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Sample records for styrene-butadiene-styrene triblock copolymer

  1. Diamino Telechelic Polybutadienes for Solventless Styrene-butadiene-styrene (SBS) Triblock Copolymer Formation

    PubMed Central

    Ji, Shengxiang; Hoye, Thomas R.; Macosko, Christopher W.

    2008-01-01

    High molecular weight, high functionality diamino telechelic polybutadienes (TPBs) were synthesized by ring-opening metathesis polymerization (ROMP) of 1,5-cyclooctadiene (COD) in the presence of a chain transfer agent, 1,8-dicyano-4-octene, followed by lithium aluminum hydride reduction. Melt coupling of diamino TPB with anhydride-terminated polystyrene (PS-anh) resulted in the formation of styrene-butadiene-styrene (SBS) triblock copolymers; ca. 80% maximum conversion of PS-anh was achieved within 30 seconds. The results from SAXS, TEM, and rheological measurements of the coupling products confirmed the formation of SBS triblock copolymers having lamellar morphology. A fluororesent-labeled PS-anh was used to study the coupling kinetics by diluting the reactants by the addition of non-functional PS. PMID:19907636

  2. Morphology and Phase Transitions in Styrene-Butadiene-Styrene Triblock Copolymer Grafted with Isobutyl-Substituted Polyhedral Oligomeric Silsesquioxanes

    SciTech Connect

    Drazkowski, Daniel B.; Lee, Andre; Haddad, Timothy S.

    2008-10-03

    Two symmetric triblock polystyrene-butadiene-polystyrene (SBS) copolymers with different initial morphologies were grafted with varying amounts of isobutyl-substituted polyhedral oligomeric silsesquioxane (POSS) molecules. The POSS octamers, R{prime}R{sub 7}Si{sub 8}O{sub 12}, were designed to contain a single silane functional group, R{prime}, which was used to graft onto the dangling 1,2-butadienes in the polybutadiene block and seven identical organic groups, R = isobutyl (iBu). Morphology and phase transitions of these iBu-POSS-modified SBS were investigated using small-angle X-ray scattering and rheological methods. It was observed that when iBu-POSS was grafted to the butadiene segment, the long-range and local order of the morphology were preserved, and the d-spacing showed a small, systematic increase with increasing POSS content. These observations suggest that grafted iBu-POSS were well-distributed within the butadiene domains and did not interact with the styrene domains; effectively, grafting of iBu-POSS to butadiene did not affect the segregation between butadiene and styrene domains. However, addition of iBu-POSS reduces the overall polystyrene volume. Consequently, from a morphology standpoint, this modification effectively shifts the phase diagram to lower styrene content. This was supported with SAXS and transition temperatures measurements made from the different host morphologies.

  3. Computation of Mechanical Properties of a Poly-(Styrene-Butadiene-Styrene) Copolymer using a Mixed Finite Element Approach

    NASA Astrophysics Data System (ADS)

    Baeurle, Stephan A.; Fredrickson, Glenn H.; Gusev, Andrei A.

    2004-03-01

    Despite of several decades of research, the nature of linear elasticity in microphase-separated copolymers with chemically connected glass-rubber phases is still not fully understood. In this presentation we discuss the results of an investigation of the linear elastic properties of a poly-(styrene-butadiene-styrene) triblock copolymer using a mixed finite element approach. The technique permits to deal with phases of full incompressibility as well as phases of near incompressibility as they occur in this two-component system. Strikingly and contrary to the common belief, we find that the continuum description is accurate and that no additional detailed molecular information is needed to reproduce the available linear elastic experimental data. The anomalous Poisson's ratio of the polybutadiene phase of 0.37, determined by previous authors and attributed to molecular characteristics of the polybutadiene phase, is found to be related to end-effect errors made in their tensile and torsional experiments. We also test the suitability of several semi-phenomenological models in reproducing the experimental measurements. We find that some of the methods provide reliable results of accuracy comparable to our mixed finite element approach.

  4. Effect of casting solvents on the properties of styrene-butadiene-styrene block copolymers studied by positron annihilation techniques. [Temperature effects

    SciTech Connect

    Djermouni, B.; Ache, H.J.

    1980-01-01

    The positron annihilation technique was used to study the properties of styrene-butadiene-styrene block copolymers obtained by casting them in four different solvents: toluene, carbon tetrachloride, ethyl acetate, and methyl ethyl ketone. The positron annihilation rates plotted as a function of temperature show in all films irregularities at -70 and +85/sup 0/C which were attributed to the onset of motions in the polybutadiene and polystyrene domaines, respectively. In addition to that, two irregularities were observed at -14 and +10/sup 0/C if a poor solvent, such as ethyl acetate or methyl ethyl ketone, was used, while films cast in a good solvent such as toluene or carbon tetrachloride show only one additional irregularity on the lambda/sup 2/-T curves at -14/sup 0/C. The latter results were explained in terms of the interfacial model by assuming that these irregularities correspond to the glass transition of interlayer phases between the pure polystyrene and the pure polybutadiene phases. The one which shows the irregularity at -14/sup 0/C could be the phase in which polybutadiene is the major component, while the transition at +10/sup 0/C can be attributed to a phase in which polystyrene is the dominating factor.

  5. Recycling cycle of materials applied to acrylonitrile-butadiene-styrene/policarbonate blends with styrene-butadiene-styrene copolymer addition

    NASA Astrophysics Data System (ADS)

    Cândido, L. H. A.; Ferreira, D. B.; Júnior, W. Kindlein; Demori, R.; Mauler, R. S.

    2014-05-01

    The scope of this research is the recycling of polymers from mobile phones hulls discarded and the performance evaluation when they are submitted to the Recycling Cycle of Materials (RCM). The studied material was the ABS/PC blend in a 70/30 proportion. Different compositions were evaluated adding virgin material, recycled material and using the copolymer SBS as impact modifier. In order to evaluate the properties of material's composition, the samples were characterized by TGA, FTIR, SEM, IZOD impact strength and tensile strength tests. At the first stage, the presented results suggest the composition containing 25% of recycled material and 5% of SBS combines good mechanical performance to the higher content of recycled material and lower content of impact modifier providing major benefits to recycling plans. Five cycles (RCM) were applied in the second stage; they evidenced a decrease trend considering the impact strength. At first and second cycle the impact strength was higher than reference material (ABS/PC blend) and from the fourth cycle it was lower. The superiority impact strength in the first and second cycles can be attributed to impact modifier effect. The thermal tests and the spectrometry didn't show the presence of degradation process in the material and the TGA curves demonstrated the process stability. The impact surface of each sample was observed at SEM. The microstructures are not homogeneous presenting voids and lamellar appearance, although the outer surface presents no defects, demonstrating good moldability. The present work aims to assess the life cycle of the material from the successive recycling processes.

  6. Characterization of the thermodynamics and deformation behavior of styrene-butadiene-styrene grafted with polyhedral oligomeric silsesquioxanes

    NASA Astrophysics Data System (ADS)

    Drazkowski, Daniel B.

    This research study uses a model nanostructure-copolymer system in order to develop a fundamental understanding of how polymers are affected by functionalized nanostructures. For this study, polyhedral oligomeric silsesquioxanes (POSS) was chosen as the model nanostructure and polystyrene-block-polybutadiene-block-polystyrene copolymer (SBS) as the model polymer host. The choice of materials and chemical reaction scheme for grafting the SBS-POSS copolymers allows for reproducible products with the opportunity for wide selection of nanostructure grafting fractions. In order to examine the effects that the nanostructure's electronic properties have on the host polymer, the organic group of the POSS nanostructures was varied. To facilitate a rigorous comparison, four sterically similar, yet electronically different POSS derivatives were selected (cyclopentyl (Cp), cyclopenyl (Cy), cyclohexenyl (Cye), and phenyl (Ph)). Ph-POSS results in the greatest changes relative to the ungrafted SBS block copolymer because its chemistry has the largest contrast to the block in which it is grafted while simultaneously having the largest affinity toward the ungrafted block. All four of the cyclic POSS were found to have some affinity toward the polystyrene phase, so iBu-POSS was investigated in order to observe the effects of incorporating a noninteracting nanostructure. Two host morphologies were examined in order to compare noninteracting (iBu) and strongly interacting (Ph) POSS nanostructures. The morphology and phase behavior observed for noninteracting POSS is consistent with simply changing polystyrene content with no noticeable change in chi. Furthermore, local and long-ranged order of the morphology is well-preserved. The interacting nanostructures reduce chi substantially and disrupt the local order of the morphology, which is equivalent to a compatibilizing effect. Deformation was studied to supplement the previous findings regarding the equilibrium morphology, and give

  7. Phase behavior of model ABC triblock copolymers

    NASA Astrophysics Data System (ADS)

    Chatterjee, Joon

    The phase behavior of poly(isoprene-b-styrene- b-ethylene oxide) (ISO), a model ABC triblock copolymer has been studied. This class of materials exhibit self-assembly, forming a large array of ordered morphologies at length scales of 5-100 nm. The formation of stable three-dimensionally continuous network morphologies is of special interest in this study. Since these nanostructures considerably impact the material properties, fundamental knowledge for designing ABC systems have high technological importance for realizing applications in the areas of nanofabrication, nanoporous media, separation membranes, drug delivery and high surface area catalysts. A comprehensive framework was developed to describe the phase behavior of the ISO triblock copolymers at weak to intermediate segregation strengths spanning a wide range of composition. Phases were characterized through a combination of characterization techniques, including small angle x-ray scattering, dynamic mechanical spectroscopy, transmission electron microscopy, and birefringence measurements. Combined with previous investigations on ISO, six different stable ordered state symmetries have been identified: lamellae (LAM), Fddd orthorhombic network (O70), double gyroid (Q230), alternating gyroid (Q214), hexagonal (HEX), and body-centered cubic (BCC). The phase map was found to be somewhat asymmetric around the fI = fO isopleth. This work provides a guide for theoretical studies and gives insight into the intricate effects of various parameters on the self-assembly of ABC triblock copolymers. Experimental SAXS data evaluated with a simple scattering intensity model show that local mixing varies continuously across the phase map between states of two- and three-domain segregation. Strategies of blending homopolymers with ISO triblock copolymer were employed for studying the swelling properties of a lamellar state. Results demonstrate that lamellar domains swell or shrink depending upon the type of homopolymer that

  8. Chain exchange in triblock copolymer micelles

    NASA Astrophysics Data System (ADS)

    Lu, Jie; Lodge, Timothy; Bates, Frank

    2015-03-01

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

  9. Self-assembly of ABA triblock copolymers under soft confinement

    NASA Astrophysics Data System (ADS)

    Sheng, Yuping; An, Jian; Zhu, Yutian

    2015-05-01

    Using Monte Carlo method, the self-assembly of ABA triblock copolymers under soft confinement is investigated in this study. The soft confinement is achieved by a poor solvent environment for the polymer, which makes the polymer aggregate into a droplet. Various effects, including the block length ratio, the solvent quality for the blocks B, and the incompatibility between blocks A and B, on the micellar structures induced by soft confinement are examined. By increasing the solvent quality of B blocks, the micellar structure transforms from stacked lamella to bud-like structure, and then to onion-like structure for A5B8A5 triblock copolymers, while the inner micellar structure changes from spherical phase to various cylindrical phase, such as inner single helix, double helixes, stacked rings and cage-like structures, for A7B4A7 triblock copolymers. Moreover, the formation pathways of some typical aggregates are examined to illustrate their growth mechanisms.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  11. Influence of magnetic nanoparticle size on the particle dispersion and phase separation in an ABA triblock copolymer.

    PubMed

    Wu, Jinrong; Li, Hui; Wu, Siduo; Huang, Guangsu; Xing, Wang; Tang, Maozhu; Fu, Qiang

    2014-02-27

    Oleic acid modified iron oxide nanoparticles (IONs) with different sizes were synthesized and mixed with styrene-butadiene-styrene block copolymer (SBS) with a lamellar structure. The octadecene segments on the oleic acid molecules have chemical affinity with the polybutadiene (PB) blocks, which makes IONs tend to be selectively confined in the microphase-separated PB domains. However, the dispersion state strongly depends on the ratio of the particle diameter (d) to the lamellar thickness (l) of the PB domains, which further changes the phase separation of SBS. When d/l ∼0.5, most of IONs are concentrated in the middle of the PB layers at low particle loading. Upon increasing the particle loading, part of IONs contact each other to form long strings due to their strong magnetic interactions. Away from the strings, IONs are either selectively dispersed in the middle and at the interfaces of the PB domains, or randomly distributed at some regions in which the phase separation of SBS is suppressed. The phase separation of SBS transforms from the lamellar structure to a cylinder structure when the IONs loading is higher than 16.7 wt %. As d is comparable to l, IONs aggregate to form clusters of 100 to 300 nm in size, but within the clusters IONs are still selectively dispersed in the PB domains instead of forming macroscopic phase separation. It is interpreted in terms of the relatively small conformational entropy of the middle blocks of SBS; thus, incorporation of nanoparticles does not lead to much loss of conformational entropy. Although incorporation of IONs with d/l ∼1 significantly increases the interfacial curvature and roughness, it has less influence on the phase separation structure of SBS due to the inhomogeneous dispersion. When d is larger than l, IONs are macroscopically separated from the SBS matrix to form clusters of hundreds of nanometers to several micrometers. More interestingly, the phase separation of SBS transforms from the lamellar

  12. Probing the association of triblock copolymers with supported lipid membranes using microcantilevers.

    PubMed

    Wang, Jinghui; Segatori, Laura; Biswal, Sibani Lisa

    2014-09-14

    Pluronics are a class of amphiphilic triblock copolymers that are known to interact with cellular membranes in interesting ways. The solubility of these triblock copolymers in free lipid membranes can be altered with temperature, allowing the possibility of tuning their membrane insertion. However, for supported lipid membranes, the asymmetric local environment and the strong influence of the solid support can alter the solubility of these triblock copolymers in lipid membranes. Here, we probe the interactions of these copolymers with supported lipid membranes using microcantilevers and fluorescence recovery after photobleaching (FRAP) measurements. We measure the solubility and interactions of triblock copolymers (F68 and F98) in supported lipid bilayers as a function of temperature and the length of the copolymer lipophilic block. A Langmuir isotherm model and a free mean area theory are applied to describe the polymer-lipid interactions at the microcantilever surface, determine association constants, and analyze the effect of triblock copolymers on lateral lipid diffusion.

  13. Multifunctional triblock copolymers for intracellular messenger RNA delivery.

    PubMed

    Cheng, Connie; Convertine, Anthony J; Stayton, Patrick S; Bryers, James D

    2012-10-01

    Messenger RNA (mRNA) is a promising alternative to plasmid DNA (pDNA) for gene vaccination applications, but safe and effective delivery systems are rare. Reversible addition-fragmentation chain transfer (RAFT) polymerization was employed to synthesize a series of triblock copolymers designed to enhance the intracellular delivery of mRNA. These materials are composed of a cationic dimethylaminoethyl methacrylate (DMAEMA) segment to mediate mRNA condensation, a hydrophilic poly(ethylene glycol) methyl ether methacrylate (PEGMA) segment to enhance stability and biocompatibility, and a pH-responsive endosomolytic copolymer of diethylaminoethyl methacrylate (DEAEMA) and butyl methacrylate (BMA) designed to facilitate cytosolic entry. The blocking order and PEGMA segment length were systematically varied to investigate the effect of different polymer architectures on mRNA delivery efficacy. These polymers were monodisperse, exhibited pH-dependent hemolytic activity, and condensed mRNA into 86-216 nm particles. mRNA polyplexes formed from polymers with the PEGMA segment in the center of the polymer chain displayed the greatest stability to heparin displacement and were associated with the highest transfection efficiencies in two immune cell lines, RAW 264.7 macrophages (77%) and DC2.4 dendritic cells (50%). Transfected DC2.4 cells were shown to be capable of subsequently activating antigen-specific T cells, demonstrating the potential of these multifunctional triblock copolymers for mRNA-based vaccination strategies.

  14. Supramolecular association of a triblock copolymer in water.

    PubMed

    Gente, Giacomo; Iovino, Alessandro; La Mesa, Camillo

    2004-06-15

    Solutions of a poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) triblock copolymer, Pluronic F(68), were investigated in isothermal and isopleth mode. Surface tension, sigma, dynamic shear viscosity, n(omega), QELS experiments, and volumetric, colligative, and refractive index measurements characterize the system behavior in a wide range of compositions and temperatures. The thermodynamic properties associated with micelle formation, above the critical micellar temperature, were determined by different experimental methods. The large entropic contributions to the system stability are ascribed to significant dehydration of the oxypropylene portion in the copolymer, consequent to micelle formation. Temperature has a pronounced effect on the association features of F(68). It gives rise to abrupt changes in QELS and rheological properties when the critical micellar temperature is approached. Such effects are explained in terms of thermally driven micellization processes and interconnection between micelles.

  15. Optical and X-ray scattering studies on a semicrystalline triblock copolymer

    NASA Astrophysics Data System (ADS)

    Shin, Dongseok; Shin, Kyusoon; Aamer, Khaled; Tew, Gregory N.; Russell, Thomas P.

    2004-03-01

    A triblock copolymer composed of semicrystalline blocks, poly(L-lactic acid-b-ethylene oxide-b-L-lactic acid), was synthesized, and its optical properties together with crystalline structures were studied. Above the melting point of poly(L-lactic acid) (PLLA), the triblock copolymer was in disordered state within the studied composition and molecular weight range, and it formed banded spherulites when crystallized. Its optical properties were measured with compensators in polarized optical microscope. The birefringence of the triblock copolymer spherulite resulted from the constructive addition of those of component blocks. The crystalline structure of the triblock copolymer, especially the lamellar orientation of each block was investigated with X-ray scattering. Samples for SAXS and WAXD were prepared via subsequent crystallization of poly(ethylene oxide) (PEO) after aligning PLLA lamella by applying shear above melting point of PEO. Detailed information about lamellar orientation depending on shear and crystallization condition will be discussed.

  16. Structure-Property Relationships of Poly(lactide)-based Triblock and Multiblock Copolymers

    NASA Astrophysics Data System (ADS)

    Panthani, Tessie Rose

    Replacing petroleum-based plastics with alternatives that are degradable and synthesized from annually renewable feedstocks is a critical goal for the polymer industry. Achieving this goal requires the development of sustainable analogs to commodity plastics which have equivalent or superior properties (e.g. mechanical, thermal, optical etc.) compared to their petroleum-based counterparts. This work focuses on improving and modulating the properties of a specific sustainable polymer, poly(lactide) (PLA), by incorporating it into triblock and multiblock copolymer architectures. The multiblock copolymers in this work are synthesized directly from dihydroxy-terminated triblock copolymers by a simple step-growth approach: the triblock copolymer serves as a macromonomer and addition of stoichiometric quantities of either an acid chloride or diisocyanate results in a multiblock copolymer. This work shows that over wide range of compositions, PLA-based multiblock copolymers have superior mechanical properties compared to triblock copolymers with equivalent chemical compositions and morphologies. The connectivity of the blocks within the multiblock copolymers has other interesting consequences on properties. For example, when crystallizable poly(L-lactide)-based triblock and multiblock copolymers are investigated, it is found that the multiblock copolymers have much slower crystallization kinetics. Additionally, the total number of blocks connected together is found to effect the linear viscoelastic properties as well as the alignment of lamellar domains under uniaxial extension. Finally, the synthesis and characterization of pressure-sensitive adhesives based upon renewable PLA-containing triblock copolymers and a renewable tackifier is detailed. Together, the results give insight into the effect of chain architecture, composition, and morphology on the mechanical behavior, thermal properties, and rheological properties of PLA-based materials.

  17. Imidazolium-Containing ABA Triblock Copolymers as Electroactive Devices.

    PubMed

    Margaretta, Evan; Fahs, Gregory B; Inglefield, David L; Jangu, Chainika; Wang, Dong; Heflin, James R; Moore, Robert B; Long, Timothy E

    2016-01-20

    Two-step reversible addition-fragmentation chain transfer (RAFT) polymerization and two subsequent postpolymerization modification steps afforded well-defined ABA triblock copolymers featuring mechanically reinforcing polystyrene outer blocks and 1-methylimidazole-neutralized poly(acrylic acid)-based central blocks. Size exclusion chromatography and (1)H NMR spectroscopy confirmed predictable molecular weights and narrow distributions. The ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm][OTf]) was incorporated at 30 wt % into polymeric films. Thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis determined the thermomechanical properties of the polymers and polymer-IL composites. Atomic force microscopy, small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) determined surface and bulk morphologies, and poly(Sty-b-AA(MeIm)-b-Sty) exhibited a change from packed cylindrical to lamellar morphology in SAXS upon IL incorporation. Electrochemical impedance spectroscopy determined the in-plane ionic conductivities of the polymer-IL membranes (σ ∼ 10(-4) S/cm). A device fabricated from poly(Sty-b-AA(MeIm)-b-Sty) with 30 wt % incorporated IL demonstrated mechanical actuation under a low applied voltage of 4 V. PMID:26699795

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

    NASA Astrophysics Data System (ADS)

    Watanabe, Hiroshi

    2006-03-01

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

  19. Unexpected consequences of block polydispersity on the self-assembly of ABA triblock copolymers.

    PubMed

    Widin, Joan M; Schmitt, Adam K; Schmitt, Andrew L; Im, Kyuhyun; Mahanthappa, Mahesh K

    2012-02-29

    Controlled/"living" polymerizations and tandem polymerization methodologies offer enticing opportunities to enchain a wide variety of monomers into new, functional block copolymer materials with unusual physical properties. However, the use of these synthetic methods often introduces nontrivial molecular weight polydispersities, a type of chain length heterogeneity, into one or more of the copolymer blocks. While the self-assembly behavior of monodisperse AB diblock and ABA triblock copolymers is both experimentally and theoretically well understood, the effects of broadening the copolymer molecular weight distribution on block copolymer phase behavior are less well-explored. We report the melt-phase self-assembly behavior of SBS triblock copolymers (S = poly(styrene) and B = poly(1,4-butadiene)) comprised of a broad polydispersity B block (M(w)/M(n) = 1.73-2.00) flanked by relatively narrow dispersity S blocks (M(w)/M(n) = 1.09-1.36), in order to identify the effects of chain length heterogeneity on block copolymer self-assembly. Based on synchrotron small-angle X-ray scattering and transmission electron microscopy analyses of seventeen SBS triblock copolymers with poly(1,4-butadiene) volume fractions 0.27 ≤ f(B) ≤ 0.82, we demonstrate that polydisperse SBS triblock copolymers self-assemble into periodic structures with unexpectedly enhanced stabilities that greatly exceed those of equivalent monodisperse copolymers. The unprecedented stabilities of these polydisperse microphase separated melts are discussed in the context of a complete morphology diagram for this system, which demonstrates that narrow dispersity copolymers are not required for periodic nanoscale assembly. PMID:22280467

  20. Unexpected Consequences of Block Polydispersity on the Self-Assembly of ABA Triblock Copolymers

    SciTech Connect

    Widin, Joan M.; Schmitt, Adam K.; Schmitt, Andrew L.; Im, Kyuhyun; Mahanthappa, Mahesh K.

    2012-05-09

    Controlled/'living' polymerizations and tandem polymerization methodologies offer enticing opportunities to enchain a wide variety of monomers into new, functional block copolymer materials with unusual physical properties. However, the use of these synthetic methods often introduces nontrivial molecular weight polydispersities, a type of chain length heterogeneity, into one or more of the copolymer blocks. While the self-assembly behavior of monodisperse AB diblock and ABA triblock copolymers is both experimentally and theoretically well understood, the effects of broadening the copolymer molecular weight distribution on block copolymer phase behavior are less well-explored. We report the melt-phase self-assembly behavior of SBS triblock copolymers (S = poly(styrene) and B = poly(1,4-butadiene)) comprised of a broad polydispersity B block (M{sub w}/M{sub n} = 1.73-2.00) flanked by relatively narrow dispersity S blocks (M{sub w}/M{sub n} = 1.09-1.36), in order to identify the effects of chain length heterogeneity on block copolymer self-assembly. Based on synchrotron small-angle X-ray scattering and transmission electron microscopy analyses of seventeen SBS triblock copolymers with poly(1,4-butadiene) volume fractions 0.27 {le} f{sub B} {le} 0.82, we demonstrate that polydisperse SBS triblock copolymers self-assemble into periodic structures with unexpectedly enhanced stabilities that greatly exceed those of equivalent monodisperse copolymers. The unprecedented stabilities of these polydisperse microphase separated melts are discussed in the context of a complete morphology diagram for this system, which demonstrates that narrow dispersity copolymers are not required for periodic nanoscale assembly.

  1. Use of amphiphilic triblock copolymers for enhancing removal efficiency of organic pollutant from contaminated media

    NASA Astrophysics Data System (ADS)

    Lee, Jun Hyup; Lee, Byungsun; Son, Intae; Kim, Jae Hong; Kim, Chunho; Yoo, Ji Yong; Wu, Jong-Pyo; Kim, Younguk

    2015-11-01

    We have studied amphiphilic triblock copolymers poly(ethylene glycol)- b-poly(propylene glycol)- b-poly(ethylene glycol) (PEG- b-PPG- b-PEG) and poly(propylene glycol)- b-poly(ethylene glycol)- b-poly(propylene glycol) (PPG- b-PEG- b-PPG) as possible substitutes for sodium dodecyl sulfate as anionic surfactants for the removal of hydrophobic contaminants. The triblock copolymers were compared with sodium dodecyl sulfate in terms of their abilities to remove toluene as hydrophobic contaminant in fuel, and the effects of polymer structure, PEG content, and concentration were studied. The PEG- b-PPG- b-PEG copolymer containing two hydrophilic PEG blocks was more effective for the removal of hydrophobic contaminant at extremely high concentration. We also measured the removal capabilities of the triblock copolymers having various PEG contents and confirmed that removal capability was greatest at 10% PEG content regardless of polymer structure. As with sodium dodecyl sulfate, the removal efficiency of a copolymer has a positive correlation with its concentration. Finally, we proposed the amphiphilic triblock copolymer of PPG- b-PEG- b-PPG bearing 10% PEG content that proved to be the most effective substitute for sodium dodecyl sulfate.

  2. Effects of compositional asymmetry in phase behavior of ABA triblock copolymer melts from Monte Carlo simulation.

    PubMed

    Wołoszczuk, S; Banaszak, M

    2010-12-01

    We simulate ABA triblock copolymer melts using a lattice Monte Carlo method, known as cooperative motion algorithm, probing various degrees of compositional asymmetry. Selected order-disorder transition lines are determined in terms of the segment incompatibility, quantified by product χN , and the triblock asymmetry parameters, α and β. We correlate the results of the simulation with the self-consistent field theory and an experimental study of polyisoprene-polystyrene-polyisoprene triblock melt by Hamersky and coworkers. In particular, we confirm the mean-field prediction that for highly asymmetric triblocks the short A -block is localized in the middle of the B -domain due to an entropic advantage. This results in the middle block relaxation and is consistent with the experimental data indicating that as the relatively short A -blocks are grown into AB diblock, from the B -block side, the order-disorder transition temperature is considerably depressed.

  3. Inducing Order from Disordered Copolymers: On Demand Generation of Triblock Morphologies Including Networks

    SciTech Connect

    Tureau, Maëva S.; Kuan, Wei-Fan; Rong, Lixia; Hsiao, Benjamin S.; Epps, III, Thomas H.

    2015-10-15

    Disordered block copolymers are generally impractical in nanopatterning applications due to their inability to self-assemble into well-defined nanostructures. However, inducing order in low molecular weight disordered systems permits the design of periodic structures with smaller characteristic sizes. Here, we have induced nanoscale phase separation from disordered triblock copolymer melts to form well-ordered lamellae, hexagonally packed cylinders, and a triply periodic gyroid network structure, using a copolymer/homopolymer blending approach, which incorporates constituent homopolymers into selective block domains. This versatile blending approach allows one to precisely target multiple nanostructures from a single disordered material and can be applied to a wide variety of triblock copolymer systems for nanotemplating and nanoscale separation applications requiring nanoscale feature sizes and/or high areal feature densities.

  4. Synthesis and Melt Self-Assembly of PS-PMMA-PLA Triblock Bottlebrush Copolymers

    SciTech Connect

    Bolton, Justin; Rzayev, Javid

    2014-07-03

    Polystyrene–poly(methyl methacrylate)–polylactide (PS–PMMA–PLA) triblock bottlebrush copolymer with nearly symmetric volume fractions was synthesized by grafting from a symmetrical triblock backbone and the resulting melt was characterized by scanning electron microscopy and small-angle X-ray scattering. The copolymer backbone was prepared by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization of solketal methacrylate (SM), 2-(bromoisobutyryl)ethyl methacrylate (BIEM), and 5-(trimethylsilyl)-4-pentyn-1-ol methacrylate (TPYM). PMMA branches were grafted by atom transfer radical polymerization from the poly(BIEM) segment, PS branches were grafted by RAFT polymerization from the poly(TPYM) block after installment of the RAFT agents, while PLA side chains were grafted from the deprotected poly(SM) block. The resulting copolymer was found to exhibit a lamellae morphology with a domain spacing of 79 nm. Differential scanning calorimetry analysis indicated that PMMA was preferentially mixing with PS while phase separating from PLA domains.

  5. Alignment of Fatty Acid-Derived Triblock Copolymers under Large Amplitude Oscillatory Shear

    NASA Astrophysics Data System (ADS)

    Ding, Wenyue; Wang, Shu; Kesava, Sameer; Gomez, Enrique; Robertson, Megan

    Linear ABA triblock copolymers find widespread utilization as thermoplastic elastomers (TPEs): materials which exhibit elastomeric behavior at room temperature and can be readily processed at elevated temperatures. Traditional TPEs are derived from fossil fuels; however, the finite availability of petroleum and the environmental impact of petroleum processing has led to an increased interest in developing alternative sources for polymers. Vegetable oils and their fatty acids are promising replacements for petroleum sources due to their abundance, low cost, lack of toxicity, biodegradability and ease of functionalization that provides convenient routes to polymerization. In this study, triblock copolymer TPEs were synthesized containing lauryl and stearyl acrylate, derived from fatty acids found in vegetable oils. Small-angle X-ray scattering experiments revealed highly aligned triblock copolymer morphologies after the application of large amplitude oscillatory shear. The temperature and frequency dependence of the degree of alignment was investigated. In contrast to prior studies on shear-aligned morphologies in bulk and thin film block copolymers, hexagonal close packed and face centered cubic spherical structures were observed.

  6. Magnetic hydrogels from alkyne/cobalt carbonyl-functionalized ABA triblock copolymers

    DOE PAGES

    Jiang, Bingyin; Hom, Wendy L.; Chen, Xianyin; Yu, Pengqing; Pavelka, Laura C.; Kisslinger, Kim; Parise, John B.; Bhatia, Surita R.; Grubbs, Robert B.

    2016-03-09

    A series of alkyne-functionalized poly(4-(phenylethynyl)styrene)-block-poly(ethylene oxide)-block-poly(4-(phenylethynyl)styrene) (PPES-b-PEO-b-PPES) ABA triblock copolymers was synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. PESn[Co2(CO)6]x-EO800-PESn[Co2(CO)6]x ABA triblock copolymer/cobalt adducts (10–67 wt % PEO) were subsequently prepared by reaction of the alkyne-functionalized PPES block with Co2(CO)8 and their phase behavior was studied by TEM. Heating triblock copolymer/cobalt carbonyl adducts at 120 °C led to cross-linking of the PPES/Co domains and the formation of magnetic cobalt nanoparticles within the PPES/Co domains. Magnetic hydrogels could be prepared by swelling the PEO domains of the cross-linked materials with water. Furthermore, swelling tests, rheological studies and actuation tests demonstrated thatmore » the water capacity and modulus of the hydrogels were dependent upon the composition of the block copolymer precursors.« less

  7. Fracture Behavior of High-Toughness, Ionically Cross-linked Triblock Copolymer Hydrogels

    NASA Astrophysics Data System (ADS)

    Henderson, Kevin; Otim, Kathryn; Shull, Kenneth

    2011-03-01

    Mechanisms for enhancing energy dissipation and hence toughness are important for the generation of robust synthetic soft materials for biomedical applications. Ionic cross-linking in particular has been explored in triblock copolymer hydrogels and affords a remarkable change in mechanical performance comparable to non-cross-linked analogs. Here we employ a physically associated base triblock copolymer network composed of hydrophobic poly(methyl methacrylate) endblocks and a hydrophilic poly(methacrylic acid) midblock capable of complexing with divalent cations. Increases in stiffness and strength have previously been reported, with the extent dependent upon the identity, concentration, and pH of a cross-linking cation solution. We delineate the measured toughness in such systems using tensile tear tests and relate the mechanical performance to a damage zone model reminiscent of loading behavior observed in double network hydrogels.

  8. Antimicrobial Behavior of Semifluorinated-Quaternized Triblock Copolymers against Airborne and Marine Microorganisms

    SciTech Connect

    Park, D.; Finlay, J; Ward, R; Weinman, C; Krishnan, S; Park, M; Sohn, K; Callow, M; Callow, J; et. al.

    2010-01-01

    Semifluorinated-quaternized triblock copolymers (SQTCs) were synthesized by chemical modification of polystyrene-block-poly(ethylene-ran-butylene)-block-polyisoprene ABC triblock copolymers. Surface characterization of the polymers was performed by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) analysis. The surface of the SQTC showed very high antibacterial activity against the airborne bacterium Staphylococcus aureus with >99 % inhibition of growth. In contrast in marine fouling assays, zoospores of the green alga Ulva settled on the SQTC, which can be attributed to the positively charged surface. The adhesion strength of sporelings (young plants) of Ulva and Navicula diatoms (a unicellular alga) was high. The SQTC did not show marked algicidal activity.

  9. Hydrophobic drug delivery by self-assembling triblock copolymer-derived nanospheres.

    PubMed

    Sheihet, Larisa; Dubin, Robert A; Devore, David; Kohn, Joachim

    2005-01-01

    We describe the synthesis and characterization of a family of biocompatible ABA-triblock copolymers that comprised of hydrophilic A-blocks of poly(ethylene glycol) and hydrophobic B-blocks of oligomers of suberic acid and desaminotyrosyl-tyrosine esters. The triblock copolymers spontaneously self-assemble in aqueous solution into nanospheres, with hydrodynamic diameters between 40 and 70 nm, that do not dissociate under chromatographic and ultracentrifugation conditions. These nanospheres form strong complexes with hydrophobic molecules, including the fluorescent dye 5-dodecanoylaminofluorescein (DAF) and the antitumor drug, paclitaxel, but not with hydrophilic molecules such as fluorescein and Oregon Green. The nanosphere-paclitaxel complexes retain in vitro the high antiproliferative activity of paclitaxel, demonstrating that these nanospheres may be useful for delivery of the hydrophobic drugs.

  10. Osmotic Pressure Measurements of the Order Disorder Transition in Acrylic Triblock Copolymer Gels

    NASA Astrophysics Data System (ADS)

    Bras, Rafael E.; Shull, Kenneth R.

    2006-03-01

    Semi-dilute solutions of PMMA-PnBA-PMMA triblock co-polymers in alcohols are excellent binder materials for a novel ceramics processing method, thermo-reversible gel casting. Processing methods based on this technology offer a low cost alternative to traditional slip and gel casting techniques. The rapid transition of these gels from freely flowing liquids to elastic solids has been attributed to the aggregation of the PMMA endblocks to form small spherical domains. We have recently begun to examine the order disorder transition of the PMMA endblocks with vapor pressure osmometry. This technique measures osmotic pressure by monitoring the equilibrium temperature of a solution droplet relative to the temperature of a pure solvent droplet. Measurements of solutions consisting of 15 vol % acrylic triblock copolymer in butanol show a significant drop in osmotic pressure between 80 and 85 C. This result indicates that the relaxation times of the ordered gels can be quite low, so that the order-disorder transition of the triblock copolymer occurs at temperatures higher than the rheologically determined gelation temperature of about 65 C.

  11. The influence of shear on the ordering temperature of a triblock copolymer melt

    NASA Astrophysics Data System (ADS)

    Nakatani, Alan I.; Morrison, Faith A.; Douglas, Jack F.; Mays, Jimmy W.; Jackson, Catheryn L.; Muthukumar, M.; Han, Charles C.

    1996-01-01

    The effect of shear on the ordering temperature of a triblock copolymer melt of polystyrene-polybutadiene-polystyrene (SBS) is examined by in situ small angle neutron scattering (SANS). Results obtained by SANS are compared to the rheologically determined order-disorder transition temperature, TRODT=115±5 °C. The SANS measurements from a Couette geometry shear cell are then used to construct a ``dynamical phase diagram'' based on characteristic changes in the scattering with temperature and shear rate, γ˙. A shear rate dependent ordering temperature, Tord(γ˙), is identified as the system is sheared isothermally from the disordered state. The scattering behavior is shown to be highly strain dependent. We compare our findings on the shear rate dependence of the ordering transition in triblock materials with previous observations on diblock copolymer materials and theoretical expectations for the shear rate dependence of the order-disorder transition temperature. A simple scaling argument leads to a good description of the shear rate dependence of Tord(γ˙) in both diblock and triblock copolymer measurements over the range of shear rates examined.

  12. Positively charged micelles based on a triblock copolymer demonstrate enhanced corneal penetration

    PubMed Central

    Li, Jingguo; Li, Zhanrong; Zhou, Tianyang; Zhang, Junjie; Xia, Huiyun; Li, Heng; He, Jijun; He, Siyu; Wang, Liya

    2015-01-01

    Purpose The cornea is a main barrier to drug penetration after topical application. The aim of this study was to evaluate the abilities of micelles generated from a positively charged triblock copolymer to penetrate the cornea after topical application. Methods The triblock copolymer poly(ethylene glycol)-poly(ε-caprolactone)-g-polyethyleneimine was synthesized, and the physicochemical properties of the self-assembled polymeric micelles were investigated, including hydrodynamic size, zeta potential, morphology, drug-loading content, drug-loading efficiency, and in vitro drug release. Using fluorescein diacetate as a model drug, the penetration capabilities of the polymeric micelles were monitored in vivo using a two-photon scanning fluorescence microscopy on murine corneas after topical application. Results The polymer was successfully synthesized and confirmed using nuclear magnetic resonance and Fourier transform infrared. The polymeric micelles had an average particle size of 28 nm, a zeta potential of approximately +12 mV, and a spherical morphology. The drug-loading efficiency and drug-loading content were 75.37% and 3.47%, respectively, which indicates that the polymeric micelles possess a high drug-loading capacity. The polymeric micelles also exhibited controlled-release behavior in vitro. Compared to the control, the positively charged polymeric micelles significantly penetrated through the cornea. Conclusion Positively charged micelles generated from a triblock copolymer are a promising vehicle for the topical delivery of hydrophobic agents in ocular applications. PMID:26451109

  13. Tailoring the LCST of PNIPAAM-b-PLA-b-PNIPAAM triblock copolymers via stereocomplexation.

    PubMed

    Zhang, Xing; Tan, Beng H; He, Chaobin

    2013-11-01

    Poly(N-isopropylacrylamide)-block-poly(l-lactic acid)-block-poly(N-isopropylacrylamide) (PNIPAAM-b-PLLA-b-PNIPAAM) and PNIPAAM-b-PDLA-b-PNIPAAM triblock copolymers with varying polylactic acid (PLA) lengths are synthesized using a combination of ring-opening polymerization and atom-transfer radical polymerization. Results of (1) H NMR and gel permeation chromatography analyses show that the copolymers have a well-defined triblock structure and the PLA segment lengths can be readily controlled with monomer feed ratio. Stereocomplexation between the enantiomeric PLA segments is confirmed with differential scanning calorimetry and wide-angle X-ray scattering. Dynamic light scattering experiments show that (1) the LCST of PNIPAAM in water could be tailored from 32 °C up to 38.5 °C by increasing the length of PLA segments and mixing copolymers of similar molecular weight with enantiomeric PLA segments to induce stereocomplexation, and (2) the LCST of each mixed copolymer system could be tailored within a 2-3 °C range of body temperature by manipulating the ratio of the enantiomeric copolymers in solution.

  14. Effects of Solvent Composition on the Assembly and Relaxation of Triblock Copolymer-Based Polyelectrolyte Gels

    SciTech Connect

    Henderson, Kevin J.; Shull, Kenneth R.

    2012-03-26

    The role of solvent selectivity has been explored extensively with regard to its role in the phase behavior of block copolymer assemblies. Traditionally, thermally induced phase separation is employed for generating micelles upon cooling a block copolymer dissolved in a selective solvent. However few amphiphilic, polyelectrolyte-containing block copolymers demonstrate a thermally accessible route of micellization, and solvent exchange routes are frequently employed instead. Here, we describe the use of mixed solvents for obtaining thermoreversible gelation behavior of poly(methyl methacrylate)-poly(methacrylic acid)-poly(methyl methacrylate) (PMMA-PMAA-PMMA) triblock copolymers. One solvent component (dimethyl sulfoxide) is a good solvent for both blocks, and the second solvent component (water) is a selective solvent for the polymer midblock. Rheological frequency sweeps at variable solvent compositions and temperatures demonstrate an adherence to time-temperature-composition superposition, so that changes in the solvent composition are analogous to changes in the Flory-Huggins interaction parameter between end block and solvent. Shift factors used for this superposition are related to the effective activation energy describing the viscosity and stress relaxation response of the triblock copolymer gels. The effectiveness of solvent exchange processes for producing hydrogels with this system is shown to originate from the ability of a small amount of added water to greatly increase the relaxation times of the self-assembled polymer gels that are formed by this process.

  15. Comprehensive triblock copolymer analysis by coupled thermal field-flow fractionation-NMR.

    PubMed

    van Aswegen, Werner; Hiller, Wolf; Hehn, Mathias; Pasch, Harald

    2013-07-12

    Thermal field-flow fractionation (ThFFF) is used as a novel fractionation technique to investigate the molecular heterogeneity of PB-b-PVP-b-PtBMA triblock copolymers. Such copolymers cause major problems in liquid chromatography due to very strong polar interactions with the stationary phase. ThFFF separates the copolymers with regard to size and/or chemical composition based on the normal and thermal diffusion coefficients. The separation mechanism in ThFFF and the chemical composition of the separated species is elucidated by online (1) H NMR. Based on the compositional analysis and a calibration of the system with the respective homopolymers, the samples are quantified regarding their molar masses, chemical compositions, and microstructures providing comprehensive information on the complex structure of these block copolymers. PMID:23722993

  16. Self-organization of triblock copolymer patterns obtained by drying and dewetting

    NASA Astrophysics Data System (ADS)

    Carvalho, A. J. F.; Pereira-da-Silva, M. A.; Faria, R. M.

    2006-07-01

    Self-organized block copolymer structures derived from dewetting of thin films are becoming important in nanotechnology because of the various spontaneous and regular sub-micrometric surface patterns that may be obtained. Here, we report on the self-organization of a poly(styrene)-b-poly(ethene-co-butene-1)-b-poly(styrene) triblock copolymer during drying of its solution over a mica substrate. Regular submicrometric arrangements with long-range order were formed at critical polymer concentrations, consisting of parallel ribbons and hexagonal arrays of dots (droplets). This variety of highly ordered structures is explained by the interplay between forming mechanisms, mainly due to “fingering instabilities” at the three-phase line of the copolymer solution during drying. The thickness of the structures was “quantized” due to the microphase separation of the block copolymer. The formation of hexagonal patterns may be attributed to Marangoni instability at the liquid film surface prior to dewetting.

  17. Bioresorbable poly(ester-ether urethane)s from L-lysine diisocyanate and triblock copolymers with different hydrophilic character.

    PubMed

    Abraham, Gustavo A; Marcos-Fernández, Angel; Román, Julio San

    2006-03-15

    Bioresorbable linear poly(ester-ether urethane)s with different hydrophilic character were synthesized from block copolymers of poly(epsilon-caprolactone)-poly(ethylene oxide)-poly(epsilon-caprolactone) (PCL-PEO-PCL) as macrodiols, and L-lysine diisocyanate (LDI). A series of PCL-PEO-PCL triblock copolymers with different PEO and PCL chain length was obtained by reacting PEO with epsilon-caprolactone. Polyurethanes were synthesized by reacting the triblock copolymers with LDI in solution using stannous 2-ethylhexanoate as catalyst. The prepared triblock copolymers and polyurethanes were fully characterized by proton nuclear magnetic resonance spectroscopy, size exclusion chromatography, differential scanning calorimetry, and wide-angle X-ray diffraction. Water uptake, hydrolytic stability, and tensile properties of polyurethanes with different composition were evaluated and discussed in terms of the chain length and molecular weight of the polymers and its block components. Water uptake seems to depend on the ethylene oxide unit content of the polyurethane regardless of the triblock structure. Mechanical properties of the synthesized polymers were strongly affected by the molecular weight achieved during polymerization. The use of triblock macrodiols with different hydrophilicity allowed the preparation of a series of polyurethanes having a broad range of properties. PMID:16317720

  18. Segmental chain dynamics of ABA triblock copolymer micelles in aqueous solution

    NASA Astrophysics Data System (ADS)

    Prabhu, Vivek; Wei, Guangmin; Nagao, Michihiro; Venkataraman, Shrinivas; Yang, Yi Yan; Hedrick, James

    The polymer physics of hierarchical, aqueous self-assembled ABA block copolymers is an active area of research for both advanced materials and biomaterial applications. Scattering-based techniques provide a direct measure of the correlations and structure across multiple length and time scales. Hierarchical clusters of micelles are formed by well-defined poly(ethylene glycol) triblock copolymers with oligo-fluorene hydrophobic end-groups in aqueous solutions. The structure and dynamics of this system was studied by small-angle neutron scattering (SANS), and static and dynamic light scattering. We will present new neutron spin-echo spectroscopy (NSE) results that provides direct insight into the segmental chain dynamics constrained by the pi-pi stacking of the oligo-fluorene end groups. The dilute cluster regime within the temperature-composition phase diagram is of current interest. Nist Materials Genome Program.

  19. Cationic triblock copolymer micelles enhance antioxidant activity, intracellular uptake and cytotoxicity of curcumin.

    PubMed

    Yoncheva, Krassimira; Kamenova, Katya; Perperieva, Teodora; Hadjimitova, Vera; Donchev, Petar; Kaloyanov, Kaloyan; Konstantinov, Spiro; Kondeva-Burdina, Magdalena; Tzankova, Virginia; Petrov, Petar

    2015-07-25

    The aim of the present study was to develop curcumin loaded cationic polymeric micelles and to evaluate their loading, preservation of curcumin antioxidant activity and intracellular uptake ability. The micelles were prepared from a triblock copolymer consisting of poly(ϵ-caprolactone) and very short poly(2-(dimethylamino) ethyl methacrylate) segments (PDMAEMA9-PCL70-PDMAEMA9). The micelles showed monomodal size distribution, mean diameter of 145 nm, positive charge (+72 mV), critical micellar concentration around 0.05 g/l and encapsulation efficiency of 87%. The ability of the micellar curcumin to scavenge the ABTS radical and hypochlorite ions was higher than that of the free curcumin. Confocal microscopy revealed that the uptake of curcumin by chronic myeloid leukemia derived K-562 cells and human multiple myeloma cells U-266 was more intensive when curcumin was loaded into the micelles. These results correlated with the higher cytotoxicity of the micellar curcumin compared to free curcumin. Intraperitoneal treatment of Wistar rats indicated that PDMAEMA-PCL-PDMAEMA copolymer, comprising very short cationic chains, did not change the levels of malondialdehyde and glutathione in livers indicating an absence of oxidative stress. Thus, PDMAEMA-PCL-PDMAEMA triblock micelles could be considered efficient and safe platform for curcumin delivery. PMID:26026253

  20. 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.

