature range. Based on in vitro drug release studies, 78% and 24% paclitaxel (PTX) were released in 24 h from micelles self-assembled by the block and random copolymers, respectively. PTX-loaded micelles formed by the block and random copolymers exhibited apparent antitumor efficacy toward the ovarian cancer cells with a particularly low half-maximal inhibitory concentration (IC50) of 27.4 and 40.2 ng/mL, respectively. Cholic acid-based micelles show promise as a versatile and potent platform for cancer chemotherapy. PMID:24725005

  5. Block and random copolymers bearing cholic acid and oligo(ethylene glycol) pendant groups: aggregation, thermosensitivity, and drug loading.

    PubMed

    Shao, Yu; Jia, Yong-Guang; Shi, Changying; Luo, Juntao; Zhu, X X

    2014-05-12

    A series of block and random copolymers consisting of oligo(ethylene glycol) and cholic acid pendant groups were synthesized via ring-opening metathesis polymerization of their norbornene derivatives. These block and random copolymers were designed to have similar molecular weights and comonomer ratios; both types of copolymers showed thermosensitivity in aqueous solutions with similar cloud points. The copolymers self-assembled into micelles in water as shown by dynamic light scattering and transmission electron microscopy. The hydrodynamic diameter of the micelles formed by the block copolymer is much larger and exhibited a broad and gradual shrinkage from 20 to 54 °C below its cloud point, while the micelles formed by the random copolymers are smaller in size but exhibited some swelling in the same temperature range. Based on in vitro drug release studies, 78% and 24% paclitaxel (PTX) were released in 24 h from micelles self-assembled by the block and random copolymers, respectively. PTX-loaded micelles formed by the block and random copolymers exhibited apparent antitumor efficacy toward the ovarian cancer cells with a particularly low half-maximal inhibitory concentration (IC50) of 27.4 and 40.2 ng/mL, respectively. Cholic acid-based micelles show promise as a versatile and potent platform for cancer chemotherapy. PMID:24725005

  6. 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

  7. Tailor-made polyfluoroacrylate and its block copolymer by RAFT polymerization in miniemulsion; improved hydrophobicity in the core-shell block copolymer.

    PubMed

    Chakrabarty, Arindam; Singha, Nikhil K

    2013-10-15

    Controlled/living radical polymerization (CRP) of a fluoroacrylate was successfully carried out in miniemulsion by Reversible Addition Fragmentation chain Transfer (RAFT) process. In this case, 2,2,3,3,4,4,4-heptafluorobutyl acrylate (HFBA) was polymerized using 2-cyanopropyl dodecyl trithiocarbonate (CPDTC) as RAFT agent, Triton X-405 and sodium dodecyl sulfonate (SDS) as surfactant, and potassium persulphate (KPS) or 2,2'-azobis isobutyronitrile (AIBN) as initiator. Being compatible with hydrophobic fluoroacrylate, this RAFT agent offered very high conversion and good control over the molecular weight of the polymer. The miniemulsion was stable without any costabilizer. The long chain dodecyl group (-C12H25) (Z-group in the RAFT agent) had beneficial effect in stabilizing the miniemulsion. When 2-cyano 2-propyl benzodithioate (CPBD) (Z=-C6H5) was used as RAFT agent, the conversion was less and particle size distribution was very broad. Block copolymerization with butyl acrylate (BA) using PHFBA as macro-RAFT agent showed core-shell morphology with the aggregation of PHFBA segment in the shell. GPC as well as DSC analysis confirmed the formation of block copolymer. The core-shell morphology was confirmed by TEM analysis. The block copolymers (PHFBA-b-PBA) showed significantly higher water contact angle (WCA) showing much better hydrophobicity compared to PHFBA alone. PMID:23953650

  8. Tailor-made polyfluoroacrylate and its block copolymer by RAFT polymerization in miniemulsion; improved hydrophobicity in the core-shell block copolymer.

    PubMed

    Chakrabarty, Arindam; Singha, Nikhil K

    2013-10-15

    Controlled/living radical polymerization (CRP) of a fluoroacrylate was successfully carried out in miniemulsion by Reversible Addition Fragmentation chain Transfer (RAFT) process. In this case, 2,2,3,3,4,4,4-heptafluorobutyl acrylate (HFBA) was polymerized using 2-cyanopropyl dodecyl trithiocarbonate (CPDTC) as RAFT agent, Triton X-405 and sodium dodecyl sulfonate (SDS) as surfactant, and potassium persulphate (KPS) or 2,2'-azobis isobutyronitrile (AIBN) as initiator. Being compatible with hydrophobic fluoroacrylate, this RAFT agent offered very high conversion and good control over the molecular weight of the polymer. The miniemulsion was stable without any costabilizer. The long chain dodecyl group (-C12H25) (Z-group in the RAFT agent) had beneficial effect in stabilizing the miniemulsion. When 2-cyano 2-propyl benzodithioate (CPBD) (Z=-C6H5) was used as RAFT agent, the conversion was less and particle size distribution was very broad. Block copolymerization with butyl acrylate (BA) using PHFBA as macro-RAFT agent showed core-shell morphology with the aggregation of PHFBA segment in the shell. GPC as well as DSC analysis confirmed the formation of block copolymer. The core-shell morphology was confirmed by TEM analysis. The block copolymers (PHFBA-b-PBA) showed significantly higher water contact angle (WCA) showing much better hydrophobicity compared to PHFBA alone.

  9. A Solution-Processable (Tetraaniline-b-Polyethylene Glycol)3 Star-Shaped Rod-Coil Block Copolymer with Enhanced Electrochromic Properties.

    PubMed

    Cao, Linyu; Gong, Chen; Yang, Jiping

    2016-02-01

    A novel electroactive star-shaped rod-coil copolymer composed of a benzene core and three symmetrically positioned tetraaniline-b-poly(ethylene glycol) arms, (TAni-b-PEG)3 rod-coil block copolymer, is synthesized successfully and characterized using Fourier transform infrared spectroscopy (FTIR), UV-vis, (1)H NMR, and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Uniform and high-quality (TAni-b-PEG)3 thin films onto indium tin oxide-coated glass surface are fabricated simply from its DMF solution. Resulting (TAni-b-PEG)3 copolymer thin films possess excellent electrochromic properties with a high optical contrast of 73.3%, superb coloration efficiency of 318.5 cm(2) C(-1) at 750 nm. Very short switching times, that is, 2.11 s and 2.14 s for coloring and bleaching times, respectively, are observed as well. The mechanism of these impressive electrochromic properties of (TAni-b-PEG)3 thin films possessed is proposed based on the atomic force microscopy investigation, star-shaped molecular geometry, synergetic electronic and ionic conductivity and amphiphilic self-assembly feature of (TAni-b-PEG)3 copolymer, which can self-assemble to form cylinder pattern consisting of quick pathways for electronic charges and ionic species, respectively. PMID:26663524

  10. Biologically inert synthetic dural substitutes. Appraisal of a medical-grade aliphatic polyurethane and a polysiloxane-carbonate block copolymer.