  1. Polydiacetylene/triblock copolymer nanoblend applied as a sensor for micellar casein: A thermodynamic approach.

    PubMed

    de Souza, Luana Cypriano; de Paula Rezende, Jaqueline; Pires, Ana Clarissa dos Santos; da Silva, Luis Henrique Mendes; da Silva, Maria do Carmo Hespanhol; Castrillon, Elkin Dario Castellon; de Andrade, Nélio José

    2016-04-15

    Polydiacetylene (PDA) and triblock copolymer nanoblends were synthesized to detect micellar casein (MC), the main milk protein and an indicator of milk quality. UV-Vis spectrum showed that MC induced blue-to-red transition in nanoblends. When nanoblends and MC were separated by dialysis membrane colorimetric response (CR) was similar, whereas a remarkable CR reduction was noticed after addition of dialyzed-MC, suggesting that small molecules present in MC (salts) caused PDA color change. Interaction enthalpy variation between nanoblends and MC showed an abrupt increase that coincided with MC concentration when colorimetric transition occurred. Copolymer hydrophobic/hydrophilic balance and presence of other molecules in the system affected nanoblends CR. MC salts were found to interact with nanoblends leading to color changes. MC concentration, MC salt release, copolymer hydrophobic/hydrophilic balance, and presence of other molecules in the system affected responses of the sensors. These results contribute to future applications of PDA/copolymer nanosensors to dairy models. PMID:26617025

  2. Modeling and self-assembly behavior of PEG-PLA-PEG triblock copolymers in aqueous solution

    NASA Astrophysics Data System (ADS)

    Wu, Xiaohan; Li, Suming; Coumes, Fanny; Darcos, Vincent; Lai Kee Him, Joséphine; Bron, Patrick

    2013-09-01

    A series of poly(ethylene glycol)-polylactide-poly(ethylene glycol) (PEG-PLA-PEG) triblock copolymers with symmetric or asymmetric chain structures were synthesized by combination of ring-opening polymerization and copper-catalyzed click chemistry. The resulting copolymers were used to prepare self-assembled aggregates by dialysis. Various architectures such as nanotubes, polymersomes and spherical micelles were observed from transmission electron microscopy (TEM), cryo-TEM and atomic force microscopy (AFM) measurements. The formation of diverse aggregates is explained by modeling from the angle of both geometry and thermodynamics. From the angle of geometry, a ``blob'' model based on the Daoud-Cotton model for star polymers is proposed to describe the aggregate structures and structural changes with copolymer composition and molar mass. In fact, the copolymer chains extend in aqueous medium to form single layer polymersomes to minimize the system's free energy if one of the two PEG blocks is short enough. The curvature of polymersomes is dependent on the chain structure of copolymers, especially on the length of PLA blocks. A constant branch number of aggregates (f) is thus required to preserve the morphology of polymersomes. Meanwhile, the aggregation number (Nagg) determined from the thermodynamics of self-assembly is roughly proportional to the total length of polymer chains. Comparing f to Nagg, the aggregates take the form of polymersomes if Nagg ~ f, and change to nanotubes if Nagg > f to conform to the limits from both curvature and aggregation number. The length of nanotubes is mainly determined by the difference between Nagg and f. However, the hollow structure becomes unstable when both PEG segments are too long, and the aggregates eventually collapse to yield spherical micelles. Therefore, this work gives new insights into the self-assembly behavior of PEG-PLA-PEG triblock copolymers in aqueous solution which present great interest for biomedical and

  3. 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

  4. Triblock siloxane copolymer surfactant: template for spherical mesoporous silica with a hexagonal pore ordering.

    PubMed

    Stébé, M J; Emo, M; Forny-Le Follotec, A; Metlas-Komunjer, L; Pezron, I; Blin, J L

    2013-02-01

    Ordered mesoporous silica materials with a spherical morphology have been prepared for the first time through the cooperative templating mechanism (CTM) by using a silicone triblock copolymer as template. The behavior of the pure siloxane copolymer amphiphile in water was first investigated. A direct micellar phase (L(1)) and a hexagonal (H(1)) liquid crystal were found. The determination of the structural parameters by SAXS measurements leads us to conclude that in the hexagonal liquid crystal phase a part of the ethylene oxide group is not hydrated as observed for the micelles. Mesoporous materials were then synthesized from the cooperative templating mechanism. The recovered materials were characterized by SAXS measurements, nitrogen adsorption-desorption analysis, and transmission and scanning electron microscopy. The results clearly evidence that one can control the morphology and the nanostructuring of the resulting material by modifying the synthesis parameters. Actually, highly ordered mesoporous materials with a spherical morphology have been obtained with a siloxane copolymer/tetramethoxysilane molar ratio of 0.10 after hydrothermal treatment at 100 °C. Our study also supports the fact that the interactions between micelles and the hydrolyzed precursor are one of the key parameters governing the formation of ordered mesostructures through the cooperative templating mechanism. Indeed, we have demonstrated that when the interactions between micelles are important, only wormhole-like structures are recovered.

  5. Protective effects of nonionic tri-block copolymers on bile acid-mediated epithelial barrier disruption.

    SciTech Connect

    Edelstein, A.; Fink, D.; Musch, M.; Valuckaite, V.; Zabornia, O.; Grubjesic, S.; Firestone, M. A.; Matthews, J. B.; Alverdy, J. C.

    2011-11-01

    Translocation of bacteria and other luminal factors from the intestine following surgical injury can be a major driver of critical illness. Bile acids have been shown to play a key role in the loss of intestinal epithelial barrier function during states of host stress. Experiments to study the ability of nonionic block copolymers to abrogate barrier failure in response to bile acid exposure are described. In vitro experiments were performed with the bile salt sodium deoxycholate on Caco-2 enterocyte monolayers using transepithelial electrical resistance to assay barrier function. A bisphenol A coupled triblock polyethylene glycol (PEG), PEG 15-20, was shown to prevent sodium deoxycholate-induced barrier failure. Enzyme-linked immunosorbent assay, lactate dehydrogenase, and caspase 3-based cell death detection assays demonstrated that bile acid-induced apoptosis and necrosis were prevented with PEG 15-20. Immunofluorescence microscopic visualization of the tight junctional protein zonula occludens 1 (ZO-1) demonstrated that PEG 15-20 prevented significant changes in tight junction organization induced by bile acid exposure. Preliminary transepithelial electrical resistance-based studies examining structure-function correlates of polymer protection against bile acid damage were performed with a small library of PEG-based copolymers. Polymer properties associated with optimal protection against bile acid-induced barrier disruption were PEG-based compounds with a molecular weight greater than 10 kd and amphiphilicity. The data demonstrate that PEG-based copolymer architecture is an important determinant that confers protection against bile acid injury of intestinal epithelia.

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

    PubMed

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

    2014-11-13

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

  7. Triblock copolymer gels - structure, fracture behavior and application in ceramic processing

    NASA Astrophysics Data System (ADS)

    Seitz, Michelle E.

    Acrylic triblock copolymer gels transition rapidly from free-flowing liquids to elastic solids and their nanoscale self-assembly leads to reproducible structure and properties. They are an ideal model system for understanding the link between gel structure and the deformation and fracture behavior of soft, self-assembled materials. While a basic understanding of gel structure and linear viscoelastic response exists, this research aims to extend this understanding to include the nonlinear mechanical response and fracture behavior as well as the effect of gel concentration, block length, endblock fraction, and homopolymer solubilization. This expanded understanding will be applied to optimize triblock design for the thermoreversible gelcasting of ceramics. Gel structure was characterized using small angle scattering and self-consistent field theory simulations while mechanical properties were studied using a combination of rheology, swelling, indentation, uniaxial compression, and fracture experiments. Birefringence and shear alignment were used to differentiate between spherical and cylindrical micelle morphologies. An effective energy barrier of 550 kJ/mol describes gels relaxation behavior over a 40°C temperature range where the relaxation times vary by a factor of 1010. At high endblock contents, gels exhibit greater permanent deformation and moduli over an order of magnitude larger than would be expected from rubber elasticity alone due to a transition from spherical to cylindrical micelles. The rate dependence of a gels energy release rate, G , is independent of the gel concentration when G is normalized by the small strain Young's modulus, E. The gels exhibit a transition from rough, slow crack propagation to smooth, fast crack propagation for a well-defined value of the characteristic length, G /E. Crack tip stresses become highly anisotropic at stress values below the failure strength of the gels and are poorly described using linear elastic fracture

  8. Reduction-sensitive amphiphilic triblock copolymers self-assemble into stimuli-responsive micelles for drug delivery.

    PubMed

    Toughraï, Smahan; Malinova, Violeta; Masciadri, Raffaello; Menon, Sindhu; Tanner, Pascal; Palivan, Cornelia; Bruns, Nico; Meier, Wolfgang

    2015-04-01

    Polymeric nanostructures obtained through self-assembly of reduction-sensitive amphiphilic triblock copolymers were investigated as potential drug delivery systems. The characteristic feature of these polymers is their cleavable disulfide bond in the center of the hydrophobic block. Therefore, the triblock copolymers can be cleaved into amphiphilic diblock copolymers. A poly(2-hydroxyethyl methacrylate)-b-poly(butyl methacrylate)-S-S-poly(butyl methacrylate)-b-poly(2-hydroxyethyl methacrylate) (PHEMA-b-(PBMA-S-S-PBMA)-b-PHEMA) triblock copolymer was synthesized. It self-assembled into micelles which were used to encapsulate hydrophobic dye molecules (Nile Red, BodiPy 630/650) as model payloads. The self-assembled nanostructures disintegrated upon reduction of the disulfide bond, releasing their cargo and yielding larger particles that formed aggregates in solution after 24 h. A burst release of payload was shown within the first 15 min, followed by a constant release over several hours. As concentration gradients of reducing agents are commonly found in biological systems, the micelles could be used as redox-sensitive nanocarriers for the intracellular delivery of drugs.

  9. Heat capacity anomaly in a self-aggregating system: Triblock copolymer 17R4 in water

    NASA Astrophysics Data System (ADS)

    Dumancas, Lorenzo V.; Simpson, David E.; Jacobs, D. T.

    2015-05-01

    The reverse Pluronic, triblock copolymer 17R4 is formed from poly(propylene oxide) (PPO) and poly(ethylene oxide) (PEO): PPO14 - PEO24 - PPO14, where the number of monomers in each block is denoted by the subscripts. In water, 17R4 has a micellization line marking the transition from a unimer network to self-aggregated spherical micelles which is quite near a cloud point curve above which the system separates into copolymer-rich and copolymer-poor liquid phases. The phase separation has an Ising-like, lower consolute critical point with a well-determined critical temperature and composition. We have measured the heat capacity as a function of temperature using an adiabatic calorimeter for three compositions: (1) the critical composition where the anomaly at the critical point is analyzed, (2) a composition much less than the critical composition with a much smaller spike when the cloud point curve is crossed, and (3) a composition near where the micellization line intersects the cloud point curve that only shows micellization. For the critical composition, the heat capacity anomaly very near the critical point is observed for the first time in a Pluronic/water system and is described well as a second-order phase transition resulting from the copolymer-water interaction. For all compositions, the onset of micellization is clear, but the formation of micelles occurs over a broad range of temperatures and never becomes complete because micelles form differently in each phase above the cloud point curve. The integrated heat capacity gives an enthalpy that is smaller than the standard state enthalpy of micellization given by a van't Hoff plot, a typical result for Pluronic systems.

  10. Expanding mesoporosity of triblock-copolymer-templated silica under weak synthesis acidity.

    PubMed

    Li, Jinjun; Hu, Qin; Tian, Hua; Ma, Chunyan; Li, Landong; Cheng, Jie; Hao, Zhengping; Qiao, Shizhang

    2009-11-01

    With initial aging at low temperature for enough time, silicas with large mesoporosity were synthesized using triblock copolymer as template agent under weak acidities. SBA-15 with periodic mesostructure and short mesochannels could be synthesized at pH 2.5-3.0 within weak acidity range, and the surface areas, pore diameters and pore volumes reached up to ca. 1000m(2)/g, 8.8nm and 2.0cm(3)/g, respectively, which were significantly higher than those of the conventional SBA-15 synthesized under strong acidities. Mesoporous silica with wormhole structure and abundant textural porosity was formed at pH approximately 3.5. The increased hydrophobic volume of the copolymer micelles at elevated pH values was responsible for the enlargement of mesoporosity in the products. The materials synthesized under weak acidities showed lower hexagonal ordering in comparison to the general SBA-15 synthesized under strong acidities because the decreased hydronium ion concentration induced relatively weaker assembly forces during the synthesis. Nonetheless, the short mesochannels and large pore diameter in the products might be beneficial to some applications in which fast diffusion of molecules is required.

  11. Structure of PEO-b-PPO-b-PEO Triblock Copolymer Inclusion Complexes with Beta-Cyclodextrin

    NASA Astrophysics Data System (ADS)

    Tsai, Chi-Chun; Cheng, Stephen Z. D.; Lotz, Bernard; Huang, Jin; Chen, Yongming

    2009-03-01

    Inclusion complexes, formed by non-covalent host-guest interactions, have been extensively investigated because they can be useful as building blocks for constructing supramolecular structures. Cyclodextrins (CDs), due to their good water-solubility and ability to include a wide range of guest molecules, have been the most intensively studied host molecules. CDs are shaped like a shallow truncated cone, with a hydrophilic outer surface as well as primary (narrower end) and secondary (wider end) hydroxyl groups on the rim of the molecule. The cavity, which is constructed with alkyl groups and glycosidic oxygen atoms, is hydrophobic and can act as a host for a great variety of hydrophobic molecular guests. A series of host-guest inclusion complexes were prepared with beta-cyclodextrin (beta-CD) and PEO-PPO-PEO triblock copolymers of varying molecular weights and compositions. The middle PPO block of the copolymers can be selectively included by beta-CD to form an inclusion complex while the PEO blocks cannot. These inclusion complexes can further self-assembled into supramolecular structures in aqueous solution. The inclusion complexes and self-assembled supramolecular structures were characterized by Nuclear Magnetic Resonance, X-ray diffraction, and Differential Scanning Calorimetry experimental methods.

  12. Dependence of aggregation behavior on concentration in triblock copolymer solutions: The effect of chain architecture

    SciTech Connect

    Han, Xiang-Gang Zhang, Xue-Feng

    2015-12-07

    Using the self-consistent field lattice technique, the effects of concentration and hydrophobic middle block length (where the chain length remains constant) on aggregation behavior are studied in amphiphilic symmetric triblock copolymer solutions. The heat capacity peak for the unimer-micelle transition and the distribution peaks for the different degrees of aggregation for micelles and small aggregates (submicelles) are calculated. Analysis of the conducted computer simulations shows that the transition broadness dependence on concentration is determined by the hydrophobic middle block length, and this dependence is distinctly different when the length of the hydrophobic middle block changes. Different size for small aggregates simultaneously appear in the transition region. As temperature decreases, the number of different size small aggregates for the large hydrophobic middle block length first ascends and then descends in aggregation degree order. These results indicate that any transition broadness change with concentration is related to the mechanism of fragmentation and fusion. These results are helpful for interpreting the aggregation process of amphiphilic copolymers at equilibrium.

  13. Equilibrium Structure of a Triblock Copolymer System Revealed by Mesoscale Simulation and Neutron Scattering

    SciTech Connect

    Do, Changwoo; Chen, Wei-Ren; Hong, Kunlun; Smith, Gregory Scott

    2013-01-01

    We have performed both mesoscale simulations and neutron scattering experiments on Pluronic L62, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer system in aqueous solution. The influence of simulation variables such PEO/PPO block ratio, interaction parameters, and coarse-graining methods is extensively investigated by covering all permutations of parameters found in the literatures. Upon increasing the polymer weight fraction from 50 wt% to 90 wt%, the equilibrium structure of the isotropic, reverse micellar, bicontinuous, worm-like micelle network, and lamellar phases are respectively predicted from the simulation depending on the choices of simulation parameters. Small angle neutron scattering (SANS) measurements show that the same polymer systems exhibit the spherical micellar, lamellar, and reverse micellar phases with the increase of the copolymer concentration at room temperature. Detailed structural analysis and comparison with simulations suggest that one of the simulation parameter sets can provide reasonable agreement with the experimentally observed structures.

  14. 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.

  15. Gas-tight triblock-copolymer membranes are converted to CO2 permeable by insertion of plant aquaporins

    PubMed Central

    Uehlein, Norbert; Otto, Beate; Eilingsfeld, Adrian; Itel, Fabian; Meier, Wolfgang; Kaldenhoff, Ralf

    2012-01-01

    We demonstrate that membranes consisting of certain triblock-copolymers were tight for CO2. Using a novel approach, we provide evidence for aquaporin facilitated CO2 diffusion. Plant aquaporins obtained from heterologous expression were inserted into triblock copolymer membranes. These were employed to separate a chamber with a solution maintaining high CO2 concentrations from one with depleted CO2 concentrations. CO2 diffusion was detected by measuring the pH change resulting from membrane CO2 diffusion from one chamber to the other. An up to 21 fold increase in diffusion rate was determined. Besides the supply of this proof of principle, we could provide additional arguments in favour of protein facilitated CO2 diffusion to the vivid on-going debate about the principles of membrane gas diffusion in living cells. PMID:22844579

  16. Nanoparticle-Induced Ellipse-to-Vesicle Morphology Transition of Rod-Coil-Rod Triblock Copolymer Aggregates.

    PubMed

    Yang, Chaoying; Li, Qing; Cai, Chunhua; Lin, Jiaping

    2016-07-12

    Cooperative self-assembly behavior of rod-coil-rod poly(γ-benzyl-l-glutamate)-block-poly(ethylene glycol)-block-poly(γ-benzyl-l-glutamate) (PBLG-b-PEG-b-PBLG) amphiphilic triblock copolymers and hydrophobic gold nanoparticles (AuNPs) was investigated by both experiments and dissipative particle dynamics (DPD) simulations. It was discovered that pure PBLG-b-PEG-b-PBLG copolymers self-assemble into ellipse-like aggregates, and the morphology transforms into vesicles as AuNPs are introduced. When the hydrophobicity of AuNPs is close to that of the copolymers, AuNPs are homogeneously distributed in the vesicle wall. While for the AuNPs with higher hydrophobicity, they are embedded in the vesicle wall as clusters. In addition to the experimental observations, DPD simulations were performed on the self-assembly behavior of triblock copolymer/nanoparticle mixtures. Simulations well reproduced the morphology transition observed in the experiments and provided additional information such as chain packing mode in aggregates. It is deduced that the main reason for the ellipse-to-vesicle transition of the aggregates is attributed to the breakage of ordered and dense packing of PBLG rods in the aggregate core by encapsulating AuNPs. This study deepens our understanding of the self-assembly behavior of rod-coil copolymer/nanoparticle mixtures and provides strategy for designing hybrid polypeptide nanostructures. PMID:27314970

  17. ABC Triblock Copolymer Worms: Synthesis, Characterization, and Evaluation as Pickering Emulsifiers for Millimeter-Sized Droplets

    PubMed Central

    2016-01-01

    Polymerization-induced self-assembly (PISA) is used to prepare linear poly(glycerol monomethacrylate)–poly(2-hydroxypropyl methacrylate)–poly(benzyl methacrylate) [PGMA–PHPMA–PBzMA] triblock copolymer nano-objects in the form of a concentrated aqueous dispersion via a three-step synthesis based on reversible addition–fragmentation chain transfer (RAFT) polymerization. First, GMA is polymerized via RAFT solution polymerization in ethanol, then HPMA is polymerized via RAFT aqueous solution polymerization, and finally BzMA is polymerized via “seeded” RAFT aqueous emulsion polymerization. For certain block compositions, highly anisotropic worm-like particles are obtained, which are characterized by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The design rules for accessing higher order morphologies (i.e., worms or vesicles) are briefly explored. Surprisingly, vesicular morphologies cannot be accessed by targeting longer PBzMA blocks—instead, only spherical nanoparticles are formed. SAXS is used to rationalize these counterintuitive observations, which are best explained by considering subtle changes in the relative enthalpic incompatibilities between the three blocks during the growth of the PBzMA block. Finally, the PGMA–PHPMA–PBzMA worms are evaluated as Pickering emulsifiers for the stabilization of oil-in-water emulsions. Millimeter-sized oil droplets can be obtained using low-shear homogenization (hand-shaking) in the presence of 20 vol % n-dodecane. In contrast, control experiments performed using PGMA–PHPMA diblock copolymer worms indicate that these more delicate nanostructures do not survive even these mild conditions. PMID:27795581

  18. Formation of ordered microphase-separated pattern during spin coating of ABC triblock copolymer

    NASA Astrophysics Data System (ADS)

    Huang, Weihuan; Luo, Chunxia; Zhang, Jilin; Han, Yanchun

    2007-03-01

    In this paper, the authors have systematically studied the microphase separation and crystallization during spin coating of an ABC triblock copolymer, polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-b-P2VP-b-PEO). The microphase separation of PS-b-P2VP-b-PEO and the crystallization of PEO blocks can be modulated by the types of the solvent and the substrate, the spinning speed, and the copolymer concentration. Ordered microphase-separated pattern, where PEO and P2VP blocks adsorbed to the substrate and PS blocks protrusions formed hexagonal dots above the P2VP domains, can only be obtained when PS-b-P2VP-b-PEO is dissolved in N,N-dimethylformamide and the films are spin coated onto the polar substrate, silicon wafers or mica. The mechanism of the formation of regular pattern by microphase separation is found to be mainly related to the inducement of the substrate (middle block P2VP wetting the polar substrate), the quick vanishment of the solvent during the early stage of the spin coating, and the slow evaporation of the remaining solvent during the subsequent stage. On the other hand, the probability of the crystallization of PEO blocks during spin coating decreases with the reduced film thickness. When the film thickness reaches a certain value (3.0nm), the extensive crystallization of PEO is effectively prohibited and ordered microphase-separated pattern over large areas can be routinely prepared. When the film thickness exceeds another definite value (12.0nm), the crystallization of PEO dominates the surface morphology. For films with thickness between these two values, microphase separation and crystallization can simultaneously occur.

  19. Mesoporous aluminosilicates assembled from dissolved LTA zeolite and triblock copolymer in the presence of tetramethylammonium hydroxide.

    PubMed

    Tanaka, Shunsuke; Okada, Hiroaki; Nakatani, Norihito; Maruo, Takanori; Nishiyama, Norikazu; Miyake, Yoshikazu

    2009-05-15

    Zeolite Na-A crystals dissolved in a HCl solution were used as a single-source of silicon and aluminum for the synthesis of mesoporous aluminosilicates via a template-assisted method with an organic base tetramethylammonium hydroxide (TMAOH). Amphiphilic triblock copolymer Pluronic F127 (EO(106)PO(70)EO(106)) was used as template. Increasing the amount of TMAOH in the synthetic solution resulted in an increase in the aluminum content of the products. On the other hand, mesostructural periodicity was deteriorated with higher content of aluminum incorporated into the mesoporous framework. The samples with low Si/Al ratios less than 5 have wormhole-like pore structure, while the samples with Si/Al ratios more than 7 possess highly ordered mesoporous structure, a body-centered Im3m symmetry, with single crystal like morphology. The samples with Si/Al ratio of 7, which prepared at TMAOH molar concentration of 25 mM in the templating solution, possess BET surface area of 470 m(2)/g, pore size of 6.4 nm, and pore volume of 0.56 cm(3)/g. Aluminum atoms have successfully been incorporated in a tetra-coordinated position and remained stable even after calcination at 600 degrees C.

  20. Structure of PS/PMMA Blends with Interfacially Active Janus Particles Derived from ABC Triblock Copolymers

    NASA Astrophysics Data System (ADS)

    Bryson, Kyle; Löbling, Tina; Müller, Axel; Hayward, Ryan; Russell, Thomas

    2014-03-01

    Kinetic trapping of bicontinuous polymer morphologies on submicron length scales through the interfacial adsorption of nanoparticles is of interest due to the unique combination of the properties of each component provided by such structures, and their potential for use as membranes and composite materials. However, this strategy is challenging to realize in polymeric systems, due to the difficulties in preparing particles that are neutrally wetted by the two polymer phases. Janus particles afford a route to circumvent the necessity of neutral wettability. Both theory and experiment have shown enhanced interfacial adsorption energies for Janus particles, as well as greater flexibility in controlling particle orientation at the interface, in comparison to homogeneous particles. Janus particles with polystyrene and poly(methyl methacrylate) (PS/PMMA) hemispheres and a crosslinked polybutadiene core were prepared from triblock copolymers. Using blends of PS and PMMA homopolymers and the Janus particles, we examined structures produced by phase separation during solvent casting and thermodynamic demixing transitions via TEM and small-angle light scattering. The results elucidate the role of particle wettability on interfacial behavior and the structure of stabilized emulsions.

  1. Phase behavior and structure of an ABC triblock copolymer dissolved in selective solvent.

    PubMed

    Shusharina, N P; Alexandridis, P; Linse, P; Balijepalli, S; Gruenbauer, H J M

    2003-01-01

    A mean-field lattice theory is applied to predict the self-assembly into ordered structures of an ABC triblock copolymer in selective solvent. More specifically, the composition-temperature phase diagram has been constructed for the system (C)14(PO)12(EO)17/water, where C stands for methylene, PO for propylene oxide and EO for ethylene oxide. The model predicts thermotropic phase transitions between the ordered hexagonal, lamellar, reverse hexagonal, and reverse cubic phases, as well as the disordered phase. The thermotropic behavior is a result of the temperature dependence of water interaction with EO- and PO-segments. The lyotropic effect (caused by changing the solvent concentration) on the formation of different structures has been found weak. The structure in the ordered phases is described by analyzing the species volume fraction profiles and the end segment and junction distributions. A "triple-layer" structure has been found for each of the ordered phases, with each layer rich in C-, PO-, and EO-segments, respectively. The blocks forming the layers are not stretched. The dependence of the domain spacing on polymer volume fraction and temperature is also considered.

  2. Time-composition superpositioning in the rheological behavior of triblock copolymer/selective co-solvent blends

    NASA Astrophysics Data System (ADS)

    Krishnan, Arjun; Bukovnik, Rudolf; Spontak, Richard

    2009-03-01

    Thermoplastic elastomers composed of styrenic triblock copolymers are of great importance in applications such as adhesives and vibration dampening due to their resilience and facile processing. The swelling of these polymers by adding midblock selective solvents or oligomers provides an easy route by which to modify the morphology and mechanical behavior of these systems. In this study we consider a ternary blend of a poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer and mixtures of two midblock selective co-solvents: a mineral oil that is liquid at ambient temperature, and a glassy tackifier resin that exhibits limited solubility in the midblock matrix. We use dynamic rheology to study the viscoelastic response of a wide variety of systems under oscillatory shear. The copolymer concentration is varied between 15 to 35 wt%, while the resin/oil ratio in the midblock-solvent matrix is independently varied. Frequency spectra acquired at ambient temperature display viscoelastic behavior that shifts in the frequency domain depending on the resin/oil ratio. At high oil loadings, the materials behave as physical gels. For each copolymer concentration, all the frequency data can be shifted by time-composition superpositioning to yield a single master-curve.

  3. Chirality Effect on Flory-Huggins Interaction Parameters in Polylactide-b-Poly(ethylene-co-1-butene)-b-Polylactide Triblock Copolymers

    NASA Astrophysics Data System (ADS)

    Cao, Weiqiang; Zhu, Lei; Rong, Lixia; Hsiao, Benjamin S.

    2009-03-01

    In this work, a set of well-defined polylactide-b-poly(ethylene-co-1-butene)-b-polylactide (PLA-PEB-PLA) triblock copolymers were synthesized by controlled ring-opening polymerization of corresponding lactide monomers (L-lactide and racemic mixture of D- and L-lactides) using Sn(Oct)2 as the catalyst. The volume fractions of PLA in the triblock copolymers were adjusted by tuning its molecular weight. The mesophase morphology and phase transitions in these triblock copolymers were studied by temperature-dependent small-angle X-ray scattering (SAXS). The Flory-Huggins interaction parameter χ between EB and lactide as a function of temperature were estimated from the order-disorder transition temperature (TODT) using the mean-field critical (χN)c values. The effects of PLA chirality on both Flory-Huggins interaction parameter and segmental lengths were investigated.

  4. Synthesis of zwitterionic polymer-based amphiphilic triblock copolymers by atom transfer radical polymerization for production of extremely stable nanoemlusions

    NASA Astrophysics Data System (ADS)

    Lee, Jin Yong; Kim, Ji Eun; Kim, Jin Woong

    2015-03-01

    In fields of soft matter, there have been growing interests in utilizing amphiphilic block copolymers due to their intriguing properties, such as surface activity as well as self-assembly. In this work, we synthesize a series of poly (2-(methacryloyloxy) ethyl phosphorylcholine)- b-poly (ɛ-caprolactone)- b-poly (2-(methacryloyloxy) ethyl phosphorylcholine) (PMPC- b-PCL- b-PMPC) triblock copolymers by using atom transfer radical polymerization (ATRP). We have a particular interest in using poly (2-(methacryloyloxy) ethyl phosphorylcholine) (PMPC) as a hydrophilic block, since it can have both electrostatic repulsion and steric repulsion in complex fluid systems. Assembling them at the oil-water interface by using the phase inversion method enables production of highly stable nanoemulsions. From the analyses of the crystallography and self-assembly behavior, we have found that the triblock copolymers assemble to form a flexible but tough molecular thin film at the interface, which is essential for the remarkable improvement in the emulsion stability.

  5. Reversible, voltage-activated formation of biomimetic membranes between triblock copolymer-coated aqueous droplets in good solvents.

    PubMed

    Tamaddoni, Nima; Taylor, Graham; Hepburn, Trevor; Michael Kilbey, S; Sarles, Stephen A

    2016-06-21

    Biomimetic membranes assembled from block copolymers attract considerable interest because they exhibit greater stability and longetivity compared to lipid bilayers, and some enable the reconstitution of functional transmembrane biomolecules. Yet to-date, block copolymer membranes have not been achieved using the droplet interface bilayer (DIB) method, which uniquely allows assembling single- and multi-membrane networks between water droplets in oil. Herein, we investigate the formation of poly(ethylene oxide)-b-poly(dimethyl siloxane)-b-poly(ethylene oxide) triblock copolymer-stabilized interfaces (CSIs) between polymer-coated aqueous droplets in solutions comprising combinations of decane, hexadecane and AR20 silicone oil. We demonstrate that triblock-coated droplets do not spontaneously adhere in these oils because all are thermodynamically good solvents for the hydrophobic PDMS middle block. However, thinned planar membranes are reversibly formed at the interface between droplets upon the application of a sufficient transmembrane voltage, which removes excess solvent from between droplets through electrocompression. At applied voltages above the threshold required to initiate membrane thinning, electrowetting causes the area of the CSI between droplets to increase while thickness remains constant; the CSI electrowetting response is similar to that encountered with lipid-based DIBs. In combination, these results reveal that stable membranes can be assembled in a manner that is completely reversible when an external pressure is used to overcome a barrier to adhesion caused by solvent-chain interactions, and they demonstrate new capability for connecting and disconnecting aqueous droplets via polymer-stabilized membranes.

  6. Bentonite-based organoclays as innovative flame retardants agents for SBS copolymer.

    PubMed

    Franchini, M Comes; Fabbri, P; Frache, A; Ori, G; Messori, M; Siligardi, C; Ricci, A

    2008-12-01

    Two organophilic bentonites, based on nitrogen-containing compounds, have been synthesised via ion exchange starting from pristine bentonite with octadecyltrimethylammonium bromide (OTAB) and with synthetic melamine-derived N2,N4-dihexadecyl-1,3,5-triazine-2,4,6-triamine (DEDMEL). The chemical and morphological characterization of the organoclays was based on XRD, TEM, Laser Granulometry, X-Ray Fluorescence and CEC capacity. Copoly(styrene-butadiene-styrene)-nanocomposites (SBS-nanocomposites) were obtained by intercalation of the SBS-copolymer into these new organoclays by melt intercalation method. XRD and TEM analysis of the organoclays and of the micro/nano-composites obtained are presented. The effect of the organoclays on the SBS-nanocomposite's flammability properties was investigated using cone calorimeter. An encouraging decrease of 20% in the peak heat released rate (PHRR) has been obtained confirming the important role of melamine's based skeleton and its derived organoclays to act as effective fire retardants and for the improvement of this important functional property in SBS copolymers. PMID:19205200

  7. Subcutaneous tri-block copolymer produces recovery from spinal cord injury.

    PubMed

    Borgens, Richard B; Bohnert, Debbie; Duerstock, Brad; Spomar, Daniel; Lee, Raphael C

    2004-04-01

    We have studied the ability of nonionic detergents and hydrophilic polymers to seal permeabilized membranes of damaged cells, rescuing them from progressive dissolution, degeneration, and death. We report that a single subcutaneous injection of the tri-block copolymer, Poloxamer 188 (P188) 6 hr after a severe compression of the adult guinea pig spinal cord is able to: (1). preserve the anatomic integrity of the cord; (2). produce a rapid recovery of nerve impulse conduction through the lesion; and (3). produce a behavioral recovery of a spinal cord dependent long tract spinal cord reflex. These observations stood out against a control group in blinded evaluation. Conduction through the lesion was monitored by stimulating the tibial nerve of the hind limb, and measuring the arrival of evoked potentials at the contralateral sensory cortex of the brain (somatosensory evoked potentials; SSEP). Behavioral recovery was determined by a return of sensitivity of formerly areflexic receptive fields of the cutaneous trunchi muscle (CTM) reflex. This contraction of back skin in response to tactile stimulation is totally dependent on the integrity of an identified bilateral column of ascending long tract axons. A statistically significant recovery of both SSEP conduction through the lesion and the CTM reflex occurred in P188-treated animals compared to vehicle-treated controls. Quantitative 3D computer reconstruction of the lesioned vertebral segment of spinal cord revealed a statistically significant sparing of spinal cord parenchyma and a significant reduction in cavitation of the spinal cord compared to control animals We determined that the proportion of P188-treated animals that recovered evoked potentials were nearly identical to that produced by a subcutaneous injection of polyethylene glycol (PEG). In contrast, P188 was not as effective as PEG in producing a recovery of CTM functioning. We discuss the likely differences in the mechanisms of action of these two polymers

  8. Hydrogels composed of cyclodextrin inclusion complexes with PLGA-PEG-PLGA triblock copolymers as drug delivery systems.

    PubMed

    Khodaverdi, Elham; Mirzazadeh Tekie, Farnaz Sadat; Hadizadeh, Farzin; Esmaeel, Haydar; Mohajeri, Seyed Ahmad; Sajadi Tabassi, Sayyed A; Zohuri, Gholamhossein

    2014-02-01

    Although conventional pharmaceuticals have many drug dosage forms on the market, the development of new therapeutic molecules and the low efficacy of instant release formulations for the treatment of some chronic diseases and specific conditions encourage scientists to invent different delivery systems. To this purpose, a supramolecular hydrogel consisting of the tri-block copolymer PLGA-PEGPLGA and α-cyclodextrin was fabricated for the first time and characterised in terms of rheological, morphological, and structural properties. Naltrexone hydrochloride and vitamin B12 were loaded, and their release profiles were determined.

  9. Low-Friction Adsorbed Layers of a Triblock Copolymer Additive in Oil-Based Lubrication.

    PubMed

    Yamada, Shinji; Fujihara, Ami; Yusa, Shin-ichi; Tanabe, Tadao; Kurihara, Kazue

    2015-11-10

    The tribological properties of the dilute solution of an ABA triblock copolymer, poly(11-acrylamidoundecanoic acid)-block-poly(stearyl methacrylate)-block-poly(11-acrylamidoundecanoic acid (A5S992A5), in poly(α-olefin) (PAO) confined between mica surfaces were investigated using the surface forces apparatus (SFA). Friction force was measured as a function of applied load and sliding velocity, and the film thickness and contact geometry during sliding were analyzed using the fringes of equal chromatic order (FECO) in the SFA. The results were contrasted with those of confined PAO films; the effects of the addition of A5S992A5 on the tribological properties were discussed. The thickness of the A5S992A5/PAO system varied with time after surface preparation and with repetitive sliding motions. The thickness was within the range from 40 to 70 nm 1 day after preparation (the Day1 film), and was about 20 nm on the following day (the Day2 film). The thickness of the confined PAO film was thinner than 1.4 nm, indicating that the A5S992A5/PAO system formed thick adsorbed layers on mica surfaces. The friction coefficient was about 0.03 to 0.04 for the Day1 film and well below 0.01 for the Day2 film, which were 1 or 2 orders of magnitude lower than the values for the confined PAO films. The time dependent changes of the adsorbed layer thickness and friction properties should be caused by the relatively low solubility of A5S992A5 in PAO. The detailed analysis of the contact geometry and friction behaviors implies that the particularly low friction of the Day2 film originates from the following factors: (i) shrinkage of the A5S992A5 molecules (mainly the poly(stearyl methacrylate) blocks) that leads to a viscoelastic properties of the adsorbed layers; and (ii) the intervening PAO layer between the adsorbed polymer layers that constitutes a high-fluidity sliding interface. Our results suggest that the block copolymer having relatively low solubility in a lubricant base oil is

  10. An asymmetric A-B-A' metallo-supramolecular triblock copolymer linked by Ni(2+)-bis-terpyridine complexes at one junction.

    PubMed

    Li, Haixia; Wei, Wei; Xiong, Huiming

    2016-02-01

    A metallo-supramolecular triblock copolymer polystyrene-b-polyisoprene-[Ni(2+)]-polystyrene (SI-[Ni(2+)]-S') has been efficiently prepared using a one-pot, two-step procedure, where the blocks are held by bis-terpyridine complexes at the junction of SI-S'. This specific metallo-supramolecular chemistry is demonstrated to be a robust approach to potentially broaden the diversity of block copolymers. The location of the metal-ligand complexes has a profound influence on the phase separation of the triblock copolymer in the bulk, which results in a distinctive phase segregation between the end blocks and leads to an unexpected asymmetry of the triblock copolymer. The metal-ligand complexes are found to be preferentially located on the adjacent spherical domain and form a core-shell structure. The resulting multiphase material exhibits distinct elastomeric properties with significant toughness and creep recovery behavior. This type of triblock copolymer is anticipated to be a novel class of hybrid thermo-plastic elastomeric material with wide tunability and functionality.

  11. 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.

  12. Mesoporous carbon-vanadium oxide films by resol-assisted, triblock copolymer-templated cooperative self-assembly.

    PubMed

    Bhaway, Sarang M; Kisslinger, Kim; Zhang, Lihua; Yager, Kevin G; Schmitt, Andrew L; Mahanthappa, Mahesh K; Karim, Alamgir; Vogt, Bryan D

    2014-11-12

    Unlike other crystalline metal oxides amenable to templating by the combined assemblies of soft and hard chemistries (CASH) method, vanadium oxide nanostructures templated by poly(ethylene oxide-b-1,4-butadiene-b-ethylene oxide) (OBO) triblock copolymers are not preserved upon high temperature calcination in argon. Triconstituent cooperative assembly of a phenolic resin oligomer (resol) and an OBO triblock in a VOCl3 precursor solution enhances the carbon yield and can prevent breakout crystallization of the vanadia during calcination. However, the calcination environment significantly influences the observed mesoporous morphology in these composite thin films. Use of an argon atmosphere in this processing protocol leads to nearly complete loss of carbon-vanadium oxide thin film mesostructure, due to carbothermal reduction of vanadium oxide. This reduction mechanism also explains why the CASH method is not more generally successful for the fabrication of ordered mesoporous vanadia. Carbonization under a nitrogen atmosphere at temperatures up to 800 °C instead enables formation of a block copolymer-templated mesoporous structure, which apparently stems from the formation of a minor fraction of a stabilizing vanadium oxynitride. Thus, judicious selection of the inert gas for template removal is critical for the synthesis of well-defined, mesoporous vanadia-carbon composite films. This resol-assisted assembly method may generally apply to the fabrication of other mesoporous materials, wherein inorganic framework crystallization is problematic due to kinetically competitive carbothermal reduction processes.

  13. Challenges in Fabrication of Mesoporous Carbon Films with Ordered Cylindrical Pores via Phenolic Oligomer Self-Assembly with Triblock Copolymers

    SciTech Connect

    Song, Lingyan; Feng, Dan; Fredin, Nathaniel J.; Yager, Kevin G.; Jones, Ronald L.; Wu, Quanyan; Zhao, Dongyuan; Vogt, Bryan D.

    2010-06-22

    Mesoporous phenol formaldehyde (PF) polymer resin and carbon films are prepared by a solution self-assembly of PF oligomers with amphiphilic triblock copolymers. After thermopolymerization of the PF to cross-link the network, the films show an ordered morphology as determined by X-ray diffraction and grazing incidence small-angle X-ray scattering (GISAXS). Our results show that the amphiphilic triblock copolymer template greatly influences the stability of the final porous mesostructures. The pyrolysis of the two-dimensional (2-D) hexagonal films with p6mm symmetry templated by Pluronic F127 yields a disordered porous structure following the template removal. Conversely, films templated by Pluronic P123 can exhibit well-ordered cylindrical pores after the template removal, but the solution composition range to yield ordered cylindrical mesopores is significantly reduced (nearly 70%) for thin films in comparison to bulk powders. We propose two dominant difficulties in fabricating well-ordered cylindrical mesopores in films: first, the stress from contraction during the pyrolysis can lead to a collapse of the mesostructure if the wall thickness is insufficient, and second, the surface wetting behavior in thin films leads to a small compositional range.

  14. The effects of ethylene oxide containing lipopolymers and tri-block copolymers on lipid bilayers of dipalmitoylphosphatidylcholine.

    PubMed Central

    Baekmark, T R; Pedersen, S; Jørgensen, K; Mouritsen, O G

    1997-01-01

    A comparative study is conducted on the influence of two types of polymeric compounds on the phase behavior of 1,2-dihexadecanoyl-s,n-glycero-3-phosphotidylcholine (DC16PC) lipid bilayers. The first polymeric compound is a lipopolymer, with two different lengths of a hydrophilic polyethylene oxide moity, anchored to the bilayer by a 1,2-dioctadecanoyl-s,n-glycero-3-phosphoethanolamine (DC18PE) lipid. The second type, which is a novel type of membrane-spanning object, is an amphiphilic tri-block copolymer composed of two hydrophilic stretches of polyethylene oxide separated by a hydrophobic stretch of polystyrene. Hence the tri-block copolymer may act as a membrane-spanning macromolecule mimicking an amphiphilic protein or polypeptide. Differential scanning calorimetry is used to determine a partial phase diagram for the lipopolymer systems and to assess the amount of lipopolymer that can be loaded into DC16PC lipid bilayers before micellization takes place. Unilamellar and micellar phase structures are investigated by fluorescence quenching using bilayer permeating dithionite. The chain length-dependent critical lipopolymer concentration, denoting the lamellar-to-micellar phase transition, compares favorably with a theoretical prediction based on free-energy considerations involving bilayer cohesion and lateral pressure exerted by the polymer chains. Images FIGURE 10 PMID:9284315

  15. Single ion conducting, polymerized ionic liquid triblock copolymer films: high capacitance electrolyte gates for n-type transistors.

    PubMed

    Choi, Jae-Hong; Xie, Wei; Gu, Yuanyan; Frisbie, C Daniel; Lodge, Timothy P

    2015-04-01

    There has been impressive progress in the fabrication and characterization of p-type organic electrolyte-gated transistors (EGTs). Unfortunately, despite the importance of n-type organic transistors for complementary circuits, fewer investigations have focused on developing electrolytes as gate dielectrics for n-type organic semiconductors. Here, we present a novel single ion conductor, a polymerized ionic liquid (PIL) triblock copolymer (PS-PIL-PS) composed of styrene (PS) and 1-[(2-acryloyloxy)ethyl]-3-butylimidazolium bis(trifluoromethylsulfonyl)imide (PIL), that conducts only the TFSI anion. This triblock copolymer acts as a gate dielectric to allow low-voltage n-type organic EGT operation. Impedance characterization of PS-PIL-PS reveals that there are three polarization regions: (1) dipolar relaxation, (2) ion migration, and (3) electric double layer (EDL) formation. These polarization regions are controlled by film thickness, and rapid EDL formation can be obtained in thinner polyelectrolyte films. In particular, a 500 nm-thick polyelectrolyte film exhibits a large capacitance of ∼1 μF/cm(2) at 10 kHz. Employing this single ion conducting PIL triblock copolymer as the gate insulator, we achieved low voltage operation (<1 V supply) of poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)) n-type organic EGTs (electron mobility of ∼0.008 cm(2)/(V·s) and ON/OFF current ratio of ∼2 × 10(3)) by preventing electrochemical doping. Furthermore, the recognition that the performance of n-type organic EGTs is diminished by 3D electrochemical doping suggests that it may be necessary to have a unipolar electrolyte to gate n-type organic semiconductors. Finally, we highlight that the use of PIL block copolymer electrolytes as gate insulators opens unique opportunities to explore the role of ion penetration in n-type organic EGTs by tuning the extent of electrochemical doping.

  16. Self-assembled supramolecular hydrogel based on PCL-PEG-PCL triblock copolymer and γ-cyclodextrin inclusion complex for sustained delivery of dexamethasone.