    PubMed

    Sakas, D E; Charnvises, K; Borges, L F; Zervas, N T

    1990-12-01

    Two types of artificial membranes, a medical-grade aliphatic polyurethane and a polysiloxane-carbonate block copolymer, were tested as substitutes for dura in 24 and 12 rabbits, respectively. The films were placed either epidurally, subdurally, or as dural grafts in equal subgroups of animals. The postoperative course was uneventful with no manifestations of convulsive disorder or cerebrospinal fluid leak. The animals were sacrificed 3, 6, or 9 months after implantation of the artificial membranes. Both types of artificial membranes were easily removed from the underlying nervous and the other surrounding tissues. The histological examination failed to reveal adhesions, neomembrane formations, or any type of foreign body reactions to the polyurethane film. The implantation of the polysiloxane-carbonate film caused no reaction when it was applied epidurally. As a dural graft, the polysiloxane-carbonate copolymer induced the formation of a thin neomembrane of one to two layers of fibroblasts which formed a watertight seal of the dural defect. A similar thin neomembrane was found to encase this artificial membrane in the group of animals in which it was implanted subdurally. There was no foreign body reaction to the polysiloxane-carbonate film. The authors conclude that these materials hold promise as dural substitutes or in the prevention of spinal dural scarring, and should be evaluated clinically.

  11. 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.

  12. Effects of copolymer composition on the formation of ionic species, hydrogen evolution, and free-radical reaction in el-irradiated styrene-butadiene random and block copolymers

    SciTech Connect

    Basheer, R.; Dole, M.

    1984-01-01

    Block and random copolymers of butadiene and styrene as well as polybutadiene and polystyrene homopolymers have been investigated with respect to formation of trapped electrons, contribution of ionic species to crosslinking, and hydrogen gas evolution due to el radiation. The decay kinetics of the disubstituted benzyl radical has also been studied. The yields of electron trapping G(e ) are measured. The G(e ) increase linearly with increased polystyrene content in block polymers, while in random copolymer a deviation from a linear relation is observed. The contribution of ionic reactions to crosslinking is about 25-35% of the total crosslinking yield. Hydrogen production in block copolymers is approximately a linear function of the weight-fraction additivity of the yield of hydrogen formation in polystrene and polybutadiene homopolymers. Energy transfer from butadiene units to styrene units in random copolymers resulted in a deviation from such an additivity relation. The decay of the disubstituted benzyl free radical in block copolymers is a second-order reaction. In random copolymer, the decay is best interpreted in terms of equation based on a second-order decay mechanism of a fraction of the free radicals decaying in the presence of other nondecaying free radicals. 24 references, 11 figures, 3 tables.

  13. Block copolymer self-assembly fundamentals and applications in formulation of nano-structured fluids

    NASA Astrophysics Data System (ADS)

    Sarkar, Biswajit

    Dispersions of nanoparticles in polymer matrices form hybrid materials that can exhibit superior structural and functional properties and find applications in e.g. thermo-plastics, electronics, polymer electrolytes, catalysis, paint formulations, and drug delivery. Control over the particle location and orientation in the polymeric matrices are essential in order to realize the enhanced mechanical, electrical, and optical properties of the nanohybrids. Block copolymers, composed of two or more different monomers, are promising for controlling particle location and orientation because of their ability to organize into ordered nanostructures. Fundamental questions pertaining to nanoparticle-polymer interfacial interactions remain open and formulate the objectives of our investigation. Particle-polymer enthalpic and entropic interactions control the nanoparticle dispersion in polymer matrices. Synthetic chemical methods for modifying the particle surface in order to control polymer-particle interactions are involved and large scale production is not possible. In the current approach, a physical method is employed to control polymer-particle interactions. The use of commercially available solvents is found to be effective in modifying particle-polymer interfacial interactions. The approach is applicable to a wide range of particle-polymer systems and can thereby enable large scale processing of polymer nanohybrids. The systems of silica nanoparticles dispersed in long-range or short-range self-assembled structures of aqueous poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers (Pluronics) is considered here. The effect of various parameters such as the presence of organic solvents, pH, and particle size on the block copolymer organization and the ensuing particle-polymer interactions are investigated. Favorable surface interactions between the deprotonated silica nanoparticle and PEO-rich domain facilitate particle

  14. 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.

  15. 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

  16. Block Copolymer Modified Epoxy Amine System for Reactive Rotational Molding: Structures, Properties and Processability

    NASA Astrophysics Data System (ADS)

    Lecocq, Eva; Nony, Fabien; Tcharkhtchi, Abbas; Gérard, Jean-François

    2011-05-01

    Poly(styrene-butadiene-methylmethacrylate) (SBM) and poly(methylmethacrylate-butyle-acrylate-methylmethacrylate) (MAM) triblock copolymers have been dissolved in liquid DGEBA epoxy resin which is subsequently polymerized by meta-xylene diamine (MXDA) or Jeffamine EDR-148. A chemorheology study of these formulations by plate-plate rheology and by thermal analysis has allowed to conclude that the addition of these copolymer blocks improve the reactive rotational moulding processability without affecting the processing time. Indeed, it prevents the pooling of the formulation at the bottom of the mould and a too rapid build up of resin viscosity of these thermosetting systems. The morphology of the cured blends examined by scanning electron microscopy (SEM) shows an increase of fracture surface area and thereby a potential increase of the toughness with the modification of epoxy system. Dynamic mechanical spectroscopy (DMA) and opalescence of final material show that the block PMMA, initially miscible, is likely to induce phase separation from the epoxy-amine matrix. Thereby, the poor compatibilisation between the toughener and the matrix has a detrimental effect on the tensile mechanical properties. The compatibilisation has to be increased to improve in synergy the processability and the final properties of these block copolymer modified formulations. First attempts could be by adapting the length and ratio of each block.

  17. Interaction of Curcumin with PEO-PPO-PEO block copolymers: a molecular dynamics study.

    PubMed

    Samanta, Susruta; Roccatano, Danilo

    2013-03-21

    Curcumin, a naturally occurring drug molecule, has been extensively investigated for its various potential usages in medicine. Its water insolubility and high metabolism rate require the use of drug delivery systems to make it effective in the human body. Among various types of nanocarriers, block copolymer based ones are the most effective. These polymers are broadly used as drug-delivery systems, but the nature of this process is poorly understood. In this paper, we propose a molecular dynamics simulation study of the interaction of Curcumin with block copolymer based on polyethylene oxide (PEO) and polypropylene oxide (PPO). The study has been conducted considering the smallest PEO and PPO oligomers and multiple chains of the block copolymer Pluronic P85. Our study shows that the more hydrophobic 1,2-dimethoxypropane (DMP) molecules and PPO block preferentially coat the Curcumin molecule. In the case of the Pluronic P85, simulation shows formation of a drug-polymer aggregate within 50 ns. This process leaves exposed the PEO part of the polymers, resulting in better solvation and stability of the drug in water.