    PubMed

    Khodaverdi, Elham; Gharechahi, Marzieh; Alibolandi, Mona; Tekie, Farnaz Sadat Mirzazadeh; Khashyarmanesh, Bibi Zahra; Hadizadeh, Farzin

    2016-01-01

    In this study, thermosensitive, water-soluble, and biodegradable triblock copolymer PCL600-PEG6000-PCL600 was used to form supramolecular hydrogel (SMGel) by inclusion complexation with γ-cyclodextrin (γ-CD). The prepared SMGel was investigated as a carrier for sustained release of dexamethasone. The triblock copolymer PCL-PEG-PCL [where PCL = polycaprolactone, PEG = poly(ethylene glycol)] was synthesized by the ring-opening polymerization method using microwave irradiation. The polymerization reaction and the copolymer structures were evaluated by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). SMGel was prepared in aqueous solution by blending an aqueous γ-CD solution with aqueous solution of PCL-PEG-PCL triblock copolymer at room temperature. The sol-to-gel transition time was measured at various concentrations of copolymer and γ-CD. As-prepared SMGel was used to prepare a sustained, controllable drug delivery system of dexamethasone sodium phosphate. The SMGel was also characterized in terms of rheological, morphological, and structural properties. Results obtained from proton nuclear magnetic resonance ( (1)H-NMR) and GPC demonstrated that microwave irradiation is a simple and reliable method for synthesis of PEG-PCL copolymer. The SMGel with excellent syringability was prepared by mixing of 20% wt γ-CD and 10% wt of copolymer within 4 s. The SMGel containing 10% wt copolymer, 20% wt γ-CD, and 0.5% or 0.1% wt dexamethasone released approximately 100% and 45% of drug over up to 23 days, respectively. It could be concluded that SMGel based on self-assembly of inclusion complexes between PCL-PEG-PCL copolymer and γ-CD could be used as a basis for injectable drug delivery systems that provide sustained and controlled release of macromolecular drugs such as dexamethasone. PMID:27051627

  17. Self-assembled supramolecular hydrogel based on PCL-PEG-PCL triblock copolymer and γ-cyclodextrin inclusion complex for sustained delivery of dexamethasone

    PubMed Central

    Khodaverdi, Elham; Gharechahi, Marzieh; Alibolandi, Mona; Tekie, Farnaz Sadat Mirzazadeh; Khashyarmanesh, Bibi Zahra; Hadizadeh, Farzin

    2016-01-01

    In this study, thermosensitive, water-soluble, and biodegradable triblock copolymer PCL600-PEG6000-PCL600 was used to form supramolecular hydrogel (SMGel) by inclusion complexation with γ-cyclodextrin (γ-CD). The prepared SMGel was investigated as a carrier for sustained release of dexamethasone. The triblock copolymer PCL-PEG-PCL [where PCL = polycaprolactone, PEG = poly(ethylene glycol)] was synthesized by the ring-opening polymerization method using microwave irradiation. The polymerization reaction and the copolymer structures were evaluated by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). SMGel was prepared in aqueous solution by blending an aqueous γ-CD solution with aqueous solution of PCL-PEG-PCL triblock copolymer at room temperature. The sol-to-gel transition time was measured at various concentrations of copolymer and γ-CD. As-prepared SMGel was used to prepare a sustained, controllable drug delivery system of dexamethasone sodium phosphate. The SMGel was also characterized in terms of rheological, morphological, and structural properties. Results obtained from proton nuclear magnetic resonance ( 1H-NMR) and GPC demonstrated that microwave irradiation is a simple and reliable method for synthesis of PEG-PCL copolymer. The SMGel with excellent syringability was prepared by mixing of 20% wt γ-CD and 10% wt of copolymer within 4 s. The SMGel containing 10% wt copolymer, 20% wt γ-CD, and 0.5% or 0.1% wt dexamethasone released approximately 100% and 45% of drug over up to 23 days, respectively. It could be concluded that SMGel based on self-assembly of inclusion complexes between PCL-PEG-PCL copolymer and γ-CD could be used as a basis for injectable drug delivery systems that provide sustained and controlled release of macromolecular drugs such as dexamethasone. PMID:27051627

  18. Low dielectric, nanoporous fluorinated polyimide films prepared from PCL-PI-PCL triblock copolymer using retro-Diels-Alder reaction.

    PubMed

    Ju, Junping; Wang, Qihua; Wang, Tingmei; Wang, Chao

    2013-08-15

    The triblock copolymers with the majority phase comprising fluorinated polyimide and the minor phase consisting of poly (ε-caprolactone) (PCL) were synthesized through Diels-Alder reaction between PI-Maleimide and PCL-Furfuryl Amine. The chemical composition and structure of the copolymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Films of the copolymers were spined and microphase-separation of the thin film was achieved by solvent annealing in N,N-dimethylformamide (DMF) vapor. The microphase-separation morphology was investigated by atomic force microscopy (AFM). Based on the microphase-separation structures, nanoporous fluorinated polyimide films were obtained after removal of the PCL block can removed via a retro-DA (Diels-Alder) reaction using a simple heating and immersing procedure. The nanoporous thin film was characterized by Transmission electron microscopy (TEM). The dielectric property of the nanoporous fluorinated polyimide films was investigated. It was found that the nanopores introduction could effectively reduce the dielectric constant from 2.82 of PI dense films to 2.10 of nanoporous PI films.

  19. Tuning self-assembly and photo-responsive behavior of azobenzene-containing triblock copolymers by combining homopolymers

    NASA Astrophysics Data System (ADS)

    Lin, Shaoliang; Wang, Yingying; Cai, Chunhua; Xing, Yaohui; Lin, Jiaping; Chen, Tao; He, Xiaohua

    2013-03-01

    The self-assembly behavior of azobenzene-based triblock copolymers poly(ethylene oxide)-block-polystyrene-block-poly[6-(4-methoxy-4‧-oxy-azobenzene) hexyl methacrylate] (PEO-b-PS-b-PMMAZO) and their mixtures with PS or PMMAZO homopolymers was studied by means of transmission electron microscopy, scanning electron microscopy, laser light scattering and UV-vis spectrophotometry. It was found that pure block copolymers self-assembled into spherical micelles with core-shell structures. The addition of PS or PMMAZO homopolymers can not only increase the aggregate size but also have a significant influence on the photo-isomerization behavior and photo-deformation behavior of the aggregate. The photo-isomerization study revealed that a complete trans-cis or cis-trans isomerization of azobenzene chromophores can be acquired when irradiated with UV or visible light for polymers both in organic solutions and in micelles. The photo-isomerization rate of azobenzene chromophores increases when PS homopolymers were incorporated into micelles, while with the addition of PMMAZO homopolymers, it decreases. The photo-induced elongation of the aggregates by irradiation of a linearly polarized laser was observed for all the samples, and the deformation degree increases with the weight fraction of azobenzene groups in the parent copolymers, as well as the PMMAZO content for the mixture micelles.

  20. Model photo-responsive elastomers based on the self-assembly of side group liquid crystal triblock copolymers (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Kurji, Zuleikha; Kornfield, Julia A.; Kuzyk, Mark G.

    2015-10-01

    We report the synthesis of azobenzene-containing coil-liquid crystal-coil triblock copolymers that form uniform and highly reproducible elastomers by self-assembly. To serve as actuators to (non-invasively) steer a fiber optic, for example in deep brain stimulation, the polymers are designed to become monodomain "single liquid crystal" elastomers during the fiber-draw process and to have a large stress/strain response to stimulation with either light or heat. A fundamental scientific question that we seek to answer is how the interplay between the concentration of photoresponsive mesogens and the proximity to the nematic-isotropic transition governs the sensitivity of the material to stimuli. Specifically, a matched pair of polymers, one with ~5% azobenzene-containing side groups (~95% cyanobiphenyl side groups) and the other with 100% cyanobiphenyl side groups were synthesized from identical triblock pre-polymers (with polystyerene end blocks and 1,2-polybutadiene midblocks). These can be blended in various ratios to prepare a series of elastomers that are precisely matched in terms of the backbone length between physical crosslinks (because each polymer is derived from the same pre-polymer), while differing in % azobenzene side groups, allowing the effect of concentration of photoresponsive groups to be unambiguously determined.

  1. Mechanical behaviour׳s evolution of a PLA-b-PEG-b-PLA triblock copolymer during hydrolytic degradation.

    PubMed

    Breche, Q; Chagnon, G; Machado, G; Girard, E; Nottelet, B; Garric, X; Favier, D

    2016-07-01

    PLA-b-PEG-b-PLA is a biodegradable triblock copolymer that presents both the mechanical properties of PLA and the hydrophilicity of PEG. In this paper, physical and mechanical properties of PLA-b-PEG-b-PLA are studied during in vitro degradation. The degradation process leads to a mass loss, a decrease of number average molecular weight and an increase of dispersity index. Mechanical experiments are made in a specific experimental set-up designed to create an environment close to in vivo conditions. The viscoelastic behaviour of the material is studied during the degradation. Finally, the mechanical behaviour is modelled with a linear viscoelastic model. A degradation variable is defined and included in the model to describe the hydrolytic degradation. This variable is linked to physical parameters of the macromolecular polymer network. The model allows us to describe weak deformations but become less accurate for larger deformations. The abilities and limits of the model are discussed.

  2. Simulation study on the structure of rod-coil-rod triblock copolymer and nanoparticle mixture within slit.

    PubMed

    Huang, Jian-Hua; Fan, Zhong-Xiang; Luo, Meng-Bo

    2013-11-28

    Self-assembly structures of rod-coil-rod ABA triblock copolymer and nanoparticle mixture within a slit are simulated by dissipative particle dynamics method. Results show that the structures are dependent on the rigidity of the rod block kθ, the interaction between the rod block and slit a(wA), the fraction of rod block f(A), and the slit height H. With an increase in kθ, we observe a transition from parallel lamellae to hexagonal cylinders. While with the increase in a(wA), the parallel lamellae at small kθ and hexagonal cylinders at large kθ change to perpendicular lamellae at large a(wA) close to a(As). At last, we present a phase diagram of structure with respect to f(A) and H at large kθ. PMID:24289376

  3. Enhanced Dispersion and Stability of Petroleum Coke Water Slurries via Triblock Copolymer and Xanthan Gum: Rheological and Adsorption Studies.

    PubMed

    Williams, Brian P; Pinge, Shubham; Kim, Young-Kwang; Kim, Juhoe; Joo, Yong Lak

    2015-08-25

    The rheology of petroleum coke (petcoke) water slurries was investigated with a variety of nonionic and anionic dispersants including poly(ethylene oxide) (PEO)-b-poly(propylene oxide) (PPO)-b-PEO triblock copolymers (trade name: Pluronic, BASF), poly(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), poly(ethylene oxide) (PEO), poly(carboxylate acid) (PCA), sodium lignosulfonate (SLS), and poly(acrylic acid) (PAA). Each effective dispersant system shared very similar rheological behavior to the others when examined at the same volume fraction from its maximum petcoke loading. Triblock copolymer, Pluronic F127 (F127), was found to be the best dispersant by comparing the maximum petcoke loading for each dispersant. The yield stress was measured as a function of petcoke loading and dispersant concentration for F127, and a minimum dispersant concentration was observed. An adsorption isotherm and atomic force microscopy (AFM) images reveal that this effective dispersion of petcoke particles by F127 is due to the formation of a uniform monolayer of brushes where hydrophobic PPO domains of F127 adhere to the petcoke surface, while hydrophilic PEO tails fill the gap between petcoke particles. F127 was then compared to other Pluronics with various PEO and PPO chain lengths, and the effects of surface and dispersant hydrophilicity were examined. Finally, xanthan gum (XG) was tested as a stabilizer in combination with F127 for potential industrial application, and F127 appears to break the XG aggregates into smaller aggregates through competitive adsorption, leading to an excellent degree of dispersion but the reduced stability of petcoke slurries. PMID:26245829

  4. Amphiphilic Surface Active Triblock Copolymers with Mixed Hydrophobic and Hydrophilic Side Chains for Tuned Marine Fouling-Release Properties

    SciTech Connect

    Park, D.; Weinman, C; Finlay, J; Fletcher, B; Paik, M; Sundaram, H; Dimitriou, M; Sohn, K; Callow, M; et al.

    2010-01-01

    Two series of amphiphilic triblock surface active block copolymers (SABCs) were prepared through chemical modification of two polystyrene-block-poly(ethylene-ran-butylene)-block-polyisoprene ABC triblock copolymer precursors. The methyl ether of poly(ethylene glycol) [M{sub n} {approx} 550 g/mol (PEG550)] and a semifluorinated alcohol (CF{sub 3}(CF{sub 2}){sub 9}(CH{sub 2}){sub 10}OH) [F10H10] were attached at different molar ratios to impart both hydrophobic and hydrophilic groups to the isoprene segment. Coatings on glass slides consisting of a thin layer of the amphiphilic SABC deposited on a thicker layer of an ABA polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene thermoplastic elastomer were prepared for biofouling assays with algae. Dynamic water contact angle analysis, X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) measurements were utilized to characterize the surfaces. Clear differences in surface structure were realized as the composition of attached side chains was varied. In biofouling assays, the settlement (attachment) of zoospores of the green alga Ulva was higher for surfaces incorporating a large proportion of the hydrophobic F10H10 side chains, while surfaces with a large proportion of the PEG550 side chains inhibited settlement. The trend in attachment strength of sporelings (young plants) of Ulva did not show such an obvious pattern. However, amphiphilic SABCs incorporating a mixture of PEG550 and F10H10 side chains performed the best. The number of cells of the diatom Navicula attached after exposure to flow decreased as the content of PEG550 to F10H10 side chains increased.

  5. Erythropoietin loaded microspheres prepared from biodegradable LPLG-PEO-LPLG triblock copolymers: protein stabilization and in-vitro release properties.

    PubMed

    Morlock, M; Kissel, T; Li, Y X; Koll, H; Winter, G

    1998-12-01

    Biodegradable microspheres containing recombinant human Erythropoietin (EPO) were prepared from ABA triblock copolymers, consisting of hydrophobic poly(l-lactic-co-glycolic acid) A blocks and hydrophilic polyethylenoxide (PEO) B blocks. Different polymer compositions were studied for the microencapsulation of EPO using a modified double-emulsion process (W/O/W). The encapsulation efficiency for EPO, ranging from 72% to 99% was quite acceptable. The formation of high molecular weight EPO aggregates, however, was higher than in poly(d,l-lactide-co-glycolide) (PLG) microparticles. Using different excipients with known protein stabilizing properties, such as Bovine Serum Albumin (BSA), Poly-l-Histidine (PH), Poly-l-Arginine (PA) or a combination of PA with Dextran 40 (D40), the EPO aggregate content was significantly reduced to <5% of the encapsulated EPO. In contrast to PLG, ABA triblockcopolymers containing >7 mol % PEO, allowed a continuous release of EPO from microspheres for up to 2 weeks under in-vitro conditions. The release profile was comparable to FITC-Dextran 40 kDa (FD 40) loaded microspheres in the initial release phase, while EPO release was leveling off at later time points. BSA additionally prolonged the EPO release, while blends of PLG and PEO did not generate continuous EPO release profiles. LPLG-PEO-LPLG triblock-copolymers (35 mol % PEO; 30 kDa) in combination with 5% BSA yielded both an acceptable level of EPO aggregates and a continuous release profile under in-vitro conditions for up to 2 weeks. The formation of EPO aggregates at later time points is probably induced by acidic cleavage products of the biodegradable polymer and requires further optimization of the ABA polymer composition.

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

    PubMed

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

    2016-03-01

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

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

    PubMed

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

    2016-03-01

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

  8. Growth of ordered silver nanoparticles in silica film mesostructured with a triblock copolymer PEO-PPO-PEO

    SciTech Connect

    Bois, L.; Chassagneux, F.; Parola, S.; Bessueille, F.; Battie, Y.; Destouches, N.; Boukenter, A.; Moncoffre, N.

    2009-07-15

    Elaboration of mesostructured silica films with a triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide, (PEO-PPO-PEO) and controlled growth of silver nanoparticles in the mesostructure are described. The films are characterized using UV-visible optical absorption spectroscopy, TEM, AFM, SEM, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). Organized arrays of spherical silver nanoparticles with diameter between 5 and 8 nm have been obtained by NaBH{sub 4} reduction. The size and the repartition of silver nanoparticles are controlled by the film mesostructure. The localization of silver nanoparticles exclusively in the upper-side part of the silica-block copolymer film is evidenced by RBS experiment. On the other hand, by using a thermal method, 40 nm long silver sticks can be obtained, by diffusion and coalescence of spherical particles in the silica-block copolymer layer. In this case, migration of silver particles toward the glass substrate-film interface is shown by the RBS experiment. - Graphical abstract: Growth of silver nanoparticles in a mesostructured block copolymer F127-silica film is performed either by a chemical route involving NaBH{sub 4} reduction or by a thermal method. An array of spherical silver nanoparticles with 10 nm diameter on the upper-side of the mesostructured film or silver sticks long of 40 nm with a preferential orientation are obtained according to the method used. a: TEM image of the Fag5SiNB sample illustrating the silver nanoparticles array obtained by the chemical process; b: HR-TEM image of the Fag20Sid2 sample illustrating the silver nanosticks obtained by the thermal process.

  9. siRNA delivery from triblock copolymer micelles with spatially-ordered compartments of PEG shell, siRNA-loaded intermediate layer, and hydrophobic core.

    PubMed

    Kim, Hyun Jin; Miyata, Kanjiro; Nomoto, Takahiro; Zheng, Meng; Kim, Ahram; Liu, Xueying; Cabral, Horacio; Christie, R James; Nishiyama, Nobuhiro; Kataoka, Kazunori

    2014-05-01

    Hydrophobized block copolymers have widely been developed for construction of polymeric micelles for stable delivery of nucleic acids as well as anticancer drugs. Herein, we elaborated an A-B-C type of triblock copolymer featuring shell-forming A-segment, nucleic acid-loading B-segment, and stable core-forming C-segment, directed toward construction of a three-layered polymeric micelle as a small interfering RNA (siRNA) vehicle. The triblock copolymer was prepared with nonionic and hydrophilic poly(ethylene glycol) (PEG), cationic poly(l-lysine) (PLys), and poly{N-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} [PAsp(DET)] bearing a hydrophobic dimethoxy nitrobenzyl ester (DN) moiety in the side chain [PEG-PLys-PAsp(DET-DN)]. The resulting triblock copolymers spontaneously formed sub-100 nm-sized polymeric micelles with a hydrophobic PAsp(DET-DN) core as well as PEG shell in an aqueous solution. This micelle was able to incorporate siRNA into the intermediate PLys layer, associated with slightly reduced size and a narrow size distribution. The triblock copolymer micelles (TCMs) stably encapsulated siRNA in serum-containing medium, whereas randomly hydrophobized triblock copolymer [PEG-PLys(DN)-PAsp(DET-DN)] control micelles (RCMs) gradually released siRNA with time and non-PEGylated diblock copolymer [PLys-PAsp(DET-DN)] control micelles (DCMs) immediately formed large aggregates. The TCMs thus induced appreciably stronger sequence-specific gene silencing in cultured cancer cells, compared to those control micelles. The siRNA delivery with TCMs was further examined in terms of cellular uptake and intracellular trafficking. The flow cytometric analysis revealed that the cellular uptake of TCMs was more efficient than that of RCMs, but less efficient than that of DCMs. The intracellular trafficking study using confocal laser scanning microscopy combined with fluorescence resonance energy transfer (FRET) revealed that the TCMs could readily release the siRNA payload

  10. Combining Ring-Opening Metathesis Polymerization and Cyclic Ester Ring-Opening Polymerization To Form ABA Triblock Copolymers from 1,5-Cyclooctadiene and D,L-Lactide

    SciTech Connect

    Pitet, Louis M.; Hillmyer, Marc A.

    2009-07-31

    ABA triblock copolymers were synthesized by combining ring-opening metathesis polymerization (ROMP) of 1,5-cyclooctadiene (COD) with ring-opening polymerization of D,L-lactide. Hydroxyl-functionalized telechelic polyCOD was prepared by taking advantage of chain transfer during ROMP of COD using the acyclic chain transfer agent cis-1,4-diacetoxy-2-butene. These hydroxy-terminated macroinitiators were used as initiators for the polymerization of lactide to form a series of triblock copolymers with compositions in the range 0.24 {le} f{sub PLA} {le} 0.89 and molecular weights ranging from 22 to 196 kg mol{sup -1}. The ordered-state morphologies of the triblocks were determined using small-angle X-ray scattering; well-ordered microstructures were observed for several samples, in accordance with the predicted dependence of morphology on composition. The mechanical properties of these materials were also investigated by performing tensile measurements; the triblocks were considerably tougher than poly(D,L-lactide), most markedly in samples with low polyCOD midblock content.

  11. Triblock Copolymers with Grafted Fluorine-Free Amphiphilic Non-Ionic Side Chains for Antifouling and Fouling-Release Applications

    SciTech Connect

    Y Cho; H Sundaram; C Weinman; M Paik; M Dimitriou; J Finlay; M Callow; J Callow; E Kramer; C Ober

    2011-12-31

    Fluorine-free, amphiphilic, nonionic surface active block copolymers (SABCs) were synthesized through chemical modification of a polystyrene-block-poly(ethylene-ran-butylene)-block-polyisoprene triblock copolymer precursor with selected amphiphilic nonionic Brij and other surfactants. Amphiphilicity was imparted by a hydrophobic aliphatic group combined with a hydrophilic poly(ethylene glycol) (PEG) group-containing moiety. The surfaces were characterized by dynamic water contact angle, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure (NEXAFS) analysis. In biofouling assays, settlement (attachment) of both spores of the green alga Ulva and cells of the diatom Navicula on SABCs modified with Brij nonionic side chains was significantly reduced relative to a PDMS standard, with a nonionic surfactant combining a PEG group and an aliphatic moiety demonstrating the best performance. Additionally, a fouling-release assay using sporelings (young plants) of Ulva and Navicula suggested that the SABC derived from nonionic Brij side chains also out-performed PDMS as a fouling-release material. Good antifouling and fouling-release properties were not demonstrated for the other two amphiphilic surfaces derived from silicone and aromatic group containing nonionic surfactants included in this study. The results suggest that small differences in chemical surface functionality impart more significant changes with respect to the antifouling settlement and fouling-release performance of materials than overall wettability behavior.

  12. The triblock copolymers hydrogel through intracameral injection may be a new potential ophthalmic drug delivery with antiscarring drugs after glaucoma filtration surgery.

    PubMed

    Qiao, Yu; Qin, Gang; Yu, Ling

    2013-01-01

    The hyperplasia of fiber cell at operation area cause scarring lead to the failure after glaucoma filtration surgery. People are looking for more safe and effective way to advance the success rate in operation. There are many researches demonstrated that ophthalmic drug delivery system can be a treatment. Among this, some biodegradable and thermosensitive triblock copolymers hydrogel are novel candidate for ocular drug release system. But whether they can be used to restrain the hyperplasia of fiber cell through intracameral injection after glaucoma filtration surgery, the research have not been reported. So it suggested a new hypothesis for intracameral injection of the triblock copolymers hydrogel as a new potential in situ sustained ophthalmic drug delivery system with antiscaring formation after glaucoma filtration surgery. Indicating that the new nanomaterials through intracameral injection treating complication of glaucoma filtration surgery is hoped to be a creative and promising ophthalmic drug delivery system in the future.

  13. Triblock Copolymer Nanovesicles for pH-Responsive Targeted Delivery and Controlled Release of siRNA to Cancer Cells.

    PubMed

    Gallon, Elena; Matini, Teresa; Sasso, Luana; Mantovani, Giuseppe; Armiñan de Benito, Ana; Sanchis, Joaquin; Caliceti, Paolo; Alexander, Cameron; Vicent, Maria J; Salmaso, Stefano

    2015-07-13

    New pH-responsive polymersomes for active anticancer oligonucleotide delivery were prepared from triblock copolymers. The delivery systems were formed by two terminal hydrophilic blocks, PEG and polyglycerolmethacrylate (poly-GMA), and a central weakly basic block, polyimidazole-hexyl methacrylate (poly-ImHeMA), which can complex with oligonucleotides and control vesicle formation/disassembly via pH variations. Targeted polymersomes were prepared by mixing folate-derivatized and underivatized copolymers. At pH 5, ds-DNA was found to complex with the pH-responsive copolymers at a N/P molar ratio above ∼2:1, which assisted the encapsulation of ds-DNA in the polymersomes, while low association was observed at pH 7.4. Cytotoxicity studies performed on folate receptor overexpressing KB and B16-F10 cells and low folate receptor expressing MCF-7 cells showed high tolerance of the polymersomes at up to 3 mg/mL concentration. Studies performed with red blood cells showed that at pH 5.0 the polymersomes have endosomolytic properties. Cytofluorimetric studies showed a 5.5-fold higher uptake of ds-DNA loaded folate-functional polymersomes in KB cells compared to nontargeted polymersomes. In addition, ds-DNA was found to be localized both in the nucleus and in the cytosol. The incubation of luciferase transfected B16-F10 cells with targeted polymersomes loaded with luciferase and Hsp90 expression silencing siRNAs yielded 31 and 23% knockdown in target protein expression, respectively. PMID:25988940

  14. Thermodynamic confinement and alpha-helix persistence length in poly(gamma-benzyl-L-glutamate)-b-poly(dimethyl siloxane)-b-poly(gamma-benzyl-L-glutamate) triblock copolymers.

    PubMed

    Papadopoulos, P; Floudas, G; Schnell, I; Lieberwirth, I; Nguyen, T Q; Klok, H-A

    2006-02-01

    The structure and the associated dynamics of a series of poly(gamma-benzyl-L-glutamate)-b-poly(dimethyl siloxane)-b-poly(gamma-benzyl-L-glutamate) (PBLG-b-PDMS-b-PBLG) triblock copolymers were investigated using small- and wide-angle X-ray scattering, NMR, transmission electron microscopy, and dielectric spectroscopy, respectively. The structural analysis revealed phase separation in the case of the longer blocks with defected alpha-helical segments embedded within the block copolymer nanodomains. The alpha-helical persistence length was found to depend on the degree of segregation; thermodynamic confinement and chain stretching results in the partial annihilation of helical defects. PMID:16471939

  15. Self-Assembly and Critical Aggregation Concentration Measurements of ABA Triblock Copolymers with Varying B Block Types: Model Development, Prediction, and Validation.

    PubMed

    Aydin, Fikret; Chu, Xiaolei; Uppaladadium, Geetartha; Devore, David; Goyal, Ritu; Murthy, N Sanjeeva; Zhang, Zheng; Kohn, Joachim; Dutt, Meenakshi

    2016-04-21

    The dissipative particle dynamics (DPD) simulation technique is a coarse-grained (CG) molecular dynamics-based approach that can effectively capture the hydrodynamics of complex systems while retaining essential information about the structural properties of the molecular species. An advantageous feature of DPD is that it utilizes soft repulsive interactions between the beads, which are CG representation of groups of atoms or molecules. In this study, we used the DPD simulation technique to study the aggregation characteristics of ABA triblock copolymers in aqueous medium. Pluronic polymers (PEG-PPO-PEG) were modeled as two segments of hydrophilic beads and one segment of hydrophobic beads. Tyrosine-derived PEG5K-b-oligo(desaminotyrosyl tyrosine octyl ester-suberate)-b-PEG5K (PEG5K-oligo(DTO-SA)-PEG5K) block copolymers possess alternate rigid and flexible components along the hydrophobic oligo(DTO-SA) chain, and were modeled as two segments of hydrophilic beads and one segment of hydrophobic, alternate soft and hard beads. The formation, structure, and morphology of the initial aggregation of the polymer molecules in aqueous medium were investigated by following the aggregation dynamics. The dimensions of the aggregates predicted by the computational approach were in good agreement with corresponding results from experiments, for the Pluronic and PEG5K-oligo(DTO-SA)-PEG5K block copolymers. In addition, DPD simulations were utilized to determine the critical aggregation concentration (CAC), which was compared with corresponding results from an experimental approach. For Pluronic polymers F68, F88, F108, and F127, the computational results agreed well with experimental measurements of the CAC measurements. For PEG5K-b-oligo(DTO-SA)-b-PEG5K block polymers, the complexity in polymer structure made it difficult to directly determine their CAC values via the CG scheme. Therefore, we determined CAC values of a series of triblock copolymers with 3-8 DTO-SA units using DPD

  16. Morphological development in solvent-cast polystyrene(PS)-polybutadiene(PB)-polystyrene (SBS) triblock copolymer thin films

    NASA Astrophysics Data System (ADS)

    Kim, Ginam

    The morphological characteristics of block copolymers have been under intensive research, because of the rich polymer-physics questions they raise and because of the need for better understanding required by adhesive, compatibilizer, and template applications. In this research, the morphological transformations in solvent-cast polystyrene (PS)/polybutadiene (PB)/polystyrene (SBS)(30 wt% PS, Mw = 112,000) triblock copolymer thin films have been studied by transmission electron microscopy (TEM) as a function of solvent evaporation rate and post-evaporation annealing. Evaporation at: (i) ˜200 nl/sec produces a microphase-separated microstructure with no long-range order; (ii) ˜5 nl/sec generates hexagonally packed PS cylinders in a PB matrix with the cylinder axis perpendicular to the film plane; (iii) ˜1.5 nl/sec leads to a duplex microstructure of PS cylinders with domains of either vertical or in-plane cylinders; (iv) ˜0.2 nl/sec produces a fully in-plane cylinder microstructure. Post-evaporation annealing converts the duplex morphology into one with only in-plane PS cylinders. The equilibrium morphology of in-plane cylinders with PB-rich surface layers is generated when films are given relatively long exposure to high solvent concentration or elevated temperature. However, alternate and metastable morphologies are generated including ones with two-phase surface structure under kinetically constrained conditions. Cross-sectional TEM indicates that the surface microstructures vary with evaporation and annealing treatment. These results are interpreted in terms of the kinetics and thermodynamics of microphase separation.

  17. Directed Self-Assembly of Triblock Copolymer on Chemical Patterns for Sub-10-nm Nanofabrication via Solvent Annealing.

    PubMed

    Xiong, Shisheng; Wan, Lei; Ishida, Yoshihito; Chapuis, Yves-Andre; Craig, Gordon S W; Ruiz, Ricardo; Nealey, Paul F

    2016-08-23

    Directed self-assembly (DSA) of block copolymers (BCPs) is a leading strategy to pattern at sublithographic resolution in the technology roadmap for semiconductors and is the only known solution to fabricate nanoimprint templates for the production of bit pattern media. While great progress has been made to implement block copolymer lithography with features in the range of 10-20 nm, patterning solutions below 10 nm are still not mature. Many BCP systems self-assemble at this length scale, but challenges remain in simultaneously tuning the interfacial energy atop the film to control the orientation of BCP domains, designing materials, templates, and processes for ultra-high-density DSA, and establishing a robust pattern transfer strategy. Among the various solutions to achieve domains that are perpendicular to the substrate, solvent annealing is advantageous because it is a versatile method that can be applied to a diversity of materials. Here we report a DSA process based on chemical contrast templates and solvent annealing to fabricate 8 nm features on a 16 nm pitch. To make this possible, a number of innovations were brought in concert with a common platform: (1) assembling the BCP in the phase-separated, solvated state, (2) identifying a larger process window for solvated triblock vs diblock BCPs as a function of solvent volume fraction, (3) employing templates for sub-10-nm BCP systems accessible by lithography, and (4) integrating a robust pattern transfer strategy by vapor infiltration of organometallic precursors for selective metal oxide synthesis to prepare an inorganic hard mask. PMID:27482932

  18. Experimental and theoretical studies on inhibition of mild steel corrosion by some synthesized polyurethane tri-block co-polymers

    NASA Astrophysics Data System (ADS)

    Kumar, Sudershan; Vashisht, Hemlata; Olasunkanmi, Lukman O.; Bahadur, Indra; Verma, Hemant; Singh, Gurmeet; Obot, Ime B.; Ebenso, Eno E.

    2016-08-01

    Polyurethane based tri-block copolymers namely poly(N-vinylpyrrolidone)-b-polyurethane-b-poly(N-vinylpyrrolidone) (PNVP-PU) and poly(dimethylaminoethylmethacrylate)-b-polyurethane-b-poly(dimethylaminoethylmethacrylate) (PDMAEMA-PU) were synthesized through atom transfer radical polymerization (ATRP) mechanism. The synthesized polymers were characterized using nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) methods. The corrosion inhibition performances of the compounds were investigated on mild steel (MS) in 0.5 M H2SO4 medium using electrochemical measurements, surface analysis, quantum chemical calculations and molecular dynamic simulations (MDS). Potentiodynamic polarization (PDP) measurements revealed that the polymers are mixed-type corrosion inhibitors. Electrochemical impedance spectroscopy (EIS) measurements showed that the polymers inhibit MS corrosion by adsorbing on MS surface to form pseudo-capacitive interface. The inhibitive effects of the polymers increase with increasing concentration and decrease with increasing temperature. The adsorption of both the polymers on MS surface obey the Langmuir adsorption isotherm and involves both physisorption and chemisorption mechanisms. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses showed that the polymers formed protective film on MS surface and shield it from direct acid attack. Quantum chemical calculations and molecular dynamic simulations studies corroborate experimental results.

  19. Kinetics of Phase Transition from Lamellar to Hexagonally Packed Cylinders for a Triblock Copolymer in a Selective Solvent

    SciTech Connect

    Liu,Y.; Li, M.; Bansil, R.; Steinhart, M.

    2007-01-01

    We examined the kinetics of the transformation from the lamellar (LAM) to the hexagonally packed cylinder (HEX) phase for the triblock copolymer, polystyrene-b-poly (ethylene-co-butylene)-b-polystyrene (SEBS) in dibutyl phthalate (DBP), a selective solvent for polystyrene (PS), using time-resolved small-angle X-ray scattering (SAXS). We observe the HEX phase with the EB block in the cores at a lower temperature than that observed for the LAM phase due to the solvent selectivity of DBP for the PS block. Analysis of the SAXS data for a deep temperature quench well below the LAM-HEX transition shows that the transformation occurs in a one-step process. We calculate the scattering using a geometric model of rippled layers with adjacent layers totally out of phase during the transformation. The agreement of the calculations with the data further supports the continuous transformation mechanism from the LAM to HEX for a deep quench. In contrast, for a shallow quench close to the order-order transition, we find agreement with a two-step nucleation and growth mechanism.

  20. Experimental and theoretical studies on inhibition of mild steel corrosion by some synthesized polyurethane tri-block co-polymers

    PubMed Central

    Kumar, Sudershan; Vashisht, Hemlata; Olasunkanmi, Lukman O.; Bahadur, Indra; Verma, Hemant; Singh, Gurmeet; Obot, Ime B.; Ebenso, Eno E.

    2016-01-01

    Polyurethane based tri-block copolymers namely poly(N-vinylpyrrolidone)-b-polyurethane-b-poly(N-vinylpyrrolidone) (PNVP-PU) and poly(dimethylaminoethylmethacrylate)-b-polyurethane-b-poly(dimethylaminoethylmethacrylate) (PDMAEMA-PU) were synthesized through atom transfer radical polymerization (ATRP) mechanism. The synthesized polymers were characterized using nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) methods. The corrosion inhibition performances of the compounds were investigated on mild steel (MS) in 0.5 M H2SO4 medium using electrochemical measurements, surface analysis, quantum chemical calculations and molecular dynamic simulations (MDS). Potentiodynamic polarization (PDP) measurements revealed that the polymers are mixed-type corrosion inhibitors. Electrochemical impedance spectroscopy (EIS) measurements showed that the polymers inhibit MS corrosion by adsorbing on MS surface to form pseudo-capacitive interface. The inhibitive effects of the polymers increase with increasing concentration and decrease with increasing temperature. The adsorption of both the polymers on MS surface obey the Langmuir adsorption isotherm and involves both physisorption and chemisorption mechanisms. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses showed that the polymers formed protective film on MS surface and shield it from direct acid attack. Quantum chemical calculations and molecular dynamic simulations studies corroborate experimental results. PMID:27515383

  1. Experimental and theoretical studies on inhibition of mild steel corrosion by some synthesized polyurethane tri-block co-polymers.

    PubMed

    Kumar, Sudershan; Vashisht, Hemlata; Olasunkanmi, Lukman O; Bahadur, Indra; Verma, Hemant; Singh, Gurmeet; Obot, Ime B; Ebenso, Eno E

    2016-01-01

    Polyurethane based tri-block copolymers namely poly(N-vinylpyrrolidone)-b-polyurethane-b-poly(N-vinylpyrrolidone) (PNVP-PU) and poly(dimethylaminoethylmethacrylate)-b-polyurethane-b-poly(dimethylaminoethylmethacrylate) (PDMAEMA-PU) were synthesized through atom transfer radical polymerization (ATRP) mechanism. The synthesized polymers were characterized using nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) methods. The corrosion inhibition performances of the compounds were investigated on mild steel (MS) in 0.5 M H2SO4 medium using electrochemical measurements, surface analysis, quantum chemical calculations and molecular dynamic simulations (MDS). Potentiodynamic polarization (PDP) measurements revealed that the polymers are mixed-type corrosion inhibitors. Electrochemical impedance spectroscopy (EIS) measurements showed that the polymers inhibit MS corrosion by adsorbing on MS surface to form pseudo-capacitive interface. The inhibitive effects of the polymers increase with increasing concentration and decrease with increasing temperature. The adsorption of both the polymers on MS surface obey the Langmuir adsorption isotherm and involves both physisorption and chemisorption mechanisms. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses showed that the polymers formed protective film on MS surface and shield it from direct acid attack. Quantum chemical calculations and molecular dynamic simulations studies corroborate experimental results. PMID:27515383

  2. Experimental and theoretical studies on inhibition of mild steel corrosion by some synthesized polyurethane tri-block co-polymers.

    PubMed

    Kumar, Sudershan; Vashisht, Hemlata; Olasunkanmi, Lukman O; Bahadur, Indra; Verma, Hemant; Singh, Gurmeet; Obot, Ime B; Ebenso, Eno E

    2016-08-12

    Polyurethane based tri-block copolymers namely poly(N-vinylpyrrolidone)-b-polyurethane-b-poly(N-vinylpyrrolidone) (PNVP-PU) and poly(dimethylaminoethylmethacrylate)-b-polyurethane-b-poly(dimethylaminoethylmethacrylate) (PDMAEMA-PU) were synthesized through atom transfer radical polymerization (ATRP) mechanism. The synthesized polymers were characterized using nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) methods. The corrosion inhibition performances of the compounds were investigated on mild steel (MS) in 0.5 M H2SO4 medium using electrochemical measurements, surface analysis, quantum chemical calculations and molecular dynamic simulations (MDS). Potentiodynamic polarization (PDP) measurements revealed that the polymers are mixed-type corrosion inhibitors. Electrochemical impedance spectroscopy (EIS) measurements showed that the polymers inhibit MS corrosion by adsorbing on MS surface to form pseudo-capacitive interface. The inhibitive effects of the polymers increase with increasing concentration and decrease with increasing temperature. The adsorption of both the polymers on MS surface obey the Langmuir adsorption isotherm and involves both physisorption and chemisorption mechanisms. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses showed that the polymers formed protective film on MS surface and shield it from direct acid attack. Quantum chemical calculations and molecular dynamic simulations studies corroborate experimental results.

  3. A numerical study of the phase behaviors of drug particle/star triblock copolymer mixtures in dilute solutions for drug carrier application.

    PubMed

    Wang, Shanhui; Tong, Chaohui; Zhu, Yuejin

    2014-04-14

    The complex microstructures of drug particle/ABA star triblock copolymer in dilute solutions have been investigated by a theoretical approach which combines the self-consistent field theory and the hybrid particle-field theory. Simulation results reveal that, when the volume fraction of drug particles is smaller than the saturation concentration, the drug particle encapsulation efficiency is 100%, and micelle loading capacity increases with increasing particle volume fraction. When the volume fraction of drug particles is equal to the saturation concentration, the micelles attain the biggest size, and micelle loading capacity reaches a maximum value which is independent of the copolymer volume fraction. When the volume fraction of drug particles is more than the saturation concentration, drug particle encapsulation efficiency decreases with increasing volume fraction of drug particles. Furthermore, it is found that the saturation concentration scales linearly with the copolymer volume fraction. The above simulation results are in good agreement with experimental results.

  4. Coating of poly(p-xylylene) by PLA-PEO-PLA triblock copolymers with excellent polymer-polymer adhesion for stent applications.

    PubMed

    Hanefeld, Phillip; Westedt, Ullrich; Wombacher, Ralf; Kissel, Thomas; Schaper, Andreas; Wendorff, Joachim H; Greiner, Andreas

    2006-07-01

    Poly(p-xylylene) (PPX) was deposited by chemical vapor deposition (CVD) on stainless steel substrates. These PPX films were coated by solution casting of poly(lactide)-poly(ethylene oxide)-poly(lactide) triblock copolymers (PLA-PEO-PLA) loaded with 14C-labeled paclitaxel. Adhesion of PLA-PEO-PLA on PPX substrate coatings was measured using the blister test method. Excellent adhesion of the block copolymers on PPX substrates was found. Stress behavior and film integrity of PLA-PEO-PLA was compared to pure PLA on unexpanded and expanded stent bodies and was found to be superior for the block copolymers. The release of paclitaxel from the biodegradable coatings was studied under physiological conditions using the scintillation counter method. Burst release of paclitaxel was observed from PLA-PEO-PLA layers regardless of composition, but an increase in paclitaxel loading was observed with increasing content of PEO. PMID:16827574

  5. A numerical study of the phase behaviors of drug particle/star triblock copolymer mixtures in dilute solutions for drug carrier application

    SciTech Connect

    Wang, Shanhui; Tong, Chaohui; Zhu, Yuejin

    2014-04-14

    The complex microstructures of drug particle/ABA star triblock copolymer in dilute solutions have been investigated by a theoretical approach which combines the self-consistent field theory and the hybrid particle-field theory. Simulation results reveal that, when the volume fraction of drug particles is smaller than the saturation concentration, the drug particle encapsulation efficiency is 100%, and micelle loading capacity increases with increasing particle volume fraction. When the volume fraction of drug particles is equal to the saturation concentration, the micelles attain the biggest size, and micelle loading capacity reaches a maximum value which is independent of the copolymer volume fraction. When the volume fraction of drug particles is more than the saturation concentration, drug particle encapsulation efficiency decreases with increasing volume fraction of drug particles. Furthermore, it is found that the saturation concentration scales linearly with the copolymer volume fraction. The above simulation results are in good agreement with experimental results.

  6. Enzymatic synthesis of a DNA triblock copolymer that is composed of natural and unnatural nucleotides.

    PubMed

    Mitomo, Hideyuki; Watanabe, Yukie; Matsuo, Yasutaka; Niikura, Kenichi; Ijiro, Kuniharu

    2015-02-01

    DNA molecules have come under the spotlight as potential templates for the fabrication of nanoscale products, such as molecular-scale electronic or photonic devices. Herein, we report an enhanced approach for the synthesis of oligoblock copolymer-type DNA by using the Klenow fragment exonuclease minus of E. coli DNA polymerase I (KF(-) ) in a multi-step reaction with natural and unnatural nucleotides. First, we confirmed the applicability of unnatural nucleotides with 7-deaza-nucleosides-which was expected because they were non-metalized nucleotides-on the unique polymerization process known as the "strand-slippage model". Because the length of the DNA sequence could be controlled by tuning the reaction time, analogous to a living polymerization reaction on this process, stepwise polymerization provided DNA block copolymers with natural and unnatural bases. AFM images showed that this DNA block copolymer could be metalized sequence-selectively. This approach could expand the utility of DNA as a template.

  7. Thermodynamic and kinetic control of charged, amphiphilic triblock copolymer assembly via interaction with organic counterions in solvent mixtures

    NASA Astrophysics Data System (ADS)

    Cui, Honggang

    2007-12-01

    Amphiphilic block copolymers, consisting of at least two types of monomers with different affinity to the dissolving solvent(s), have been recognized as a molecular building unit for their chemical tunability and design flexibility. Amphiphilic block copolymers with a chargeable block have structural features of polyelectrolytes, block copolymers and surfactants. The combination of these different features offers great flexibility for developing novel assembled morphologies at the nanoscale and outstanding ability to control and manipulate those morphologies. The nanostructures, formed from the spontaneous association of amphiphilic block copolymer in selective solvents, show promise for applications in nanotechnology and pharmaceuticals, including drug delivery, tissue engineering and bio-imaging. A basic knowledge of their modes of self-assembly and their correspondence to application-related properties is just now being developed and poses a considerable scientific challenge. The goal of this dissertation is to investigate the associative behavior of charged, amphiphilic block copolymers in solvent mixtures while in the presence of organic counterions. Self-assembly of poly (acrylic acid)- block-poly (methyl acrylate)-block-polystyrene (PAA- b-PMA-b-PS) triblock copolymers produces nanodomains in THF/water solution specifically through the interaction with organic counterions (polyamines). These assembled structures can include classic micelles (spheres, cylinders and vesicles), but, more importantly, include non-classic micelles (disks, toroids, branched micelles and segmented micelles). Each micelle structure is stable and reproducible at different assembly conditions. The assembled micellar structures depend on not only solution components (thermodynamics) but also mixing procedure and consequent self-assembly pathway (kinetics). The key factors that determine the thermodynamic interactions that partially define the assembled structures and the kinetic

  8. Poly(2-methyl-2-oxazoline)-b-poly(tetrahydrofuran)-b-poly(2-methyl-2-oxazoline) amphiphilic triblock copolymers: synthesis, physicochemical characterizations, and hydrosolubilizing properties.

    PubMed

    Rasolonjatovo, Bazoly; Gomez, Jean-Pierre; Même, William; Gonçalves, Cristine; Huin, Cécile; Bennevault-Celton, Véronique; Le Gall, Tony; Montier, Tristan; Lehn, Pierre; Cheradame, Hervé; Midoux, Patrick; Guégan, Philippe

    2015-03-01

    Block copolymers assembled into micelles have gained a lot of attention to improve drug delivery. The recent drawbacks of the poly(ethylene oxide) blocks (PEO) contained in amphiphilic pluronics derivatives made of a central poly(propylene oxide) block surrounded by two PEO blocks were recently revealed, opening the way to the design of new amphiphilic block copolymers able to self-assemble in water and to entrap molecules of interest. Here, a family of p(methyloxazoline)-b-p(tetrahydrofuran)-b-p(methyloxazoline) triblock copolymers (called TBCP) is synthesized using cationic ring opening polymerization. Studies of micelle formation using dynamic light scattering, isothermal titration calorimetry (ITC), NMR diffusion-ordered spectroscopy (DOSY), and fluorescence experiments lead us to draw a relationship between copolymer structure and the physicochemical properties of the block copolymers (critical micellar concentration (CMC), Nagg, core diameter, shell thickness, etc.). The packing parameter of the block copolymers indicates the formation of a core-corona structure. Hydrosolubilizing properties of TBCPs were exemplified with curcumin selected as a highly insoluble drug model. Curcumin, a natural polyphenolic compound, has shown a large spectrum of biological and pharmacological activity, including anti-inflammatory, antimicrobial, antioxidant, and anticarcinogenic activities. An optimized formulation process reveals that the aggregation number is the parameter affecting drug encapsulation. Patch clamp experiments carried out to study the interaction of TBCP with the cell membrane demonstrate their permeation property suitable to promote the cellular internalization of curcumin. PMID:25517924

  9. ROP and ATRP Fabricated Dual Targeted Redox Sensitive Polymersomes Based on pPEGMA-PCL-ss-PCL-pPEGMA Triblock Copolymers for Breast Cancer Therapeutics.

    PubMed

    Kumar, Arun; Lale, Shantanu V; Mahajan, Shveta; Choudhary, Veena; Koul, Veena

    2015-05-01

    To minimize cardiotoxicity and to increase the bioavailability of doxorubicin, polymersomes based on redox sensitive amphiphilic triblock copolymer poly(polyethylene glycol methacrylate)-poly(caprolactone)-s-s-poly(caprolactone)-poly(polyethylene glycol methacrylate) (pPEGMA-PCL-ss-PCL-pPEGMA) with disulfide linkage were designed and developed. The polymers were synthesized by ring opening polymerization (ROP) of ε-caprolactone followed by atom transfer radical polymerization (ATRP) of PEGMA. The triblock copolymers demonstrated various types of nanoparticle morphologies by varying hydrophobic/hydrophilic content of polymer blocks, with PEGMA content of ∼18% in the triblock copolymer leading to the formation of polymersomes in the size range ∼150 nm. High doxorubicin loading content of ∼21% was achieved in the polymersomes. Disulfide linkages were incorporated in the polymeric backbone to facilitate degradation of the nanoparticles by the intracellular tripeptide glutathione (GSH), leading to intracellular drug release. Release studies showed ∼59% drug release in pH 5.5 in the presence of 10 mM GSH, whereas only ∼19% was released in pH 7.4. In cellular uptake studies, dual targeted polymersomes showed ∼22-fold increase in cellular uptake efficiency in breast cancer cell lines (BT474 and MCF-7) as compared to nontargeted polymersomes with higher apoptosis rates. In vivo studies on Ehrlich's ascites tumor (EAT) bearing Swiss albino mouse model showed ∼85% tumor regression as compared to free doxorubicin (∼42%) without any significant cardiotoxicity associated with doxorubicin. The results indicate enhanced antitumor efficacy of the redox sensitive biocompatible nanosystem and shows promise as a potential drug nanocarrier in cancer therapeutics.

  10. Amphiphilic triblock copolymers with PEGylated hydrocarbon structures as environmentally friendly marine antifouling and fouling-release coatings.

    PubMed

    Zhou, Zhaoli; Calabrese, David R; Taylor, Warren; Finlay, John A; Callow, Maureen E; Callow, James A; Fischer, Daniel; Kramer, Edward J; Ober, Christopher K

    2014-01-01

    The ideal marine antifouling (AF)/fouling-release (FR) coating should be non-toxic, while effectively either resisting the attachment of marine organisms (AF) or significantly reducing their strength of attachment (FR). Many recent studies have shown that amphiphilic polymeric materials provide a promising solution to producing such coatings due to their surface dual functionality. In this work, poly(ethylene glycol) (PEG) of different molecular weights (Mw = 350, 550) was coupled to a saturated difunctional alkyl alcohol to generate amphiphilic surfactants (PEG-hydrocarbon-OH). The resulting macromolecules were then used as side chains to covalently modify a pre-synthesized PS8 K-b-P(E/B)25 K-b-PI10 K (SEBI or K3) triblock copolymer, and the final polymers were applied to glass substrata through an established multilayer surface coating technique to prepare fouling resistant coatings. The coated surfaces were characterized with AFM, XPS and NEXAFS, and evaluated in laboratory assays with two important fouling algae, Ulva linza (a green macroalga) and Navicula incerta, a biofilm-forming diatom. The results suggest that these polymer-coated surfaces undergo surface reconstruction upon changing the contact medium (polymer/air vs polymer/water), due to the preferential interfacial aggregation of the PEG segment on the surface in water. The amphiphilic polymer-coated surfaces showed promising results as both AF and FR coatings. The sample with longer PEG chain lengths (Mw = 550 g mol(-1)) exhibited excellent properties against both algae, highlighting the importance of the chemical structures on ultimate biological performance. Besides reporting synthesis and characterization of this new type of amphiphilic surface material, this work also provides insight into the nature of PEG/hydrocarbon amphiphilic coatings, and this understanding may help in the design of future generations of fluorine-free, environmentally friendly AF/FR polymeric coatings. PMID:24730510

  11. Amphiphilic triblock copolymers with PEGylated hydrocarbon structures as environmentally friendly marine antifouling and fouling-release coatings.

    PubMed

    Zhou, Zhaoli; Calabrese, David R; Taylor, Warren; Finlay, John A; Callow, Maureen E; Callow, James A; Fischer, Daniel; Kramer, Edward J; Ober, Christopher K

    2014-01-01

    The ideal marine antifouling (AF)/fouling-release (FR) coating should be non-toxic, while effectively either resisting the attachment of marine organisms (AF) or significantly reducing their strength of attachment (FR). Many recent studies have shown that amphiphilic polymeric materials provide a promising solution to producing such coatings due to their surface dual functionality. In this work, poly(ethylene glycol) (PEG) of different molecular weights (Mw = 350, 550) was coupled to a saturated difunctional alkyl alcohol to generate amphiphilic surfactants (PEG-hydrocarbon-OH). The resulting macromolecules were then used as side chains to covalently modify a pre-synthesized PS8 K-b-P(E/B)25 K-b-PI10 K (SEBI or K3) triblock copolymer, and the final polymers were applied to glass substrata through an established multilayer surface coating technique to prepare fouling resistant coatings. The coated surfaces were characterized with AFM, XPS and NEXAFS, and evaluated in laboratory assays with two important fouling algae, Ulva linza (a green macroalga) and Navicula incerta, a biofilm-forming diatom. The results suggest that these polymer-coated surfaces undergo surface reconstruction upon changing the contact medium (polymer/air vs polymer/water), due to the preferential interfacial aggregation of the PEG segment on the surface in water. The amphiphilic polymer-coated surfaces showed promising results as both AF and FR coatings. The sample with longer PEG chain lengths (Mw = 550 g mol(-1)) exhibited excellent properties against both algae, highlighting the importance of the chemical structures on ultimate biological performance. Besides reporting synthesis and characterization of this new type of amphiphilic surface material, this work also provides insight into the nature of PEG/hydrocarbon amphiphilic coatings, and this understanding may help in the design of future generations of fluorine-free, environmentally friendly AF/FR polymeric coatings.

  12. Thermosensitive aqueous gels with tunable sol-gel transition temperatures from thermo- and pH-responsive hydrophilic ABA triblock copolymer.

    PubMed

    O'Lenick, Thomas G; Jiang, Xueguang; Zhao, Bin

    2010-06-01

    This article reports on the synthesis of a well-defined hydrophilic ABA triblock copolymer composed of a poly(ethylene oxide) (PEO) middle block and thermo- and pH-sensitive outer blocks and the study of sol-gel transitions of its aqueous solutions at various pH values. The doubly responsive linear triblock copolymer, poly(methoxydi(ethylene glycol) methacrylate-co-methacrylic acid)-b-PEO-b-poly(methoxydi(ethylene glycol) methacrylate-co-methacrylic acid) (P(DEGMMA-co-MAA)-b-PEO-b-P(DEGMMA-co-MAA)), was prepared by atom transfer radical polymerization of a mixture of DEGMMA and tert-butyl methacrylate with a molar ratio of 100: 5 from a difunctional PEO macroinitiator and subsequent removal of tert-butyl groups using trifluoroacetic acid. Dynamic light scattering studies showed that the critical micellization temperature (CMT) of this ABA triblock copolymer in a 0.2 wt % aqueous solution was dependent on the solution pH and can be varied in a large temperature range (>20 degrees C). To study the sol-gel transitions, a 12.0 wt % aqueous solution of the triblock copolymer with a pH of 4.89 was made; its pH value can be readily changed and well controlled by the injection of either a 1.0 M HCl or a 1.0 M KOH solution. From rheological measurements, the sol-gel transition temperature (T(sol-gel)) versus pH curve was found to closely trace the CMT versus pH curve, though there was a shift. By cycling the solution pH between 3.2 and 5.4, we showed that the T(sol-gel) at a specific pH was reproducible. Moreover, multiple sol-gel-sol transitions were realized by judiciously controlling the temperature and pH simultaneously, demonstrating the possibility of achieving on-demand sol-gel transitions by using two external stimuli. In addition, the effect of polymer concentration on T(sol-gel) at pH = 4.0 was investigated. The sol-gel transition temperature increased with the decrease of polymer concentration and the critical gelation concentration was found to be between 4 and

  13. Directed Self-Assembly of Poly(2-vinylpyridine)-b-polystyrene-b-poly(2-vinylpyridine) Triblock Copolymer with Sub-15 nm Spacing Line Patterns Using a Nanoimprinted Photoresist Template.

    PubMed

    Sun, Zhiwei; Chen, Zhenbin; Zhang, Wenxu; Choi, Jaewon; Huang, Caili; Jeong, Gajin; Coughlin, E Bryan; Hsu, Yautzong; Yang, XiaoMin; Lee, Kim Y; Kuo, David S; Xiao, Shuaigang; Russell, Thomas P

    2015-08-01

    Low molecular weight P2VP-b-PS-b-P2VP triblock copolymer (poly(2-vinlypyridine)-block-polystyrene-block-poly(2-vinylpyridine)] is doped with copper chloride and microphase separated into lamellar line patterns with ultrahigh area density. Salt-doped P2VP-b-PS-b-P2VP triblock copolymer is self-assembled on the top of the nanoimprinted photoresist template, and metallic nanowires with long-range ordering are prepared with platinum-salt infiltration and plasma etching. PMID:26088198

  14. Complex self-assembly of reverse poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) triblock copolymers with long hydrophobic and extremely lengthy hydrophilic blocks.

    PubMed

    Cambón, Adriana; Figueroa-Ochoa, Edgar; Juárez, Josué; Villar-Álvarez, Eva; Pardo, Alberto; Barbosa, Silvia; Soltero, J F Armando; Taboada, Pablo; Mosquera, Víctor

    2014-05-15

    Amphiphilic block copolymers have emerged during last years as a fascinating substrate material to develop micellar nanocontainers able to solubilize, protect, transport, and release under external or internal stimuli different classes of cargos to diseased cells or tissues. However, this class of materials can also induce biologically relevant actions, which complement the therapeutic activity of their cargo molecules through their mutual interactions with biologically relevant entities (cellular membranes, proteins, organelles...); these interactions at the same time, are regulated by the nature, conformation, and state of the copolymeric chains. For these reasons, in this paper we investigated the self-assembly process and physico-chemcial properties of two reverse triblock poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) block copolymers, BO14EO378BO14 and BO21EO385BO21, which have been recently found to be very useful as drug delivery nanovehicles and biological response modifiers under certain conditions (A. Cambón et al. Int. J. Pharm. 2013, 445, 47-57) in order to obtain a clear picture of the solution behavior of this class or block copolymers and to understand their biological activity. These block copolymers are characterized by possessing long BO blocks and extremely lengthy central EO ones, which provide them with a rich rheological behavior characterized by the formation of flowerlike micelles with sizes ranging from 20 to 40 nm in aqueous solution and the presence of intermicellar bridging even at low copolymers concentrations as denoted by atomic force microscopy. Bridging is also clearly observed by analyzing the rheological response of these block copolymers both storage and loss moduli upon changes on time, temperature, and or concentration. Strikingly, the relatively wide Poisson distribution of the polymeric chains make the present copolymers behave rather distinctly to conventional associative thickeners. The observed rich

  15. Biomimetic Nanocomposites of Calcium Phosphate and Self-Assembling Triblock and Pentablock Copolymers

    SciTech Connect

    Enlow, Drew Lenzen

    2006-01-01

    In an effort to mimic the growth of natural bone, self-assembling, micelle and gel-forming copolymers were used as a template for calcium phosphate precipitation. Because of the cationic characteristics imparted by PDEAEM end group additions to commercially available Pluronic{reg_sign} Fl27, a direct ionic attraction mechanism was utilized and a polymer-brushite nanocomposite spheres were produced. Brushite coated spherical micelles with diameters of ~40 nm, and agglomerates of these particles (on the order of 0.5 μm) were obtained. Thickness and durability of the calcium phosphate coating, and the extent of agglomeration were studied. The coating has been shown to be robust enough to retain its integrity even below polymer critical micelle concentration and/or temperature. Calcium phosphate-polymer gel nanocomposites were also prepared. Gel samples appeared as a single phase network of agglomerated spherical micelles, and had a final calcium phosphate concentration of up to 15 wt%. Analysis with x-ray diffraction and NMR indicated a disordered brushite phase with the phosphate groups linking inorganic phase to the polymer.

  16. Single-ion BAB triblock copolymers as highly efficient electrolytes for lithium-metal batteries

    NASA Astrophysics Data System (ADS)

    Bouchet, Renaud; Maria, Sébastien; Meziane, Rachid; Aboulaich, Abdelmaula; Lienafa, Livie; Bonnet, Jean-Pierre; Phan, Trang N. T.; Bertin, Denis; Gigmes, Didier; Devaux, Didier; Denoyel, Renaud; Armand, Michel

    2013-05-01

    Electrochemical energy storage is one of the main societal challenges of this century. The performances of classical lithium-ion technology based on liquid electrolytes have made great advances in the past two decades, but the intrinsic instability of liquid electrolytes results in safety issues. Solid polymer electrolytes would be a perfect solution to those safety issues, miniaturization and enhancement of energy density. However, as in liquids, the fraction of charge carried by lithium ions is small (<20%), limiting the power performances. Solid polymer electrolytes operate at 80 °C, resulting in poor mechanical properties and a limited electrochemical stability window. Here we describe a multifunctional single-ion polymer electrolyte based on polyanionic block copolymers comprising polystyrene segments. It overcomes most of the above limitations, with a lithium-ion transport number close to unity, excellent mechanical properties and an electrochemical stability window spanning 5 V versus Li+/Li. A prototype battery using this polyelectrolyte outperforms a conventional battery based on a polymer electrolyte.

  17. Single-ion BAB triblock copolymers as highly efficient electrolytes for lithium-metal batteries.

    PubMed

    Bouchet, Renaud; Maria, Sébastien; Meziane, Rachid; Aboulaich, Abdelmaula; Lienafa, Livie; Bonnet, Jean-Pierre; Phan, Trang N T; Bertin, Denis; Gigmes, Didier; Devaux, Didier; Denoyel, Renaud; Armand, Michel

    2013-05-01

    Electrochemical energy storage is one of the main societal challenges of this century. The performances of classical lithium-ion technology based on liquid electrolytes have made great advances in the past two decades, but the intrinsic instability of liquid electrolytes results in safety issues. Solid polymer electrolytes would be a perfect solution to those safety issues, miniaturization and enhancement of energy density. However, as in liquids, the fraction of charge carried by lithium ions is small (<20%), limiting the power performances. Solid polymer electrolytes operate at 80 °C, resulting in poor mechanical properties and a limited electrochemical stability window. Here we describe a multifunctional single-ion polymer electrolyte based on polyanionic block copolymers comprising polystyrene segments. It overcomes most of the above limitations, with a lithium-ion transport number close to unity, excellent mechanical properties and an electrochemical stability window spanning 5 V versus Li(+)/Li. A prototype battery using this polyelectrolyte outperforms a conventional battery based on a polymer electrolyte.

  18. Multiscale Modeling of Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide) Triblock Copolymer Micelles in Aqueous Solution.

    PubMed

    Bedrov, Dmitry; Ayyagari, Chakravarthy; Smith, Grant D

    2006-05-01

    We present a multiscale modeling approach for simulation of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer micelles in aqueous solution. We rely on systematic elimination of computationally expensive degrees of freedom yet retain implicitly their influence on the remaining degrees freedom in a coarser-grained model. Quantum chemistry (QC) calculations, atomistic explicit solvent (AES) molecular dynamics (MD) simulations, and coarse-grained implicit solvent (CGIS) simulations have been applied to investigate physical properties of these important self-assembling triblock copolymers. High-level QC calculations have been used to parametrize classical atomistic force fields that implicitly take into account and reproduce the important energetic and structural features due to correlations of electronic degrees of freedom. AES MD simulations utilizing the QC-based force fields have been used to provide structural and conformational properties of polymers in aqueous solution which were subsequently used for parametrization of the CGIS model using the Inverted Boltzmann method. The CGIS simulations were then employed to investigate structural properties of two PEO-PPO-PEO micelles (EO13-PO30-EO13 and EO99-PO65-EO99 also known as Pluronic L64 and F127, respectively) in aqueous solution.

  19. Biodegradable nanoparticles of mPEG-PLGA-PLL triblock copolymers as novel non-viral vectors for improving siRNA delivery and gene silencing.

    PubMed

    Du, Jing; Sun, Ying; Shi, Qiu-Sheng; Liu, Pei-Feng; Zhu, Ming-Jie; Wang, Chun-Hui; Du, Lian-Fang; Duan, You-Rong

    2012-01-01

    Degradation of mRNA by RNA interference is one of the most powerful and specific mechanisms for gene silencing. However, insufficient cellular uptake and poor stability have limited its usefulness. Here, we report efficient delivery of siRNA via the use of biodegradable nanoparticles (NPs) made from monomethoxypoly(ethylene glycol)-poly(lactic-co-glycolic acid)-poly-l-lysine (mPEG-PLGA-PLL) triblock copolymers. Various physicochemical properties of mPEG-PLGA-PLL NPs, including morphology, size, surface charge, siRNA encapsulation efficiency, and in vitro release profile of siRNA from NPs, were characterized by scanning electron microscope, particle size and zeta potential analyzer, and high performance liquid chromatography. The levels of siRNA uptake and targeted gene inhibition were detected in human lung cancer SPC-A1-GFP cells stably expressing green fluorescent protein. Examination of the cultured SPC-A1-GFP cells with fluorescent microscope and flow cytometry showed NPs loading Cy3-labeled siRNA had much higher intracellular siRNA delivery efficiencies than siRNA alone and Lipofectamine-siRNA complexes. The gene silencing efficiency of mPEG-PLGA-PLL NPs was higher than that of commercially available transfecting agent Lipofectamine while showing no cytotoxicity. Thus, the current study demonstrates that biodegradable NPs of mPEG-PLGA-PLL triblock copolymers can be potentially applied as novel non-viral vectors for improving siRNA delivery and gene silencing.

  20. "Near perfect" amphiphilic conetwork based on end-group cross-linking of polydimethylsiloxane triblock copolymer via atom transfer radical polymerization.

    PubMed

    Xu, Jianfeng; Qiu, Ming; Ma, Bomou; He, Chunju

    2014-09-10

    Novel amphiphilic conetworks (APCNs) with uniform channel size were synthesized through end-cross-linking of well-defined amphiphilic triblock copolymers via atom transfer radical polymerization (ATRP). A new ditelechelic polydimethylsiloxane macroinitiator was synthesized to initiate the polymerization of N,N-dimethylacrylamide. The resulting triblock copolymers show well-defined molecular weight with narrow polydisperisty, which are telechelic modified by allylamine and fully cross-linked with polyhydrosiloxanes through hydrosilylation. Transmission electron microscopy shows that the APCN has the behavior of microphase separation with small channel size and uniform phase domain. The resulting APCNs with idealized microstructure exhibit a combination of excellent properties, i.e., superhigh mechanical strength (4 ± 1 MPa) and elongation ratio (175 ± 25%), outstanding oxygen permeability (350 ± 150 barrers), a high water uptake property, and excellent biocompatibility, indicating that in this way, "near perfect" networks are obtained. These results are better than those reported in the literature, suggesting a promising semipermeable barrier for islet encapsulation in relative biomaterial fields.

  1. Biodegradable Nanoparticles of mPEG-PLGA-PLL Triblock Copolymers as Novel Non-Viral Vectors for Improving siRNA Delivery and Gene Silencing

    PubMed Central

    Du, Jing; Sun, Ying; Shi, Qiu-Sheng; Liu, Pei-Feng; Zhu, Ming-Jie; Wang, Chun-Hui; Du, Lian-Fang; Duan, You-Rong

    2012-01-01

    Degradation of mRNA by RNA interference is one of the most powerful and specific mechanisms for gene silencing. However, insufficient cellular uptake and poor stability have limited its usefulness. Here, we report efficient delivery of siRNA via the use of biodegradable nanoparticles (NPs) made from monomethoxypoly(ethylene glycol)-poly(lactic-co-glycolic acid)-poly-l-lysine (mPEG-PLGA-PLL) triblock copolymers. Various physicochemical properties of mPEG-PLGA-PLL NPs, including morphology, size, surface charge, siRNA encapsulation efficiency, and in vitro release profile of siRNA from NPs, were characterized by scanning electron microscope, particle size and zeta potential analyzer, and high performance liquid chromatography. The levels of siRNA uptake and targeted gene inhibition were detected in human lung cancer SPC-A1-GFP cells stably expressing green fluorescent protein. Examination of the cultured SPC-A1-GFP cells with fluorescent microscope and flow cytometry showed NPs loading Cy3-labeled siRNA had much higher intracellular siRNA delivery efficiencies than siRNA alone and Lipofectamine-siRNA complexes. The gene silencing efficiency of mPEG-PLGA-PLL NPs was higher than that of commercially available transfecting agent Lipofectamine while showing no cytotoxicity. Thus, the current study demonstrates that biodegradable NPs of mPEG-PLGA-PLL triblock copolymers can be potentially applied as novel non-viral vectors for improving siRNA delivery and gene silencing. PMID:22312268

  2. Tertiary-amine-containing thermo- and pH-sensitive hydrophilic ABA triblock copolymers: effect of different tertiary amines on thermally induced sol-gel transitions.

    PubMed

    Henn, Daniel M; Wright, Roger A E; Woodcock, Jeremiah W; Hu, Bin; Zhao, Bin

    2014-03-11

    This Article reports on the synthesis of a series of well-defined, tertiary-amine-containing ABA triblock copolymers, composed of a poly(ethylene oxide) (PEO) central block and thermo- and pH-sensitive outer blocks, and the study of the effect of different tertiary amines on thermally induced sol-gel transition temperatures (T(sol-gel)) of their 10 wt % aqueous solutions. The doubly responsive ABA triblock copolymers were prepared from a difunctional PEO macroinitiator by atom transfer radical polymerization of methoxydi(ethylene glycol) methacrylate and ethoxydi(ethylene glycol) methacrylate at a feed molar ratio of 30:70 with ∼5 mol % of either N,N-diethylaminoethyl methacrylate (DEAEMA), N,N-diisopropylaminoethyl methacrylate, or N,N-di(n-butyl)aminoethyl methacrylate. The chain lengths of thermosensitive outer blocks and the molar contents of tertiary amines were very similar for all copolymers. Using rheological measurements, we determined the pH dependences of T(sol-gel) of 10 wt % aqueous solutions of these copolymers in a phosphate buffer. The T(sol-gel) versus pH curves of all polymers exhibited a sigmoidal shape. The T(sol-gel) increased with decreasing pH; the changes were small on both high and low pH sides. At a specific pH, the T(sol-gel) decreased with increasing the hydrophobicity of the tertiary amine, and upon decreasing pH the onset pH value for the T(sol-gel) to begin to increase noticeably was lower for the more hydrophobic tertiary amine-containing copolymer. In addition, we studied the effect of different tertiary amines on the release behavior of FITC-dextran from 10 wt % micellar gels in an acidic medium at 37 and 27 °C. The release profiles for three studied hydrogels at 37 °C were essentially the same, suggesting that the release was dominated by the diffusion of FITC-dextran. At 27 °C, the release was significantly faster for the DEAEMA-containing copolymer, indicating that both diffusion and gel dissolution contributed to the

  3. Volume shrinkage and rheological studies of epoxidised and unepoxidised poly(styrene-block-butadiene-block-styrene) triblock copolymer modified epoxy resin-diamino diphenyl methane nanostructured blend systems.

    PubMed

    George, Sajeev Martin; Puglia, Debora; Kenny, Josè M; Parameswaranpillai, Jyotishkumar; Vijayan P, Poornima; Pionteck, Jűrgen; Thomas, Sabu

    2015-05-21

    Styrene-block-butadiene-block-styrene (SBS) copolymers epoxidised at different epoxidation degrees were used as modifiers for diglycidyl ether of the bisphenol A-diamino diphenyl methane (DGEBA-DDM) system. Epoxy systems containing modified epoxidised styrene-block-butadiene-block-styrene (eSBS) triblock copolymer with compositions ranging from 0 to 30 wt% were prepared and the curing reaction was monitored in situ using rheometry and pressure-volume-temperature (PVT) analysis. By controlling the mole percent of epoxidation, we could generate vesicles, worm-like micelles and core-shell nanodomains. At the highest mole percent of epoxidation, the fraction of the epoxy miscible component in the triblock copolymer (epoxidised polybutadiene (PB)) was maximum. This gave rise to core-shell nanodomains having a size of 10-15 nm, in which the incompatible polystyrene (PS) becomes the core, the unepoxidised PB becomes the shell and the epoxidised PB interpenetrates with the epoxy phase. On the other hand, the low level of epoxidation gave rise to bigger domains having a size of ∼1 μm and the intermediate epoxidation level resulted in a worm-like structure. This investigation specifically focused on the importance of cure rheology on nanostructure formation, using rheometry. The reaction induced phase separation of the PS phase in the epoxy matrix was carefully explored through rheological measurements. PVT measurements during curing were carried out to understand the volume shrinkage of the blend, confirming that shrinkage behaviour is related to the block copolymer phase separation process during curing. The volume shrinkage was found to be maximum in the case of blends with unmodified SBS, where a heterogeneous morphology was observed, while a decrease in the shrinkage was evidenced in the case of SBS epoxidation. It could be explained by two effects: (1) solubility of the epoxidised block copolymer in the DGEBA leads to the formation of nanoscopic domains upon

  4. Volume shrinkage and rheological studies of epoxidised and unepoxidised poly(styrene-block-butadiene-block-styrene) triblock copolymer modified epoxy resin-diamino diphenyl methane nanostructured blend systems.

    PubMed

    George, Sajeev Martin; Puglia, Debora; Kenny, Josè M; Parameswaranpillai, Jyotishkumar; Vijayan P, Poornima; Pionteck, Jűrgen; Thomas, Sabu

    2015-05-21

    Styrene-block-butadiene-block-styrene (SBS) copolymers epoxidised at different epoxidation degrees were used as modifiers for diglycidyl ether of the bisphenol A-diamino diphenyl methane (DGEBA-DDM) system. Epoxy systems containing modified epoxidised styrene-block-butadiene-block-styrene (eSBS) triblock copolymer with compositions ranging from 0 to 30 wt% were prepared and the curing reaction was monitored in situ using rheometry and pressure-volume-temperature (PVT) analysis. By controlling the mole percent of epoxidation, we could generate vesicles, worm-like micelles and core-shell nanodomains. At the highest mole percent of epoxidation, the fraction of the epoxy miscible component in the triblock copolymer (epoxidised polybutadiene (PB)) was maximum. This gave rise to core-shell nanodomains having a size of 10-15 nm, in which the incompatible polystyrene (PS) becomes the core, the unepoxidised PB becomes the shell and the epoxidised PB interpenetrates with the epoxy phase. On the other hand, the low level of epoxidation gave rise to bigger domains having a size of ∼1 μm and the intermediate epoxidation level resulted in a worm-like structure. This investigation specifically focused on the importance of cure rheology on nanostructure formation, using rheometry. The reaction induced phase separation of the PS phase in the epoxy matrix was carefully explored through rheological measurements. PVT measurements during curing were carried out to understand the volume shrinkage of the blend, confirming that shrinkage behaviour is related to the block copolymer phase separation process during curing. The volume shrinkage was found to be maximum in the case of blends with unmodified SBS, where a heterogeneous morphology was observed, while a decrease in the shrinkage was evidenced in the case of SBS epoxidation. It could be explained by two effects: (1) solubility of the epoxidised block copolymer in the DGEBA leads to the formation of nanoscopic domains upon

  5. Adsorption of a PEO-PPO-PEO triblock copolymer on metal oxide surfaces with a view to reducing protein adsorption and further biofouling.

    PubMed

    Yang, Y; Poleunis, C; Románszki, L; Telegdi, J; Dupont-Gillain, C C

    2013-01-01

    Abstract Biomolecule adsorption is the first stage of biofouling. The aim of this work was to reduce the adsorption of proteins on stainless steel (SS) and titanium surfaces by modifying them with a poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-PEO triblock copolymer. Anchoring of the central PPO block of the copolymer is known to be favoured by hydrophobic interaction with the substratum. Therefore, the surfaces of metal oxides were first modified by self-assembly of octadecylphosphonic acid. PEO-PPO-PEO preadsorbed on the hydrophobized surfaces of titanium or SS was shown to prevent the adsorption of bovine serum albumin (BSA), fibrinogen and cytochrome C, as monitored by quartz crystal microbalance (QCM). Moreover, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry were used to characterize the surfaces of the SS and titanium after competitive adsorption of PEO-PPO-PEO and BSA. The results show that the adsorption of BSA is well prevented on hydrophobized surfaces, in contrast to the surfaces of native metal oxides.

  6. Reversibly shielded DNA polyplexes based on bioreducible PDMAEMA-SS-PEG-SS-PDMAEMA triblock copolymers mediate markedly enhanced nonviral gene transfection.

    PubMed

    Zhu, Caihong; Zheng, Meng; Meng, Fenghua; Mickler, Frauke Martina; Ruthardt, Nadia; Zhu, Xiulin; Zhong, Zhiyuan

    2012-03-12

    Reversibly shielded DNA polyplexes based on bioreducible poly(dimethylaminoethyl methacrylate)-SS-poly(ethylene glycol)-SS-poly(dimethylaminoethyl methacrylate) (PDMAEMA-SS-PEG-SS-PDMAEMA) triblock copolymers were designed, prepared and investigated for in vitro gene transfection. Two PDMAEMA-SS-PEG-SS-PDMAEMA copolymers with controlled compositions, 6.6-6-6.6 and 13-6-13 kDa, were obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization of dimethylaminoethyl methacrylate (DMAEMA) using CPADN-SS-PEG-SS-CPADN (CPADN: 4-cyanopentanoic acid dithionaphthalenoate; PEG: 6 kDa) as a macro-RAFT agent. Like their nonreducible PDMAEMA-PEG-PDMAEMA analogues, PDMAEMA-SS-PEG-SS-PDMAEMA triblock copolymers could effectively condense DNA into small particles with average diameters less than 120 nm and close to neutral zeta potentials (0 ∼ +6 mV) at and above an N/P ratio of 3/1. The resulting polyplexes showed excellent colloidal stability against 150 mM NaCl, which contrasts with polyplexes of 20 kDa PDMAEMA homopolymer. In the presence of 10 mM dithiothreitol (DTT), however, polyplexes of PDMAEMA-SS-PEG-SS-PDMAEMA were rapidly deshielded and unpacked, as revealed by significant increase of positive surface charges as well as increase of particle sizes to over 1000 nm. Release of DNA in response to 10 mM DTT was further confirmed by gel retardation assays. These polyplexes, either stably or reversibly shielded, revealed a low cytotoxicity (over 80% cell viability) at and below an N/P ratio of 12/1. Notably, in vitro transfection studies showed that reversibly shielded polyplexes afforded up to 28 times higher transfection efficacy as compared to stably shielded control under otherwise the same conditions. Confocal laser scanning microscope (CLSM) studies revealed that reversibly shielded polyplexes efficiently delivered and released pDNA into the perinuclei region as well as nuclei of COS-7 cells. Hence, reduction-sensitive reversibly shielded DNA

  7. The effects of carbonation on the leaching characteristics of cadmium, nickel, and lead

    SciTech Connect

    Bonen, D.

    1995-12-31

    The effect of polymer modifier type on the performance (fracture and fatigue behavior) of AC-5 asphalt mixture was studied. Three polymer modidfiers belonging to the group of thermoplastic polymers, styrene-butadiene-styrene block copolymer, ethylene vinyl acetate, and polyethylene were considered.

  8. Mean-field coarse-grained model for poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer systems.

    PubMed

    García Daza, Fabián A; Colville, Alexander J; Mackie, Allan D

    2015-03-31

    The microscopic modeling of surfactant systems is of the utmost importance in understanding the mechanisms related to the micellization process because it allows for prediction and comparison with experimental data of diverse equilibrium system properties. In this work, we present a coarse-grained model for Pluronics, a trademarked type of triblock copolymer, from simulations based on a single-chain mean-field theory (SCMF). This microscopic model is used to quantify the micellization process of these nonionic surfactants at 37 °C and has been shown to be able to quantitatively reproduce experimental data of the critical micelle concentration (CMC) along with other equilibrium properties. In particular, these results correctly capture the experimental behavior with respect to the lengths of the hydrophobic and hydrophilic moieties of the surfactants for low and medium hydrophobicities. However, for the more highly hydrophobic systems with low CMCs, a deviation is found which has been previously attributed to nonequilibrium effects in the experimental data (Garcı́a Daza, F. A.; Mackie, A. D. Low Critical Micelle Concentration Discrepancy between Theory and Experiment. J. Phys. Chem. Lett. 2014, 5, 2027-2032).

  9. Nanoparticles of Block Ionomer Complexes from Double Hydrophilic Poly(acrylic acid)- b-poly(ethylene oxide)- b-poly(acrylic acid) Triblock Copolymer and Oppositely Charged Surfactant

    NASA Astrophysics Data System (ADS)

    Peng, Zhiping; Sun, Yuelong; Liu, Xinxing; Tong, Zhen

    2010-01-01

    The novel water-dispersible nanoparticles from the double hydrophilic poly(acrylic acid)- b-poly(ethylene oxide)- b-poly(acrylic acid) (PAA- b-PEO- b-PAA) triblock copolymer and oppositely charged surfactant dodecyltrimethyl ammonium bromide (DTAB) were prepared by mixing the individual aqueous solutions. The structure of the nanoparticles was investigated as a function of the degree of neutralization (DN) by turbidimetry, dynamic light scattering (DSL), ζ-potential measurement, and atomic force microscope (AFM). The neutralization of the anionic PAA blocks with cationic DTAB accompanied with the hydrophobic interaction of alkyl tails of DTAB led to formation of core-shell nanoparticles with the core of the DTAB neutralized PAA blocks and the shell of the looped PEO blocks. The water-dispersible nanoparticles with negative ζ-potential were obtained over the DN range from 0.4 to 2.0 and their sizes depended on the DN. The looped PEO blocks hindered the further neutralization of the PAA blocks with cationic DTAB, resulting in existence of some negative charged PAA- b-PEO- b-PAA backbones even when DN > 1.0. The spherical and ellipsoidal nature of these nanoparticles was observed with AFM.

  10. Fabrication of Hollow Porous Silica Using a Combined Emulsion Sol-Gel Process and Amphiphilic Triblock Copolymer for Loading of Quercetin.

    PubMed

    Lee, Sang Gil; Kim, Young Ho; Bae, Jun Tae; Lee, Chung Hee; Pyo, Hyeong Bae; Kang, Kuk Hyoun; Lee, Dong Kyu

    2015-10-01

    Flavonoids have recently attracted significant interest as potential reducing agents, hydrogen-donating antioxidants, and singlet oxygen-quenchers. Quercetin, in particular, induces the expression of a gene, known to be associated with cell protection, in dose- and time-dependent manners. Therefore, quercetin may be used as an effective cosmeceutical material useful in the protection of dermal skin. In this study, hollow porous silica spheres used to load quercetin were prepared by using a combined emulsion sol-gel process and triblock copolymer as a template. Fabrication of hollow porous silica spheres was performed under various conditions such as the molar ratios of H2O/TEOS (Rw) and weight ratios of poloxamer 184/poloxamer 407. Loading of quercetin in hollow porous silica spheres was devised to improve the stability of quercetin and to consider the possibility as a raw cosmetic material. The surface of inclusion complexes of quercetin in hollow porous silicas was modified to enhance the stability of quercetin. The physicochemical properties of the samples were investigated using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA)-differential thermal analysis (DTA) and Brunauer-Emmett-Teller (BET) surface area and porosity analysis. Determination of quercetin concentration was carried out by high-performance liquid chromatography (HPLC) analysis. PMID:26726443

  11. Hydration of cations: a key to understanding of specific cation effects on aggregation behaviors of PEO-PPO-PEO triblock copolymers.

    PubMed

    Lutter, Jacob C; Wu, Tsung-yu; Zhang, Yanjie

    2013-09-01

    This work reports results from the interactions of a series of monovalent and divalent cations with a triblock copolymer, poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO). Phase transition temperatures of the polymer in the presence of chloride salts with six monovalent and eight divalent cations were measured using an automated melting point apparatus. The polymer undergoes a two-step phase transition, consisting of micellization of the polymer followed by aggregation of the micelles, in the presence of all the salts studied herein. The results suggest that hydration of cations plays a key role in determining the interactions between the cations and the polymer. The modulation of the phase transition temperature of the polymer by cations can be explained as a balance between three interactions: direct binding of cations to the oxygen in the polymer chains, cations sharing one water molecule with the polymer in their hydration layer, and cations interacting with the polymer via two water molecules. Monovalent cations Na(+), K(+), Rb(+), and Cs(+) do not bind to the polymer, while Li(+) and NH4(+) and all the divalent cations investigated including Mg(2+), Ca(2+), Sr(2+), Ba(2+), Co(2+), Ni(2+), Cu(2+), and Cd(2+) bind to the polymer. The effects of the cations correlate well with their hydration thermodynamic properties. Mechanisms for cation-polymer interactions are discussed.

  12. Self-assembled polymersomes formed by symmetric, asymmetric and side-chain-tethered coil-rod-coil triblock copolymers.

    PubMed

    Lin, Yung-Lung; Chang, Hung-Yu; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2014-03-21

    Self-assembly behaviors of coil-rod-coil copolymers in selective solvents are explored by dissipative particle dynamics. The morphological phase diagram as a function of rod length and coil length shows five distinct types of aggregates, including spherical micelles, worm-like micelles, disk-like aggregates, honeycomb structures, and polymersomes. Small polymersomes are formed at rather poor alignment associated with monolayered rod domains. Some of the rods are even lying perpendicular to the radial direction. For symmetric copolymers (CmRxCm), the condition of vesicle formation is restricted to short coil and rod lengths. To favor the formation of CRC-polymersomes, two architecture modifications are adopted. One is to increase the coil length asymmetrically to be CmRxCn, where n > m. The other one is to tether a T-block onto the middle of the rod-block as Cm(RxTy)Cm copolymers. For those CRC-polymersomes, structural, transport, and mechanical properties of the vesicular membrane are determined, including membrane thickness, area density of coil blocks, order parameter, solvent permeability, frequency of flip-flop, membrane tension, and stretching and bending moduli. The influences of the coil length (n) and tethered block length (y) on membrane properties are examined. Finally, the mechanism of membrane fusion between CRC-polymersomes is investigated. The fusion process involves four stages and in the contact region the rods lying perpendicular to the radial direction of the polymersome play the key role. The encounter of two vesicles may result in a fused, hemifused, or non-fused polymersome. The final fate is determined by the competition between membrane tension and the steric barrier of the coil corona. The fusion outcome may change if the tension is altered by manipulating the lumen pressure.

  13. Self-assembled polymersomes formed by symmetric, asymmetric and side-chain-tethered coil-rod-coil triblock copolymers.

    PubMed

    Lin, Yung-Lung; Chang, Hung-Yu; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2014-03-21

    Self-assembly behaviors of coil-rod-coil copolymers in selective solvents are explored by dissipative particle dynamics. The morphological phase diagram as a function of rod length and coil length shows five distinct types of aggregates, including spherical micelles, worm-like micelles, disk-like aggregates, honeycomb structures, and polymersomes. Small polymersomes are formed at rather poor alignment associated with monolayered rod domains. Some of the rods are even lying perpendicular to the radial direction. For symmetric copolymers (CmRxCm), the condition of vesicle formation is restricted to short coil and rod lengths. To favor the formation of CRC-polymersomes, two architecture modifications are adopted. One is to increase the coil length asymmetrically to be CmRxCn, where n > m. The other one is to tether a T-block onto the middle of the rod-block as Cm(RxTy)Cm copolymers. For those CRC-polymersomes, structural, transport, and mechanical properties of the vesicular membrane are determined, including membrane thickness, area density of coil blocks, order parameter, solvent permeability, frequency of flip-flop, membrane tension, and stretching and bending moduli. The influences of the coil length (n) and tethered block length (y) on membrane properties are examined. Finally, the mechanism of membrane fusion between CRC-polymersomes is investigated. The fusion process involves four stages and in the contact region the rods lying perpendicular to the radial direction of the polymersome play the key role. The encounter of two vesicles may result in a fused, hemifused, or non-fused polymersome. The final fate is determined by the competition between membrane tension and the steric barrier of the coil corona. The fusion outcome may change if the tension is altered by manipulating the lumen pressure. PMID:24651905

  14. Filamentous, mixed micelles of triblock copolymers enhance tumor localization of indocyanine green in a murine xenograft model

    PubMed Central

    Kim, Tae Hee; Mount, Christopher W; Dulken, Benjamin W; Ramos, Jenelyn; Fu, Caroline J; Khant, Htet A; Chiu, Wah; Gombotz, Wayne R; Pun, Suzie H

    2012-01-01

    Polymeric micelles formed by the self-assembly of amphiphilic block copolymers can be used to encapsulate hydrophobic drugs for tumor-delivery applications. Filamentous carriers with high aspect ratios offer potential advantages over spherical carriers, including prolonged circulation times. In this work, mixed micelles comprised of poly (ethylene oxide)-poly-[(R)-3-hydroxybutyrate]-poly (ethylene oxide) (PEO-PHB-PEO) and Pluronic F-127 (PF-127) were used to encapsulate a near-infrared fluorophore. The micelle formulations were assessed for tumor accumulation after tail vein injection to xenograft tumor-bearing mice by non-invasive optical imaging. The mixed micelle formulation that facilitated the highest tumor accumulation was shown by cryo-electron microscopy to be filamentous in structure compared to spherical structures of pure PF-127 micelles. In addition, increased dye loading efficiency and dye stability was attained in this mixed micelle formulation compared to pure PEO-PHB-PEO micelles. Therefore, the optimized PEO-PHB-PEO/PF-127 mixed micelle formulation offers advantages for cancer delivery over micelles formed from the individual copolymer components. PMID:22118658

  15. Filamentous, mixed micelles of triblock copolymers enhance tumor localization of indocyanine green in a murine xenograft model.

    PubMed

    Kim, Tae Hee; Mount, Christopher W; Dulken, Benjamin W; Ramos, Jenelyn; Fu, Caroline J; Khant, Htet A; Chiu, Wah; Gombotz, Wayne R; Pun, Suzie H

    2012-01-01

    Polymeric micelles formed by the self-assembly of amphiphilic block copolymers can be used to encapsulate hydrophobic drugs for tumor-delivery applications. Filamentous carriers with high aspect ratios offer potential advantages over spherical carriers, including prolonged circulation times. In this work, mixed micelles composed of poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide) (PEO-PHB-PEO) and Pluronic F-127 (PF-127) were used to encapsulate a near-infrared fluorophore. The micelle formulations were assessed for tumor accumulation after tail vein injection to xenograft tumor-bearing mice by noninvasive optical imaging. The mixed micelle formulation that facilitated the highest tumor accumulation was shown by cryo-electron microscopy to be filamentous in structure compared to spherical structures of pure PF-127 micelles. In addition, increased dye loading efficiency and dye stability were attained in this mixed micelle formulation compared to pure PEO-PHB-PEO micelles. Therefore, the optimized PEO-PHB-PEO/PF-127 mixed micelle formulation offers advantages for cancer delivery over micelles formed from the individual copolymer components.

  16. Creep-resistant porous structures based on stereo-complex forming triblock copolymers of 1,3-trimethylene carbonate and lactides.

    PubMed

    Zhang, Zheng; Grijpma, Dirk W; Feijen, Jan

    2004-04-01

    Stereo-complexes (poly(ST-TMC-ST)) of enantiomeric triblock copolymers based on 1,3-trimethylene carbonate (TMC) and L- or D-lactide (poly(LLA-TMC-LLA) and poly(DLA-TMC-DLA)) were prepared. Films of poly(ST-TMC-ST) could be prepared by solvent casting mixtures of equal amounts of poly(LLA-TMC-LLA) and poly(DLA-TMC-DLA) solutions and by compression moulding co-precipitates. Although compression moulding was performed at 191 degrees C, thermal degradation was not apparent and materials with good tensile properties could be obtained. For compression-moulded poly(ST-TMC-ST) specimens containing approximately 16 mol % lactide, the values for E-modulus, yield stress and elongation at break were respectively 17, 1.7 MPa and 90%. Also a very low long-term creep rate of 2.2 x 10(-7)s(-1) was determined when specimens were loaded to 20% of the yield stress. When compared with compression-moulded poly(TMC), poly(ST-TMC-ST) specimens deform at a rate that is one to two orders of magnitude lower. Furthermore, poly(ST-TMC-ST) specimens showed complete dimensional recovery within 24 h after loading to 20% and 40% of the yield stress for 40 and 5.5 h, respectively. Highly porous poly(TMC) and poly(ST-TMC-ST) structures with interconnected pores were prepared by a method combining co-precipitation, compression moulding and salt leaching. After prolonged compressive deformation, solid and porous poly(ST-TMC-ST) discs showed significantly better recovery behaviour than poly(TMC) discs. PMID:15332603

  17. Robust conductive mesoporous carbon-silica composite films with highly ordered and oriented orthorhombic structures from triblock-copolymer template co-assembly

    SciTech Connect

    Song, Lingyan; Feng, Dan; Campbell, Casey G; Gu, Dong; Forster, Aaron M; Yager, Kevin G; Fredin, Nathaniel; Lee, Hae-Jeong; Jones, Ronald L; Zhao, Dongyuan; Vogt, Bryan D

    2012-07-11

    In this work, we describe a facile approach to improve the robustness of conductive mesoporous carbon-based thin films by the addition of silica to the matrix through the triconstituent organic-inorganic-organic co-assembly of resol (carbon precursor) and tetraethylorthosilicate (silica precursor) with triblock-copolymer Pluronic F127. The pyrolysis of the resol-silica-pluronic F127 film yields a porous composite thin film with well-defined mesostructure. X-Ray diffraction (XRD), grazing incidence small angle X-ray scattering (GISAXS), and electron microscopy measurements indicate that the obtained carbon-based thin films have a highly ordered orthorhombic mesostructure (Fmmm) with uniform large pore size (~3 nm). The orthorhombic mesostructure is oriented and the (010) plane is parallel to the silicon wafer substrate. The addition of silica to the matrix impacts the pore size, surface area, porosity, modulus and conductivity. For composite films with approximately 40 wt% silica, the conductivity is decreased by approximately an order of magnitude in comparison to a pure carbon mesoporous film, but the conductivity is comparable to typical printed carbon inks used in electrochemical sensing, {approx}10 S cm-1. The mechanical properties of these mesoporous silica-carbon hybrid films are similar to the pure carbon analogs with a Young's modulus between 10 GPa and 15 GPa, but the material is significantly more porous. Moreover, the addition of silica to the matrix appears to improve the adhesion of the mesoporous film to a silicon wafer. These mesoporous silica-carbon composite films have appropriate characteristics for use in sensing applications.