  18. Temperature and anion responsive self-assembly of ionic liquid block copolymers coating gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Junbo; Zhao, Jianlong; Wu, Wenlan; Liang, Ju; Guo, Jinwu; Zhou, Huiyun; Liang, Lijuan

    2016-06-01

    In this paper, double hydrophilic ionic liquid block copolymers (ILBCs), poly poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)]- block-(N-isopropylacrylamide) (PMMPImB- b-PNIPAAm) was first synthesized by reversible additionfragmentation chain transfer (RAFT) and then attached on the surface of gold nanoparticles (Au NPs) via a strong gold-sulfur bonding for preparing hybrid nanoparticles (PMMPImB- b-PNIPAAm-@-Au NPs). The hybrid NPs had a three layers micelle-like structure, including a gold core, thermo-responsive inner shell and anion responsive outer corona. The self-assembling behavior of thermal- and anion-response from shell and corona were respectively investigated by change of temperature and addition of (CF3SO2)2N-. The results showed the hybrid NPs retained a stable dispersion beyond the lower critical solution temperature (LCST) because of the space or electrostatic protecting by outer PMMPImB. However, with increasing concentration of (CF3SO2)2N-, the micellization of self-assembling PMMPImB- b-PNIPAAm-@-Au NPs was induced to form micellar structure containing the core with hydrophobic PMMPImB-(CF3SO2)2N- surrounded by composite shell of Au NPs-PNIPAAm via the anionresponsive properties of ILBCs. These results indicated that the block copolymers protected plasmonic nanoparticles remain self-assembling properties of block copolymers when phase transition from outer corona polymer.

  19. Colloidal inverse bicontinuous cubic membranes of block copolymers with tunable surface functional groups.

    PubMed

    La, Yunju; Park, Chiyoung; Shin, Tae Joo; Joo, Sang Hoon; Kang, Sebyung; Kim, Kyoung Taek

    2014-06-01

    Analogous to the complex membranes found in cellular organelles, such as the endoplasmic reticulum, the inverse cubic mesophases of lipids and their colloidal forms (cubosomes) possess internal networks of water channels arranged in crystalline order, which provide a unique nanospace for membrane-protein crystallization and guest encapsulation. Polymeric analogues of cubosomes formed by the direct self-assembly of block copolymers in solution could provide new polymeric mesoporous materials with a three-dimensionally organized internal maze of large water channels. Here we report the self-assembly of amphiphilic dendritic-linear block copolymers into polymer cubosomes in aqueous solution. The presence of precisely defined bulky dendritic blocks drives the block copolymers to form spontaneously highly curved bilayers in aqueous solution. This results in the formation of colloidal inverse bicontinuous cubic mesophases. The internal networks of water channels provide a high surface area with tunable surface functional groups that can serve as anchoring points for large guests such as proteins and enzymes. PMID:24848240

  20. Synthesis and Structure of Fully Conjugated Block Copolymers Utilized in Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Lee, Youngmin; Aplan, Melissa; Wang, Qing; Gomez, Enrique D.

    2015-03-01

    Fully conjugated block copolymers have the potential to overcome many of the limitations of mixtures and blends as photoactive layers in solar cells; furthermore, they may serve as model systems to study fundamental questions regarding optoelectric properties and charge transfer. However, the synthesis of fully conjugated block copolymers remains a challenging issue in the fieldchallenge. We have optimized the two-step synthesis of P3HT-b-PFTBT, which is composed comprised of Grignard metathesis for polymerization of P3HT followed by chain extension through a Suzuki-Miyaura polycondenstation. We find that the concentration of the Grignard reagent is critical for end-group control such that P3HT is terminated by H at one end and Br at the other. Furthermore, we can utilize an asymmetric feed ratio of monomers for the Suzuki-Miyaura reaction to minimize the amount of uncoupled homopolymers and to control the molecular weight of the second block. We investigated the chemical composition, structure and electrical characteristics of the polymers prepared by the different synthetic methods, and demonstrate that we can utilize these strategies for the synthesis of block copolymers beyond P3HT-b-PFTBT.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Thermal Analysis, Structural Studies and Morphology of Spider Silk-like Block Copolymers

    NASA Astrophysics Data System (ADS)

    Huang, Wenwen

    Spider silk is a remarkable natural block copolymer, which offers a unique combination of low density, excellent mechanical properties, and thermal stability over a wide range of temperature, along with biocompatibility and biodegrability. The dragline silk of Nephila clavipes, is one of the most well understood and the best characterized spider silk, in which alanine-rich hydrophobic blocks and glycine-rich hydrophilic blocks are linked together generating a functional block copolymer with potential uses in biomedical applications such as guided tissue repair and drug delivery. To provide further insight into the relationships among peptide amino acid sequence, block length, and physical properties, in this thesis, we studied synthetic proteins inspired by the genetic sequences found in spider dragline silks, and used these bioengineered spider silk block copolymers to study thermal, structural and morphological features. To obtain a fuller understanding of the thermal dynamic properties of these novel materials, we use a model to calculate the heat capacity of spider silk block copolymer in the solid or liquid state, below or above the glass transition temperature, respectively. We characterize the thermal phase transitions by temperature modulated differential scanning calorimetry (TMDSC) and thermogravimetric analysis (TGA). We also determined the crystallinity by TMDSC and compared the result with Fourier transform infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). To understand the protein-water interactions with respect to the protein amino acid sequence, we also modeled the specific reversing heat capacity of the protein-water system, Cp(T), based on the vibrational, rotational and translational motions of protein amino acid residues and water molecules. Advanced thermal analysis methods using TMDSC and TGA show two glass transitions were observed in all samples during heating. The low temperature glass transition, Tg(1), is related to

  7. Filtration on block copolymer solution used in directed self assembly lithography

    NASA Astrophysics Data System (ADS)

    Umeda, Toru; Takakura, Tomoyuki; Tsuzuki, Shuichi

    2016-03-01

    In this paper, we presented the filtration effects on block copolymers (BCP) that are commonly used in directed self-assembly lithographic (DSAL) imaging schemes. Specifically we focused on filtration effects on micro-contaminants such as metal ions and metal induced gels. Gel removal efficiency studies carried out with HDPE, Nylon and PTFE filters pointed out that Nylon 6,6 membrane is the most effective in removing gels in block copolymer (BCP) solutions. Metal removal efficiency studies were conducted using multistep filtrations such as repetitive filtration of single membrane material and combination of different type of membranes. Results showed that a combination of Nylon-6,6 and ion-exchange filters is highly effective in reducing metals such as Li, Mg and Al to > 99.99% efficiency. The mechanism of metal removal efficiency is discussed in detail.