  18. Influence of triblock copolymer (pluronic F127) on enhancing the physico-chemical properties and photocatalytic response of mesoporous TiO2

    NASA Astrophysics Data System (ADS)

    Samsudin, Emy Marlina; Hamid, Sharifah Bee Abd; Juan, Joon Ching; Basirun, Wan Jefrey

    2015-11-01

    The utilization of triblock copolymer, pluronic F127 as a structure directing agent for the preparation of TiO2 played an important role in enhancing the photocatalytic degradation rate of atrazine by a factor of 1.7. The mesoporous F127-TiO2 showed significant modification of morphology, particle and crystallite size, and presence of defect energy belt within the catalyst forbidden band as proven via photoluminescence spectra and x-ray photon spectroscopy. Hence the photogenerated carriers have longer lifespan to migrate to the catalyst surface for redox activities. Furtherance, surface reactive {0 0 1} facets proven by the formation of new geometrical single crystal of square and rhombus surfaces in F127-TiO2 facilitates atrazine degradation as well. The increased surface area of F127-TiO2 promotes greater atrazine absorption, thus governs improved interaction between absorbed atrazine molecules and surface generated active radicals as a pre-requisite for good photocatalytic activity. Interestingly, using the same synthesis procedure, it was observed that the addition of pluronic F127 significantly affects anatase crystal structure as opposed to the more thermodynamically stable rutile, generating 61% and 25% of total crystallite size modification for anatase and rutile, respectively. However, there were no changes on the final composition of anatase and rutile crystal structure. In overall, enhancement of the photocatalytic degradation of atrazine is ruled out to the following factors (1) modification of geometrical structures and size, (2) narrowing of band gap due to defect energy belt, (3) longer lifespan of photoexcited charges to the catalyst surface, (4) enhanced surface textural properties and (5) increased exposure of reactive {0 0 1} facets, which were all observed in F127-TiO2.

  19. Thermoreversible hydrogels based on triblock copolymers of poly(ethylene glycol) and carboxyl functionalized poly(ε-caprolactone): The effect of carboxyl group substitution on the transition temperature and biocompatibility in plasma.

    PubMed

    Safaei Nikouei, Nazila; Vakili, Mohammad Reza; Bahniuk, Markian S; Unsworth, Larry; Akbari, Ali; Wu, Jianping; Lavasanifar, Afsaneh

    2015-01-01

    In this study we report on the development, characterization and plasma protein interaction of novel thermoresponsive in situ hydrogels based on triblock copolymers of poly(ethylene glycol) (PEG) and poly(α-carboxyl-co-benzyl carboxylate)-ε-caprolactone (PCBCL) having two different degrees of carboxyl group substitution on the PCBCL block. Block copolymers were synthesized through ring-opening polymerization of α-benzyl carboxylate-ε-caprolactone by dihydroxy PEG, leading to the production of poly(α-benzyl carboxylate-ε-caprolactone)-PEG-poly(α-benzyl carboxylate-ε-caprolactone) (PBCL-PEG-PBCL). This was followed by partial debenzylation of PBCL blocks under controlled conditions, leading to the preparation of PCBCL-PEG-PCBCL triblock copolymers with 30 and 54mol.% carboxyl group substitution. Prepared PCBCL-PEG-PCBCL block copolymers have been shown to have a concentration-dependent sol to gel transition as a result of an increase in temperature above ∼29°C, as evidenced by the inverse flow method, differential scanning calorimetry and dynamic mechanical analysis. The sol-gel transition temperature/concentration and dynamic mechanical properties of the gel were found to be dependent on the level of carboxyl group substitution. Both hydrogels (30 and 54mol.% carboxyl group substitution) showed similar amounts of protein adsorption but striking differences in the profiles of the adsorbed proteome. Additionally, the two systems showed similarities in their clot formation kinetics but substantial differences in clot endpoints. The results show great promise for the above-mentioned thermoreversible in situ hydrogels as biocompatible materials for biomedical applications. PMID:25451305

  20. Biodegradable tri-block copolymer poly(lactic acid)-poly(ethylene glycol)-poly(l-lysine)(PLA-PEG-PLL) as a non-viral vector to enhance gene transfection.

    PubMed

    Fu, Chunhua; Sun, Xiaoli; Liu, Donghua; Chen, Zhijing; Lu, Zaijun; Zhang, Na

    2011-02-23

    Low cytotoxicity and high gene transfection efficiency are critical issues in designing current non-viral gene delivery vectors. The purpose of the present work was to synthesize the novel biodegradable poly (lactic acid)-poly(ethylene glycol)-poly(l-lysine) (PLA-PEG-PLL) copolymer, and explore its applicability and feasibility as a non-viral vector for gene transport. PLA-PEG-PLL was obtained by the ring-opening polymerization of Lys(Z)-NCA onto amine-terminated NH(2)-PEG-PLA, then acidolysis to remove benzyloxycarbonyl. The tri-block copolymer PLA-PEG-PLL combined the characters of cationic polymer PLL, PLA and PEG: the self-assembled nanoparticles (NPs) possessed a PEG loop structure to increase the stability, hydrophobic PLA segments as the core, and the primary ɛ-amine groups of lysine in PLL to electrostatically interact with negatively charged phosphate groups of DNA to deposit with the PLA core. The physicochemical properties (morphology, particle size and surface charge) and the biological properties (protection from nuclease degradation, plasma stability, in vitro cytotoxicity, and in vitro transfection ability in HeLa and HepG2 cells) of the gene-loaded PLA-PEG-PLL nanoparticles (PLA-PEG-PLL NPs) were evaluated, respectively. Agarose gel electrophoresis assay confirmed that the PLA-PEG-PLL NPs could condense DNA thoroughly and protect DNA from nuclease degradation. Initial experiments showed that PLA-PEG-PLL NPs/DNA complexes exhibited almost no toxicity and higher gene expression (up to 21.64% in HepG2 cells and 31.63% in HeLa cells) than PEI/DNA complexes (14.01% and 24.22%). These results revealed that the biodegradable tri-block copolymer PLA-PEG-PLL might be a very attractive candidate as a non-viral vector and might alleviate the drawbacks of the conventional cationic vectors/DNA complexes for gene delivery in vivo.

  1. Polydispersity-Driven Morphological Transitions in ABC Triblock Terpolymers

    NASA Astrophysics Data System (ADS)

    Meuler, Adam J.; Ellison, Christopher J.; Evans, Christopher M.; Hillmyer, Marc A.; Bates, Frank S.

    2008-03-01

    The use of synthetic polymerization techniques (e.g., controlled radical polymerizations) that often yield polydispersity indices greater than 1.1 is becoming more widespread. Advances in these methodologies have increased the number of monomers amenable to incorporation in block copolymers and will potentially drive commercial costs down. Since many block copolymer properties are governed by the underlying mesostructure, understanding the influence of polydispersity on morphological behavior should prove vital to the success of block copolymer commercialization efforts. This presentation will focus on polydispersity-driven morphological transitions in poly(isoprene-b-styrene-b-ethylene oxide) (ISO) triblock terpolymers. ISO triblocks with polydisperse polystyrene blocks were prepared by anionic polymerization and their morphological behavior was characterized using small-angle x-ray scattering and dynamic mechanical spectroscopy. Only lamellar microstructures were identified along the fI = fS isopleth for polydisperse ISO triblocks, while an orthorhombic network (O^70) was previously identified in monodisperse ISO triblocks.

  2. Biodegradable Tri-Block Copolymer Poly(lactic acid)-poly(ethylene glycol)-poly(l-lysine)(PLA-PEG-PLL) as a Non-Viral Vector to Enhance Gene Transfection

    PubMed Central

    Fu, Chunhua; Sun, Xiaoli; Liu, Donghua; Chen, Zhijing; Lu, Zaijun; Zhang, Na

    2011-01-01

    Low cytotoxicity and high gene transfection efficiency are critical issues in designing current non-viral gene delivery vectors. The purpose of the present work was to synthesize the novel biodegradable poly (lactic acid)-poly(ethylene glycol)-poly(l-lysine) (PLA-PEG-PLL) copolymer, and explore its applicability and feasibility as a non-viral vector for gene transport. PLA-PEG-PLL was obtained by the ring-opening polymerization of Lys(Z)-NCA onto amine-terminated NH2-PEG-PLA, then acidolysis to remove benzyloxycarbonyl. The tri-block copolymer PLA-PEG-PLL combined the characters of cationic polymer PLL, PLA and PEG: the self-assembled nanoparticles (NPs) possessed a PEG loop structure to increase the stability, hydrophobic PLA segments as the core, and the primary ɛ-amine groups of lysine in PLL to electrostatically interact with negatively charged phosphate groups of DNA to deposit with the PLA core. The physicochemical properties (morphology, particle size and surface charge) and the biological properties (protection from nuclease degradation, plasma stability, in vitro cytotoxicity, and in vitro transfection ability in HeLa and HepG2 cells) of the gene-loaded PLA-PEG-PLL nanoparticles (PLA-PEG-PLL NPs) were evaluated, respectively. Agarose gel electrophoresis assay confirmed that the PLA-PEG-PLL NPs could condense DNA thoroughly and protect DNA from nuclease degradation. Initial experiments showed that PLA-PEG-PLL NPs/DNA complexes exhibited almost no toxicity and higher gene expression (up to 21.64% in HepG2 cells and 31.63% in HeLa cells) than PEI/DNA complexes (14.01% and 24.22%). These results revealed that the biodegradable tri-block copolymer PLA-PEG-PLL might be a very attractive candidate as a non-viral vector and might alleviate the drawbacks of the conventional cationic vectors/DNA complexes for gene delivery in vivo. PMID:21541064

  3. Order-Order Transition of C → sdG → sL → S in ABC Triblock Copolymer Thin Film Induced by Solvent Vapor.

    PubMed

    Luo, Chunxia; Huang, Weihuan; Han, Yanchun

    2009-04-01

    The morphology transition of polystyrene-block-poly(butadiene)-block-poly(2-vinylpyridine) (SBV) triblock thin film induced in benzene vapor showing weak selectivity for PS is investigated. The order-order transitions (OOT) in the sequence of core-shell cylinders (C), sphere in 'diblock gyroid' (sdG), sphere in lamella (sL) and sphere (S) are observed. The projection along (111) direction in Gyroid phase (sdG(111)) is found to epitaxially grow from C(001) in the film. Instead of sdG(111), sdG(110)(0.1875) develops to the phase of sL. Consequently, the film experiences the transition sequence of sdG(111) → sdG(211) → sdG(110)(0.25)  → sdG(110)(0.1875) between C and sL. The mechanism is analyzed from the total surface area of the blocks.

  4. Comparative Fluorescence Resonance Energy-Transfer Study in Pluronic Triblock Copolymer Micelle and Niosome Composed of Biological Component Cholesterol: An Investigation of Effect of Cholesterol and Sucrose on the FRET Parameters.

    PubMed

    Roy, Arpita; Kundu, Niloy; Banik, Debasis; Sarkar, Nilmoni

    2016-01-14

    The formation of pluronic triblock copolymer (F127)-cholesterol-based niosome and its interaction with sugar (sucrose) molecules have been investigated. The morphology of F127-cholesterol -based niosome in the presence of sucrose has been successfully demonstrated using dynamic light scattering (DLS) and transmission electron microscopic (TEM) techniques. The DLS profiles and TEM images clearly suggest that the size of the niosome aggregates increases significantly in the presence of sucrose. In addition to structural characterization, a detailed comparative fluorescence resonance energy transfer (FRET) study has been carried out in these F127-containing aggregates, involving coumarin 153 (C153) as donor (D) and rhodamine 6G (R6G) as an acceptor (A) to monitor the dynamic heterogeneity of the systems. Besides, time-resolved anisotropy and fluorescence correlation spectroscopy measurements have been carried out to monitor the rotational and lateral diffusion motion in these F127-cholesterol-based aggregates using C153 and R6G, respectively. During the course of FRET study, we have observed multiple time constants of FRET inside the F127-cholesterol-based niosomes in contrast with the F127 micelle. This corresponds to the presence of more than one preferential donor-acceptor (D-A) distance in niosomes than in F127 micelle. FRET has also been successfully used to probe the effect of sucrose on the morphology of F127-cholesterol-based niosome. In the presence of sucrose, the time constant of FRET further increases as the D-A distances increase in sucrose-decorated niosome. Finally, the excitation-wavelength-dependent FRET studies have indicated that as the excitation of donor molecules varies from 408 to 440 nm the contribution of the faster rise component of the acceptor enhances considerably, which clearly establishes the dynamics heterogeneity of both systems. Our findings also indicate that FRET is completely intravesicular in nature in these block copolymer

  5. Comparative Fluorescence Resonance Energy-Transfer Study in Pluronic Triblock Copolymer Micelle and Niosome Composed of Biological Component Cholesterol: An Investigation of Effect of Cholesterol and Sucrose on the FRET Parameters.

    PubMed

    Roy, Arpita; Kundu, Niloy; Banik, Debasis; Sarkar, Nilmoni

    2016-01-14

    The formation of pluronic triblock copolymer (F127)-cholesterol-based niosome and its interaction with sugar (sucrose) molecules have been investigated. The morphology of F127-cholesterol -based niosome in the presence of sucrose has been successfully demonstrated using dynamic light scattering (DLS) and transmission electron microscopic (TEM) techniques. The DLS profiles and TEM images clearly suggest that the size of the niosome aggregates increases significantly in the presence of sucrose. In addition to structural characterization, a detailed comparative fluorescence resonance energy transfer (FRET) study has been carried out in these F127-containing aggregates, involving coumarin 153 (C153) as donor (D) and rhodamine 6G (R6G) as an acceptor (A) to monitor the dynamic heterogeneity of the systems. Besides, time-resolved anisotropy and fluorescence correlation spectroscopy measurements have been carried out to monitor the rotational and lateral diffusion motion in these F127-cholesterol-based aggregates using C153 and R6G, respectively. During the course of FRET study, we have observed multiple time constants of FRET inside the F127-cholesterol-based niosomes in contrast with the F127 micelle. This corresponds to the presence of more than one preferential donor-acceptor (D-A) distance in niosomes than in F127 micelle. FRET has also been successfully used to probe the effect of sucrose on the morphology of F127-cholesterol-based niosome. In the presence of sucrose, the time constant of FRET further increases as the D-A distances increase in sucrose-decorated niosome. Finally, the excitation-wavelength-dependent FRET studies have indicated that as the excitation of donor molecules varies from 408 to 440 nm the contribution of the faster rise component of the acceptor enhances considerably, which clearly establishes the dynamics heterogeneity of both systems. Our findings also indicate that FRET is completely intravesicular in nature in these block copolymer

  6. The Membrane-Active Tri-Block Copolymer Pluronic F-68 Profoundly Rescues Rat Hippocampal Neurons from Oxygen–Glucose Deprivation-Induced Death through Early Inhibition of Apoptosis

    PubMed Central

    Shelat, Phullara B.; Plant, Leigh D.; Wang, Janice C.; Lee, Elizabeth

    2013-01-01

    Pluronic F-68, an 80% hydrophilic member of the Pluronic family of polyethylene-polypropylene-polyethylene tri-block copolymers, protects non-neuronal cells from traumatic injuries and rescues hippocampal neurons from excitotoxic and oxidative insults. F-68 interacts directly with lipid membranes and restores membrane function after direct membrane damage. Here, we demonstrate the efficacy of Pluronic F-68 in rescuing rat hippocampal neurons from apoptosis after oxygen–glucose deprivation (OGD). OGD progressively decreased neuronal survival over 48 h in a severity-dependent manner, the majority of cell death occurring after 12 h after OGD. Administration of F-68 for 48 h after OGD rescued neurons from death in a dose-dependent manner. At its optimal concentration (30 μm), F-68 rescued all neurons that would have died after the first hour after OGD. This level of rescue persisted when F-68 administration was delayed 12 h after OGD. F-68 did not alter electrophysiological parameters controlling excitability, NMDA receptor-activated currents, or NMDA-induced increases in cytosolic calcium concentrations. However, F-68 treatment prevented phosphatidylserine externalization, caspase activation, loss of mitochondrial membrane potential, and BAX translocation to mitochondria, indicating that F-68 alters apoptotic mechanisms early in the intrinsic pathway of apoptosis. The profound neuronal rescue provided by F-68 after OGD and the high level of efficacy with delayed administration indicate that Pluronic copolymers may provide a novel, membrane-targeted approach to rescuing neurons after brain ischemia. The ability of membrane-active agents to block apoptosis suggests that membranes or their lipid components play prominent roles in injury-induced apoptosis. PMID:23884935

  7. Multifunctional triblock co-polymer mP3/4HB-b-PEG-b-lPEI for efficient intracellular siRNA delivery and gene silencing.

    PubMed

    Zhou, Li; Chen, Zhifei; Wang, Feifei; Yang, Xiuqun; Zhang, Biliang

    2013-04-01

    A non-viral siRNA carrier composed of mono-methoxy-poly (3-hydroxybutyrate-co-4-hydroxybutyrate)-block-polyethylene glycol-block-linear polyethyleneimine (mP3/4HB-b-PEG-b-lPEI) was synthesized using 1800 Da linear polyethyleneimine and evaluated for siRNA delivery. Our study demonstrated that siRNA could be efficiently combined with mP3/4HB-b-PEG-b-lPEI (mAG) co-polymer and was protected from nuclease degradation. The combined siRNA were released from the complexes easily under heparin competition. The particle size of the mAG/siRNA complexes was 158 nm, with a ζ-potential of around 28 mV. Atomic force microscopy images displayed spherical and homogeneously distributed complexes. The mAG block co-polymer displayed low cytotoxicity and efficient cellular uptake of Cy3-siRNA in A549 cells by flow cytometry and confocal microscopy. In vitro transfection efficiency of the block co-polymer was assessed using siRNA against luciferase in cultured A549-Luc, HeLa-Luc, HLF-Luc, A375-Luc and MCF-7-Luc cells. A higher transfection efficiency and lower cytotoxicity was obtained by mAG block co-polymer in five cell lines. Furthermore, a remarkable improvement in luciferase gene silencing efficiency of the mAG complex (up to 90-95%) over that of Lipofectamine™ 2000 (70-82%) was observed in HLF-Luc and A375-Luc cells. Additionally, a mAG/p65-siRNA complex also showed a better capability than Lipofectamine™ 2000/p65-siRNA complex to drastically reduce the p65 mRNA level down to 10-16% in HeLa, U251 and HUVEC cells at an N/P ratio of 70. PMID:23295402

  8. Internal Nanoparticle Structure of Temperature-Responsive Self-Assembled PNIPAM-b-PEG-b-PNIPAM Triblock Copolymers in Aqueous Solutions: NMR, SANS, and Light Scattering Studies.

    PubMed

    Filippov, Sergey K; Bogomolova, Anna; Kaberov, Leonid; Velychkivska, Nadiia; Starovoytova, Larisa; Cernochova, Zulfiya; Rogers, Sarah E; Lau, Wing Man; Khutoryanskiy, Vitaliy V; Cook, Michael T

    2016-05-31

    In this study, we report detailed information on the internal structure of PNIPAM-b-PEG-b-PNIPAM nanoparticles formed from self-assembly in aqueous solutions upon increase in temperature. NMR spectroscopy, light scattering, and small-angle neutron scattering (SANS) were used to monitor different stages of nanoparticle formation as a function of temperature, providing insight into the fundamental processes involved. The presence of PEG in a copolymer structure significantly affects the formation of nanoparticles, making their transition to occur over a broader temperature range. The crucial parameter that controls the transition is the ratio of PEG/PNIPAM. For pure PNIPAM, the transition is sharp; the higher the PEG/PNIPAM ratio results in a broader transition. This behavior is explained by different mechanisms of PNIPAM block incorporation during nanoparticle formation at different PEG/PNIPAM ratios. Contrast variation experiments using SANS show that the structure of nanoparticles above cloud point temperatures for PNIPAM-b-PEG-b-PNIPAM copolymers is drastically different from the structure of PNIPAM mesoglobules. In contrast with pure PNIPAM mesoglobules, where solidlike particles and chain network with a mesh size of 1-3 nm are present, nanoparticles formed from PNIPAM-b-PEG-b-PNIPAM copolymers have nonuniform structure with "frozen" areas interconnected by single chains in Gaussian conformation. SANS data with deuterated "invisible" PEG blocks imply that PEG is uniformly distributed inside of a nanoparticle. It is kinetically flexible PEG blocks which affect the nanoparticle formation by prevention of PNIPAM microphase separation. PMID:27159129

  9. Effects of Bile Salt Sodium Glycodeoxycholate on the Self-Assembly of PEO-PPO-PEO Triblock Copolymer P123 in Aqueous Solution.

    PubMed

    Bayati, Solmaz; Galantini, Luciano; Knudsen, Kenneth D; Schillén, Karin

    2015-12-22

    A comprehensive experimental study on the interaction between the PEO-PPO-PEO block copolymer P123 (EO20PO68EO20) and the anionic bile salt sodium glycodeoxycholate (NaGDC) in water has been performed. The work was aimed at investigating the suitability of using P123 as bile salt sequestrant beside the fundamental aspects of PEO-PPO-PEO block copolymer-bile salt interactions. Various experimental techniques including dynamic and static light scattering, small-angle X-ray scattering, and differential scanning calorimetry (DSC) were employed in combination with electrophoretic mobility measurements. The system was investigated at a constant P123 concentration of 1.74 mM and with varying bile salt concentrations up to approximately 250 mM NaGDC (or a molar ratio n(NaGDC)/n(P123) = 144). In the mixed P123-NaGDC solutions, the endothermic process related to the self-assembly of P123 was observed to gradually decrease in enthalpy and shift to higher temperatures upon progressive addition of NaGDC. To explain this effect, the formation of NaGDC micelles carrying partly dehydrated P123 unimers was proposed and translated into a stoichiometric model, which was able to fit the experimental DSC data. In the mixtures at low molar ratios, NaGDC monomers associated with the P123 micelle forming a charged "P123 micelle-NaGDC" complex with a dehydrated PPO core. These complexes disintegrated upon increasing NaGDC concentration to form small "NaGDC-P123" complexes visualized as bile salt micelles including one or a few P123 copolymer chains.

  10. Impact of hydrogenation on physicochemical and biomedical properties of pH-sensitive PMAA-b-HTPB-b-PMAA triblock copolymer drug carriers.

    PubMed

    Xu, Feng; Xu, Jing-Wen; Luo, Yan-Ling

    2016-05-01

    pH-Sensitive poly(methacrylic acid)-block-hydroxyl-terminated polybutadiene-block-poly(methacrylic acid) (PMAA-b-HTPB-b-PMAA) was synthesized and then hydrogenated in this work. The chain structure, phase behavior and thermal properties were characterized by(1)H NMR, FTIR, XRD, DSC, TGA, etc., and the physicochemical and biomedical properties were investigated via fluorescence spectroscopy, TEM, DLS, loading and release of drug and MTT, and so on. The experimental results indicated that the hydrogenation led to the change in the chain aggregate structure of hydrophobic HTPB blocks and the formation of more stable spherical core-shell micelle aggregates, and the critical micelle concentration decreased from 41.8 mg L(-1)before hydrogenation to 4.4 mg L(-1)after hydrogenation. The hydrogenated block copolymer micelle aggregates exhibited pH-triggered response, and could entrap twice as much hydrophobic drug as the unhydrided counterparts and the encapsulation efficiency was significantly improved, which makes them fine to meet the requirements for drug carriers. Therefore, the hydrogenated PMAA-b-HTPB-b-PMAA copolymer micelles as drug target release carriers can be well used in the field of prevention and treatment of cancers. PMID:26939939

  11. Living polymerization of butadiene at both chain ends via a bimetallic nickel initiator. Preparation of hydroxytelechelic poly(butadiene) and symmetric poly(isocyanide-b-butadiene-b-isocyanide) elastomeric triblock copolymers

    SciTech Connect

    Deming, T.J.; Novak, B.M. ); Ziller, J.W. )

    1994-03-23

    A bifunctional nickel initiator, bis([mu]-trifluoroacetato) ([eta][sup 3]:[eta][sup 3]-2,2[prime]-biallyl)dinickel(II), IV, was synthesized to promote the living polymerization of butadiene to high cis-1,4-content polymer with both chain ends active. Other potential initiators, [1,4-phenylenebis(([eta][sup 3]-1-allyl)nickel trifluoroacetate)][sub n], II, and [1,4-cyclohexanediylbis(([eta][sup 3]-1-allyl)-nickel trifluoroacetate)][sub n], III, were found to be completely ineffective due to intermolecular carboxylate bridges which gave the complexes polymeric structures. The intramolecular bridges in IV and its molecularity were confirmed by X-ray crystallography. IV cocrystallizes in space group P[bar 1] with 0.5 equiv of 2.3-bis((trifluoroacetoxy)methyl)-1,3-butadiene in the unit cell with constants of a = 9.5600(8) [angstrom], b = 9.6554(9) [angstrom], c = 11.7615(10) [angstrom]; [alpha] = 73.711(7)[degree], [beta] = 73.537(7)[degree], [gamma]= 71.938(7)[degree]; V = 967.50(15) [angstrom][sup 3]; and Z = 2. Refinement of the model, which contained a disordered C[sub 6]H[sub 8] unit, led to convergence with R[sub F] = 5.8%, R[sub WF] = 6.9%, and GOF = 2.21 for 276 variables refined against those 2852 data with [vert bar]F[sub o][vert bar]> 3.0[sigma]/([vert bar]F[sub o][vert bar]). The living polybutadiene samples were successfully used to prepare triblock copolymers of the structure poly(1-phenylethyl isocyanide-b-butadiene-b-1-phenylethyl isocyanide). 24 refs., 5 figs., 1 tab.

  12. Sustained intra-articular release of celecoxib from in situ forming gels made of acetyl-capped PCLA-PEG-PCLA triblock copolymers in horses.

    PubMed

    Petit, Audrey; Redout, Everaldo M; van de Lest, Chris H; de Grauw, Janny C; Müller, Benno; Meyboom, Ronald; van Midwoud, Paul; Vermonden, Tina; Hennink, Wim E; René van Weeren, P

    2015-01-01

    In this study, the intra-articular tolerability and suitability for local and sustained release of an in situ forming gel composed of an acetyl-capped poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide) (PCLA-PEG-PCLA) copolymer loaded with celecoxib was investigated in horse joints. The systems were loaded with two dosages of celecoxib, 50 mg/g ('low CLB gel') and 260 mg/g ('high CLB gel'). Subsequently, they were injected into the joints of five healthy horses. For 72 h after intra-articular injection, they induced a transient inflammatory response, which was also observed after application of Hyonate(®), a commercial formulation containing hyaluronic acid for the intra-articular treatment of synovitis in horses. However, only after administration of the 'high CLB gel' the horses showed signs of discomfort (lameness score: 1.6 ± 1.3 on a 5-point scale) 1 day after injection, which completely disappeared 3 days after injection. Importantly, there was no indication of cartilage damage. Celecoxib Cmax in the joints was reached at 8 h and 24 h after administration of the 'low CLB gel' and 'high CLB gel', respectively. In the joints, concentrations of celecoxib were detected 4 weeks post administration. Celecoxib was also detected in plasma at concentrations of 150 ng/ml at day 3 post administration and thereafter its concentration dropped below the detection limit. These results show that the systems were well tolerated after intra-articular administration and showed local and sustained release of celecoxib for 4 weeks with low and short systemic exposure to the drug, demonstrating that these injectable in situ forming hydrogels are promising vehicles for intra-articular drug delivery. PMID:25890740

  13. Surface rheology of PEO-PPO-PEO triblock copolymers at the air-water interface: comparison of spread and adsorbed layers.

    PubMed

    Blomqvist, B Rippner; Wärnheim, T; Claesson, P M

    2005-07-01

    The dilatational rheological properties of monolayers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)-type block copolymers at the air-water interface have been investigated by employing an oscillating ring trough method. The properties of adsorbed monolayers were compared to spread layers over a range of surface concentrations. The studied polymers were PEO26-PPO39-PEO26 (P85), PEO103-PPO40-PEO103 (F88), and PEO99-PPO65-PEO99 (F127). Thus, two of the polymers have similar PPO block size and two of them have similar PEO block size, which allows us to draw conclusions about the relationship between molecular structure and surface dilatational rheology. The dilatational properties of adsorbed monolayers were investigated as a function of time and bulk solution concentration. The time dependence was found to be rather complex, reflecting structural changes in the layer. When the dilatational modulus measured at different concentrations was replotted as a function of surface pressure, one unique master curve was obtained for each polymer. It was found that the dilatational behavior of spread (Langmuir) and adsorbed (Gibbs) monolayers of the same polymer is close to identical up to surface concentrations of approximately 0.7 mg/m2. At higher coverage, the properties are qualitatively alike with respect to dilatational modulus, although some differences are noticeable. Relaxation processes take place mainly within the interfacial layers by a redistribution of polymer segments. Several conformational transitions were shown to occur as the area per molecule decreased. PEO desorbs significantly from the interface at segmental areas below 20 A(2), while at higher surface coverage, we propose that segments of PPO are forced to leave the interface to form a mixed sublayer in the aqueous region. PMID:15982044

  14. Morphologies in Sulfonated Styrenic Pentablock Copolymer Membranes

    NASA Astrophysics Data System (ADS)

    Choi, Jae-Hong; Bramson, Matt; Winey, Karen I.

    2010-03-01

    Membranes of pentablock and triblock copolymers consisting of poly(tert-butyl styrene) (TBS), hydrogenated polyisoprene (HI), and partially sulfonated poly(styrene-ran-styrene sulfonate) (SS) were studied using small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The TBS-HI-SS-HI-TBS pentablock and TBS-HI-SS triblock copolymer membranes exhibit anisotropic microphase separated morphologies. Because the pentablock and triblock copolymers can be expected to have complex morphologies, thermal annealing was conducted to promote well-defined morphologies. The annealed membranes exhibit stronger peaks and more high order reflections in SAXS patterns, as well as better defined microstructures in the TEM. Electron microcopy studies with various staining protocols are underway to establish the morphology of the pentablock copolymer membranes including the size and shape of the three microdomains (TBS, HI and SS). We gratefully acknowledge Kraton Polymers, Inc. for materials.

  15. Self-assembly of the triblock copolymer 17R4 poly(propylene oxide)₁₄-poly(ethylene oxide)₂₄-poly(propylene oxide)₁₄ in D₂O.

    PubMed

    Kumi, Bryna C; Hammouda, Boualem; Greer, Sandra C

    2014-11-15

    Our recent investigation of the three regions of the phase diagram of 17R4 in D2O (Huff et al., 2011) has led us to study the copolymer structure in this system by small-angle neutron scattering, rheometry, and dynamic light scattering. In region I at low temperatures and copolymer concentrations (0-30°C, 0.1-0.2 mass fraction ω), the cloudy solution contains the copolymer in large clusters made of hydrophobic PPO-rich "knots" bridged by dissolved hydrophilic PEO chains. These clusters vanish in region I at the lower temperatures and concentrations (below 39°C and ω=0.01). In region I over long times (weeks) at 25°C, a white liquid/gel film forms at the air-D2O interface. In region II at temperatures above the micellization line (above about 35°C, at ω=0.22) the large clusters dissipate and unimers coexist with "flower micelles," where the PPO blocks are the centers of the micelles and the PEO blocks loop into the solvent. In region III at still higher temperatures (above about 40°C at ω=0.2), the solution separates into coexisting liquid phases, where the upper phase of higher copolymer concentration is in region II, and the lower phase is in region I. The concentrated upper phase may contain micelles so crowded as to form a network. PMID:25203912

  16. Multiblock copolymers exhibiting spatio-temporal structure with autonomous viscosity oscillation

    PubMed Central

    Onoda, Michika; Ueki, Takeshi; Shibayama, Mitsuhiro; Yoshida, Ryo

    2015-01-01

    Here we report an ABA triblock copolymer that can express microscopic autonomous formation and break-up of aggregates under constant condition to generate macroscopic viscoelastic self-oscillation of the solution. The ABA triblock copolymer is designed to have hydrophilic B segment and self-oscillating A segment at the both sides by RAFT copolymerization. In the A segment, a metal catalyst of chemical oscillatory reaction, i.e., the Belousov-Zhabotinsky (BZ) reaction, is introduced as a chemomechanical transducer to change the aggregation state of the polymer depending on the redox states. Time-resolved DLS measurements of the ABA triblock copolymer confirm the presence of a transitional network structure of micelle aggregations in the reduced state and a unimer structure in the oxidized state. This autonomous oscillation of a well-designed triblock copolymer enables dynamic biomimetic softmaterials with spatio-temporal structure. PMID:26511660

  17. Mechanistic analysis of Zein nanoparticles/PLGA triblock in situ forming implants for glimepiride

    PubMed Central

    Ahmed, Osama Abdelhakim Aly; Zidan, Ahmed Samir; Khayat, Maan

    2016-01-01

    Objectives The study aims at applying pharmaceutical nanotechnology and D-optimal fractional factorial design to screen and optimize the high-risk variables affecting the performance of a complex drug delivery system consisting of glimepiride–Zein nanoparticles and inclusion of the optimized formula with thermoresponsive triblock copolymers in in situ gel. Methods Sixteen nanoparticle formulations were prepared by liquid–liquid phase separation method according to the D-optimal fractional factorial design encompassing five variables at two levels. The responses investigated were glimepiride entrapment capacity (EC), particle size and size distribution, zeta potential, and in vitro drug release from the prepared nanoparticles. Furthermore, the feasibility of embedding the optimized Zein-based glimepiride nanoparticles within thermoresponsive triblock copolymers poly(lactide-co-glycolide)-block-poly(ethylene glycol)-block-poly(lactide-co-glycolide) in in situ gel was evaluated for controlling glimepiride release rate. Results Through the systematic optimization phase, improvement of glimepiride EC of 33.6%, nanoparticle size of 120.9 nm with a skewness value of 0.2, zeta potential of 11.1 mV, and sustained release features of 3.3% and 17.3% drug released after 2 and 24 hours, respectively, were obtained. These desirability functions were obtained at Zein and glimepiride loadings of 50 and 75 mg, respectively, utilizing didodecyldimethylammonium bromide as a stabilizer at 0.1% and 90% ethanol as a common solvent. Moreover, incorporating this optimized formulation in triblock copolymers-based in situ gel demonstrated pseudoplastic behavior with reduction of drug release rate as the concentration of polymer increased. Conclusion This approach to control the release of glimepiride using Zein nanoparticles/triblock copolymers-based in situ gel forming intramuscular implants could be useful for improving diabetes treatment effectiveness. PMID:26893561

  18. Effect of poly(ethylene oxide) homopolymer and two different poly(ethylene oxide-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers on morphological, optical, and mechanical properties of nanostructured unsaturated polyester.

    PubMed

    Builes, Daniel H; Hernández-Ortiz, Juan P; Corcuera, Ma Angeles; Mondragon, Iñaki; Tercjak, Agnieszka

    2014-01-22

    Novel nanostructured unsaturated polyester resin-based thermosets, modified with poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), and two poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) block copolymers (BCP), were developed and analyzed. The effects of molecular weights, blocks ratio, and curing temperatures on the final morphological, optical, and mechanical properties were reported. The block influence on the BCP miscibility was studied through uncured and cured mixtures of unsaturated polyester (UP) resins with PEO and PPO homopolymers having molecular weights similar to molecular weights of the blocks of BCP. The final morphology of the nanostructured thermosetting systems, containing BCP or homopolymers, was investigated, and multiple mechanisms of nanostructuration were listed and explained. By considering the miscibility of each block before and after curing, it was determined that the formation of the nanostructured matrices followed a self-assembly mechanism or a polymerization-induced phase separation mechanism. The miscibility between PEO or PPO blocks with one of two phases of UP matrix was highlighted due to its importance in the final thermoset properties. Relationships between the final morphology and thermoset optical and mechanical properties were examined. The mechanisms and physics behind the morphologies lead toward the design of highly transparent, nanostructured, and toughened thermosetting UP systems. PMID:24354274

  19. Effect of poly(ethylene oxide) homopolymer and two different poly(ethylene oxide-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers on morphological, optical, and mechanical properties of nanostructured unsaturated polyester.

    PubMed

    Builes, Daniel H; Hernández-Ortiz, Juan P; Corcuera, Ma Angeles; Mondragon, Iñaki; Tercjak, Agnieszka

    2014-01-22

    Novel nanostructured unsaturated polyester resin-based thermosets, modified with poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), and two poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) block copolymers (BCP), were developed and analyzed. The effects of molecular weights, blocks ratio, and curing temperatures on the final morphological, optical, and mechanical properties were reported. The block influence on the BCP miscibility was studied through uncured and cured mixtures of unsaturated polyester (UP) resins with PEO and PPO homopolymers having molecular weights similar to molecular weights of the blocks of BCP. The final morphology of the nanostructured thermosetting systems, containing BCP or homopolymers, was investigated, and multiple mechanisms of nanostructuration were listed and explained. By considering the miscibility of each block before and after curing, it was determined that the formation of the nanostructured matrices followed a self-assembly mechanism or a polymerization-induced phase separation mechanism. The miscibility between PEO or PPO blocks with one of two phases of UP matrix was highlighted due to its importance in the final thermoset properties. Relationships between the final morphology and thermoset optical and mechanical properties were examined. The mechanisms and physics behind the morphologies lead toward the design of highly transparent, nanostructured, and toughened thermosetting UP systems.

  20. 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.

  1. 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.

  2. Bioinspired catecholic copolymers for antifouling surface coatings.

    PubMed

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

    2013-05-01

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

  3. 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.

  4. Triblock copolyampholytes from 5-(N,N-dimethyl amino)isoprene styrene, and methacrylic acid: Synthesis and solution properties

    NASA Astrophysics Data System (ADS)

    Bieringer, R.; Abetz, V.; Müller, A. H. E.

    ABC triblock copolymers of the type poly[5-(N,N-dimethyl amino)isoprene]-block-polystyrene-block-poly(tert-butyl methacrylate) (AiST) were synthesized and hydrolyzed to yield poly[5-(N,N-dimethyl amino)isoprene]-block-polystyrene-block-poly(methacrylic acid) (AiSA) triblock copolyampholytes. Due to a complex solubility behavior the solution properties of these materials had to be investigated in THF/water solvent mixtures. Potentiometric titrations of AiSA triblock copolyampholytes showed two inflection points with the A block being deprotonated prior to the Ai hydrochloride block thus forming a polyzwitterion at the isoelectric point (iep). The aggregation behavior was studied by dynamic light scattering (DLS) and freeze-fracture/transmission electron microscopy (TEM). Large vesicular structures with almost pH-independent radii were observed.

  5. Templated self-assembly of square symmetry arrays from an ABC triblock terpolymer.

    PubMed

    Chuang, Vivian P; Gwyther, Jessica; Mickiewicz, Rafal A; Manners, Ian; Ross, Caroline A

    2009-12-01

    Self-assembly provides the ability to create well-controlled nanostructures with electronic or chemical functionality and enables the synthesis of a wide range of useful devices. Diblock copolymers self-assemble into periodic arrays of microdomains with feature sizes of typically 10-50 nm, and have been used to make a wide range of devices such as silicon capacitors and transistors, photonic crystals, and patterned magnetic media(1-3). However, the cylindrical or spherical microdomains in diblock copolymers generally form close-packed structures with hexagonal symmetry, limiting their device applications. Here we demonstrate self-assembly of square-symmetry patterns from a triblock terpolymer in which one organometallic block imparts high etch selectivity and etch resistance. Long-range order is imposed on the microdomain arrays by self-assembly on topographical substrates, and the orientation of both square lattices and in-plane cylinders is controlled by the substrate chemistry. Pattern transfer is demonstrated by making an array of square-packed 30 nm tall, 20 nm diameter silica pillars. Templated self-assembly of triblock terpolymers can generate nanostructures with geometries that are unattainable from diblock copolymers, significantly enhancing the capabilities of block copolymer lithography.

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

    PubMed

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

    2015-06-28

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

  7. 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.

  8. 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

  9. Morphologies of ABC Triblock Terpolymer Melts Containing Poly(Cyclohexadiene): Effects of Conformational Asymmetry

    SciTech Connect

    Kumar, Rajeev; Sides, Scott W.; Goswami, Monojoy; Sumpter, Bobby G.; Hong, Kunlun; Wu, Xiaodong; Russell, Thomas P.; Gido, Samuel P.; Misichronis, Konstantinos; Rangou, Sofia; Avgeropoulos, Apostolos; Tsoukatos, Thodoris; Hadjichristidis, Nikos; Beyer, Frederick L.; Mays, Jimmy W.

    2013-02-12

    We have synthesized linear ABC triblock terpolymers containing poly(1,3-cyclohexadiene), PCHD, as an end block and characterized their morphologies in the melt. Specifically, we have studied terpolymers containing polystyrene (PS), polybutadiene (PB), and polyisoprene (PI) as the other blocks. Systematically varying the ratio of 1,2- /1,4-microstructures of poly(1,3-cyclohexadiene), we have studied the effects of conformational asymmetry among the three blocks on the morphologies using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and self-consistent field theory (SCFT) performed with PolySwift++. Our work reveals that the triblock terpolymer melts containing a high percentage of 1,2-microstructures in the PCHD block are disordered at 110 °C for all the samples, independent of sequence and volume fraction of the blocks. In contrast, the triblock terpolymer melts containing a high percentage of 1,4-microstructure form regular morphologies known from the literature. The accuracy of the SCFT calculations depends on calculating the χ parameters that quantify the repulsive interactions between different monomers. Simulations using χ values obtained from solubility parameters and group contribution methods are unable to reproduce the morphologies as seen in the experiments. However, SCFT calculations accounting for the enhancement of the χ parameter with an increase in the conformational asymmetry lead to an excellent agreement between theory and experiments. These results highlight the importance of conformational asymmetry in tuning the χ parameter and, in turn, morphologies in block copolymers.

  10. Morphologies of ABC triblock terpolymer melts containing poly(cyclohexadiene): effects of conformational asymmetry.

    PubMed

    Kumar, Rajeev; Sides, Scott W; Goswami, Monojoy; Sumpter, Bobby G; Hong, Kunlun; Wu, Xiaodong; Russell, Thomas P; Gido, Samuel P; Misichronis, Konstantinos; Rangou, Sofia; Avgeropoulos, Apostolos; Tsoukatos, Thodoris; Hadjichristidis, Nikos; Beyer, Frederick L; Mays, Jimmy W

    2013-02-12

    We have synthesized linear ABC triblock terpolymers containing poly(1,3-cyclohexadiene), PCHD, as an end block and characterized their morphologies in the melt. Specifically, we have studied terpolymers containing polystyrene (PS), polybutadiene (PB), and polyisoprene (PI) as the other blocks. Systematically varying the ratio of 1,2- /1,4-microstructures of poly(1,3-cyclohexadiene), we have studied the effects of conformational asymmetry among the three blocks on the morphologies using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and self-consistent field theory (SCFT) performed with PolySwift++. Our work reveals that the triblock terpolymer melts containing a high percentage of 1,2-microstructures in the PCHD block are disordered at 110 °C for all the samples, independent of sequence and volume fraction of the blocks. In contrast, the triblock terpolymer melts containing a high percentage of 1,4-microstructure form regular morphologies known from the literature. The accuracy of the SCFT calculations depends on calculating the χ parameters that quantify the repulsive interactions between different monomers. Simulations using χ values obtained from solubility parameters and group contribution methods are unable to reproduce the morphologies as seen in the experiments. However, SCFT calculations accounting for the enhancement of the χ parameter with an increase in the conformational asymmetry lead to an excellent agreement between theory and experiments. These results highlight the importance of conformational asymmetry in tuning the χ parameter and, in turn, morphologies in block copolymers. PMID:23259866

  11. Fluorine-Containing ABC Linear Triblock Terpolymers: Synthesis and Self-assembly in Solution

    SciTech Connect

    He, Lihong; Hinestrosa Salazar, Juan P; Pickel, Joseph M; Kilbey, II, S Michael; Mays, Jimmy; Zhang, Shanju; Bucknall, David G.; Hong, Kunlun

    2011-01-01

    In this paper a fluorine-containing monomer, 2-fluroroethyl methacrylate (2FEMA) was used to synthesize the linear triblock terpolymer poly(n-butyl methacrylate)-poly(methyl methacrylate)-poly(2-fluoroethyl methacrylate) (PnBMA-PMMA-P2FEMA). A kinetic study of the homopolymerization of 2FEMA by reversible addition-fragmentation chain transfer (RAFT) polymerization showed that it demonstrates living character and produces well defined polymers with reasonably narrow polydispersities (~1.30). Triblock terpolymers were prepared sequentially using a purified Macro-CTA at 70 oC, resulting in final terpolymers with high Dp for each block (>150) and with polydispersities between 1.6 and 2.1. The structure and molecular weights of the resultant PnBMA-PMMA-P2FEMA triblock terpolymers were characterized via 1H NMR, 19F NMR, and gel permeation chromatography (GPC). Self-assembly of these polymers was carried out in a selective solvent and the micellar aggregates (MAs) thereby formed were analyzed using scanning electron microscopy (SEM) and dynamic light scattering (DLS). It was confirmed from SEM that these copolymers could directly self-organize into large compound micelles in tetrahydrofuran/methanol with different diameters, depending on polymer composition.

  12. Structural materials research for lighter-than-air systems

    NASA Technical Reports Server (NTRS)

    Alley, V. L., Jr.; Mchatton, A. D.

    1975-01-01

    Inflatable systems have widespread applications in military, government, and industrial sectors. Improvements in inflatable materials have followed each salient advancement in textiles. The new organic fiber, Kevlar, is a recent and most significant advancement that justified reexamination of old and new inflatable materials' applications. A fertile frontier exists in integrating Kevlar with various other material combinations, in optimization of geometric features, and in selection of thermomechanical characteristics' compatibility with the environment. Expectations regarding Kevlar have been justified by the performance of two experimental materials. Styrene-butadiene-styrene block copolymers appear promising as a constituent adhesive for low temperature applications. Biaxial testing for both strength and material elastic properties is a technology area needing greater awareness and technology growth along with improved facilities. Because of dramatic materials' advancements, inflatable systems appear to be moving toward an increased position in tomorrow's aerospace industry.

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

    NASA Astrophysics Data System (ADS)

    Cho, Junhan

    2014-03-01

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

  14. Hierarchical templating of a BiFeO3-CoFe2O4 multiferroic nanocomposite by a triblock terpolymer film.

    PubMed

    Choi, Hong Kyoon; Aimon, Nicolas M; Kim, Dong Hun; Sun, Xue Yin; Gwyther, Jessica; Manners, Ian; Ross, Caroline A

    2014-09-23

    A process route to fabricate templated BiFeO3/CoFe2O4 (BFO/CFO) vertical nanocomposites is presented in which the self-assembly of the BFO/CFO is guided using a self-assembled triblock terpolymer. A linear triblock terpolymer was selected instead of a diblock copolymer in order to produce a square-symmetry template, which had a period of 44 nm. The triblock terpolymer pattern was transferred to a (001) Nb:SrTiO3 substrate to produce pits that formed preferential sites for the nucleation of CFO crystals, in contrast to the BFO, which wetted the flat regions of the substrate. The crystallographic orientation and magnetic properties of the templated BFO/CFO were characterized.

  15. Rational design of ABC triblock terpolymer solution nanostructures with controlled patch morphology

    NASA Astrophysics Data System (ADS)

    Löbling, Tina I.; Borisov, Oleg; Haataja, Johannes S.; Ikkala, Olli; Gröschel, André H.; Müller, Axel H. E.

    2016-06-01

    Block copolymers self-assemble into a variety of nanostructures that are relevant for science and technology. While the assembly of diblock copolymers is largely understood, predicting the solution assembly of triblock terpolymers remains challenging due to complex interplay of block/block and block/solvent interactions. Here we provide guidelines for the self-assembly of linear ABC triblock terpolymers into a large variety of multicompartment nanostructures with C corona and A/B cores. The ratio of block lengths NC/NA thereby controls micelle geometry to spheres, cylinders, bilayer sheets and vesicles. The insoluble blocks then microphase separate to core A and surface patch B, where NB controls the patch morphology to spherical, cylindrical, bicontinuous and lamellar. The independent control over both parameters allows constructing combinatorial libraries of unprecedented solution nanostructures, including spheres-on-cylinders/sheets/vesicles, cylinders-on-sheets/vesicles, and sheets/vesicles with bicontinuous or lamellar membrane morphology (patchy polymersomes). The derived parameters provide a logical toolbox towards complex self-assemblies for soft matter nanotechnologies.

  16. Rational design of ABC triblock terpolymer solution nanostructures with controlled patch morphology

    PubMed Central

    Löbling, Tina I.; Borisov, Oleg; Haataja, Johannes S.; Ikkala, Olli; Gröschel, André H.; Müller, Axel H. E.

    2016-01-01

    Block copolymers self-assemble into a variety of nanostructures that are relevant for science and technology. While the assembly of diblock copolymers is largely understood, predicting the solution assembly of triblock terpolymers remains challenging due to complex interplay of block/block and block/solvent interactions. Here we provide guidelines for the self-assembly of linear ABC triblock terpolymers into a large variety of multicompartment nanostructures with C corona and A/B cores. The ratio of block lengths NC/NA thereby controls micelle geometry to spheres, cylinders, bilayer sheets and vesicles. The insoluble blocks then microphase separate to core A and surface patch B, where NB controls the patch morphology to spherical, cylindrical, bicontinuous and lamellar. The independent control over both parameters allows constructing combinatorial libraries of unprecedented solution nanostructures, including spheres-on-cylinders/sheets/vesicles, cylinders-on-sheets/vesicles, and sheets/vesicles with bicontinuous or lamellar membrane morphology (patchy polymersomes). The derived parameters provide a logical toolbox towards complex self-assemblies for soft matter nanotechnologies. PMID:27352897

  17. Rational design of ABC triblock terpolymer solution nanostructures with controlled patch morphology.

    PubMed

    Löbling, Tina I; Borisov, Oleg; Haataja, Johannes S; Ikkala, Olli; Gröschel, André H; Müller, Axel H E

    2016-06-29

    Block copolymers self-assemble into a variety of nanostructures that are relevant for science and technology. While the assembly of diblock copolymers is largely understood, predicting the solution assembly of triblock terpolymers remains challenging due to complex interplay of block/block and block/solvent interactions. Here we provide guidelines for the self-assembly of linear ABC triblock terpolymers into a large variety of multicompartment nanostructures with C corona and A/B cores. The ratio of block lengths NC/NA thereby controls micelle geometry to spheres, cylinders, bilayer sheets and vesicles. The insoluble blocks then microphase separate to core A and surface patch B, where NB controls the patch morphology to spherical, cylindrical, bicontinuous and lamellar. The independent control over both parameters allows constructing combinatorial libraries of unprecedented solution nanostructures, including spheres-on-cylinders/sheets/vesicles, cylinders-on-sheets/vesicles, and sheets/vesicles with bicontinuous or lamellar membrane morphology (patchy polymersomes). The derived parameters provide a logical toolbox towards complex self-assemblies for soft matter nanotechnologies.

  18. 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.

  19. Well-defined organic nanotubes from multicomponent bottlebrush copolymers.

    PubMed

    Huang, Kun; Rzayev, Javid

    2009-05-20

    Bottlebrush copolymers are comblike macromolecules with densely grafted polymeric branches that adopt a cylindrical shape in solutions. We demonstrate a new method for the preparation of organic nanotubes by single molecule templating of core-shell bottlebrush copolymers. Multicomponent bottlebrush copolymers with well-defined structural parameters are synthesized by a combination of different living polymerization methods. Tubular structures can be prepared by cross-linking the shell layer and selectively etching out the core. The shape and size of original bottlebrush macromolecules are preserved during these transformations, which leads to the formation of well-defined organic nanotubes. The length and diameter of nanotubes are dictated by the length of the backbones and branches of the polymeric precursors, respectively. Water-soluble nanotubes with a hydrophobic interior can be prepared from bottlebrush copolymers with triblock copolymer branches. Herein, we outline molecular design strategies to fabricate nanotubes with controlled lengths, open pores, and different solubility characteristics.

  20. Synthesis, Characterization (Molecular-Morphological) and Theoretical Morphology Predictions of Poly(cyclohexadiene) Containing Linear Triblock Terpolymers

    SciTech Connect

    Kumar, Rajeev; Dadmun, Mark D; Sumpter, Bobby G; Mays, Jimmy; Avgeropoulos, Apostolos; Zafeiropoulos, N.E.; Misichoronis, K.; Rangou, S.; Ashcraft, E.

    2013-01-01

    The synthesis via anionic polymerization of six linear triblock terpolymers with various sequences of blocks such as PS (polystyrene), PB (polybutadiene), PI (polyisoprene) and PCHD (poly(1,3-cyclohexadiene)) is reported. The synthesis of the terpolymers was accomplished by the use of anionic polymerization with high vacuum techniques and sequential monomer addition. Molecular characterization of the samples was performed via size exclusion chromatography and membrane osmometry to measure polydispersity indices and the number-average molecular weights, respectively. Proton nuclear magnetic resonance spectroscopy was adopted to verify the type of microstructure for the polydienes as well as to calculate the molar composition. Structural characterization was performed via transmission electron microscopy and small angle X-ray scattering and several morphologies were observed including one which has not been reported previously. Real-space self-consistent field theory (SCFT) without a priori knowledge about the symmetry of the periodic structures was used to elucidate the thermodynamics of the synthesized triblock copolymers.

  1. New Linear and Star-Shaped Thermogelling Poly([R]-3-hydroxybutyrate) Copolymers.

    PubMed

    Barouti, Ghislaine; Liow, Sing Shy; Dou, Qingqing; Ye, Hongye; Orione, Clément; Guillaume, Sophie M; Loh, Xian Jun

    2016-07-18

    The synthesis of multi-arm poly([R]-3-hydroxybutyrate) (PHB)-based triblock copolymers (poly([R]-3-hydroxybutyrate)-b-poly(N-isopropylacrylamide)-b-[[poly(methyl ether methacrylate)-g-poly(ethylene glycol)]-co-[poly(methacrylate)-g-poly(propylene glycol)

  2. Mixing thermodynamics of block-random copolymers

    NASA Astrophysics Data System (ADS)

    Beckingham, Bryan Scott

    regular mixing prediction, XA-ArB = fB2 XA-B, thereby confirming the utility of this simple relationship in designing block copolymers with targeted interaction strengths using only these two common monomers. Thus, this fB 2 scaling is a useful "design rule" for tuning the interblock segregation strength in A-ArB (and B-ArB) block-random copolymers using styrene and isoprene as constituents. The reduction in XA-ArB over X A-B permits the synthesis of polymers having much larger M and domain spacing d while maintaining a thermally-accessible ODT; measured domain spacings are found to closely follow the expected scaling, d ~ X1/6M2/3. The decoupling of the order-disorder transition temperature from polymer molecular weight---and thereby interdomain spacing---provides an additional means to alter the polymer structure-property dynamic through synthesis, in addition to more common molecular variations, such as changes in block sequence, length of the blocks, and number of blocks. A similar examination of the interaction energy densities between E (hydrogenated Bd) and both hydrogenated derivatives of random copolymers of styrene and isoprene (SrhI and VCHrhI) found large positive deviations from regular mixing in the E-SrhI system and smaller but significant negative deviations in the E-VCHrhI system. Nevertheless, a ternary mixing model ("copolymer equation"), using independently-determined values of the three component interaction energy densities, is found to provide a good representation of the experimental interaction energies. Random copolymer blocks are also incorporated into linear A-B-C triblock copolymers, and the extent of block microphase separation in nonfrustrated E-hI-ArhI, where A is either S or VCH, triblock copolymers forming a "three-domain, four-layer" lamellar morphology is examined. Specifically, the extent of separation between the B and C blocks is probed, for the case where the B and C blocks are sufficiently compatible that they would not be

  3. Junction-Controlled Elasticity of Single-Walled Carbon Nanotube Dispersions in Acrylic Copolymer Gels and Solutions

    SciTech Connect

    Schoch, Andrew B.; Shull, Kenneth R.; Brinson, L. Catherine

    2008-08-26

    Oscillatory shear rheometry is used to study the mechanical response of single-walled carbon nanotubes dispersed in solutions of acrylic diblock or triblock copolymers in 2-ethyl-1-hexanol. Thermal transitions in the copolymer solutions provide a route for the easy processing of these composite materials, with excellent dispersion of the nanotubes as verified by near-infrared photoluminescence spectroscopy. The nanotube dispersions form elastic networks with properties that are controlled by the junction points between nanotubes, featuring a temperature-dependent elastic response that is controlled by the dynamic properties of the matrix copolymer solution. The data are consistent with the formation of micelle-like aggregates around the nanotubes. At low temperatures the core-forming poly(methyl methacrylate) blocks are glassy, and the overall mechanical response of the composite does not evolve with time. At higher temperatures the enhanced mobility of the core-forming blocks enables the junctions to achieve more intimate nanotube-nanotube contact, and the composite modulus increases with time. These aging effects are observed in both diblock and triblock copolymer solutions but are partially reversed in the triblock solutions by cooling through the gel transition of the triblock copolymer. This result is attributed to the generation of internal stresses during gelation and the ability of these stresses to break or weaken the nanotube junctions.

  4. 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.

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

    PubMed

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

    2012-08-01

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

  6. Toward Anisotropic Hybrid Materials: Directional Crystallization of Amphiphilic Polyoxazoline-Based Triblock Terpolymers.

    PubMed

    Rudolph, Tobias; von der Lühe, Moritz; Hartlieb, Matthias; Norsic, Sebastien; Schubert, Ulrich S; Boisson, Christophe; D'Agosto, Franck; Schacher, Felix H

    2015-10-27

    We present the design and synthesis of a linear ABC triblock terpolymer for the bottom-up synthesis of anisotropic organic/inorganic hybrid materials: polyethylene-block-poly(2-(4-(tert-butoxycarbonyl)amino)butyl-2-oxazoline)-block-poly(2-iso-propyl-2-oxazoline) (PE-b-PBocAmOx-b-PiPrOx). The synthesis was realized via the covalent linkage of azide-functionalized polyethylene and alkyne functionalized poly(2-alkyl-2-oxazoline) (POx)-based diblock copolymers exploiting copper-catalyzed azide-alkyne cycloaddition (CuAAC) chemistry. After purification of the resulting triblock terpolymer, the middle block was deprotected, resulting in a primary amine in the side chain. In the next step, solution self-assembly into core-shell-corona micelles in aqueous solution was investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Subsequent directional crystallization of the corona-forming block, poly(2-iso-propyl-2-oxazoline), led to the formation of anisotropic superstructures as demonstrated by electron microscopy (SEM and TEM). We present hypotheses concerning the aggregation mechanism as well as first promising results regarding the selective loading of individual domains within such anisotropic nanostructures with metal nanoparticles (Au, Fe3O4). PMID:26372093

  7. ABC triblock terpolymer self-assembled core-shell-corona nanotubes with high aspect ratios.

    PubMed

    Wang, Lulu; Huang, Haiying; He, Tianbai

    2014-08-01

    Nanotubes have attracted considerable attention due to their unique 1D hollow structure; however, the fabrication of pure nanotubes via block copolymer self-assembly remains a challenge. In this work, the successful preparation of core-shell-corona (CSC) nanotubular micelles with uniform diameter and high aspect ratio is reported, which is achieved via self-assembly of a poly (styrene-b-4-vinyl pyridine-b-ethylene oxide) triblock terpolymer in binary organic solvents with assistance of solution thermal annealing. Via direct visualization of trapped intermediates, the nanotube is believed to be formed via large sphere-large solid cylinderical aggregates-nanotube transformations, wherein the unique solid to hollow transition accompanied with the unidirectional growth is distinct from conventional pathway. In addition, by virtue of the CSC structure, gold nanoparticles are able to be selectively incorporated into different micellar domains of the nanotubes, which may have potential applications in nanoscience and nanotechnology.

  8. Equilibrium crystal phases of triblock Janus colloids

    NASA Astrophysics Data System (ADS)

    Reinhart, Wesley F.; Panagiotopoulos, Athanassios Z.

    2016-09-01

    Triblock Janus colloids, which are colloidal spheres decorated with attractive patches at each pole, have recently generated significant interest as potential building blocks for functional materials. Their inherent anisotropy is known to induce self-assembly into open structures at moderate temperatures and pressures, where they are stabilized over close-packed crystals by entropic effects. We present a numerical investigation of the equilibrium phases of triblock Janus particles with many different patch geometries in three dimensions, using Monte Carlo simulations combined with free energy calculations. In all cases, we find that the free energy difference between crystal polymorphs is less than 0.2 kBT per particle. By varying the patch fraction and interaction range, we show that large patches stabilize the formation of structures with four bonds per patch over those with three. This transition occurs abruptly above a patch fraction of 0.30 and has a strong dependence on the interaction range. Furthermore, we find that a short interaction range favors four bonds per patch, with longer range increasingly stabilizing structures with only three bonds per patch. By quantifying the effect of patch geometry on the stability of the equilibrium crystal structures, we provide insights into the fundamental design rules for constructing complex colloidal crystals.

  9. Equilibrium crystal phases of triblock Janus colloids.

    PubMed

    Reinhart, Wesley F; Panagiotopoulos, Athanassios Z

    2016-09-01

    Triblock Janus colloids, which are colloidal spheres decorated with attractive patches at each pole, have recently generated significant interest as potential building blocks for functional materials. Their inherent anisotropy is known to induce self-assembly into open structures at moderate temperatures and pressures, where they are stabilized over close-packed crystals by entropic effects. We present a numerical investigation of the equilibrium phases of triblock Janus particles with many different patch geometries in three dimensions, using Monte Carlo simulations combined with free energy calculations. In all cases, we find that the free energy difference between crystal polymorphs is less than 0.2 kBT per particle. By varying the patch fraction and interaction range, we show that large patches stabilize the formation of structures with four bonds per patch over those with three. This transition occurs abruptly above a patch fraction of 0.30 and has a strong dependence on the interaction range. Furthermore, we find that a short interaction range favors four bonds per patch, with longer range increasingly stabilizing structures with only three bonds per patch. By quantifying the effect of patch geometry on the stability of the equilibrium crystal structures, we provide insights into the fundamental design rules for constructing complex colloidal crystals. PMID:27609002

  10. 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.

  11. Increasing the Mechanical Strength of Block Polymer Ion Gels Through the Stepwise Self-Assembly of a Thermoresponsive ABC Triblock Terpolymer

    NASA Astrophysics Data System (ADS)

    Hall, Cecilia; Zhou, Can; Danielsen, Scott; Lodge, Timothy

    Blends of network-forming block polymers and ionic liquids have remarkable potential for solid electrolytes, as they allow the combination of desirable mechanical and electrical properties. While ABA triblock copolymers have successfully been implemented as the network component of ion gels, these networks contain looped defects, where the endblocks of the polymer loop back into the same spherical core instead of forming a bridge between two cores. We demonstrate that the ABC triblock terpolymer poly(ethylene-alt-propylene)-block-poly(ethylene oxide)-block-poly(N-isopropylacrylamide) (PEP-b-PEO-b-PNIPAm) in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide forms a thermoreversible gel network with negligible looping defects. PEP-core micelles exist at all temperatures, while cooling causes association of the PNIPAm micelle corona to form a bridging network. Small-angle x-ray scattering and dynamic light scattering were used to characterize the high-temperature micelles. These gels show enhanced mechanical properties and the ability to form gels at lower concentrations than the corresponding thermoresponsive ABA triblock copolymers.

  12. In vitro drug release behavior, mechanism and antimicrobial activity of rifampicin loaded low molecular weight PLGA-PEG-PLGA triblock copolymeric nanospheres.

    PubMed

    Gajendiran, M; Divakar, S; Raaman, N; Balasubramanian, S

    2013-12-01

    Poly (lactic-co-glycolic acid) (PLGA (92:8)) and a series of PLGA-PEG-PLGA tri block copolymers were synthesized by direct melt polycondensation. The copolymers were characterized by FTIR, and 1HNMR spectroscopic techniques, viscosity, gel permeation chromatography (GPC) and powder x-ray diffraction (XRD). The rifampicin (RIF) loaded polymeric nanospheres (NPs) were prepared by ultrasonication-W/O emulsification technique. The NPs have been characterized by field emission scanning electron microscopy (FESEM), TEM, powder X-ray diffraction (XRD), UVvisible spectroscopy and DLS measurements. The drug loaded triblock copolymeric NPs have five folds higher drug content and drug loading efficiency than that of PLGA microspheres (MPs). The in vitro drug release study shows that the drug loaded NPs showed an initial burst release after that sustained release up to 72 h. All the triblock copolymeric NPs follow anomalous drug diffusion mechanism while the PLGA MPs follow non-Fickian super case-II mechanism up to 12 h. The overall in-vitro release follows second order polynomial kinetics up to 72 h. The antimicrobial activity of the RIF loaded polymer NPs was compared with that of pure RIF and tetracycline (TA). The RIF loaded triblock copolymeric NPs inhibited the bacterial growth more effectively than the pure RIF and TA.

  13. Structure and Self-Assembly of Oligocarbonate-Fluorene End Functionalized Poly (ethylene glycol) ABA Triblock Polymer

    NASA Astrophysics Data System (ADS)

    Wei, Guangmin; Prabhu, Vivek; Venkataraman, Shrinivas; Yang, Yi Yan; Hedrick, James; Vivek Prabhu Team; Shrinivas Venkataraman, Yi Yan Yang Collaboration; James Hedrick Collaboration

    Hierarchical structures of oligocarbonate-fluorene end-functionalized poly(ethylene glycol) triblock copolymer (P(F-TMC)m-PEG444-P(F-TMC)m) were characterized by light scattering, atomic force microscopy, and Ultraviolet-visible spectroscopy in dilute regime in water, a poor solvent of F-TMC block. The evidence for pai-pai stacked of F-TMC block in self-assembled structure was provided. The self-assembly behavior is highly dependent on concentration and F-TMC block length, m. The presence of clusters dominates the population of scatterers once m is larger than 2, where there is no clear evidence of a separation of micelles and clusters. The molecular aggregation driven by F-TMC groups appears too strong to permit labile micelle-cluster dynamics as observed with m = 2 and 1.2. The non-mean field scaling of the aggregation number, when compared to models for triblock copolymers, highlights the need for a molecular-based model to predict the self-assembly at low end-group numbers. In our case, the end-groups are oligomers, so the comparison to Flory scaling may not be justified.

  14. Preparation and in vitro evaluation of doxorubicin-loaded Fe3O4 magnetic nanoparticles modified with biocompatible copolymers

    PubMed Central

    Akbarzadeh, Abolfazl; Mikaeili, Haleh; Zarghami, Nosratollah; Mohammad, Rahmati; Barkhordari, Amin; Davaran, Soodabeh

    2012-01-01

    Background Superparamagnetic iron oxide nanoparticles are attractive materials that have been widely used in medicine for drug delivery, diagnostic imaging, and therapeutic applications. In our study, superparamagnetic iron oxide nanoparticles and the anticancer drug, doxorubicin hydrochloride, were encapsulated into poly (D, L-lactic-co-glycolic acid) poly (ethylene glycol) (PLGA-PEG) nanoparticles for local treatment. The magnetic properties conferred by superparamagnetic iron oxide nanoparticles could help to maintain the nanoparticles in the joint with an external magnet. Methods A series of PLGA:PEG triblock copolymers were synthesized by ring-opening polymerization of D, L-lactide and glycolide with different molecular weights of polyethylene glycol (PEG2000, PEG3000, and PEG4000) as an initiator. The bulk properties of these copolymers were characterized using 1H nuclear magnetic resonance spectroscopy, gel permeation chromatography, Fourier transform infrared spectroscopy, and differential scanning calorimetry. In addition, the resulting particles were characterized by x-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometry. Results The doxorubicin encapsulation amount was reduced for PLGA:PEG2000 and PLGA:PEG3000 triblock copolymers, but increased to a great extent for PLGA:PEG4000 triblock copolymer. This is due to the increased water uptake capacity of the blended triblock copolymer, which encapsulated more doxorubicin molecules into a swollen copolymer matrix. The drug encapsulation efficiency achieved for Fe3O4 magnetic nanoparticles modified with PLGA:PEG2000, PLGA:PEG3000, and PLGA:PEG4000 copolymers was 69.5%, 73%, and 78%, respectively, and the release kinetics were controlled. The in vitro cytotoxicity test showed that the Fe3O4-PLGA:PEG4000 magnetic nanoparticles had no cytotoxicity and were biocompatible. Conclusion There is potential for use of these nanoparticles for biomedical application. Future work

  15. Tribological Behavior of Aqueous Copolymer Lubricant in Mixed Lubrication Regime.

    PubMed

    Ta, Thi D; Tieu, A Kiet; Zhu, Hongtao; Zhu, Qiang; Kosasih, Prabouno B; Zhang, Jie; Deng, Guanyu

    2016-03-01

    Although a number of experiments have been attempted to investigate the lubrication of aqueous copolymer lubricant, which is applied widely in metalworking operations, a comprehensive theoretical investigation at atomistic level is still lacking. This study addresses the influence of loading pressure and copolymer concentration on the structural properties and tribological performance of aqueous copolymer solution of poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO) at mixed lubrication using a molecular dynamic (MD) simulation. An effective interfacial potential, which has been derived from density functional theory (DFT) calculations, was employed for the interactions between the fluid's molecules and iron surface. The simulation results have indicated that the triblock copolymer is physisorption on iron surface. Under confinement by iron surfaces, the copolymer molecules form lamellar structure in aqueous solution and behave differently from its bulk state. The lubrication performance of aqueous copolymer lubricant increases with concentration, but the friction reduction is insignificant at high loading pressure. Additionally, the plastic deformation of asperity is dependent on both copolymer concentration and loading pressure, and the wear behavior shows a linear dependence of friction force on the number of transferred atoms between contacting asperities. PMID:26828119

  16. High-temperature solvent stability of sol-gel germania triblock polymer coatings in capillary microextraction on-line coupled to high-performance liquid chromatography.

    PubMed

    Segro, Scott S; Malik, Abdul

    2010-09-10

    Germania-based sol-gel organic-inorganic hybrid coatings were prepared for on-line coupling of capillary microextraction with high-performance liquid chromatography. For this, a germania-based sol-gel precursor, tetra-n-butoxygermane and a hydroxy-terminated triblock copolymer, poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) were used. These sol-gel germania triblock polymer coatings were chemically anchored to the inner walls of a fused silica capillary (0.25 mm I.D.) in course of its evolution from the sol solution. Scanning electron microscopy images of the sol-gel germania triblock polymer coating were obtained to estimate the coating thickness. For the first time, the analyte distribution constants between a sol-gel germania organic-inorganic hybrid coating and the samples (K(cs)) were determined. For a variety of analytes from different chemical classes, including polycyclic aromatic hydrocarbons (PAHs), ketones, alcohols, phenols and amines, the K(cs) values ranged from 8.1 x 10(1) to 5.6 x 10(4). Also, for the first time, the stability of the sol-gel germania-based coating in high-temperature reversed-phase solvent environment was evaluated. The sol-gel germania triblock polymer coatings were capable of surviving exposure to high-temperature solvent conditions (200 degrees C) with little change in extraction capabilities. This demonstrates that sol-gel germania triblock polymer hybrid materials might be suitable for further applications in high-temperature HPLC. The reproducibility of the method for preparation of the sol-gel germania triblock polymer coatings was also evaluated, and the capillary-to-capillary RSD values ranged from 5.3 to 6.5%. The use of higher flow rates in extraction was found to significantly reduce the time required (from 30-40 to 10-15 min) to reach equilibrium between the sol-gel germania triblock polymer coating and the analytes in the sample solution.

  17. 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

  18. 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.

  19. Rheology and Relaxation Timescales of ABA Triblock Polymer Gels

    NASA Astrophysics Data System (ADS)

    Peters, Andrew; Lodge, Timothy

    When dissolved in a midblock selective solvent, ABA polymers form gels composed of aggregated end block micelles bridged by the midblocks. While much effort has been devoted to the study of the structure of these systems, the dynamics of these systems has received less attention. We examine the underlying mechanism of shear relaxation of ABA triblock polymer gels, especially as a function of chain length, composition, and concentration. Recent work using time-resolved small-angle neutron scattering of polystyrene (PS)-block-poly(ethylene-alt-propylene) (PEP) in squalane has elucidated many aspects of the dynamics of diblock chain exchange. By using rheology to study bulk relaxation phenomena of the triblock equivalent, PS-PEP-PS, we apply the knowledge gained from the chain exchange studies to bridge the gap between the molecular and macroscopic relaxation phenomena in PS-PEP-PS triblock gels.

  20. 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.

  1. 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.

  2. Thermosensitive AB4 four-armed star PNIPAM-b-HTPB multiblock copolymer micelles for camptothecin drug release.

    PubMed

    Luo, Yan-Ling; Fu, Jing-Yu; Xu, Feng; Chen, Ya-Shao; Zhang, Bin

    2014-01-01

    Thermo-sensitive poly(N-isoproplacrylamide)m-block-hydroxyl-terminated polybutadiene-block-poly(N-isoproplacrylamide)m (PNIPAMm-b-HTPB-b-PNIPAMm, m = 1 or 2) block copolymers, AB4 four-armed star multiblock and linear triblock copolymers, were synthesized by ATRP with HTPB as central blocks, and characterization was performed by (1)H NMR, Fourier transform infrared, and size exclusion chromatography. 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, nanoparticle analyzer, transmission electron microscope (TEM), dynamic light scattering, 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 of 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:24236748

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

    PubMed

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

    2015-04-01

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

  4. Assembly of a photosynthetic reaction center with ABA tri-block polymersomes: highlights on protein localization.

    PubMed

    Tangorra, R R; Operamolla, A; Milano, F; Hassan Omar, O; Henrard, J; Comparelli, R; Italiano, F; Agostiano, A; De Leo, V; Marotta, R; Falqui, A; Farinola, G M; Trotta, M

    2015-10-01

    The reconstitution of the integral membrane protein photosynthetic reaction center (RC) in polymersomes, i.e. artificial closed vesicles, was achieved by the micelle-to-vesicle transition technique, a very mild protocol based on size exclusion chromatography often used to drive the incorporation of proteins contemporarily to liposome formation. An optimized protocol was used to successfully reconstitute the protein in a fully active state in polymersomes formed by the tri-block copolymers PMOXA22-PDMS61-PMOXA22. The RC is very sensitive to its solubilizing environment and was used to probe the positioning of the protein in the vesicles. According to charge-recombination experiments and to the enzymatic activity assay, the RC is found to accommodate in the PMOXA22 region of the polymersome, facing the water bulk solution, rather than in the PDMS61 transmembrane-like region. Furthermore, polymersomes were found to preserve protein integrity efficiently as the biomimetic lipid bilayers but show a much longer temporal stability than lipid based vesicles.

  5. Thermosensitive block copolymer hydrogels based on poly(ɛ-caprolactone) and polyethylene glycol for biomedical applications: state of the art and future perspectives.

    PubMed

    Boffito, Monica; Sirianni, Paolo; Di Rienzo, Anna Maria; Chiono, Valeria

    2015-03-01

    This review focuses on the challenges associated with the design and development of injectable hydrogels of synthetic origin based on FDA approved blocks, such as polyethylene glycol (PEG) and poly(ɛ-caprolactone) (PCL). An overview of recent studies on inverse thermosensitive PEG/PCL hydrogels is provided. These systems have been proposed to overcome the limitations of previously introduced degradable thermosensitive hydrogels [e.g., PEG/poly(lactide-co-glycolic acid) hydrogels]. PEG/PCL hydrogels are advantageous due to their higher gel strength, slower degradation rate and availability in powder form. Particularly, triblock PEG/PCL copolymers have been widely investigated, with PCL-PEG-PCL (PCEC) hydrogels showing superior gel strength and slower degradation kinetics than PEG-PCL-PEG (PECE) hydrogels. Compared to triblock PEG/PCL copolymers, concentrated solutions of multiblock PEG/PCL copolymers were stable due to their slower crystallization rate. However, the resulting hydrogel gel strength was low. Inverse thermosensitive triblock PEG/PCL hydrogels have been mainly applied in tissue engineering, to decrease tissue adherence or, in combination with bioactive molecules, to promote tissue regeneration. They have also found application as in situ drug delivery carriers. On the other hand, the wide potentialities of multiblock PEG/PCL hydrogels, associated with the stability of their water-based solutions under storage, their higher degradation time compared to triblock copolymer hydrogels and the possibility to insert bioactive building blocks along the copolymer chains, have not been fully exploited yet. A critical discussion is provided to highlight advantages and limitations of currently developed themosensitive PEG/PCL hydrogels, suggesting future strategies for the realization of PEG/PCL-based copolymers with improved performance in the different application fields.

  6. 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

  7. Cell sealant

    SciTech Connect

    Markin, C.; Book, R.J.; James, D.A.

    1988-04-26

    An electrochemical cell is described comprising an anode, a cathode and an electrolyte disposed within an open ended cylindrical metallic cell container, with an insulative cell top member being positioned within the open end of a sealant at the interface between the cell top member and the metallic cell container. The sealant is a mixture of a Type 2 BUR asphalt and an elastomeric material selected from the group consisting of (cis-1,4-polyisoprene), styrene-butadiene copolymer (SBR), cis-1,4-polybutadiene and styrene butadiene styrene (SBS), styrene isoprene styrene (SIS), neoprene (poly-chloprene), acrylonitrile-butadiene copolymer (NBR), ethylene-propylene elastomers (EPR), butyl rubber (copolymers of isobutylene), urethane, nitrile (polymers of butadiene and acrylonitrile), polysulfide, polyacrylate, silicone, chlorosulfonated polyethylene, and EPDM (terpolymers of ethylene, propylene and diene monomers), and mixtures thereof, and wherein the elastomeric material is substantially inert to the electrolyte and is present in an amount between 0.5% to 10% by weight of the asphalt.

  8. 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).

  9. Field-Theoretic Studies of Nanostructured Triblock Polyelectrolyte Gels

    NASA Astrophysics Data System (ADS)

    Audus, Debra; Fredrickson, Glenn

    2012-02-01

    Recently, experimentalists have developed nanostructured, reversible gels formed from triblock polyelectrolytes (Hunt et al. 2011, Lemmers et al. 2010, 2011). These gels have fascinating and tunable properties that reflect a heterogeneous morphology with domains on the order of tens of nanometers. The complex coacervate domains, aggregated oppositely charged end-blocks, are embedded in a continuous aqueous matrix and are bridged by uncharged, hydrophilic polymer mid-blocks. We report on simulation studies that employ statistical field theory models of triblock polyelectrolytes, and we explore the equilibrium self-assembly of these remarkable systems. As the charge complexation responsible for the formation of coacervate domains is driven by electrostatic correlations, we have found it necessary to pursue full ``field-theoretic simulations'' of the models, as opposed to the familiar self-consistent field theory approach. Our investigations have focused on morphological trends with mid- and end-block lengths, polymer concentration, salt concentration and charge density.

  10. 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.

  11. Aggregation of poly(acrylic acid)-containing elastin-mimetic copolymers

    PubMed Central

    Paik, Bradford A.; Blanco, Marco A.; Jia, Xinqiao; Roberts, Christopher J.; Kiick, Kristi L.

    2015-01-01

    Polymer-peptide conjugates were produced via the copper-catalyzed alkyne-azide cycloaddition of poly(tert butyl acrylate) (PtBA) and elastin-like peptides. An azide-functionalized polymer was produced via atom-transfer radical polymerization (ATRP) followed by conversion of bromine end groups to azide groups. Subsequent reaction of the polymer with a bis-alkyne-functionalized, elastin-like peptide proceeded with high efficiency, yielding di- and tri-block conjugates, which after deprotection, yielded poly(acrylic acid) (PAA)-based diblock and triblock copolymers. These conjugates were solubilized in dimethyl formamide, and titration of phosphate buffered saline (PBS) induced aggregation. The presence of polydisperse spherical aggregates was confirmed by dynamic light scattering and transmission electron microscopy. Additionally, a coarse-grained molecular model was designed to reasonably capture inter- and intramolecular interactions for the conjugates and its precursors. This model was used to assess the effect of the different interacting molecular forces on the conformational thermodynamic stability of the copolymers. Our results indicated that the PAA’s ability to hydrogen-bond with both itself and the peptide is the main interaction for stabilizing the diblocks and triblocks and driving their self-assembly, while interactions between peptides are suggested to play only a minor role on the conformational and thermodynamic stability of the conjugates. PMID:25611563

  12. Network of nano-droplets by a tri-block polymer

    NASA Astrophysics Data System (ADS)

    Sharifi, Soheil; Doodman, Esmaeil

    2014-11-01

    Mixtures of oil in water nano-droplets with two molecular weights of a tri-block polymer was studied by quasi elastic light scattering and small angle X-ray scattering. The results showed that the size and interaction of droplets didn't change with increase of the tri-block polymer length but the order parameters increased. The increase of length of the tri-block biopolymer changed the dynamics of the droplets. A network formation is resulted with increase of the amount of tri-block polymer in the microemulsions.

  13. Synthesis of Electroneutralized Amphiphilic Copolymers with Peptide Dendrons for Intramuscular Gene Delivery.

    PubMed

    Pu, Linyu; Wang, Jiali; Li, Na; Chai, Qiuxia; Irache, Juan M; Wang, Gang; Tang, James Zhenggui; Gu, Zhongwei

    2016-06-01

    Intramuscular gene delivery materials are of great importance in plasmid-based gene therapy system, but there is limited information so far on how to design and synthesize them. A previous study showed that the peptide dendron-based triblock copolymer with its components arranged in a reversed biomembrane architecture could significantly increase intramuscular gene delivery and expression. Herein, we wonder whether copolymers with biomembrane-mimicking arrangement may have similar function on intramuscular gene delivery. Meanwhile, it is of great significance to uncover the influence of electric charge and molecular structure on the function of the copolymers. To address the issues, amphiphilic triblock copolymers arranged in hydrophilic-hydrophobic-hydrophilic structure were constructed despite the paradoxical characteristics and difficulties in synthesizing such hydrophilic but electroneutral molecules. The as-prepared two copolymers, dendronG2(l-lysine-OH)-poly propylene glycol2k(PPG2k)-dendronG2(l-lysine-OH) (rL2PL2) and dendronG3(l-lysine-OH)-PPG2k-dendronG3(l-lysine-OH) (rL3PL3), were in similar structure but had different hydrophilic components and surface charges, thus leading to different capabilities in gene delivery and expression in skeletal muscle. rL2PL2 was more efficient than Pluronic L64 and rL3PL3 when mediating luciferase, β-galactosidase, and fluorescent protein expressions. Furthermore, rL2PL2-mediated growth-hormone-releasing hormone expression could significantly induce mouse body weight increase in the first 21 days after injection. In addition, both rL2PL2 and rL3PL3 showed good in vivo biosafety in local and systemic administration. Altogether, rL2PL2-mediated gene expression in skeletal muscle exhibited applicable potential for gene therapy. The study revealed that the molecular structure and electric charge were critical factors governing the function of the copolymers for intramuscular gene delivery. It can be concluded that, combined

  14. Determining the structure and properties of complex coacervate crosslinked triblock copolymer hydrogels

    NASA Astrophysics Data System (ADS)

    Krogstad, Daniel; Choi, Soo-Hyung; Spruell, Jason; Lynd, Nathaniel; Kramer, Edward; Tirrell, Matthew

    2012-02-01

    The mechanical properties and structures of functionalized P(AGE-b-EO-b-AGE) hydrogels utilizing complex coacervation as a physical crosslink have been studied. The effects of variables such as polymer concentration, salt concentration, pH, stoichiometric ratios and temperature have been investigated by rheology and SAXS. It was found that the organization of the cores has a very strong effect on the mechanical properties. This can be observed as the storage modulus increases significantly between 15 and 16 wt% corresponding to a transition from a disordered gel to a BCC structure. Another dramatic change is observed when the storage modulus drops between 25 and 30 wt% as the hexagonal structure becomes predominant. Just as polymer concentration causes changes in structure and thus the properties, salt concentration has a similar effect due to the electrostatic nature of the hydrogels. As salt is added, the electrostatic interactions in the cores are screened until they are weak enough that the polymers are dissolved into the matrix. The mechanical properties and the physical nature of the crosslinks lead to the possibility of these gels being used as an injectable drug delivery system.

  15. Crystallization of bifonazole and acetaminophen within the matrix of semicrystalline, PEO-PPO-PEO triblock copolymers.

    PubMed

    Chen, Zhen; Liu, Zhengsheng; Qian, Feng

    2015-02-01

    The morphology and microstructure of crystalline drug/polymer solid dispersions could influence their physical stability and dissolution performance. In this study, the drug crystallization mechanism within PEG, PPG, and poloxamer matrix was investigated, and the resultant microstructure of various solid dispersions of acetaminophen (ACM) and bifonazole (BFZ) in the aforementioned polymers was characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide/small-angle X-ray diffraction (WAXD/SAXS). With a stronger molecular interaction with the PEG segments, ACM decreased the crystallization onset temperature and crystallinity of PEG and poloxamers much more than BFZ. The stronger molecular interaction and better miscibility between ACM and PEG also induced a more defective lamellar structure in the ACM solid dispersions compared with that in the BFZ systems, as revealed by DSC and SAXS investigation. Observed under polarized optical microscopy, PEG, PPG, and poloxamer could all significantly improve the crystallization rate of ACM and BFZ, because of the largely reduced Tg of the solid dispersions by these low Tg polymers. Moreover, when the drug loading was below 60%, crystallization of BFZ in PEG or poloxamer occurred preferably along the radial direction of PEG spherulite, rather than the perpendicular direction, which was attributed to the geometric restriction of well-ordered polymer lamellar structure in the BFZ solid dispersions. Similar phenomena were not observed in the ACM solid dispersions regardless of the drug loading, presumably because ACM could diffuse freely across the perpendicular direction of the PEG spherulite, through the well-connected interlamellar or interfibrillar spaces produced by the defective PEG lamellar structure. The different drug-polymer interaction also caused a difference in the microstructure of polymer crystal, as well as a difference in drug distribution within the polymer matrix, which then synergistically facilitated a "confined crystallization" process to reduce the drug crystallite size below 100 nm.

  16. Investigation of mixed fluorinated and triblock copolymer liquid crystals: imprint for mesostructured bimodal silica.

    PubMed

    Assaker, Karine; Naboulsi, Issam; Stébé, Marie-José; Emo, Mélanie; Blin, Jean-Luc

    2015-05-15

    Due to the difference in «mutual phobicity» between fluorocarbon and hydrocarbon chains, mixtures of fluorinated and hydrogenated surfactants are excellent candidates to design bimodal systems having two types of mesopores. In literature, only a few papers deal with these bimodal systems. Here hexagonal liquid crystal mixtures of the polyoxyethylene fluoroalkyl ether [R(F)8(EO)9] and the Pluronic [P123] have been used to template this kind of mesostructure through the liquid crystal mechanism, which is barely considered. After the detailed investigation of the R(F)8(EO)9/P123/water liquid crystal domain, materials have been synthesized and characterized by small angle X-ray scattering, transmission electron microscopy and nitrogen adsorption-desorption analysis. Our results show that this system provides two separate pore sizes in the materials over the mesoporous range. The ratio between the small mesopores and the large ones depends on the proportion between the porogens in the mixture. Nonetheless, we also outline that a minimum quantity of silica is required to recover the two hexagonal networks.

  17. 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.

  18. 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

  19. Chemical vapor deposition graphene transfer process to a polymeric substrate assisted by a spin coater

    NASA Astrophysics Data System (ADS)

    Kessler, Felipe; da Rocha, Caique O. C.; Medeiros, Gabriela S.; Fechine, Guilhermino J. M.

    2016-03-01

    A new method to transfer chemical vapor deposition graphene to polymeric substrates is demonstrated here, it is called direct dry transfer assisted by a spin coater (DDT-SC). Compared to the conventional method DDT, the improvement of the contact between graphene-polymer due to a very thin polymeric film deposited by spin coater before the transfer process prevented air bubbles and/or moisture and avoided molecular expansion on the graphene-polymer interface. An acrylonitrile-butadiene-styrene copolymer, a high impact polystyrene, polybutadiene adipate-co-terephthalate, polylactide acid, and a styrene-butadiene-styrene copolymer are the polymers used for the transfers since they did not work very well by using the DDT process. Raman spectroscopy and optical microscopy were used to identify, to quantify, and to qualify graphene transferred to the polymer substrates. The quantity of graphene transferred was substantially increased for all polymers by using the DDT-SC method when compared with the DDT standard method. After the transfer, the intensity of the D band remained low, indicating low defect density and good quality of the transfer. The DDT-SC transfer process expands the number of graphene applications since the polymer substrate candidates are increased.

  20. Viscosity modification of high-oleic sunflower oil with polymeric additives for the design of new biolubricant formulations.

    PubMed

    Quinchia, L A; Delgado, M A; Valencia, C; Franco, J M; Gallegos, C

    2009-03-15

    Although most common lubricants contain mineral or synthetic oils as basestocks, new environmental regulations are demanding environmentally friendly lubricants. In this sense, vegetable oils represent promising alternatives to mineral-based lubricants because of their high biodegradability, good lubricity, and low volatility. However, their poor thermooxidative stability and the small range of viscosity represent a clear disadvantage to be used as suitable biolubricants. The main objective of this work was to develop new environmentally friendly lubricant formulations with improved kinematic viscosity values and viscosity thermal susceptibility. With this aim, a high-oleic sunflower oil (HOSO) was blended with polymeric additives, such as ethylene vinyl acetate (EVA) and styrene-butadiene-styrene (SBS) copolymers, at different concentrations (0.5-5% w/w). Dynamic viscosity and density measurements were performed in a rotational rheometer and capillary densimeter, respectively, in a temperature range between 25 and 120 degrees C. An Arrhenius-like equation fits the evolution of viscosity with temperature fairly well. Both EVA and SBS copolymers may be satisfactorily used as additives to increase the viscosity of HOSO, thus improving the low viscosity values of this oil. HOSO viscosity increases with polymer concentration. Specifically, EVA/HOSO blends exhibit higher viscosity values, which are needed for applications such as lubrication of bearings and four-stroke engines. On the other hand, viscositythermal susceptibility of HOSO samples increases with EVA or SBS concentration.

  1. Biocompatible fluorinated polyglycerols for droplet microfluidics as an alternative to PEG-based copolymer surfactants.

    PubMed

    Wagner, Olaf; Thiele, Julian; Weinhart, Marie; Mazutis, Linas; Weitz, David A; Huck, Wilhelm T S; Haag, Rainer

    2016-01-01

    In droplet-based microfluidics, non-ionic, high-molecular weight surfactants are required to stabilize droplet interfaces. One of the most common structures that imparts stability as well as biocompatibility to water-in-oil droplets is a triblock copolymer surfactant composed of perfluoropolyether (PFPE) and polyethylene glycol (PEG) blocks. However, the fast growing applications of microdroplets in biology would benefit from a larger choice of specialized surfactants. PEG as a hydrophilic moiety, however, is a very limited tool in surfactant modification as one can only vary the molecular weight and chain-end functionalization. In contrast, linear polyglycerol offers further side-chain functionalization to create custom-tailored, biocompatible droplet interfaces. Herein, we describe the synthesis and characterization of polyglycerol-based triblock surfactants with tailored side-chain composition, and exemplify their application in cell encapsulation and in vitro gene expression studies in droplet-based microfluidics.

  2. Phase separations in a copolymer copolymer mixture

    NASA Astrophysics Data System (ADS)

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

    2006-01-01

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

  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. 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

  5. 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

  6. 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.

  7. Phase Behavior and Micellar Packing of Impurity-Free Pluronic Block Copolymers in Water

    NASA Astrophysics Data System (ADS)

    Ryu, Chang Yeol; Park, Hanjin

    We have investigated the impacts of the non-micellizable polymeric impurities on the micellar packing and solution phase behavior of Pluronic block copolymers in water. In particular, small angle x-ray scattering, rheology and dynamic light scattering techniques have been employed to elucidate how the low MW impurities affect the micellar packing and solution phase diagram in water, when ordered cubic structures of spherical micelles are formed. A silica slurry method has been developed using the competitive adsorption of the PEO-PPO-PEO triblock copolymers over the low MW polymeric impurities for a large scale purification of Pluronics and it purity of Pluronics has been assessed by interaction chromatography. Based on the comparative studies on micellar packing between As-Received (AR) and Purified (Pure) Pluronic F108 solutions, we found experimental evidence to support the hypothesis that the inter-micellar distance of Pluronic cubic structures in aqueous solution is governed by the effective polymer concentration in terms of PEO-PPO-PEO triblock copolymers. Removal of the impurities in AR F108 offers an important clue on window into the onset of BCC ordering via hydrodynamic contact between micelles in solution. NSF DMR Polymers.

  8. Effect of chain architecture on the surface energy of block copolymer melts

    NASA Astrophysics Data System (ADS)

    Matsen, Mark

    2010-03-01

    Careful experimental studies of ABA triblock copolymer melts by Khanna et al. [Macromolecules, 39, 9346, 2006] have detected an entropic advantage of placing the A-rich domain next to a surface as opposed to the B-rich domain. This preference is also corroborated by a self-consistent field theory (SCFT) calculation. Their proposed explanation is that B blocks avoid the surface, because otherwise they would lose the entropy associated with bridging and looping. However, a more thorough investigation of the SCFT reveals that the preference is due to an entropic advantage of having the end segments of the A-rich domain next to a surface. Furthermore, we use a simple lattice-model argument to intuitively explain that the entropy due to bridging and looping becomes irrelevant when the contour length of the B block is much smaller than the width of the B-rich domain, which is the normal situation in triblock copolymer melts. Our new chain-end explanation could be tested experimentally by examining other architectures such as A2B starblock copolymers.

  9. 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.

  10. EPR study of the formation of radicals in PP with antioxidants irradiated with gamma rays

    NASA Astrophysics Data System (ADS)

    Silva, P.; Albano, C.; Perera, R.