  8. Block copolymer with simultaneous electric and ionic conduction for use in lithium ion batteries

    DOEpatents

    Javier, Anna Esmeralda K; Balsara, Nitash Pervez; Patel, Shrayesh Naran; Hallinan, Jr., Daniel T

    2013-10-08

    Redox reactions that occur at the electrodes of batteries require transport of both ions and electrons to the active centers. Reported is the synthesis of a block copolymer that exhibits simultaneous electronic and ionic conduction. A combination of Grignard metathesis polymerization and click reaction was used successively to synthesize the block copolymer containing regioregular poly(3-hexylthiophene) (P3HT) and poly(ethylene oxide) (PEO) segments. The P3HT-PEO/LiTFSI mixture was then used to make a lithium battery cathode with LiFePO.sub.4 as the only other component. All-solid lithium batteries of the cathode described above, a solid electrolyte and a lithium foil as the anode showed capacities within experimental error of the theoretical capacity of the battery. The ability of P3HT-PEO to serve all of the transport and binding functions required in a lithium battery electrode is thus demonstrated.

  9. Solubilization of the novel anionic amphiphilic photosensitizer TPCS 2a by nonionic Pluronic block copolymers.

    PubMed

    Lilletvedt, M; Smistad, G; Tønnesen, H H; Høgset, A; Kristensen, S

    2011-06-14

    The influence of four nonionic Pluronic block copolymers (L44, F68, P123 and F127) on the solubilization and aggregation of the novel anionic amphiphilic photosensitizer TPCS(2a), intended for use in the technology of photochemical internalization (PCI), was evaluated in aqueous media as part of pharmaceutical preformulation studies. The evaluation was performed by use of UV-Vis spectroscopy for diluted samples of TPCS(2a) (3×10(-6)M), and capillary viscosimetry, freezing point depression measurements and atomic force microscopy (AFM) at pharmaceutical relevant concentrations (2; 10 or 30 mg/ml TPCS(2a)). The critical micelle concentration (CMC) of the Pluronics in presence of TPCS(2a) was determined spectrophotometrically. The Pluronic block copolymers solubilized the photosensitizer above CMC at ambient temperature by formation of vehicle-drug complexes apparently organized in networks of varying viscosity and morphology, which were sensitive towards the addition of neutral and charged excipients. PMID:21530656

  10. Tailor-Made Onion-Like Stereocomplex Crystals in Incompatible Enantiomeric Polylactide Containing Block Copolymer Blends

    SciTech Connect

    Sun,L.; Zhu, L.; Rong, L.; Hsiao, B.

    2006-01-01

    Stereocomplexes formed by blending enantiomeric PLA block copolymers have demonstrated great potential for applications in biomedical devices. Here, we successfully synthesized well-defined enantiomeric PLA containing block copolymers by living ring-opening polymerization of L- and D-lactides from hydroxyl-terminated hydrophilic [poly(ethylene oxide) or PEO] and hydrophobic [poly(ethylene-co-1,2-butylene) or PEB] oligomers. Quantitative stereocomplex formation was achieved by equimolar mixing of the incompatible PEO-b-PLLA and PEB-b-PDLA. Intriguingly, in the blend of PEB-b-PDLA and PEO-b-PLLA with different PEB and PEO molecular weights, onion-like stereocomplex crystals were observed because of unbalanced surface stresses caused by different PEO and PEB molecular weights.

  11. Laser Writing Block Copolymer Self-Assembly on Graphene Light-Absorbing Layer.

    PubMed

    Jin, Hyeong Min; Lee, Seung Hyun; Kim, Ju Young; Son, Seung-Woo; Kim, Bong Hoon; Lee, Hwan Keon; Mun, Jeong Ho; Cha, Seung Keun; Kim, Jun Soo; Nealey, Paul F; Lee, Keon Jae; Kim, Sang Ouk

    2016-03-22

    Recent advance of high-power laser processing allows for rapid, continuous, area-selective material fabrication, typically represented by laser crystallization of silicon or oxides for display applications. Two-dimensional materials such as graphene exhibit remarkable physical properties and are under intensive development for the manufacture of flexible devices. Here we demonstrate an area-selective ultrafast nanofabrication method using low intensity infrared or visible laser irradiation to direct the self-assembly of block copolymer films into highly ordered manufacturing-relevant architectures at the scale below 12 nm. The fundamental principles underlying this light-induced nanofabrication mechanism include the self-assembly of block copolymers to proceed across the disorder-order transition under large thermal gradients, and the use of chemically modified graphene films as a flexible and conformal light-absorbing layers for transparent, nonplanar, and mechanically flexible surfaces. PMID:26871736

  12. 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.

  13. Laser Writing Block Copolymer Self-Assembly on Graphene Light-Absorbing Layer.

    PubMed

    Jin, Hyeong Min; Lee, Seung Hyun; Kim, Ju Young; Son, Seung-Woo; Kim, Bong Hoon; Lee, Hwan Keon; Mun, Jeong Ho; Cha, Seung Keun; Kim, Jun Soo; Nealey, Paul F; Lee, Keon Jae; Kim, Sang Ouk

    2016-03-22

    Recent advance of high-power laser processing allows for rapid, continuous, area-selective material fabrication, typically represented by laser crystallization of silicon or oxides for display applications. Two-dimensional materials such as graphene exhibit remarkable physical properties and are under intensive development for the manufacture of flexible devices. Here we demonstrate an area-selective ultrafast nanofabrication method using low intensity infrared or visible laser irradiation to direct the self-assembly of block copolymer films into highly ordered manufacturing-relevant architectures at the scale below 12 nm. The fundamental principles underlying this light-induced nanofabrication mechanism include the self-assembly of block copolymers to proceed across the disorder-order transition under large thermal gradients, and the use of chemically modified graphene films as a flexible and conformal light-absorbing layers for transparent, nonplanar, and mechanically flexible surfaces.

  14. The Influence of Block Copolymers on the Rheology of Silica-Filled Polyisoprene

    NASA Astrophysics Data System (ADS)

    Gurovich, Daniel; Macosko, Christopher; Tirrell, Matthew

    2000-03-01

    The properties of filled polymeric materials depend on the balance between filler-filler and polymer-filler interactions. Polar surfaces of silica particles interact strongly with like polar surfaces, but not with the polyisoprene (PI) matrix. Thus, silica is difficult to disperse in polyisoprene, and the resulting dispersions tend to agglomerate upon aging. Polydimethyl siloxane (PDMS) strongly adsorbs onto silica surfaces via hydrogen bonds. Therefore, a PDMS-PI block copolymer is expected to anchor to a silica surface via its PDMS block and modify polymer-filler interactions. In the present work, precipitated silica, polyisoprene, and PDMS-PI copolymer are mixed in different formulations. The dynamic rheological properties of the resulting materials are measured, and the low-frequency storage modulus is used to assess filler-filler networking. The state of dispersion is visualized by transmission electron microscopy. The effects of aging on dispersions of different formulations are compared.

  15. Dielectric relaxation of thin films of polyamide random copolymers

    NASA Astrophysics Data System (ADS)

    Taniguchi, Natsumi; Fukao, Koji; Sotta, Paul; Long, Didier R.