    2007-12-01

    The behavior of different compounds of polypropylene (PP) with stabilizers such as buthyl-hydroxy-toluene (BHT), Chimassorb 944 (Hals) (CHIM), and a copolymer of styrene-butadiene-styrene (SBS) was studied using electron paramagnetic resonance (EPR). A characteristic spectra for pure PP irradiated in air was obtained for all the samples just after being irradiated [M. Dole, The Radiation Chemistry of Macromolecules, Vol. 2, Academic Press, 1973]. A change in the lineshape of the spectra from a pure PP's EPR signal to that of nitroxyl radical as a function of time was observed. The total free radical concentration (TFRC) decayed until approximately 800 h in the PP-HALS and until around 2000 h in all other cases, when the TFRC began to increase in all the cases, except in that of PP-BHT. In this last case, the EPR signal was not detectable after 4000 h. The BHT and the SBS diluted the free radical concentrations, being them smaller when they are present. The behavior observed in all the samples is consistent with the formation of nitroxyl radicals by gamma rays.

  11. Hypersonic properties of polymer films and multi-layers

    NASA Astrophysics Data System (ADS)

    Sharp, James; Walker, Paul; Young, Eric; Goussev, Vitali; Akimov, Andrey; Kent, Anthony

    2012-02-01

    Picosecond acoustic measurements were performed on ultrathin films of polymers and thin film polymer multilayers supported on silicon (Si) substrates using a state of the art THz acoustic technique. In these experiments, a high power laser is used to excite picosecond duration strain pulses in an aluminium film evaporated on the reverse side of the Si substrate. These strain pulses then propagate through the substrate and interact with the polymer film/multi-layer. Vibrations in the film are detected optically using the same (pump-probe) beam which is passed through an optical delay line and reflected from the surface of the polymer film/multi-layer. Ultrathin films of polystyrene and a styrene-butadiene-styrene block copolymer were found to exhibit quantized closed-pipe organ like modes in the 0- 50 GHz regime that were attributed to vibrations of the entire polymer film. Thin film polystyrene/polyvinylpyrrolidone multilayer structures were found to display folded phonon dispersion curves that are characteristic of super-lattice structures. These structures have potential applications in GHz and THz optical switching and biosensing applications.

  12. (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.

  13. Nanoporous polysulfone membranes via a degradable block copolymer precursor for redox flow batteries

    DOE PAGES

    Gindt, Brandon P.; Abebe, Daniel G.; Tang, Zhijiang J.; Lindsey, Melanie B.; Chen, Jihua; Elgammal, Ramez A.; Zawodzinski, Thomas A.; Fujiwara, Tomoko

    2016-01-01

    In this study, nanoporous polysulfone (PSU) membranes were fabricated via post-hydrolysis of polylactide (PLA) from PLA–PSU–PLA triblock copolymer membranes. The PSU scaffold was thermally crosslinked before sacrificing PLA blocks. The resulting nanopore surface was chemically modified with sulfonic acid moieties. The membranes were analyzed and evaluated as separators for vanadium redox flow batteries. Nanoporous PSU membranes prepared by this new method and further chemically modified to a slight degree exhibited unique behavior with respect to their ionic conductivity when exposed to solutions of increasing acid concentration.

  14. Nanoporous polysulfone membranes via a degradable block copolymer precursor for redox flow batteries

    SciTech Connect

    Gindt, Brandon P.; Abebe, Daniel G.; Tang, Zhijiang J.; Lindsey, Melanie B.; Chen, Jihua; Elgammal, Ramez A.; Zawodzinski, Thomas A.; Fujiwara, Tomoko

    2016-01-01

    In this study, nanoporous polysulfone (PSU) membranes were fabricated via post-hydrolysis of polylactide (PLA) from PLA–PSU–PLA triblock copolymer membranes. The PSU scaffold was thermally crosslinked before sacrificing PLA blocks. The resulting nanopore surface was chemically modified with sulfonic acid moieties. The membranes were analyzed and evaluated as separators for vanadium redox flow batteries. Nanoporous PSU membranes prepared by this new method and further chemically modified to a slight degree exhibited unique behavior with respect to their ionic conductivity when exposed to solutions of increasing acid concentration.

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

    NASA Astrophysics Data System (ADS)

    Kim, In

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

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

    NASA Astrophysics Data System (ADS)

    Zheng, Wang; Bao-Hui, Li

    2016-01-01

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

  17. Fabrication of biomolecule copolymer hybrid nanovesicles as energy conversion systems

    NASA Astrophysics Data System (ADS)

    Ho, Dean; Chu, Benjamin; Lee, Hyeseung; Brooks, Evan K.; Kuo, Karen; Montemagno, Carlo D.

    2005-12-01

    This work demonstrates the integration of the energy-transducing proteins bacteriorhodopsin (BR) from Halobacterium halobium and cytochrome c oxidase (COX) from Rhodobacter sphaeroides into block copolymeric vesicles towards the demonstration of coupled protein functionality. An ABA triblock copolymer-based biomimetic membrane possessing UV-curable acrylate endgroups was synthesized to serve as a robust matrix for protein reconstitution. BR-functionalized polymers were shown to generate light-driven transmembrane pH gradients while pH gradient-induced electron release was observed from COX-functionalized polymers. Cooperative behaviour observed from composite membrane functionalized by both proteins revealed the generation of microamp-range currents with no applied voltage. As such, it has been shown that the fruition of technologies based upon bio-functionalizing abiotic materials may contribute to the realization of high power density devices inspired by nature.

  18. 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

  19. PLA-PEG-PLA copolymer-based polymersomes as nanocarriers for delivery of hydrophilic and hydrophobic drugs: preparation and evaluation with atorvastatin and lisinopril.

    PubMed

    Danafar, H; Rostamizadeh, K; Davaran, S; Hamidi, M

    2014-10-01

    Tri-block poly(lactide)-poly(ethylene glycol)-poly(lactide) (PLA-PEG-PLA) copolymers were synthesized and used to prepare polymersomes loaded separately by the hydrophobic and hydrophilic model drugs, atorvastatin and lisinopril, respectively. The resulting nanostructures were characterized by various techniques such as FTIR, DSC, PCS and AFM. The polymersomes exhibited high encapsulation efficiencies of almost 78% and 70.8% for atorvastatin and lisinopril, respectively. Investigation on FTIR and DSC results revealed that such a high encapsulation efficiency is due to strong interaction between atorvastatin and the copolymer. The impact of drug/copolymer ratio and copolymer composition on drug-loading efficiency and drug release behavior were also studied. The results showed that in case of lisinopril, polymersomes exhibited a triphasic drug release, while for atorvastatin a biphasic release profile was obtained. Overall, the results indicated that PLA-PEG-PLA polymersomes can be considered as a promising carrier for both hydrophilic and hydrophobic drugs. PMID:23944838

  20. PLA-PEG-PLA copolymer-based polymersomes as nanocarriers for delivery of hydrophilic and hydrophobic drugs: preparation and evaluation with atorvastatin and lisinopril.

    PubMed

    Danafar, H; Rostamizadeh, K; Davaran, S; Hamidi, M

    2014-10-01

    Tri-block poly(lactide)-poly(ethylene glycol)-poly(lactide) (PLA-PEG-PLA) copolymers were synthesized and used to prepare polymersomes loaded separately by the hydrophobic and hydrophilic model drugs, atorvastatin and lisinopril, respectively. The resulting nanostructures were characterized by various techniques such as FTIR, DSC, PCS and AFM. The polymersomes exhibited high encapsulation efficiencies of almost 78% and 70.8% for atorvastatin and lisinopril, respectively. Investigation on FTIR and DSC results revealed that such a high encapsulation efficiency is due to strong interaction between atorvastatin and the copolymer. The impact of drug/copolymer ratio and copolymer composition on drug-loading efficiency and drug release behavior were also studied. The results showed that in case of lisinopril, polymersomes exhibited a triphasic drug release, while for atorvastatin a biphasic release profile was obtained. Overall, the results indicated that PLA-PEG-PLA polymersomes can be considered as a promising carrier for both hydrophilic and hydrophobic drugs.

  1. Self-assembling triblock proteins for biofunctional surface modification

    NASA Astrophysics Data System (ADS)

    Fischer, Stephen E.

    Despite the tremendous promise of cell/tissue engineering, significant challenges remain in engineering functional scaffolds to precisely regulate the complex processes of tissue growth and development. As the point of contact between the cells and the scaffold, the scaffold surface plays a major role in mediating cellular behaviors. In this dissertation, the development and utility of self-assembling, artificial protein hydrogels as biofunctional surface modifiers is described. The design of these recombinant proteins is based on a telechelic triblock motif, in which a disordered polyelectrolyte central domain containing embedded bioactive ligands is flanked by two leucine zipper domains. Under moderate conditions of temperature and pH, the leucine zipper end domains form amphiphilic alpha-helices that reversibly associate into homo-trimeric aggregates, driving hydrogel formation. Moreover, the amphiphilic nature of these helical domains enables surface adsorption to a variety of scaffold materials to form biofunctional protein coatings. The nature and stability of these coatings in various solution conditions, and their interaction with mammalian cells is the primary focus of this dissertation. In particular, triblock protein coatings functionalized with cell recognition sequences are shown to produce well-defined surfaces with precise control over ligand density. The impact of this is demonstrated in multiple cell types through ligand density-dependent cell-substrate interactions. To improve the stability of these physically self-assembled coatings, two covalent crosslinking strategies are described---one in which a zero-length chemical crosslinker (EDC) is utilized and a second in which disulfide bonds are engineered into the recombinant proteins. These targeted crosslinking approaches are shown to increase the stability of surface adsorbed protein layers with minimal effect on the presentation of many bioactive ligands. Finally, to demonstrate the versatility

  2. The Tricontinuous 3ths(5) Phase: A New Morphology in Copolymer Melts

    NASA Astrophysics Data System (ADS)

    Fischer, Michael; de Campo, Liliana; Kirkensgaard, Jacob; Hyde, Stephen; Schroeder-Turk, Gerd

    2015-03-01

    Self-assembly remains one of the most efficient routes to the formation of ordered nanostructures, including the double gyroid network phase in diblock copolymers based on two intergrown network domains. This talk demonstrates the use of self-consistent field theory to show that a tricontinuous structure with monoclinic symmetry, called 3ths(5), based on the intergrowth of three distorted ths nets, is an equilibrium phase of triblock star-copolymer melts when an extended molecular core is introduced. The introduction of the core enhances the role of chain stretching by enforcing larger structural length scales, thus destabilizing the hexagonal columnar phase in favor of morphologies with less packing frustration. This study further demonstrates that the introduction of molecular cores is a general concept for tuning the relative importance of entropic and enthalpic free energy contributions, hence providing a tool to stabilize an extended repertoire of self-assembled nanostructured materials.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  4. Highly protein-resistant coatings and suspension cell culture thereon from amphiphilic block copolymers prepared by RAFT polymerization.

    PubMed

    Haraguchi, Kazutoshi; Kubota, Kazuomi; Takada, Tetsuo; Mahara, Saori

    2014-06-01

    Novel amphiphilic block copolymers composed of hydrophobic (poly(2-methoxyethyl acrylate): M) and hydrophilic (poly(N,N-dimethylacrylamide): D) segments were synthesized by living radical polymerization: a reversible addition-fragmentation chain-transfer polymerization. Two types of amphiphilic block copolymers, triblock (MDM) and 4-arm block ((MD)4) copolymers with specific compositions (D/M = (750-1500)/250), were prepared by a versatile one-pot synthesis. These copolymers show good adhesion to various types of substrates (e.g., polystyrene, polycarbonate, polypropylene, Ti, and glass), and the surface coating showed high protein repellency and a low contact angle for water, regardless of the substrate. The two opposing characteristics of high protein repellency and good substrate adhesion were achieved by the combined effects of the molecular architecture of the block copolymers, the high molecular weight, and the characteristics of each segment, that is, low protein adsorption capability of both segments and low glass transition temperature of the hydrophobic segment. Further, a polystyrene dish coated with the MDM block copolymer could be sterilized by γ-ray irradiation and used as a good substrate for a suspension cell culture that exhibits low cell adhesion and good cell growth. PMID:24773089

  5. Highly protein-resistant coatings and suspension cell culture thereon from amphiphilic block copolymers prepared by RAFT polymerization.

    PubMed

    Haraguchi, Kazutoshi; Kubota, Kazuomi; Takada, Tetsuo; Mahara, Saori

    2014-06-01

    Novel amphiphilic block copolymers composed of hydrophobic (poly(2-methoxyethyl acrylate): M) and hydrophilic (poly(N,N-dimethylacrylamide): D) segments were synthesized by living radical polymerization: a reversible addition-fragmentation chain-transfer polymerization. Two types of amphiphilic block copolymers, triblock (MDM) and 4-arm block ((MD)4) copolymers with specific compositions (D/M = (750-1500)/250), were prepared by a versatile one-pot synthesis. These copolymers show good adhesion to various types of substrates (e.g., polystyrene, polycarbonate, polypropylene, Ti, and glass), and the surface coating showed high protein repellency and a low contact angle for water, regardless of the substrate. The two opposing characteristics of high protein repellency and good substrate adhesion were achieved by the combined effects of the molecular architecture of the block copolymers, the high molecular weight, and the characteristics of each segment, that is, low protein adsorption capability of both segments and low glass transition temperature of the hydrophobic segment. Further, a polystyrene dish coated with the MDM block copolymer could be sterilized by γ-ray irradiation and used as a good substrate for a suspension cell culture that exhibits low cell adhesion and good cell growth.

  6. Directed self-assembly of high-chi block copolymer for nano fabrication of bit patterned media via solvent annealing

    NASA Astrophysics Data System (ADS)

    Xiong, Shisheng; Chapuis, Yves-Andre; Wan, Lei; Gao, He; Li, Xiao; Ruiz, Ricardo; Nealey, Paul F.

    2016-10-01

    We report the formation of nanoimprint master templates that can be used for the fabrication of bit patterned media (BPM). The template was formed by directed self-assembly, with solvent annealing, of a symmetric ABA triblock copolymer to form perpendicularly oriented lamellae on chemical patterns. We used a high-χ block copolymer, poly(2-vinyl pyridine)-block-polystyrene-block-poly(2-vinyl pyridine) to achieve smaller feature sizes than are possible with polystyrene-block-poly(methyl methacrylate). The work shows that triblock copolymers can provide a large processing window in terms of pitch commensurability. Using block-selective infiltration (atomic layer deposition with sequential long soaking/purge cycles), an alumina composite with high etch resistance was specifically incorporated into the polar and hydrophilic P2VP domains. Subsequently, the surface pattern was successfully transferred into underlying Si substrates by etching with a fluorine-containing plasma to create a nanoimprint master. The line/space pattern of the nanoimprint master met the BPM fabrication requirement of defectivity <10-3. For demonstration purposes, the nanoimprint master was used to imprint a replica pattern of photoresist on a quartz wafer.

  7. Directed self-assembly of high-chi block copolymer for nano fabrication of bit patterned media via solvent annealing.

    PubMed

    Xiong, Shisheng; Chapuis, Yves-Andre; Wan, Lei; Gao, He; Li, Xiao; Ruiz, Ricardo; Nealey, Paul F

    2016-10-14

    We report the formation of nanoimprint master templates that can be used for the fabrication of bit patterned media (BPM). The template was formed by directed self-assembly, with solvent annealing, of a symmetric ABA triblock copolymer to form perpendicularly oriented lamellae on chemical patterns. We used a high-χ block copolymer, poly(2-vinyl pyridine)-block-polystyrene-block-poly(2-vinyl pyridine) to achieve smaller feature sizes than are possible with polystyrene-block-poly(methyl methacrylate). The work shows that triblock copolymers can provide a large processing window in terms of pitch commensurability. Using block-selective infiltration (atomic layer deposition with sequential long soaking/purge cycles), an alumina composite with high etch resistance was specifically incorporated into the polar and hydrophilic P2VP domains. Subsequently, the surface pattern was successfully transferred into underlying Si substrates by etching with a fluorine-containing plasma to create a nanoimprint master. The line/space pattern of the nanoimprint master met the BPM fabrication requirement of defectivity <10(-3). For demonstration purposes, the nanoimprint master was used to imprint a replica pattern of photoresist on a quartz wafer. PMID:27606926

  8. Directed self-assembly of high-chi block copolymer for nano fabrication of bit patterned media via solvent annealing.

    PubMed

    Xiong, Shisheng; Chapuis, Yves-Andre; Wan, Lei; Gao, He; Li, Xiao; Ruiz, Ricardo; Nealey, Paul F

    2016-10-14

    We report the formation of nanoimprint master templates that can be used for the fabrication of bit patterned media (BPM). The template was formed by directed self-assembly, with solvent annealing, of a symmetric ABA triblock copolymer to form perpendicularly oriented lamellae on chemical patterns. We used a high-χ block copolymer, poly(2-vinyl pyridine)-block-polystyrene-block-poly(2-vinyl pyridine) to achieve smaller feature sizes than are possible with polystyrene-block-poly(methyl methacrylate). The work shows that triblock copolymers can provide a large processing window in terms of pitch commensurability. Using block-selective infiltration (atomic layer deposition with sequential long soaking/purge cycles), an alumina composite with high etch resistance was specifically incorporated into the polar and hydrophilic P2VP domains. Subsequently, the surface pattern was successfully transferred into underlying Si substrates by etching with a fluorine-containing plasma to create a nanoimprint master. The line/space pattern of the nanoimprint master met the BPM fabrication requirement of defectivity <10(-3). For demonstration purposes, the nanoimprint master was used to imprint a replica pattern of photoresist on a quartz wafer.

  9. PCL-PDMS-PCL copolymer-based microspheres mediate cardiovascular differentiation from embryonic stem cells

    NASA Astrophysics Data System (ADS)

    Song, Liqing

    Poly-epsilon-caprolactone (PCL) based copolymers have received much attention as drug or growth factor delivery carriers and tissue engineering scaffolds due to their biocompatibility, biodegradability, and tunable biophysical properties. Copolymers of PCL and polydimethylsiloxane (PDMS) also have shape memory behaviors and can be made into thermoresponsive shape memory polymers for various biomedical applications such as smart sutures and vascular stents. However, the influence of biophysical properties of PCL-PDMS-PCL copolymers on stem cell lineage commitment is not well understood. In this study, PDMS was used as soft segments of varying length to tailor the biophysical properties of PCL-based co-polymers. While low elastic modulus (<10 kPa) of the tri-block copolymer PCL-PDMS-PCL affected cardiovascular differentiation of embryonic stem cells, the range of 60-100 MPa PCL-PDMS-PCL showed little influence on the differentiation. Then different size (30-140 mum) of microspheres were fabricated from PCL-PDMS-PCL copolymers and incorporated within embryoid bodies (EBs). Mesoderm differentiation was induced using bone morphogenetic protein (BMP)-4 for cardiovascular differentiation. Differential expressions of mesoderm progenitor marker KDR and vascular markers CD31 and VE-cadherin were observed for the cells differentiated from EBs incorporated with microspheres of different size, while little difference was observed for cardiac marker alpha-actinin expression. Small size of microspheres (30 mum) resulted in higher expression of KDR while medium size of microspheres (94 mum) resulted in higher CD31 and VE-cadherin expression. This study indicated that the biophysical properties of PCL-based copolymers impacted stem cell lineage commitment, which should be considered for drug delivery and tissue engineering applications.

  10. 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.

  11. Antimicrobial Graft Copolymer Gels.

    PubMed

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

    2016-08-01

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

  12. Multicompartment Core Micelles of Triblock Terpolymers in Organic Media

    SciTech Connect

    Schacher, Felix; Walther, Andreas; Ruppel, Markus A; Drechsler, Markus; Muller, Axel

    2009-01-01

    The formation of multicompartment micelles featuring a spheres on sphere core morphology in acetone as a selective solvent is presented. The polymers investigated are ABC triblock terpolymers, polybutadieneb-poly(2-vinyl pyridine)-b-poly(tert-butyl methacrylate) (BVT), which were synthesized via living sequential anionic polymerization in THF. Two polymers with different block lengths of the methacrylate moiety were studied with respect to the formation of multicompartmental aggregates. The micelles were analyzed by static and dynamic light scattering as well as by transmission electron microscopy. Cross-linking of the polybutadiene compartment could be accomplished via two different methods, cold vulcanization and with photopolymerization after the addition of a multifunctional acrylate. In both cases, the multicompartmental character of the micellar core is fully preserved, and the micelles could be transformed into core-stabilized nanoparticles. The successful cross-linking of the polybutadiene core is indicated by 1H NMR and by the transfer of the aggregates into nonselective solvents such as THF or dioxane.

  13. Surface properties and biocompatibility of A-B-A type block copolymer membranes consisting of poly(gamma-benzyl-L-glutamate) as the A component and polyisoprene as the B component.

    PubMed

    Yoda, R; Komatsuzaki, S; Hayashi, T

    1995-11-01

    The surface characteristics of A-B-A type triblock copolymer (GIG) membranes consisting of alpha-helical poly (gamma-benzyl-L-glutamate) (PBLG) as the A component and polyisoprene (PI) as the B component were investigated by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The XPS measurements showed the copolymer composition of the outermost surface to be quite different from the bulk composition. Results of contact angle measurements indicated the existence of an interfacial region between the alpha-helical A component and the B component at the surfaces of the block copolymer membranes. Finally, the results of in vivo tests on tissue compatibility indicate that the GIG block copolymer membranes have good biocompatibility. PMID:8589188

  14. A multiscale modeling study of loss processes in block-copolymer-based solar cell nanodevices.

    PubMed

    Donets, Sergii; Pershin, Anton; Christlmaier, Martin J A; Baeurle, Stephan A

    2013-03-01

    Flexible photovoltaic devices possess promising perspectives in opto-electronic technologies, where high mobility and/or large-scale applicability are important. However, their usefulness in such applications is currently still limited due to the low level of optimization of their performance and durability. For the improvement of these properties, a better understanding and control of small-scale annihilation phenomena involved in the photovoltaic process, such as exciton loss and charge carrier loss, is necessary, which typically implicates multiple length- and time-scales. Here, we study the causes for their occurrence on the example of nanostructured diblock- and triblock-copolymer systems by making use of a novel solar-cell simulation algorithm and explore new routes to optimize their photovoltaic properties. A particular focus is set on the investigation of exciton and charge carrier loss phenomena and their dependence on the inter-monomeric interaction strength, chain architecture, and external mechanical loading. Our simulation results reveal that in the regime from low up to intermediate χ-parameters an increasing number of continuous percolation paths is created. In this parameter range, the internal quantum efficiency (IQE) increases up to a maximum, characterized by a minimum in the number of charge losses due to charge recombination. In the regime of high χ-parameters both block-copolymer systems form nanostructures with a large number of bottlenecks and dead ends. These lead to a large number of charge losses due to charge recombination, charge trapping, and a deteriorated exciton dissociation, resulting in a significant drop in the IQE. Moreover, we find that the photovoltaic performance of the triblock-copolymer material decreases with increasing mechanical loading, caused by a growing number of charge losses due to charge recombination and charge accumulation. Finally, we demonstrate that the process of charge trapping in defects can be reversed

  15. A multiscale modeling study of loss processes in block-copolymer-based solar cell nanodevices

    NASA Astrophysics Data System (ADS)

    Donets, Sergii; Pershin, Anton; Christlmaier, Martin J. A.; Baeurle, Stephan A.

    2013-03-01

    Flexible photovoltaic devices possess promising perspectives in opto-electronic technologies, where high mobility and/or large-scale applicability are important. However, their usefulness in such applications is currently still limited due to the low level of optimization of their performance and durability. For the improvement of these properties, a better understanding and control of small-scale annihilation phenomena involved in the photovoltaic process, such as exciton loss and charge carrier loss, is necessary, which typically implicates multiple length- and time-scales. Here, we study the causes for their occurrence on the example of nanostructured diblock- and triblock-copolymer systems by making use of a novel solar-cell simulation algorithm and explore new routes to optimize their photovoltaic properties. A particular focus is set on the investigation of exciton and charge carrier loss phenomena and their dependence on the inter-monomeric interaction strength, chain architecture, and external mechanical loading. Our simulation results reveal that in the regime from low up to intermediate χ-parameters an increasing number of continuous percolation paths is created. In this parameter range, the internal quantum efficiency (IQE) increases up to a maximum, characterized by a minimum in the number of charge losses due to charge recombination. In the regime of high χ-parameters both block-copolymer systems form nanostructures with a large number of bottlenecks and dead ends. These lead to a large number of charge losses due to charge recombination, charge trapping, and a deteriorated exciton dissociation, resulting in a significant drop in the IQE. Moreover, we find that the photovoltaic performance of the triblock-copolymer material decreases with increasing mechanical loading, caused by a growing number of charge losses due to charge recombination and charge accumulation. Finally, we demonstrate that the process of charge trapping in defects can be reversed

  16. 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.

  17. Separation of parent homopolymers from polystyrene and poly(ethylene oxide) based block copolymers by liquid chromatography under limiting conditions of desorption-3. Study of barrier efficiency according to block copolymers' chemical composition.

    PubMed

    Rollet, Marion; Pelletier, Bérengère; Berek, Dušan; Maria, Sébastien; Phan, Trang N T; Gigmes, Didier

    2016-09-01

    Liquid Chromatography under Limiting Conditions of Desorption (LC LCD) is a powerful separation tool for multicomponent polymer systems. This technique is based on a barrier effect of an appropriate solvent, which is injected in front of the sample, and which decelerates the elution of selected macromolecules. In this study, the barrier effects have been evaluated for triblock copolymers polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-b-PEO-b-PS) according to the content of polystyrene (wt% PS) and PEO-block molar mass. PS-b-PEO-b-PS samples were prepared by Atom Transfer Radical Polymerization (ATRP). The presence of respective parent homopolymers was investigated by applying optimized LC LCD conditions. It was found that the barrier composition largely affects the efficiency of separation and it ought to be adjusted for particular composition range of block copolymers.

  18. 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.

  19. 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

  20. Hydrothermal Synthesis and Processing of Barium Titanate Nanoparticles Embedded in Polymer Films.

    PubMed

    Toomey, Michael D; Gao, Kai; Mendis, Gamini P; Slamovich, Elliott B; Howarter, John A

    2015-12-30

    Barium titanate nanoparticles embedded in flexible polymer films were synthesized using hydrothermal processing methods. The resulting films were characterized with respect to material composition, size distribution of nanoparticles, and spatial location of particles within the polymer film. Synthesis conditions were varied based on the mechanical properties of the polymer films, ratio of polymer to barium titanate precursors, and length of aging time between initial formulations of the solution to final processing of nanoparticles. Block copolymers of poly(styrene-co-maleic anhydride) (SMAh) were used to spatially separate titanium precursors based on specific chemical interactions with the maleic anhydride moiety. However, the glassy nature of this copolymer restricted mobility of the titanium precursors during hydrothermal processing. The addition of rubbery butadiene moieties, through mixing of the SMAh with poly(styrene-butadiene-styrene) (SBS) copolymer, increased the nanoparticle dispersion as a result of greater diffusivity of the titanium precursor via higher mobility of the polymer matrix. Additionally, an aminosilane was used as a means to retard cross-linking in polymer-metalorganic solutions, as the titanium precursor molecules were shown to react and form networks prior to hydrothermal processing. By adding small amounts of competing aminosilane, excessive cross-linking was prevented without significantly impacting the quality and composition of the final barium titanate nanoparticles. X-ray diffraction and X-ray photoelectron spectroscopy were used to verify nanoparticle compositions. Particle sizes within the polymer films were measured to be 108 ± 5 nm, 100 ± 6 nm, and 60 ± 5 nm under different synthetic conditions using electron microscopy. Flexibility of the films was assessed through measurement of the glass transition temperature using dynamic mechanical analysis. Dielectric permittivity was measured using an impedance analyzer.

  1. 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.

  2. 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.

  3. 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.

  4. Ultraviolet absorbing copolymers

    DOEpatents

    Gupta, Amitava; Yavrouian, Andre H.

    1982-01-01

    Photostable and weather stable absorping copolymers have been prepared from acrylic esters such as methyl methacrylate containing 0.1 to 5% of an 2-hydroxy-allyl benzophenone, preferably the 4,4' dimethoxy derivative thereof. The pendant benzophenone chromophores protect the acrylic backbone and when photoexcited do not degrade the ester side chain, nor abstract hydrogen from the backbone.

  5. Bimodal mesoporous carbon synthesized from large organic precursor and amphiphilic tri-block copolymer by self assembly

    SciTech Connect

    Saha, Dipendu; Contescu, Cristian I; Gallego, Nidia C

    2012-01-01

    Owing to several disadvantages of traditional hard template based synthesis, soft-template or self-assembly was adopted to synthesize mesoporous carbon. In this work, we have introduced hexaphenol as a new and large organic precursor for the synthesis of mesoporous carbon by self-assembly with pluronic P123 as structure dictating agent. The resultant mesoporous carbon is bimodal in nature with median pore widths of 29 and 45 and BET surface area of 312 m2/g. Unlike previously synthesized mesoporous carbon, this carbon possesses negligible micropore volume. This mesoporous carbon is very suitable candidate for several applications including membrane separation, chemical sensor or selective sorption of larger molecules.

  6. Novel Thermosensitive Pentablock Copolymers for Sustained Delivery of Proteins in the Treatment of Posterior Segment Diseases

    PubMed Central

    Patel, Sulabh P.; Vaishya, Ravi; Yang, Xiaoyan; Pal, Dhananjay; Mitra, Ashim K.

    2015-01-01

    Biodegradable and injectable in situ thermosensitive hydrogels were investigated for sustained delivery of protein therapeutics in the treatment of ocular posterior segment neovascular diseases. A series of triblock (TB, polycaprolac-tone-polyethylene glycol-polycaprolactone (PCL-PEG-PCL), B-A-B) and pentablock copolymers (PBCs) (polylactic acid (PLA)-PCL-PEG-PCL-PLA (C-B-A-B-C) and PEG-PCL-PLA-PCL-PEG (A-B-C-B-A)) were synthesized and evaluated for their thermosensitive behavior. Effects of molecular weight, hydrophobicity and block arrangement on polymer crystallinity, sol-gel transition, micelle size, viscosity and in vitro drug release were examined. Results from sol-gel transition studies demonstrated that aqueous solutions of block copolymers can immediately transform to hydrogel upon exposure to physiological temperature. PBC provide significantly longer sustained release (more than 20 days) of IgG relative to TB copolymers. Moreover, kinematic viscosity of aqueous solution at 25°C for A-B-C-B-A type of PBCs was noticeably lower than the TB (B-A-B) copolymers and other PBCs with C-B-A-B-C block arrangements suggesting desired syringeability. The presence of PLA blocks in PBCs (C-B-A-B-C and A-B-C-B-A) significantly reduces crystallinity. Hence, it is anticipated that PBCs will have a faster rate of degradation relative to PCL-PEG-PCL based TB copolymers. PBCs also exhibited excellent cell viability and biocompatibility on ARPE-19 (human retinal pigment epithelial cell line) and RAW-264.7 (mouse macrophage cells), likely rendering it safe for ocular applications. Owing to biodegradability, thermosensitivity, ease of handling and biocompatibility PBC hydrogels can be considered as promising biomaterial for sustained delivery of protein therapeutics to the back of the eye. PMID:25315374

  7. 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.

  8. 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.

  9. Imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1992-01-01

    Imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly(arylene ethers) in polar aprotic solvents and by chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The resulting block copolymers have one glass transition temperature or two, depending upon the particular structure and/or the compatibility of the block units. Most of these block copolymers form tough, solvent resistant films with high tensile properties.

  10. Composition and properties of porous blend membranes containing tertiary amine based amphiphilic copolymers with different sequence structures.

    PubMed

    Yao, Zhikan; Cui, Yue; Zheng, Ke; Zhu, Baoku; Zhu, Liping

    2015-01-01

    Four tertiary amine based amphiphilic copolymers with similar composition but different sequence structures in terms of diblock (Poly(dimethylamino-2-ethyl methacrylate-b-methyl methacrylate) (P(MMA-b-DMAEMA))), triblock (P(DMAEMA-b-MMA-b-DMAEMA)), four-armed diblock (P(MMA-b-DMAEMA)4) and random (P(MMA-r-DMAEMA)) were synthesized and used for fabricating functional porous membranes by blending method. The retention ratios and surface enrichment ratios of the copolymers in blend membranes were determined by hydrogen nuclear magnetic resonance ((1)H-NMR) and X-ray photoelectron spectroscopy (XPS). The composition of the formed membranes was investigated and the durability was experimentally tested. The hydrophilicity of the membranes was evaluated by water contact angle measurement. The performance of membranes under different conditions including water fluxes at different pH and various ionic strength, the adsorption capabilities for Cr(VI) and negatively charged dye sunset yellow at different pH was studied. The results show that tertiary amine based amphiphilic copolymers with block and multi-armed sequence structures enable the blend membranes with higher copolymer retention ratios, more surface tertiary amine groups contents and better composition stability as well as more sensitive to the variation of pH, ionic strength, higher equilibrium anions, and negatively charged dyes uptakes.

  11. 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.

  12. Hydrazone Self-Crosslinking of Multiphase Elastin-Like Block Copolymer Networks

    PubMed Central

    Krishna, Urlam Murali; Martinez, Adam W.; Caves, Jeffrey M.; Chaikof, Elliot L.

    2011-01-01

    Biosynthetic strategies for the production of recombinant elastin-like protein (ELP) triblock copolymers have resulted in elastomeric protein hydrogels, formed through rapid physical crosslinking upon warming of concentrated solutions. However, the strength of physically crosslinked networks can be limited, and options for non-toxic chemical crosslinking of these networks are not optimal. In this report, we modify two recombinant elastin-like proteins with aldehyde and hydrazide functionalities. When combined, these modified recombinant proteins self-crosslink through hydrazone bonding without requiring initiators or producing by-products. Crosslinked materials are evaluated for water content and swelling upon hydration, and subject to tensile and compressive mechanical tests. Hydrazone crosslinking is a viable method for increasing the mechanical strength of elastin-like protein polymers, in a manner that is likely to lend itself to the biocompatible in situ formation of chemically and physically crosslinked ELP hydrogels. PMID:22154858

  13. Structure-property relationships in ABA copolymer gels with A homopolymer additions

    NASA Astrophysics Data System (ADS)

    Seitz, Michelle; Rottsolk, Rebecca; Page, Kirt; Shull, Kenneth

    2009-03-01

    ABA acrylic triblock copolymers with poly(methyl methacrylate) endblocks and poly(butyl acrylate) midblocks transition from free flowing liquids to elastic solids with decreasing temperature in alcohol solvents. Homopolymer PMMA chains can be solubilized in the micelle cores if they are shorter than the endblocks. Indentation and compression tests were used to determine gel's modulus and large strain behavior. Gels with volume fractions of PMMA less than ˜0.2 are highly elastic and have moduli dictated by stretching of bridging midblocks. At higher PMMA contents, gels exhibit greater permanent deformation and moduli over an order of magnitude larger than would be expected from rubber elasticity alone. Small angle X-ray and neutron scattering and mean field simulations were used to correlate changes in gel structure and micelle morphology with the addition of homopolymer.

  14. Block copolymer self-assembly-directed synthesis of mesoporous gyroidal superconductors.

    PubMed

    Robbins, Spencer W; Beaucage, Peter A; Sai, Hiroaki; Tan, Kwan Wee; Werner, Jörg G; Sethna, James P; DiSalvo, Francis J; Gruner, Sol M; Van Dover, Robert B; Wiesner, Ulrich

    2016-01-01

    Superconductors with periodically ordered mesoporous structures are expected to have properties very different from those of their bulk counterparts. Systematic studies of such phenomena to date are sparse, however, because of a lack of versatile synthetic approaches to such materials. We demonstrate the formation of three-dimensionally continuous gyroidal mesoporous niobium nitride (NbN) superconductors from chiral ABC triblock terpolymer self-assembly-directed sol-gel-derived niobium oxide with subsequent thermal processing in air and ammonia gas. Superconducting materials exhibit a critical temperature (T c) of about 7 to 8 K, a flux exclusion of about 5% compared to a dense NbN solid, and an estimated critical current density (J c) of 440 A cm(-2) at 100 Oe and 2.5 K. We expect block copolymer self-assembly-directed mesoporous superconductors to provide interesting subjects for mesostructure-superconductivity correlation studies. PMID:27152327

  15. Block copolymer self-assembly–directed synthesis of mesoporous gyroidal superconductors

    PubMed Central

    Robbins, Spencer W.; Beaucage, Peter A.; Sai, Hiroaki; Tan, Kwan Wee; Werner, Jörg G.; Sethna, James P.; DiSalvo, Francis J.; Gruner, Sol M.; Van Dover, Robert B.; Wiesner, Ulrich

    2016-01-01

    Superconductors with periodically ordered mesoporous structures are expected to have properties very different from those of their bulk counterparts. Systematic studies of such phenomena to date are sparse, however, because of a lack of versatile synthetic approaches to such materials. We demonstrate the formation of three-dimensionally continuous gyroidal mesoporous niobium nitride (NbN) superconductors from chiral ABC triblock terpolymer self-assembly–directed sol-gel–derived niobium oxide with subsequent thermal processing in air and ammonia gas. Superconducting materials exhibit a critical temperature (Tc) of about 7 to 8 K, a flux exclusion of about 5% compared to a dense NbN solid, and an estimated critical current density (Jc) of 440 A cm−2 at 100 Oe and 2.5 K. We expect block copolymer self-assembly–directed mesoporous superconductors to provide interesting subjects for mesostructure-superconductivity correlation studies. PMID:27152327

  16. Interactions in random copolymers

    NASA Astrophysics Data System (ADS)

    Marinov, Toma; Luettmer-Strathmann, Jutta

    2002-04-01

    The description of thermodynamic properties of copolymers in terms of simple lattice models requires a value for the effective interaction strength between chain segments, in addition to parameters that can be derived from the properties of the corresponding homopolymers. If the monomers are chemically similar, Berthelot's geometric-mean combining rule provides a good first approximation for interactions between unlike segments. In earlier work on blends of polyolefins [1], we found that the small-scale architecture of the chains leads to corrections to the geometric-mean approximation that are important for the prediction of phase diagrams. In this work, we focus on the additional effects due to sequencing of the monomeric units. In order to estimate the effective interaction for random copolymers, the small-scale simulation approach developed in [1] is extended to allow for random sequencing of the monomeric units. The approach is applied here to random copolymers of ethylene and 1-butene. [1] J. Luettmer-Strathmann and J.E.G. Lipson. Phys. Rev. E 59, 2039 (1999) and Macromolecules 32, 1093 (1999).

  17. 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

  18. 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.

  19. Time-dependent Ginzburg-Landau model for nonfrustrated linear ABC triblock terpolymers.

    PubMed

    Millett, Paul C

    2015-08-01

    A time-dependent Ginzburg-Landau (TDGL) model is proposed to simulate the ordering of linear ABC triblock terpolymers. The model, in its current form, is applicable to nonfrustrated triblock systems, with the specific condition that χAC≫χAB≈χBC. Simulations are presented that demonstrate the model's ability to evolve a wide variety of morphologies throughout time, including tetragonal, core-shell hexagonal, three-phase lamellar, and beads-in-lamellar phases. The model also incorporates an interaction term to study templated substrates for directed self-assembly. The efficiency of the TDGL model enables large-scale simulations that allow investigation of self-assembly, and directed self-assembly, processes that may exhibit very small defect concentrations.

  20. Time-dependent Ginzburg-Landau model for nonfrustrated linear A B C triblock terpolymers

    NASA Astrophysics Data System (ADS)

    Millett, Paul C.

    2015-08-01

    A time-dependent Ginzburg-Landau (TDGL) model is proposed to simulate the ordering of linear A B C triblock terpolymers. The model, in its current form, is applicable to nonfrustrated triblock systems, with the specific condition that χA C≫χA B≈χB C . Simulations are presented that demonstrate the model's ability to evolve a wide variety of morphologies throughout time, including tetragonal, core-shell hexagonal, three-phase lamellar, and beads-in-lamellar phases. The model also incorporates an interaction term to study templated substrates for directed self-assembly. The efficiency of the TDGL model enables large-scale simulations that allow investigation of self-assembly, and directed self-assembly, processes that may exhibit very small defect concentrations.

  1. Reactive triblock polymers from tandem ring-opening polymerization for nanostructured vinyl thermosets

    SciTech Connect

    Amendt, Mark A.; Pitet, Louis M.; Moench, Sarah; Hillmyer, Marc A.

    2013-03-07

    Multiply functional hydroxyl telechelic poly(cyclooctene-s-5-norbornene-2-methylene methacrylate) was synthesized by ring opening metathesis (co)polymerization of cis-cyclooctene and 5-norbornene-2-methylene methacrylate using the second generation Grubbs catalyst in combination with a symmetric chain transfer agent bearing hydroxyl functionality. The resulting hydroxyl-telechelic polymer was used as a macroinitiator for the ring opening transesterification polymerization of d,l-lactide to form reactive poly(lactide)-b-poly(cyclooctene-s-5-norbornene-2-methylene methacrylate)-b-poly(lactide) triblock polymers. Subsequently, the triblocks were crosslinked by free radical copolymerization with several vinyl monomers including styrene, divinylbenzene, methyl methacrylate, and ethyleneglycol dimethacrylate. Certain conditions led to optically transparent thermosets with mesoscale phase separation as evidenced by small angle X-ray scattering, differential scanning calorimetry and transmission electron microscopy. Disordered, bicontinuous structures with nanoscopic domains were generated in several cases, rendering the samples attractive for size-selective membrane applications.

  2. Controlled Thermoresponsive Hydrogels by Stereocomplexed PLA-PEG-PLA Prepared via Hybrid Micelles of Pre-Mixed Copolymers with Different PEG Lengths

    SciTech Connect

    Abebe, Daniel G.; Fujiwara, Tomoko

    2012-09-05

    The stereocomplexed hydrogels derived from the micelle mixture of two enantiomeric triblock copolymers, PLLA-PEG-PLLA and PDLA-PEG-PDLA, reported in 2001 exhibited sol-to-gel transition at approximately body temperature upon heating. However, the showed poor storage modulus (ca. 1000 Pa) determined their insufficiency as injectable implant biomaterials for many applications. In this study, the mechanical property of these hydrogels was significantly improved by the modifications of molecular weights and micelle structure. Co-micelles composed of block copolymers with two sizes of PEG block length were shown to possess unique and dissimilar properties from the micelles composed of single-sized block copolymers. The stereomixture of PLA-PEG-PLA comicelles showed a controllable sol-to-gel transition at a wide temperature range of 4 and 80 C. The sol-gel phase diagram displays a linear relationship of temperature versus copolymer composition; hence, a transition at body temperature can be readily achieved by adjusting the mixed copolymer ratio. The resulting thermoresponsive hydrogels exhibit a storage modulus notably higher (ca. 6000 Pa) than that of previously reported hydrogels. As a physical network solely governed by self-reorganization of micelles, followed by stereocomplexation, this unique system offers practical, safe, and simple implantable biomaterials.

  3. Controlled thermoresponsive hydrogels by stereocomplexed PLA-PEG-PLA prepared via hybrid micelles of pre-mixed copolymers with different PEG lengths.

    PubMed

    Abebe, Daniel G; Fujiwara, Tomoko

    2012-06-11

    The stereocomplexed hydrogels derived from the micelle mixture of two enantiomeric triblock copolymers, PLLA-PEG-PLLA and PDLA-PEG-PDLA, reported in 2001 exhibited sol-to-gel transition at approximately body temperature upon heating. However, the showed poor storage modulus (ca. 1000 Pa) determined their insufficiency as injectable implant biomaterials for many applications. In this study, the mechanical property of these hydrogels was significantly improved by the modifications of molecular weights and micelle structure. Co-micelles composed of block copolymers with two sizes of PEG block length were shown to possess unique and dissimilar properties from the micelles composed of single-sized block copolymers. The stereomixture of PLA-PEG-PLA comicelles showed a controllable sol-to-gel transition at a wide temperature range of 4 and 80 °C. The sol-gel phase diagram displays a linear relationship of temperature versus copolymer composition; hence, a transition at body temperature can be readily achieved by adjusting the mixed copolymer ratio. The resulting thermoresponsive hydrogels exhibit a storage modulus notably higher (ca. 6000 Pa) than that of previously reported hydrogels. As a physical network solely governed by self-reorganization of micelles, followed by stereocomplexation, this unique system offers practical, safe, and simple implantable biomaterials. PMID:22537225

  4. "Cross" Supermicelles via the Hierarchical Assembly of Amphiphilic Cylindrical Triblock Comicelles.

    PubMed

    Li, Xiaoyu; Gao, Yang; Boott, Charlotte E; Hayward, Dominic W; Harniman, Robert; Whittell, George R; Richardson, Robert M; Winnik, Mitchell A; Manners, Ian

    2016-03-30

    Self-assembled "cross" architectures are well-known in biological systems (as illustrated by chromosomes, for example); however, comparable synthetic structures are extremely rare. Herein we report an in depth study of the hierarchical assembly of the amphiphilic cylindrical P-H-P triblock comicelles with polar (P) coronal ends and a hydrophobic (H) central periphery in a selective solvent for the terminal segments which allows access to "cross" supermicelles under certain conditions. Well-defined P-H-P triblock comicelles M(PFS-b-PtBA)-b-M(PFS-b-PDMS)-b-M(PFS-b-PtBA) (M = micelle segment, PFS = polyferrocenyldimethylsilane, PtBA = poly(tert-butyl acrylate), and PDMS = polydimethylsiloxane) were created by the living crystallization-driven self-assembly (CDSA) method. By manipulating two factors in the supermicelles, namely the H segment-solvent interfacial energy (through the central H segment length, L1) and coronal steric effects (via the PtBA corona chain length in the P segment, L2 related to the degree of polymerization DP2) the aggregation of the triblock comicelles could be finely tuned. This allowed a phase-diagram to be constructed that can be extended to other triblock comicelles with different coronas on the central or end segment where "cross" supermicelles were exclusively formed under predicted conditions. Laser scanning confocal microscopy (LSCM) analysis of dye-labeled "cross" supermicelles, and block "cross" supermicelles formed by addition of a different unimer to the arm termini, provided complementary characterization to transmission electron microscopy (TEM) and dynamic light scattering (DLS) and confirmed the existence of these "cross" supermicelles as kinetically stable, micron-size colloidally stable structures in solution. PMID:26878261

  5. Polyether/Polyester Graft Copolymers

    NASA Technical Reports Server (NTRS)

    Bell, Vernon L., Jr.; Wakelyn, N.; Stoakley, D. M.; Proctor, K. M.

    1986-01-01

    Higher solvent resistance achieved along with lower melting temperature. New technique provides method of preparing copolymers with polypivalolactone segments grafted onto poly (2,6-dimethyl-phenylene oxide) backbone. Process makes strong materials with improved solvent resistance and crystalline, thermally-reversible crosslinks. Resulting graft copolymers easier to fabricate into useful articles, including thin films, sheets, fibers, foams, laminates, and moldings.