    2015-05-01

    We investigate the relaxation behavior of thin films of a polyamide random copolymer, PA66/6I, with various film thicknesses using dielectric relaxation spectroscopy. Two dielectric signals are observed at high temperatures, the α process and the relaxation process due to electrode polarization (the EP process). The relaxation time of the EP process has a Vogel-Fulcher-Tammann type of temperature dependence, and the glass transition temperature, Tg, evaluated from the EP process agrees very well with the Tg determined from the thermal measurements. The fragility index derived from the EP process increases with decreasing film thickness. The relaxation time and the dielectric relaxation strength of the EP process are described by a linear function of the film thickness d for large values of d , which can be regarded as experimental evidence for the validity of attributing the observed signal to the EP process. Furthermore, there is distinct deviation from this linear law for thicknesses smaller than a critical value. This deviation observed in thinner films is associated with an increase in the mobility and/or diffusion constant of the charge carriers responsible for the EP process. The α process is located in a higher-frequency region than the EP process at high temperatures but merges with the EP process at lower temperatures near the glass transition region. The thickness dependence of the relaxation time of the α process is different from that of the EP process. This suggests that there is decoupling between the segmental motion of the polymers and the translational motion of the charge carriers in confinement.

  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. 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.

  19. Low-(T_g) Block Copolymer Electrolytes for Lithium Ion Batteries

    NASA Astrophysics Data System (ADS)

    Soo, P. P.; Mayes, A. M.

    1997-03-01

    Novel electrolytes for lithium ion batteries employ a block copolymer architecture to achieve both high ionic conductivity and dimensional stability at ambient temperatures. These polymers consist of a conducting methacrylate block with pendant PEO side chains (PMnG) coupled to a low-(T_g) lauryl methacrylate block (PLMA). They were observed to microphase separate over a broad temperature range and displayed rheologically solid-like behavior. Both blocks are fully amorphous, allowing for a high ionic mobility when doped. In-situ a.c. impedance studies were conducted on PMnG-b-PLMA doped with LiCF(_3)SO(_3) to measure ionic conductivity as a function of temperature. The enhancement of ionic mobility by plasticizing with polyethylene glycol dimethylether will be discussed. Furthermore, the effects of block composition and morphology will be considered in the context of structural properties and electrolyte performance.

  20. Role of Polyalanine Domains in -Sheet Formation in Spider Silk Block Copolymers

    SciTech Connect

    Rabotyagova, O.; Cebe, P; Kaplan, D

    2010-01-01

    Genetically engineered spider silk-like block copolymers were studied to determine the influence of polyalanine domain size on secondary structure. The role of polyalanine block distribution on {beta}-sheet formation was explored using FT-IR and WAXS. The number of polyalanine blocks had a direct effect on the formation of crystalline {beta}-sheets, reflected in the change in crystallinity index as the blocks of polyalanines increased. WAXS analysis confirmed the crystalline nature of the sample with the largest number of polyalanine blocks. This approach provides a platform for further exploration of the role of specific amino acid chemistries in regulating the assembly of {beta}-sheet secondary structures, leading to options to regulate material properties through manipulation of this key component in spider silks.

  1. 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.

  2. Streamlined etch integration with a unique neutral layer for self-assembled block copolymers (BCPs)

    NASA Astrophysics Data System (ADS)

    Hockey, Mary Ann; Xu, Kui; Wang, Yubao; Guerrero, Douglas J.; Calderas, Eric

    2014-03-01

    A multifunctional hardmask neutral layer (HM NL) was developed to improve etch resistance capabilities, enhance reflectance control, and match the surface energy properties required for polystyrene block copolymers (PS-b-PMMA). This HM NL minimizes the number of substrate deposition steps required in graphoepitaxy directed self-assembly (DSA) process flows. A separate brush layer is replaced by incorporating neutral layer properties into the hardmask to achieve microphase separation of BCP during thermal annealing. The reflection control and etch resistance capabilities are inherent in the chemical composition, thus eliminating the need for separate thin film layers to address absorbance and etch criteria. We initially demonstrated successful implementation of the HM NL using conventional PS-b-PMMA. A series of BCP formulations were synthesized with L0 values ranging from 28 nm to 17 nm to test the versatility of the HM NL. Quality "fingerprint" patterns or microphase separation using 230°-250°C annealing for 3-5 minutes was achieved for an array of modified BCP materials. The HM NL had water contact angles at 78°-80° and polarities in the 5-6 dyne/cm range. The scope of BCP platform compositions evaluated consists of a 20° water contact angle variance and a 10-dyne/cm range in polarities. All BCP derivatives were coated directly onto the HM NL followed by thermal annealing followed by SEM analysis for effective "fingerprint" patterns. We offer a simplified alternative path for high etch resistance in a graphoepitaxy DSA flow employing a single-layer hardmask for etch resistance demonstrated to be compatible with diverse BCP-modified chemical formulations.

  3. 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

  4. Relationship between Structural and Stress Relaxation in a Block-Copolymer Melt

    SciTech Connect

    Patel, Amish J.; Narayanan, Suresh; Sandy, Alec; Mochrie, Simon G. J.; Garetz, Bruce A.; Watanabe, Hiroshi; Balsara, Nitash P.

    2006-06-30

    The relationship between structural relaxation on molecular length scales and macroscopic stress relaxation was explored in a disordered block-copolymer melt. Experiments show that the structural relaxation time, measured by x-ray photon correlation spectroscopy is larger than the terminal stress relaxation time, measured by rheology, by factors as large as 100. We demonstrate that the structural relaxation data are dominated by the diffusion of intact micelles while the stress relaxation data are dominated by contributions due to disordered concentration fluctuations.

  5. Selective gas transfer through binary polymeric systems based on block-copolymers.

    PubMed

    Beckman, I N; Teplyakov, V V

    2015-08-01

    Evaluation of several versions of phenomenological theory of gas permeability in selective polymeric membranes is presented, along with the appropriate experimental methods for verification of these versions. The main focus is on a description of stationary mass transfer across membranes (films) containing dispersion inclusions of various shapes of one polymer in a matrix of another. Considering heterogeneous media as a membrane material, it was assumed that diffusion and sorption properties of inclusions are different from those of the dispersing medium. The problem of choosing optimal shape of inclusions is evaluated from the point of view of targeted permeability and selectivity of a membrane with respect to gases. To confirm this theoretical approach, the experimental results of the studies of diffusion (permeability) of permanent gases in polymeric membranes of different structures were used. The target gases included noble gases, hydrogen, nitrogen, oxygen, CO2, and methane. The target polymers included glassy polyvinyltrimethylsilane (PVTMS, T(gl)=155-180 °C), rubberlike polydimethylsiloxane (PDMS, T(gl)=-120 °C), and two-phase block-copolymers based on these materials within a wide range of composition, including the region of phase inversion. In addition, available experimental literature data on gas permeation parameters for polyarylat-polysiloxane, polysulfon-polysiloxane, and polycarbonate-polysiloxane block-copolymers are utilized. In order to describe the stationary gas permeability for two-phase systems (from diluted dispersion of one polymer in another to concentrated dispersion and complete phase inversion) the empiric approaches based on modified Maxwell equations are offered. The requirements for two-phase systems with high permeability and selectivity parameters for gas separation are identified. The permeability parameters are predicted for C1-C4 hydrocarbons in block-copolymers based on PDMS dispersion in PVTMS, phase inversion, and PVTMS

  6. Formation and growth of lithium metal dendrites through solid block copolymer membranes

    NASA Astrophysics Data System (ADS)

    Harry, Katherine; Higa, Kenneth; Balsara, Nitash

    Dendrite growth from lithium metal in electrochemical systems is the primary problem that precludes the wide use of lithium metal as an anode material. While polystyrene-block-poly(ethylene oxide) copolymer electrolytes extend cell life by suppressing dendrite growth, dendrites eventually do grow and the batteries fail by a short-circuit. In situ hard X-ray microtomography experiments coupled with stress simulations shed light on the formation and growth of dendritic structures through stiff solid polymer electrolyte membranes.

  7. 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

  8. High-Concentration Aqueous Dispersions of Nanoscale 2D Materials Using Nonionic, Biocompatible Block Copolymers.

    PubMed

    Mansukhani, Nikhita D; Guiney, Linda M; Kim, Peter J; Zhao, Yichao; Alducin, Diego; Ponce, Arturo; Larios, Eduardo; Yacaman, Miguel Jose; Hersam, Mark C

    2016-01-20

    Conditions for the dispersion of molybdenum disulfide (MoS2) in aqueous solution at concentrations up to 0.12 mg mL(-1) using a range of nonionic, biocompatible block copolymers (i.e., Pluronics and Tetronics) are identified. Furthermore, the optimal Pluronic dispersant for MoS2 is found to be effective for a range of other 2D materials such as molybdenum diselenide, tungsten diselenide, tungsten disulfide, tin selenide, and boron nitride.

  9. Self-assembled block copolymer-nanoparticle hybrids: interplay between enthalpy and entropy.

    PubMed

    Sarkar, Biswajit; Alexandridis, Paschalis

    2012-11-13

    The dispersion of nanoparticles in ordered block copolymer nanostructures can provide control over particle location and orientation, and pave the way for engineered nanomaterials that have enhanced mechanical, electrical, or optical properties. Fundamental questions pertaining to the role of enthalpic and entropic particle-polymer interactions remain open and motivate the present work. We consider here a system of 10.6 nm silica nanoparticles (NPs) dispersed in ordered cylinders formed by hydrated poly(ethylene oxide)-poly(propylene oxide) block copolymers (Pluronic P105: EO(37)PO(56)EO(37)). Protonation of silica was used to vary the NP-polymer enthalpic interactions, while polar organic solvents (glycerol, DMSO, ethanol, and DMF) were used to modulate the NP-polymer entropic interactions. The introduction of deprotonated NPs in the place of an equal mass of water did not affect the lattice parameter of the PEO-PPO-PEO block copolymer hexagonal lyotropic liquid crystalline structures. However, the dispersion of protonated NPs led to an increase in the lattice parameter, which was attributed to stronger NP-polymer hydrogen bonding (enthalpic) interactions. Dispersion of protonated NPs into cylindrical structures formed by Pluronic P105 in 80/20 water/organic solvents does not influence the lattice parameter, different from the case of protonated NP in plain water. Organic solvents appear to screen the NP-polymer hydrogen bonding interactions.

  10. Amphiphilic Spider Silk-Like Block Copolymers with Tunable Physical Properties and Morphology for Biomedical Applications

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    Silk-based materials are important candidates for biomedical applications because of their excellent biocompatibility and biodegradability. To generate silk amphiphilic biopolymers with potential use in guided tissue repair and drug delivery, a novel family of spider silk-like block copolymers was synthesized by recombinant DNA technology. Block copolymer thermal properties, structural conformations, protein-water interactions, and self-assembly morphologies were studied with respect to well controlled protein amino acid sequences. A theoretical model was used to predict the heat capacity of the protein and protein-water complex. Using thermal analysis, two glass transitions were observed: Tg1 is related to conformational changes caused by bound water removal, while Tg2 (>Tg1) is the glass transition of dry protein. Real-time infrared spectroscopy and X-ray diffraction confirmed that different secondary structural changes occur during the two Tg relaxations. Using scanning electron microscopy, fibrillar networks and hollow vesicles are observed, depending on protein block copolymer sequence. This study provides a deeper understanding of the relationship between protein physical properties and amino acid sequence, with implications for design of other protein-based materials. Support was provided from the NSF CBET-0828028 and the MRI Program under DMR-0520655 for thermal analysis instrumentation.

  11. Selective directed self-assembly of coexisting morphologies using block copolymer blends

    DOE PAGES

    Stein, A.; Wright, G.; Yager, K. G.; Doerk, G. S.; Black, C. T.

    2016-08-02

    Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. We expand on traditional DSA chemical patterning. Moreover, a blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This contrastsmore » with typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist.« less

  12. 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.

  13. 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.

  14. Selective directed self-assembly of coexisting morphologies using block copolymer blends

    PubMed Central

    Stein, A.; Wright, G.; Yager, K. G.; Doerk, G. S.; Black, C. T.

    2016-01-01

    Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. Here we expand on traditional DSA chemical patterning. A blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This is in contrast to the typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist. PMID:27480327

  15. Giant phospholipid/block copolymer hybrid vesicles: mixing behavior and domain formation.

    PubMed

    Nam, Jin; Beales, Paul A; Vanderlick, T Kyle

    2011-01-01

    Lipids and block copolymers can be individually assembled into unsupported, spherical membranes (liposomes or polymersomes), each having their own particular benefits and limitations. Here we demonstrate the preparation of microscale, hybrid "lipopolymersomes" composed of the common lipid POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine) and the commercially available copolymer PBd-b-PEO (polybutadiene-b-poly(ethylene oxide)) with the goal of incorporating the advantageous qualities of the unitary systems into mixed-membrane capsules. We investigate the lipopolymersomes using confocal fluorescence microscopy and demonstrate that these hybrid membranes are well mixed on nanoscopic length scales within the permittable compositional windows for hybrid vesicle formation. We measure the intramembrane dynamics and mechanical properties of these hybrid membranes by fluorescence recovery after photobleaching (FRAP) and micropipet aspiration, respectively. For the first time, we demonstrate the demixing of lipid-rich and polymer-rich membrane domains within the same vesicle membrane. This is achieved by the biotinylation of one of the constituent species and cross linking with the protein NeutrAvidin. The resultant domain patterning is dependent upon which component carries the biotin functionality: cross linking of the copolymer species results in domains that ripen into a single, large, copolymer-rich island, and cross linking of the lipids yields many small, "spot-like", lipid-rich domains within a copolymer-rich matrix. We discuss these morphological differences in terms of the fluidity and mechanical properties of the membrane phases and the possible resultant interdomain interactions within the membrane. These heterogeneous hybrid lipopolymersomes could find applications in fields such as targeted delivery, controlled release, and environmental detection assays where these capsules possess the characteristics of biocompatible lipid membranes combined with

  16. Block copolymer as a nanostructuring agent for high-efficiency and annealing-free bulk heterojunction organic solar cells.

    PubMed

    Renaud, Cédric; Mougnier, Sébastien-Jun; Pavlopoulou, Eleni; Brochon, Cyril; Fleury, Guillaume; Deribew, Dargie; Portale, Giuseppe; Cloutet, Eric; Chambon, Sylvain; Vignau, Laurence; Hadziioannou, Georges

    2012-04-24

    The addition of a block copolymer to the polymer/fullerene blend is a novel approach to the fabrication of organic solar cells. The block copolymer (P3HT-b-P4VP) is used as nanostructuring agent in the active layer. A significant enhancement of the cell efficiency is observed, in correlation with morphology control, both before (as-cast) and after the annealing process.

  17. Monodisperse Block Copolymer Particles with Controllable Size, Shape, and Nanostructure

    NASA Astrophysics Data System (ADS)

    Shin, Jae Man; Kim, Yongjoo; Kim, Bumjoon; PNEL Team

    Shape-anisotropic particles are important class of novel colloidal building block for their functionality is more strongly governed by their shape, size and nanostructure compared to conventional spherical particles. Recently, facile strategy for producing non-spherical polymeric particles by interfacial engineering received significant attention. However, achieving uniform size distribution of particles together with controlled shape and nanostructure has not been achieved. Here, we introduce versatile system for producing monodisperse BCP particles with controlled size, shape and morphology. Polystyrene-b-polybutadiene (PS-b-PB) self-assembled to either onion-like or striped ellipsoid particle, where final structure is governed by amount of adsorbed sodium dodecyl sulfate (SDS) surfactant at the particle/surrounding interface. Further control of molecular weight and particle size enabled fine-tuning of aspect ratio of ellipsoid particle. Underlying physics of free energy for morphology formation and entropic penalty associated with bending BCP chains strongly affects particle structure and specification.

  18. Cooperative catalysis with block copolymer micelles: a combinatorial approach.

    PubMed

    Bukhryakov, Konstantin V; Desyatkin, Victor G; O'Shea, John-Paul; Almahdali, Sarah R; Solovyeva, Vera; Rodionov, Valentin O

    2015-02-01

    A rapid approach to identifying complementary catalytic groups using combinations of functional polymers is presented. Amphiphilic polymers with "clickable" hydrophobic blocks were used to create a library of functional polymers, each bearing a single functionality. The polymers were combined in water, yielding mixed micelles. As the functional groups were colocalized in the hydrophobic microphase, they could act cooperatively, giving rise to new modes of catalysis. The multipolymer "clumps" were screened for catalytic activity, both in the presence and absence of metal ions. A number of catalyst candidates were identified across a wide range of model reaction types. One of the catalytic systems discovered was used to perform a number of preparative-scale syntheses. Our approach provides easy access to a range of enzyme-inspired cooperative catalysts.

  19. Morphological study of semicrystalline block copolymers by x-ray scattering

    SciTech Connect

    Quiram, D.J.; Register, R.A.

    1995-12-31

    The morphology of a series of semicrystalline block copolymers was investigated using small-angle x-ray scattering (SAXS) and optical microscopy (OM). All of the polymers studied contained a crystallizable polyethylene block (hydrogenated high 1,4-polybutadiene) attached to one or two amorphous blocks. These block copolymers allowed for the examination of a number of issues in crystallization. First, the distinction between crystallization from a homogeneous melt or from a microphase separated state was made through SAXS data. The melt either exhibited scattering reminiscent of a correlation hole effect or of a microphase separated state. In regards to crystallization from a microphase separated state, the influence of melt segregation strength was examined. This was gauged by the appearance of higher order SAXS peaks in the microphase separated state prior to crystallization. In the semicrystalline block, there was the consideration of the orientation of chain folding in the lamellae. Chain folding has previously been observed with the chain axis both parallel and perpendicular to the plane of the lamellae. Both SAXS and OM were used to elucidate this matter.

  20. Fully aromatic block copolymers for fuel cell membranes with densely sulfonated nanophase domains.

    PubMed

    Takamuku, Shogo; Jannasch, Patric

    2011-03-01

    Two multiblock copoly(arylene ether sulfone)s with similar block lengths and ion exchange capacities (IECs) were prepared by a coupling reaction between a non-sulfonated precursor block and a highly sulfonated precursor block containing either fully disulfonated diarylsulfone or fully tetrasulfonated tetraaryldisulfone segments. The latter two precursor blocks were sulfonated via lithiation-sulfination reactions whereby the sulfonic acid groups were exclusively placed in ortho positions to the many sulfone bridges, giving these blocks IECs of 4.1 and 4.6 meq·g⁻¹, respectively. Copolymer membranes with IECs of 1.4 meq·g⁻¹ displayed well-connected hydrophilic nanophase domains and had decomposition temperatures at, or above, 300 °C under air. The copolymer with the tetrasulfonated tetraaryldisulfone segments showed a proton conductivity of 0.13 S·cm⁻¹ at 80 °C under fully humidified conditions, and surpassed that of a perfluorosulfonic acid membrane (NRE212) by a factor of 5 at -20 °C over time.

  1. Block Copolymer-Based Supramolecular Elastomers with High Extensibility and Large Stress Generation Capability

    NASA Astrophysics Data System (ADS)

    Noro, Atsushi; Hayashi, Mikihiro

    We prepared block copolymer-based supramolecular elastomers with high extensibility and large stress generation capability. Reversible addition fragmentation chain transfer polymerizations were conducted under normal pressure and high pressure to synthesize several large molecular weight polystyrene-b-[poly(butyl acrylate)-co-polyacrylamide]-b-polystyrene (S-Ba-S) block copolymers. Tensile tests revealed that the largest S-Ba-S with middle block molecular weight of 3140k achieved a breaking elongation of over 2000% with a maximum tensile stress of 3.6 MPa and a toughness of 28 MJ/m3 while the reference sample without any middle block hydrogen bonds, polystyrene-b-poly(butyl acrylate)-b-polystyrene with almost the same molecular weight, was merely viscous and not self-standing. Hence, incorporation of hydrogen bonds into a long soft middle block was found to be beneficial to attain high extensibility and large stress generation capability probably due to concerted combination of entropic changes and internal potential energy changes originaing from the dissociation of multiple hydrogen bonds by elongation. This work was supported by JSPS KAKENHI Grant Numbers 13J02357, 24685035, 15K13785, and 23655213 for M.H. and A.N. A.N. also expresses his gratitude for Tanaka Rubber Science & Technology Award by Enokagaku-Shinko Foundation, Japan.

  2. A New Hydrotropic Block Copolymer Micelle System for Aqueous Solubilization of Paclitaxel

    PubMed Central

    Huh, Kang Moo; Min, Hyun Soo; Lee, Sang Cheon; Lee, Hong Jae; Kim, Sungwon; Park, Kinam

    2008-01-01

    Paclitaxel (PTX), a potent anti-cancer drug, is poorly soluble in water, and this has been a major limitation in developing patient friendly formulations for clinical applications. Recent studies on polymeric micelles, especially hydrotropic polymer micelles, have suggested an alternative formulation of PTX based on their high loading capacity and physical stability in aqueous media. The present study aims at aqueous solubilization of PTX in polymer micelles without using any organic solvents that is usually required for solubilization in polymer micelles. Poly(ethylene glycol) was used as a hydrophilic block and, as a hydrotropic block, poly(4-(2-vinylbenzyloxy-N-picolylnicotinamide)) (P(2-VBOPNA)) was synthesized by atom transfer radical polymerization. The hydrotropic block copolymers did not form a micellar structure at pH 2 or below due to protonation of PNA groups, but the aqueous solubility of PTX increased significantly by the hydrotropic activity of P(2-VBOPNA). At pH values higher than 2, the PTX solubility increased even further due to deprotonation of 2-VBOPNA, leading to effective polymer micellization. A longer hydrotropic block resulted in higher aqueous PTX solubility, and slightly slower release rate from the micelles. The hydrotropic block copolymers synthesized in this study are able to form PTX-loaded polymeric micelles in aqueous solution without using any organic solvents. PMID:18155795

  3. Flash NanoPrecipitation of organic actives via confined micromixing and block copolymer stabilization

    NASA Astrophysics Data System (ADS)

    Johnson, Brian K.

    This dissertation provides a method and the understanding required to produce nanoparticles of organic actives using Flash NanoPrecipitation . The process comprises mixing a solvent phase containing molecularly dissolved amphiphilic block copolymer and an organic active with an anti-solvent. One block of the copolymer precipitates to alter the nucleation and growth of the organic active while the other remains in solution for particle stabilization. A custom built confined impinging jets (CIJ) mixer provides optimum micromixing at the laboratory or full scale within milliseconds. Comparison to other reactor designs is provided. The resulting nanoparticles have functional surfaces tailored to meet the needs of pharmaceutical or specialty chemical formulations. Example beta-carotene nanoparticles with a polyethylene oxide surface are produced at high concentration, high yield, low stabilizer content, and a size suitable for sterile filtration or larger. The technical challenges in nanoparticle production are explained via the characteristic times for mixing, copolymer aggregation, and organic active particle formation. The time for Flash NanoPrecipitation is shown to depend strongly on the time for copolymer aggregation, and control of the organic nucleation versus growth is critical to achieve nanoparticles. Mixing operating lines explain the impact of solubility differences between the colloidal stabilizer and the organic active as function of mixing rate. Techniques to measure the solubility of the copolymer and DeltaG° , DeltaH°, and DeltaS° of micellization are demonstrated. An analytical CIJ mixer is developed by quantifying the characteristic time and physical mechanism of mixing. The methodology described to find an absolute mixing lifetime is also applied to a vortex mixer at a spectrum of flow ratios away from one. Dimensional analysis using the process Damkohler number, defined as the ratio of the mixing to the process time, is applied to precipitation

  4. Micellization of amphiphilic block copolymers in binary and ternary solvent mixtures.

    PubMed

    Sarkar, Biswajit; Ravi, Venkataramanan; Alexandridis, Paschalis

    2013-01-15

    Amphiphilic block copolymers of the poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) family (commercially available as Pluronics or Poloxamers) are well-known for self-assembling in water (selective solvent for PEO) into micelles with a PPO-rich core and a hydrated PEO corona. The micellization of two PEO-PPO-PEO block copolymers (Pluronic P105: EO(37)PO(56)EO(37) and Pluronic F127: EO(100)PO(65)EO(100)) has been studied in binary mixed solvents consisting of water and one of the following organic solvents: ethanol, glycerol, D(+)-glucose monohydrate, propylene carbonate, or triacetin, and also in ternary mixtures of water with 50/50 wt% ethanol+glycerol or 50/50 wt% ethanol+propylene carbonate. Glycerol, glucose, propylene carbonate and triacetin were found to promote micellization when added to water. Glycerol and glucose interact favorably with water, and reduce the block copolymer critical micelle concentration (cmc) by dehydrating the PEO-PPO interface as well as changing the bulk solvent properties. Propylene carbonate and triacetin act by locating at the PEO-PPO interface and increasing its hydrophobicity. The addition of ethanol to water provides better solvent conditions for the block copolymers compared to plain water, and disfavors the formation of micelles. In the case of ternary solvents consisting of water, ethanol (that prevents micelle formation), and glycerol or propylene carbonate (that favor micelle formation), the observed changes in the cmc are subtle. For Pluronic P105, the cmc increase is greater for ethanol+propylene carbonate (50/50 wt%) than for ethanol+glycerol (50/50 wt%). For Pluronic F127, the cmcs remain the same as in plain water, i.e., the effects of the two organic solvents compensate each other. The difference between the free energy of micellization in plain water and that in solvent mixtures varies linearly with the cosolvent concentration, and collapses into a single line for each solvent mixture type when normalized with

  5. Structure-rheology relationship in weakly amphiphilic block copolymer Langmuir monolayers.

    PubMed

    Li Destri, Giovanni; Miano, Fausto; Marletta, Giovanni

    2014-04-01

    The linear viscoelastic behavior in the low-frequency regime at the water/air interface of three different polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) copolymer monolayers, with block length ratio varying from 66-33 to 50-50 and 25-75 in molecular units, was studied and related to the interfacial behavior, characterized by means of Langmuir isotherms, and their structure, characterized by means of the atomic force microscopy technique. The two monolayers with the highest PMMA amount showed a single phase transition at about 12 mN/m, the viscoelastic behavior changing from a predominantly elastic to a viscoelastic one. This change in the viscoelastic properties was ascribed to the beginning of entanglement among the PMMA coronas of the predominantly circular quasi-2D micelles formed by the two copolymer systems. Conversely, the polymer with the lowest PMMA amount, despite having the same PMMA block length of the PS-PMMA 50-50 block copolymer, was found to behave as a viscoelastic system at any surface pressure value. This characteristic behavior cannot therefore be simply related to the molecular weight difference, but it has been put in connection to the irregular micelle structure observed in this case, consisting of a mixture of spherical and wormlike micelles, and to the different conformation adopted by the PMMA block. By blending this copolymer with an immiscible elastic homopolymer, namely poly(2-vinylpyridine), it was possible to tune the micelle nanostructure, obtaining regular circular quasi-2D micelles, with viscoelastic properties as expected for the PMMA-rich copolymer monolayers. To the best of our knowledge, this study shows for the first time the explicit dependence upon the relative block length and, in turn, upon the nanostructure of the quasi-2D micelles, of the viscoelastic properties of Langmuir monolayers and suggests that molecular weight and intermolecular interactions are not the only parameters governing the polymer conformation and

  6. 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.

  7. "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