  6. Forming Reversible Gels with Triblock Polyelectrolytes: a Field-theoretic Study

    NASA Astrophysics Data System (ADS)

    Audus, Debra; Fredrickson, Glenn

    2011-03-01

    Recently, two research groups have formed reversible gels using triblock polyelectrolytes (Lemmers et al. 2010; Hunt et al., in preparation). This gel formation is driven by a phenomenon called complex coacervation, in which two oppositely charged homopolymers in solution phase separate into a polymer rich phase, known as a coacervate, and a solution phase. If instead, the polymers are triblocks with a neutral midblock and charged end blocks, under appropriate conditions they will microphase separate into micelles with cores of coacervated charged groups and coronas of neutral midblocks. These neutral midblocks act as bridges between the micelles, thereby creating a gel. One of the advantages of forming gels in this way is that the coacervate domains, and thus the gel, can be easily tuned by varying parameters such as pH, salt concentration and temperature. In order to understand the microstructures and solution sensitivity of these reversible gels, we have numerically simulated field-theoretic models of triblock polyelectrolyte mixtures in an implicit solvent. Because coacervation is driven by charge correlations, the usual mean-field assumption fails, and it is necessary to study the model beyond the level of SCFT.

  7. 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

  8. 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

  9. Encapsulation of MEH-PPV:PCBM Hybrids in the Cores of Block Copolymer Micellar Assemblies: Photoinduced Electron Transfer in a Nanoscale Donor-Acceptor System.

    PubMed

    Wang, Suxiao; Ryan, James William; Singh, Amita; Beirne, Jason Gerard; Palomares, Emilio; Redmond, Gareth

    2016-01-12

    The objective of this work is to demonstrate that conjugated polymer:fullerene hybrid nanoparticles encapsulated in the hydrophobic cores of triblock copolymer micelles may successfully act as spatially confined donor-acceptor systems capable of facilitating photoinduced charge carrier separation. To this end, aqueous dispersions of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) nanoparticles were first prepared by solubilization of the polymer in the cores of poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) triblock copolymer, Pluronic F-127 micelles. A number of significant optical spectroscopic changes were observed on transfer of the conjugated polymer from a nonaqueous solvent to the aqueous micellar environment. These were primarily attributed to increased interchain interactions due to conjugated polymer chain collapse during encapsulation in the micellar cores. When prepared in buffer solution, the micelles exhibited good long-term collodial stability. When MEH-PPV micelles were blended by the addition of controlled amounts of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), the observed correspondence of photoluminescence emission quenching, quantum yield decreases, and emission lifetime shortening with increasing PCBM concentration indicated efficient photoinduced donor-to-acceptor charge transfer between MEH-PPV and the fullerenes in the cores of the micelles, an assignment that was confirmed by transient absorption spectroscopic monitoring of carrier photogeneration and recombination. PMID:26653672

  10. Polyplex Micelles with Double-Protective Compartments of Hydrophilic Shell and Thermoswitchable Palisade of Poly(oxazoline)-Based Block Copolymers for Promoted Gene Transfection.

    PubMed

    Osawa, Shigehito; Osada, Kensuke; Hiki, Shigehiro; Dirisala, Anjaneyulu; Ishii, Takehiko; Kataoka, Kazunori

    2016-01-11

    Improving the stability of polyplex micelles under physiological conditions is a critical issue for promoting gene transfection efficiencies. To this end, hydrophobic palisade was installed between the inner core of packaged plasmid DNA (pDNA) and the hydrophilic shell of polyplex micelles using a triblock copolymer consisting of hydrophilic poly(2-ethyl-2-oxazoline), thermoswitchable amphiphilic poly(2-n-propyl-2-oxazoline) (PnPrOx) and cationic poly(L-lysine). The two-step preparation procedure, mixing the triblock copolymer with pDNA below the lower critical solution temperature (LCST) of PnPrOx, followed by incubation above the LCST to form a hydrophobic palisade of the collapsed PnPrOx segment, induced the formation of spatially aligned hydrophilic-hydrophobic double-protected polyplex micelles. The prepared polyplex micelles exhibited significant tolerance against attacks from nuclease and polyanions compared to those without hydrophobic palisades, thereby promoting gene transfection. These results corroborated the utility of amphiphilic poly(oxazoline) as a molecular thermal switch to improve the stability of polyplex gene carriers relevant for physiological applications.

  11. Influence of poly(ethylene oxide)-based copolymer on protein adsorption and bacterial adhesion on stainless steel: modulation by surface hydrophobicity.

    PubMed

    Yang, Yi; Rouxhet, Paul G; Chudziak, Dorota; Telegdi, Judit; Dupont-Gillain, Christine C

    2014-06-01

    The aim of the present work is to study the adhesion of Pseudomonas NCIMB 2021, a typical aerobic marine microorganism, on stainless steel (SS) substrate. More particularly, the potential effect on adhesion of adsorbed poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer is investigated. Bacterial attachment experiments were carried out using a modified parallel plate flow chamber, allowing different surface treatments to be compared in a single experiment. The amount of adhering bacteria was determined via DAPI staining and fluorescence microscopy. X-ray photoelectron spectroscopy (XPS) was used to characterize the surface chemical composition of SS and hydrophobized SS before and after PEO-PPO-PEO adsorption. The adsorption of bovine serum albumin (BSA), a model protein, was investigated to test the resistance of PEO-PPO-PEO layers to protein adsorption. The results show that BSA adsorption and Pseudomonas 2021 adhesion are significantly reduced on hydrophobized SS conditioned with PEO-PPO-PEO. Although PEO-PPO-PEO is also found to adsorb on SS, it does not prevent BSA adsorption nor bacterial adhesion, which is attributed to different PEO-PPO-PEO adlayer structures on hydrophobic and hydrophilic surfaces. The obtained results open the way to a new strategy to reduce biofouling on metal oxide surfaces using PEO-PPO-PEO triblock copolymer.

  12. Towards entropy-driven interstitial micelles at elevated temperatures from selective A1BA2 triblock solutions.

    PubMed

    Wołoszczuk, S; Jurga, S; Banaszak, M

    2016-08-01

    We simulate selective A1BA2-A and A1BA2-B triblock solutions (that is, mixtures of the A1BA2 triblock with a solvent of either type A or type B) using a lattice Monte Carlo method. Although the simulated triblock chains are compositionally symmetric in terms of the A to B volume ratio, the A1 block is significantly shorter than the A2 block. For the pure A1BA2 melt the phase behavior is relatively well known, including the existence and stability of the recently discovered interstitial micelles which were found at the very strong segregation limit. In this paper, we investigate the stability of the interstitial micelles as a function of triblock volume fraction in a selective solvent of either type A or type B. The main finding of this paper is that adding a selective solvent of type A shifts the stability of the interstitial micelles into significantly higher temperatures which may provide a pathway towards experimental studies of interstitial micelles in real triblock solutions. We also find that adding selective solvents to the A1BA2 melt gives rise to a variety of nonlamellar nanostructures for temperatures and compositions at which the interstitial micelles are stable. PMID:27627353

  13. Towards entropy-driven interstitial micelles at elevated temperatures from selective A 1 BA 2 triblock solutions

    NASA Astrophysics Data System (ADS)

    Wołoszczuk, S.; Jurga, S.; Banaszak, M.

    2016-08-01

    We simulate selective A 1 B A 2 -A and A 1 B A 2 -B triblock solutions (that is, mixtures of the A 1 B A 2 triblock with a solvent of either type A or type B ) using a lattice Monte Carlo method. Although the simulated triblock chains are compositionally symmetric in terms of the A to B volume ratio, the A 1 block is significantly shorter than the A 2 block. For the pure A 1 B A 2 melt the phase behavior is relatively well known, including the existence and stability of the recently discovered interstitial micelles which were found at the very strong segregation limit. In this paper, we investigate the stability of the interstitial micelles as a function of triblock volume fraction in a selective solvent of either type A or type B . The main finding of this paper is that adding a selective solvent of type A shifts the stability of the interstitial micelles into significantly higher temperatures which may provide a pathway towards experimental studies of interstitial micelles in real triblock solutions. We also find that adding selective solvents to the A 1 B A 2 melt gives rise to a variety of nonlamellar nanostructures for temperatures and compositions at which the interstitial micelles are stable.

  14. In-situ crosslinkable and self-assembling elastin-like polypeptide block copolymers for cartilage tissue repair

    NASA Astrophysics Data System (ADS)

    Lim, Dong Woo

    This work describes the development of genetically engineered elastin-like polypeptide (ELP) block copolymers as in-situ gelling scaffolds for cartilage tissue repair. The central hypothesis underlying this work is that ELP based biopolymers can be exploited as injectable biomaterials by rapid chemical crosslinking. To prove this, gene libraries encoding ELP having different molecular weights and amino acid sequences, and ELP block copolymers composed of various ELP blocks having diverse amino acid composition, length, and phase transition behavior were synthesized by recursive directional ligation, expressed in E. Coli and purified by inverse transition cycling. Mannich-type condensation of hydroxymethylphosphines (HMPs) with primary- and secondary-amines of amino acids was developed as a new crosslinking method of polypeptides. Chemically crosslinked ELP hydrogels were formed rapidly in an aqueous solution by reaction of ELPs containing periodic lysine residues with HMPs. The crosslinking density and mechanical property of the ELP hydrogels were controlled at the sequence level by varying the Lys density in ELPs composed of mono-block as well as by segregation of the Lys residues within specific blocks of tri-block architectures. Fibroblasts embedded in ELP hydrogels survived the crosslinking process and were viable after in vitro culture for at least 3 days. The DNA content of fibroblasts within the tri-block gels was significantly higher than that in the mono-block gels at day 3. These results suggest that the HMP crosslinked ELP block copolymer hydrogels show finely tuned mechanical properties and different microenvironments for cell viability as well as potential as in-situ crosslinkable biopolymers for tissue repair applications with load-bearing environments. As an alternative, rheological behavior of the ELP block copolymers and ELP-grafted hyaluronic acids (HAs) as artificial extracellular matrices (ECMs) showed that they were thermally aggregated into

  15. Phthalimide Copolymer Solar Cells

    NASA Astrophysics Data System (ADS)

    Xin, Hao; Guo, Xugang; Ren, Guoqiang; Kim, Felix; Watson, Mark; Jenekhe, Samson

    2010-03-01

    Photovoltaic properties of bulk heterojunction solar cells based on phthalimide donor-acceptor copolymers have been investigated. Due to the strong π-π stacking of the polymers, the state-of-the-art thermal annealing approach resulted in micro-scale phase separation and thus negligible photocurrent. To achieve ideal bicontinuous morphology, different strategies including quickly film drying and mixed solvent for film processing have been explored. In these films, nano-sale phase separation was achieved and a power conversion efficiency of 3.0% was obtained. Absorption and space-charge limited current mobility measurements reveal similar light harvesting and hole mobilities in all the films, indicating that the morphology is the dominant factor determining the photovoltaic performance. Our results demonstrate that for highly crystalline and/or low-solubility polymers, finding a way to prevent polymer aggregation and large scale phase separation is critical to realizing high performance solar cells.

  16. Hyperviscous diblock copolymer vesicles

    NASA Astrophysics Data System (ADS)

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

    2002-03-01

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

  17. Thermodynamics of the multi-stage self-assembly of pH-sensitive gradient copolymers in aqueous solutions.

    PubMed

    Černochová, Zulfiya; Bogomolova, Anna; Borisova, Olga V; Filippov, Sergey K; Černoch, Peter; Billon, Laurent; Borisov, Oleg V; Štěpánek, Petr

    2016-08-10

    The self-assembly thermodynamics of pH-sensitive di-block and tri-block gradient copolymers of acrylic acid and styrene was studied for the first time using isothermal titration calorimetry (ITC) and dynamic light scattering (DLS) performed at varying pH. We were able to monitor each step of micellization as a function of decreasing pH. The growth of micelles is a multi-stage process that is pH dependent with several exothermic and endothermic components. The first step of protonation of the acrylic acid monomer units was accompanied mainly by conformational changes and the beginning of self-assembly. In the second stage of self-assembly, the micelles become larger and the number of micelles becomes smaller. While solution acidity increases, the isothermal calorimetry data show a broad deep minimum corresponding to an exothermic process attributed to an increase in the size of hydrophobic domains and an increase in the structure's hydrophobicity. The minor change in heat capacity (ΔCp) confirms the structural changes during this exothermic process. The exothermic process terminates deionization of acrylic acid. The pH-dependence of the ζ-potential of the block gradient copolymer micelles exhibits a plateau in the regime corresponding to the pH-controlled variation of the micellar dimensions. The onset of micelle formation and the solubility of the gradient copolymers were found to be dependent on the length of the gradient block. PMID:27451979

  18. Polydispersity-Driven Block Copolymer Amphiphile Self-Assembly into Prolate-Spheroid Micelles

    SciTech Connect

    Schmitt, Andrew L.; Repollet-Pedrosa, Milton H.; Mahanthappa, Mahesh K.

    2013-09-26

    The aqueous self-assembly behavior of polydisperse poly(ethylene oxide-b-1,4-butadiene-b-ethylene oxide) (OBO) macromolecular triblock amphiphiles is examined to discern the implications of continuous polydispersity in the hydrophobic block on the resulting aqueous micellar morphologies of otherwise monodisperse polymer surfactants. The chain length polydispersity and implicit composition polydispersity of these samples furnishes a distribution of preferred interfacial curvatures, resulting in dilute aqueous block copolymer dispersions exhibiting coexisting spherical and rod-like micelles with vesicles in a single sample with a O weight fraction, w{sub O}, of 0.18. At higher w{sub O} = 0.51-0.68, the peak in the interfacial curvature distribution shifts and we observe the formation of only American football-shaped micelles. We rationalize the formation of these anisotropically shaped aggregates based on the intrinsic distribution of preferred curvatures adopted by the polydisperse copolymer amphiphiles and on the relief of core block chain stretching by chain-length-dependent intramicellar segregation.

  19. Synthesis of poly(poly(ethylene glycol) methacrylate)-polyisobutylene ABA block copolymers by the combination of quasiliving carbocationic and atom transfer radical polymerizations.

    PubMed

    Szabó, Ákos; Szarka, Györgyi; Iván, Béla

    2015-01-01

    Systematic investigations are carried out on the synthesis of a series of new, unique ABA-type triblock copolymers consisting of the hydrophobic and chemically inert polyisobutylene (PIB) inner and the hydrophilic comb-shaped poly(poly(ethylene glycol) methacrylate) (PPEGMA) polymacromonomer as an outer block. Telechelic PIB macroinitiators with narrow molecular weight distributions (MWD) are synthesized by quasiliving carbocationic polymerization of isobutylene with a bifunctional initiator followed by quantitative chain end derivatizations. Atom transfer radical polymerization (ATRP) of PEGMAs with various molecular weights is investigated by using these macroinitiators. It is found that CuBr is an inefficient ATRP catalyst, while CuCl leads to high, nearly complete conversions of the PEGMA macromonomers. Gel permeation chromatography (GPC) analyses reveal slow initiation of PEGMA at relatively high PIB/PEGMA ratios or with PEGMAs of higher molecular weights due to steric hindrance between the macroinitiator and macromonomer. The occurrence of slow initiation, and not permanent termination, is proven by highly efficient ATRP of a low-molecular-weight monomer, methyl methacrylate, with the block copolymers as macroinitiators. Successful synthesis of PPEGMA-PIB-PPEGMA ABA block copolymers is obtained by using either low-molecular-weight PEGMA or relatively low macroinitiator/macromonomer ratios. Differential scanning calorimetry (DSC) indicates phase separation and significant suppression of the crystallinity of the pendant poly(ethylene glycol) (PEG) chains in these new block copolymers. PMID:25353143

  20. 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.

  1. Copolymer Crystallization: Approaching Equilibrium

    NASA Astrophysics Data System (ADS)

    Crist, Buckley; Finerman, Terry

    2002-03-01

    Random ethylene-butene copolymers of uniform chemical composition and degree of polymerization are crystallized by evaporation of thin films (1 μ m - 5 μ m) from solution. Macroscopic films ( 100 μm) formed by sequential layer deposition are characterized by density, calorimetry and X-ray techniques. Most notable is the density, which in some cases implies a crystalline fraction nearly 90% of the equilibrium value calculated from Flory theory. Melting temperature of these solution deposited layers is increased by as much as 8 ^oC over Tm for the same polymer crystallized from the melt. Small-angle X-ray scattering indicates that the amorphous layer thickness is strongly reduced by this layered crystallization process. X-ray diffraction shows a pronounced orientation of chain axes and lamellar normals parallel to the normal of the macroscopic film. It is clear that solvent enhances chain mobility, permitting proper sequences to aggregate and crystallize in a manner that is never achieved in the melt.

  2. Multifunctional triblock Nanocarrier (PAMAM-PEG-PLL) for the efficient intracellular siRNA delivery and gene silencing.

    PubMed

    Patil, Mahesh L; Zhang, Min; Minko, Tamara

    2011-03-22

    A novel triblock poly(amido amine)-poly(ethylene glycol)-poly-l-lysine (PAMAM-PEG-PLL) nanocarrier was designed, synthesized, and evaluated for the delivery of siRNA. The design of the nanocarrier is unique and provides a solution to most of the common problems associated with the delivery and therapeutic applications of siRNA. Every component in the triblock nanocarrier plays a significant role and performs multiple functions: (1) tertiary amine groups in the PAMAM dendrimer work as a proton sponge and play a vital role in the endosomal escape and cytoplasmic delivery of siRNA; (2) PEG, a linker connecting PLL and PAMAM dendrimers renders nuclease stability and protects siRNA in human plasma; (3) PLL provides primary amines to form polyplexes with siRNA through electrostatic interaction and also acts as penetration enhancer; and (4) conjugation to PEG and PAMAM reduced toxicity of PLL and the entire triblock nanocarrier PAMAM-PEG-PLL. The data obtained show that the polyplexes resulted from the conjugation of siRNA, and the proposed nanocarriers were effectively taken up by cancer cells and induced the knock down of the target BCL2 gene. In addition, triblock nanocarrier/siRNA polyplexes showed excellent stability in human plasma.

  3. Copolymers For Capillary Gel Electrophoresis

    DOEpatents

    Liu, Changsheng; Li, Qingbo

    2005-08-09

    This invention relates to an electrophoresis separation medium having a gel matrix of at least one random, linear copolymer comprising a primary comonomer and at least one secondary comonomer, wherein the comonomers are randomly distributed along the copolymer chain. The primary comonomer is an acrylamide or an acrylamide derivative that provides the primary physical, chemical, and sieving properties of the gel matrix. The at least one secondary comonomer imparts an inherent physical, chemical, or sieving property to the copolymer chain. The primary and secondary comonomers are present in a ratio sufficient to induce desired properties that optimize electrophoresis performance. The invention also relates to a method of separating a mixture of biological molecules using this gel matrix, a method of preparing the novel electrophoresis separation medium, and a capillary tube filled with the electrophoresis separation medium.

  4. Crystalline imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1995-01-01

    Crystalline imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly)arylene ethers) in polar aprotic solvents and chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The block copolymers of the invention have one glass transition temperature or two, depending on the particular structure and/or the compatibility of the block units. Most of these crystalline block copolymers for tough, solvent resistant films with high tensile properties. While all of the copolymers produced by the present invention are crystalline, testing reveals that copolymers with longer imide blocks or higher imide content have increased crystallinity.

  5. Gold nanoparticles modified with self-assembled hybrid monolayer of triblock aptamers as a photoreversible anticoagulant.

    PubMed

    Huang, San-Shan; Wei, Shih-Chun; Chang, Huan-Tsung; Lin, Han-Jia; Huang, Chih-Ching

    2016-01-10

    We demonstrated that thrombin-binding aptamer-conjugated gold nanoparticles (TBA-Au NPs), prepared from a self-assembled hybrid monolayer (SAHM) of triblock aptamers on Au NPs (13 nm), can effectively inhibit thrombin activity toward fibrinogen. The first block poly(adenine) at the end of the triblock TBA was used for the self-assembly on Au NP surface. The second block, in the middle of TBA, was composed of oligonucleotides that could hybridize with each other. The third block, containing TBA15 (15-base, binding to the exosite I of thrombin) and TBA29 (29-base, binding to the exosite II of thrombin) provided bivalent interaction with thrombin. The SAHM triblock aptamers have optimal distances between TBA15 and TBA29, aptamer density, and orientation on the Au NP surfaces. These properties strengthen the interactions with thrombin (Kd=1.5 × 10(-11)M), resulting in an extremely high anticoagulant potency. The thrombin clotting time mediated by SAHM TBA15/TBA29-Au NPs was >10 times longer than that of four commercially available drugs (heparin, argatroban, hirudin, or warfarin). In addition, the rat-tail bleeding assay time further demonstrated that the SAHM TBA15/TBA29-Au NPs were superior to heparin. The SAHM TBA15/TBA29-Au NPs exhibited excellent stability in the human plasma (half-life >14 days) and good biocompatibility (low cytotoxicity and hemolysis). Most interestingly, the inhibition by SAHM TBA15/TBA29-Au NPs was controllable by the irradiation of green laser, via heat transfer-induced TBA release from Au NPs. Therefore, these easily prepared (self-assembled), low cost (non-thiolated aptamer), photo-controllable, multivalent TBA15/TBA29-Au NPs (high density of TBA15/TBA29 on Au NPs) show good potential for the treatment of various diseases related to blood-clotting disorders. Our study opens up the possibility of regulation of molecule binding, protein recognition, and enzyme activity using SAHM aptamer-functionalized nanomaterials.

  6. Gold nanoparticles modified with self-assembled hybrid monolayer of triblock aptamers as a photoreversible anticoagulant.

    PubMed

    Huang, San-Shan; Wei, Shih-Chun; Chang, Huan-Tsung; Lin, Han-Jia; Huang, Chih-Ching

    2016-01-10

    We demonstrated that thrombin-binding aptamer-conjugated gold nanoparticles (TBA-Au NPs), prepared from a self-assembled hybrid monolayer (SAHM) of triblock aptamers on Au NPs (13 nm), can effectively inhibit thrombin activity toward fibrinogen. The first block poly(adenine) at the end of the triblock TBA was used for the self-assembly on Au NP surface. The second block, in the middle of TBA, was composed of oligonucleotides that could hybridize with each other. The third block, containing TBA15 (15-base, binding to the exosite I of thrombin) and TBA29 (29-base, binding to the exosite II of thrombin) provided bivalent interaction with thrombin. The SAHM triblock aptamers have optimal distances between TBA15 and TBA29, aptamer density, and orientation on the Au NP surfaces. These properties strengthen the interactions with thrombin (Kd=1.5 × 10(-11)M), resulting in an extremely high anticoagulant potency. The thrombin clotting time mediated by SAHM TBA15/TBA29-Au NPs was >10 times longer than that of four commercially available drugs (heparin, argatroban, hirudin, or warfarin). In addition, the rat-tail bleeding assay time further demonstrated that the SAHM TBA15/TBA29-Au NPs were superior to heparin. The SAHM TBA15/TBA29-Au NPs exhibited excellent stability in the human plasma (half-life >14 days) and good biocompatibility (low cytotoxicity and hemolysis). Most interestingly, the inhibition by SAHM TBA15/TBA29-Au NPs was controllable by the irradiation of green laser, via heat transfer-induced TBA release from Au NPs. Therefore, these easily prepared (self-assembled), low cost (non-thiolated aptamer), photo-controllable, multivalent TBA15/TBA29-Au NPs (high density of TBA15/TBA29 on Au NPs) show good potential for the treatment of various diseases related to blood-clotting disorders. Our study opens up the possibility of regulation of molecule binding, protein recognition, and enzyme activity using SAHM aptamer-functionalized nanomaterials. PMID:26643617

  7. Polyether-polyester graft copolymer

    NASA Technical Reports Server (NTRS)

    Bell, Vernon L. (Inventor)

    1987-01-01

    Described is a polyether graft polymer having improved solvent resistance and crystalline thermally reversible crosslinks. The copolymer is prepared by a novel process of anionic copolymerization. These polymers exhibit good solvent resistance and are well suited for aircraft parts. Previous aromatic polyethers, also known as polyphenylene oxides, have certain deficiencies which detract from their usefulness. These commercial polymers are often soluble in common solvents including the halocarbon and aromatic hydrocarbon types of paint thinners and removers. This limitation prevents the use of these polyethers in structural articles requiring frequent painting. In addition, the most popular commercially available polyether is a very high melting plastic. This makes it considerably more difficult to fabricate finished parts from this material. These problems are solved by providing an aromatic polyether graft copolymer with improved solvent resistance and crystalline thermally reversible crosslinks. The graft copolymer is formed by converting the carboxyl groups of a carboxylated polyphenylene oxide polymer to ionic carbonyl groups in a suitable solvent, reacting pivalolactone with the dissolved polymer, and adding acid to the solution to produce the graft copolymer.

  8. Phase behavior and kinetics of disorder-order and order-order transitions in multi-block copolymers in selective solvents

    NASA Astrophysics Data System (ADS)

    Nie, Huifen

    The primary aim of this thesis is to investigate the phase behavior and kinetics of the disorder-order transition (ODT) and the order-order transition (OOT) in block copolymer solutions in selective solvents, using small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS) techniques. The kinetics of the ODT and OOT in a triblock of polystyrene (PS) and poly(ethylene-co-butylene) (PEB), in mineral oil, a selective solvent for the middle PEB block, was followed by time-resolved SAXS using temperature ramp and rapid temperature quench techniques. In semi-dilute solutions, spherical micelles exhibited liquid-like ordering at elevated temperatures and ordered onto body-centered-cubic (BCC) lattice at intermediate temperatures. In concentrated solutions, both BCC ordering of spherical micelles and hexagonal packing (HEX) of cylindrical micelles were detected. The disorder to order transformation kinetics exhibit two-stage growth: the first stage reflecting the temperature equilibration and supercooling of the micellar fluid, and the second stage corresponding to the nucleation and growth of the ordered state. The order-order transformation from HEX to BCC was characterized by a continuous shift in the primary peak position and simultaneous growth of all higher order Bragg diffraction peaks in the scattering profiles. The data were interpreted in terms of a model, according to which cylindrical micelles exhibit fluctuations with a characteristic wavelength along the cylindrical axis before breaking up into spherical micelles. Our results show that the wavelength of the fluctuation remains unchanged while the amplitude of the fluctuations grows with time. The association behavior of triblock, pentablock, and heptablock copolymers of polystyrene and polybutadiene in selective solvents was examined by SANS measurement. Comparison of the scattering profiles shows that: (i) multiblock copolymers with the outer block in a poor solvent environment have a

  9. Impacts of Repeat Unit Structure and Copolymer Architecture on Thermal and Solution Properties in Homopolymers, Copolymers, and Copolymer Blends

    NASA Astrophysics Data System (ADS)

    Marrou, Stephen Raye

    Gradient copolymers are a relatively new type of copolymer architecture in which the distribution of comonomers gradually varies over the length of the copolymer chain, resulting in a number of unusual properties derived from the arrangement of repeat units. For example, nanophase-segregated gradient copolymers exhibit extremely broad glass transition temperatures (Tgs) resulting from the wide range of compositions present in the nanostructure. This dissertation presents a number of studies on how repeat unit structure and copolymer architecture dictate bulk and solution properties, specifically taking inspiration from the gradient copolymer architecture and comparing the response from this compositionally heterogeneous material to other more conventional materials. The glass transition behavior of a range of common homopolymers was studied to determine the effects of subunit structure on Tg breadth, observing a significant increase in T g breadth with increasing side chain length in methacrylate-based homopolymers and random copolymers. Additionally, increasing the composition distribution of copolymers, either by blending individual random copolymers of different overall composition or synthesizing random copolymers to high conversion, resulted in significant increases to Tg breadth. Plasticization of homopolymers and random copolymers with low molecular weight additives also served to increase the Tg breadth; the most dramatic effect was observed in the selective plasticization of a styrene/4-vinylpyridine gradient copolymer with increases in T g breadth to values above 100 °C. In addition, the effects of repeat unit structure and copolymer architecture on other polymer properties besides Tg were also investigated. The intrinsic fluorescence of styrene units in styrene-containing copolymers was studied, noting the impact of repeat unit structure and copolymer architecture on the resulting fluorescence spectra in solution. The impact of repeat unit structure on

  10. Solubility of block copolymer surfactants in compressed CO{sub 2} using a lattice fluid hydrogen-bonding model

    SciTech Connect

    Takishima, Shigeki; O`Neill, M.L.; Johnston, K.P.

    1997-07-01

    Supercritical carbon dioxide (CO{sub 2}) is an environmentally benign alternative to organic solvents in chemical processing. The solubilities of the homopolymers poly(ethylene glycol), poly(ethylene glycol) dimethyl ether (PEGDME), and poly(propylene glycol) (PPG) in CO{sub 2} were correlated with a lattice fluid hydrogen-bonding (LFHB) model, which was then used to predict solubilities of Pluronic L (PEG-PPG-PEG) and Pluronic R (PPG-PEG-PPG) triblock copolymers. Simple averaging rules were developed to evaluate the physical properties of the copolymers without introducing any adjustable parameters. For a given average molecular weight, the predictions of the model were quite reasonable and in some cases perhaps more accurate than the data, due to the large polydispersity of the samples. The model predicts the effects of total molecular weight, PEG/PPG ratio, terminal functional groups, temperature, and density on solubility. The much higher solubility of PPG versus PEG is due primarily to steric hindrance from the methyl branch, which weakens segment-segment interactions, and to a lesser extent to the stronger hydrogen bond donor strength of a primary (in the case of PEG) versus a secondary (in the case of PPG) alcohol terminal group. Consequently, the predicted solubilities of Pluronic L surfactants, which have stronger hydrogen bond donors on the terminal groups, are not much smaller than those of Pluronic R surfactants for given molecular weights of the blocks.

  11. Mixed interactions in random copolymers

    NASA Astrophysics Data System (ADS)

    Marinov, Toma; Luettmer-Strathmann, Jutta

    2002-03-01

    The description of thermodynamic properties of copolymers in terms of simple lattice models requires a value for the mixed interaction strength (ɛ_12) between unlike chain segments, in addition to parameters that can be derived from the properties of the corresponding homopolymers. If the monomers are chemically similar, Berthelot's geometric-mean combining rule provides a good first approximation for ɛ_12. In earlier work on blends of polyolefins [1], we found that the small-scale architecture of the chains leads to corrections to the geometric-mean approximation that are important for the prediction of phase diagrams. In this work, we focus on the additional effects due to sequencing of the monomeric units. In order to estimate the mixed interaction ɛ_12 for random copolymers, the small-scale simulation approach developed in [1] is extended to allow for random sequencing of the monomeric units. The approach is applied here to random copolymers of ethylene and 1-butene. [1] J. Luettmer-Strathmann and J.E.G. Lipson. Phys. Rev. E 59, 2039 (1999) and Macromolecules 32, 1093 (1999).

  12. Phase Behavior of Symmetric Sulfonated Block Copolymers

    SciTech Connect

    Park, Moon Jeong; Balsara, Nitash P.

    2008-08-21

    Phase behavior of poly(styrenesulfonate-methylbutylene) (PSS-PMB) block copolymers was studied by varying molecular weight, sulfonation level, and temperature. Molecular weights of the copolymers range from 2.9 to 117 kg/mol. Ordered lamellar, gyroid, hexagonally perforated lamellae, and hexagonally packed cylinder phases were observed in spite of the fact that the copolymers are nearly symmetric with PSS volume fractions between 0.45 and 0.50. The wide variety of morphologies seen in our copolymers is inconsistent with current theories on block copolymer phase behavior such as self-consistent field theory. Low molecular weight PSS-PMB copolymers (<6.2 kg/mol) show order-order and order-disorder phase transitions as a function of temperature. In contrast, the phase behavior of high molecular weight PSS-PMB copolymers (>7.7 kg/mol) is independent of temperature. Due to the large value of Flory-Huggins interaction parameter, x, between the sulfonated and non-sulfonated blocks, PSS-PMB copolymers with PSS and PMB molecular weights of 1.8 and 1.4 kg/mol, respectively, show the presence of an ordered gyroid phase with a 2.5 nm diameter PSS network. A variety of methods are used to estimate x between PSS and PMB chains as a function of sulfonation level. Some aspects of the observed phase behavior of PSS-PMB copolymers can be rationalized using x.

  13. Copolymers of fluorinated polydienes and sulfonated polystyrene

    DOEpatents

    Mays, Jimmy W.; Gido, Samuel P.; Huang, Tianzi; Hong, Kunlun

    2009-11-17

    Copolymers of fluorinated polydienes and sulfonated polystyrene and their use in fuel cell membranes, batteries, breathable chemical-biological protective materials, and templates for sol-gel polymerization.

  14. Self-assembly of Random Copolymers

    PubMed Central

    Li, Longyu; Raghupathi, Kishore; Song, Cunfeng; Prasad, Priyaa; Thayumanavan, S.

    2014-01-01

    Self-assembly of random copolymers has attracted considerable attention recently. In this feature article, we highlight the use of random copolymers to prepare nanostructures with different morphologies and to prepare nanomaterials that are responsive to single or multiple stimuli. The synthesis of single-chain nanoparticles and their potential applications from random copolymers are also discussed in some detail. We aim to draw more attention to these easily accessible copolymers, which are likely to play an important role in translational polymer research. PMID:25036552

  15. Enhancement of deoxyribozyme activity by cationic copolymers.

    PubMed

    Gao, Jueyuan; Shimada, Naohiko; Maruyama, Atsushi

    2015-02-01

    Deoxyribozymes, or DNAzymes, are DNA molecules with enzymatic activity. DNAzymes with ribonuclease activity have various potential applications in biomedical and bioanalytical fields; however, most constructs have limited turnover despite optimization of reaction conditions and DNAzyme structures. A cationic comb-type copolymer accelerates DNA hybridization and strand exchange rates, and we hypothesized that the copolymer would enhance deoxyribozyme activity by promoting turnover. The copolymer did not change DNAzyme activity under single-turnover conditions, suggesting that the copolymer affects neither the folding structure of DNAzyme nor the association of a divalent cation, a catalytic cofactor, to DNAzyme. The copolymer enhanced activity of the evaluated DNAzyme over a wide temperature range under multiple-turnover conditions. The copolymer increased the DNAzyme kcat/KM by fifty-fold at 50 °C, the optimal temperature for the DNAzyme in the absence of the copolymer. The acceleration effect was most significant when the reaction temperature was slightly higher than the melting temperature of the enzyme/substrate complex; acceleration of two orders of magnitude was observed. We concluded that the copolymer accelerated the turnover step without influencing the chemical cleavage step. In contrast to the copolymer, a cationic surfactant, CTAB, strongly inhibited the DNAzyme activity under either single- or multiple-turnover conditions. PMID:26218121

  16. Mg ATP and Antioxidants Augment the Radioprotective Effect of Surfactant Copolymers

    PubMed Central

    Soneru, Alexander P.; Beckett, Michael A.; Weichselbaum, Ralph R.; Lee, Raphael C.

    2011-01-01

    Background Mediated by reactive oxygen species, the damaging effects of high-intensity ionizing irradiation on tissues are dose, frequency, oxygen concentration and tissue property dependent. Intense ionizing irradiation exposure may cause rapid cellular necrosis by peroxidation of membrane lipids leading to membrane disruption. This leads to a loss of the transmembrane ionic gradients and a subsequent depletion of the cellular ATP store, followed by cellular generation of reactive oxygen species. When membrane disruption is extensive, acute cellular necrosis follows. Triblock copolymer surfactants, such as Poloxamer 188 (P188), are able to seal damaged rhabdomyocyte membranes, increasing post-irradiation viability. Methods Separated rat rhabdomyocytes were exposed to 40 Gy (60Co 1.5 Gy min−1) irradiation and treated at 20 minutes with combination permutations of P188, N-acetylcysteine (NAC) and Mg-ATP. Cell viability at 18 and 48 hours was determined using Calcein-AM and Ethidium Homodimer-1 staining. Results At 18 hours after irradiation, the combined administration of P188, ATP, and NAC restored cell viability rates to near sham-exposed levels of 60%. At 48 hours post-irradiation, cell viability dropped substantially to the 7%–20% range, regardless of attempted intervention. Nevertheless, the combination of P188, ATP and NAC more than doubled cell viability at the 48-hour time point. Neither 8 kDa polyethylene glycol nor 10 kDa neutral dextran were as effective in enhancing cell viability. Conclusions These results indicate that antioxidants and cellular energy substrates improve the efficacy of membrane-sealing copolymer surfactants in prolonging cellular viability following massive radiation exposure. PMID:22048491

  17. X-ray scattering studies of ordered block copolymer melts during uniaxial extensional flow

    NASA Astrophysics Data System (ADS)

    Burghardt, Wesley; Mao, Ruinan; McCready, Erica

    2012-02-01

    We present the design and implementation of a new apparatus for in situ x-ray scattering studies of polymer melts during homogenous uniaxial extensional flow. The instrument is based on the commercial SER extensional flow fixture, which employs counter-rotating drums to deform a strip of polymer melt, which is incorporated into a custom-built convection oven designed to facilitate x-ray access to the sample and operation in a synchrotron environment. Here we report measurements of extensional flow-induced structural changes in a cylindrically ordered styrene-ethylene butylene-styrene triblock copolymer melt. At early stages, SAXS data reveal that the ordered microstructure deforms affinely until Hencky strains of ˜ 0.2. A global re-orientation process leads to alignment of microdomains predominantly along the stretching direction after Hencky strains of ˜ 1. Further stretching does not lead to further qualitative changes in 2-D SAXS patterns. Relaxation of both microdomain orientation and d-spacing is observed following cessation of extensional flow, albeit with different characteristic time scales. In situ x-ray scattering data are compared with off-line measurements of transient extensional viscosity, performed using the SER fixture in a rotational rheometer.

  18. The Effect of Physiologically Relevant Additivies on the Rheological Properties of Concentrated Pluronic Copolymer Gels

    SciTech Connect

    Jiang,J.; Li, C.; Lombardi, J.; Colby, R.; Rigas, B.; Rafailovich, M.; Sokolov, J.

    2008-01-01

    The high concentration triblock copolymer poly(ethylene oxide)99-poly(propylene oxide)69-poly(ethylene oxide)99 (Pluronic F127) aqueous solutions with the addition of different components commonly used in physiologically relevant applications were characterized by rheological measurements, differential scanning calorimetry (DSC) and small angle X-ray/neutron scattering. The sol-gel transition temperature, as well as the storage modulus of the F127 solution depend both on the concentration of polymer and of clay. Above the gel transition, the storage modulus of the solutions increased with clay concentration. Yield strain is independent of polymer and clay concentrations. Two different kinds of inorganic salts, sodium chloride (NaCl) and calcium chloride (CaCl2) were added into the polymer and polymer-clay solutions. The sol-gel transition temperature decreased noticeably, but the storage modulus decreased only a small amount with increasing concentration of inorganic salts. Addition of salts to polymer-clay solutions resulted in precipitation of the clays which decreased the modulus. No effect on the mechanical properties was observed with the addition of common serum proteins. However, addition of 0.5-10% glucose decreased the transition temperature between 3 and 7 , without significantly affecting the modulus. The depression of the transition temperature by glucose was similar to that found with salts and indicated that the mechanism, namely competition for water, may be similar.

  19. Transport of nanoparticulate material in self-assembled block copolymer micelle solutions and crystals.

    PubMed

    Cheng, Vicki A; Walker, Lynn M

    2016-01-01

    Water soluble poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) [PEO-PPO-PEO] triblock copolymers self-assemble into thermoreversible micellar crystals comprised of periodically spaced micelles. The micelles have PPO cores surrounded by hydrated PEO coronas and the dimensions of the unit cell of the organized micelles is on the order of several to tens of nanometers. Fluorescence recovery after photobleaching (FRAP) is used to quantify nanoparticle transport in these nanostructured polymer micelle systems. Diffusivity of bovine serum albumin (BSA, Dh ∼ 7 nm) is quantified across a wide range of polymer, or micelle, concentrations covering both the disordered fluid as well as the structured micellar crystal to understand the effects of nanoscale structure on particle transport. Measured particle diffusivity in these micellar systems is reduced by as much as four orders of magnitude when compared to diffusivity in free solution. Diffusivity in the disordered micellar fluid is best understood in terms of diffusion through a polymeric solution, while transport in the structured micellar phase is possibly due to hopping between interstitial sites. These results not only show that the nanoscale structures of the micelles have a measureable impact on particle diffusivity, but also demonstrate the ability to tune nanoscale transport in self-assembled materials.

  20. Understanding the surface chemistry of amphiphilic copolymer thin films in aqueous environments

    NASA Astrophysics Data System (ADS)

    Buss, Hilda; Lynd, Nathaniel; Zuckermann, Ronald; Kramer, Ed; Segalman, Rachel

    2014-03-01

    Controlling the surface chemistry of polymer coatings which are stable in aqueous environment is a complex problem which depends heavily on the hydrophobicity of the polymer. Poly(styrene)- b-(ethyleneoxide-co-allylgycidylether)- b-poly(styrene) [PS- b-(PEO-co-AGE)- b-PS] triblock copolymers functionalized at the pendant allyl groups with fluorinated moieties are a promising class of polymers for applications in antifouling coatings. These polymers gain their water stability from the PS blocks and their antifouling character from the PEO block. Surface active fluorinated groups are used to direct the surface chemistry of the film during annealing. However, the surface can rearrange or become damaged upon immersion in water. Near edge X-ray absorption fine structure spectroscopy (NEXAFS) of films after soaking in water shows that the surface composition as characterized by the PS and PEO content in the first 6 nm of the film is directly related to the relative sizes of the PS and the P(EO-co-AGE) blocks as well as the fluorine content.

  1. 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

  2. Dimensionally Stable Ether-Containing Polyimide Copolymers

    NASA Technical Reports Server (NTRS)

    Fay, Catharine C. (Inventor); St.Clair, Anne K. (Inventor)

    1999-01-01

    Novel polyimide copolymers containing ether linkages were prepared by the reaction of an equimolar amount of dianhydride and a combination of diamines. The polyimide copolymers described herein possess the unique features of low moisture uptake, dimensional stability, good mechanical properties, and moderate glass transition temperatures. These materials have potential application as encapsulants and interlayer dielectrics.

  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. Thermochemical characteristics of chitosan-polylactide copolymers

    NASA Astrophysics Data System (ADS)

    Goruynova, P. E.; Larina, V. N.; Smirnova, N. N.; Tsverova, N. E.; Smirnova, L. A.

    2016-05-01

    The energies of combustion of chitosan and its block-copolymers with different polylactide contents are determined in a static bomb calorimeter. Standard enthalpies of combustion and formation are calculated for these substances. The dependences of the thermochemical characteristics on block-copolymer composition are determined and discussed.

  5. 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

  6. Microwave-assisted facile synthesis of a new tri-block chitosan conjugate with improved mucoadhesion.

    PubMed

    Badhe, Ravindra V; Nanda, Rabindra K; Chejara, Dharmesh R; Choonara, Yahya E; Kumar, Pradeep; du Toit, Lisa C; Pillay, Viness

    2015-10-01

    A new chitosan-based tri-block conjugate, O-PEG-chitosan-N-cysteine was synthesized using microwave irradiation. For synthesis of this derivative, chitosan was modified to a PEG-chitosan conjugate followed by PEG-chitosan-cysteine using 6-O PEGylation and 2-N-thiolation, respectively. The synthesized derivative was characterized using various analytical techniques such as FT-IR and (1)H NMR spectroscopy. The conjugate was also analyzed for its biochemical, biodegradation and mucoadhesive properties. The modified chitosan conjugate exhibited improved mucoadhesion behavior (14.0 h) with greater biodegradation compared to the parent polymer (6.3h). The in silico modeling corroborated with the in vitro study demonstrating a stable complex between mucin and O-PEG-chitosan-N-cysteine conjugate (ΔE=-60.100 kcal/mol) compared to mucin and chitosan conjugate. The synthesis proposed herein, involves the use of microwave irradiation which causes a substantial reduction in the reaction time (approximately 2.30 h) compared to conventional method (35 h).

  7. Preparation and characterization of amphiphilic triblock terpolymer-based nanofibers as antifouling biomaterials.

    PubMed

    Cho, Youngjin; Cho, Daehwan; Park, Jay Hoon; Frey, Margaret W; Ober, Christopher K; Joo, Yong Lak

    2012-05-14

    Antifouling surfaces are critical for the good performance of functional materials in various applications including water filtration, medical implants, and biosensors. In this study, we synthesized amphiphilic triblock terpolymers (tri-BCPs, coded as KB) and fabricated amphiphilic nanofibers by electrospinning of solutions prepared by mixing the KB with poly(lactic acid) (PLA) polymer. The resulting fibers with amphiphilic polymer groups exhibited superior antifouling performance to the fibers without such groups. The adsorption of bovine serum albumin (BSA) on the amphiphilic fibers was about 10-fold less than that on the control surfaces from PLA and PET fibers. With the increase of the KB content in the amphiphilic fibers, the resistance to adsorption of BSA was increased. BSA was released more easily from the surface of the amphiphilic fibers than from the surface of hydrophobic PLA or PET fibers. We have also investigated the structural conformation of KB in fibers before and after annealing by contact angle measurements, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and coarse-grained molecular dynamics (CGMD) simulation to probe the effect of amphiphilic chain conformation on antifouling. The results reveal that the amphiphilic KB was evenly distributed within as-spun hybrid fibers, while migrated toward the core from the fiber surface during thermal treatment, leading to the reduction in antifouling. This suggests that the antifouling effect of the amphiphilic fibers is greatly influenced by the arrangement of amphiphilic groups in the fibers.

  8. Microwave-assisted facile synthesis of a new tri-block chitosan conjugate with improved mucoadhesion.

    PubMed

    Badhe, Ravindra V; Nanda, Rabindra K; Chejara, Dharmesh R; Choonara, Yahya E; Kumar, Pradeep; du Toit, Lisa C; Pillay, Viness

    2015-10-01

    A new chitosan-based tri-block conjugate, O-PEG-chitosan-N-cysteine was synthesized using microwave irradiation. For synthesis of this derivative, chitosan was modified to a PEG-chitosan conjugate followed by PEG-chitosan-cysteine using 6-O PEGylation and 2-N-thiolation, respectively. The synthesized derivative was characterized using various analytical techniques such as FT-IR and (1)H NMR spectroscopy. The conjugate was also analyzed for its biochemical, biodegradation and mucoadhesive properties. The modified chitosan conjugate exhibited improved mucoadhesion behavior (14.0 h) with greater biodegradation compared to the parent polymer (6.3h). The in silico modeling corroborated with the in vitro study demonstrating a stable complex between mucin and O-PEG-chitosan-N-cysteine conjugate (ΔE=-60.100 kcal/mol) compared to mucin and chitosan conjugate. The synthesis proposed herein, involves the use of microwave irradiation which causes a substantial reduction in the reaction time (approximately 2.30 h) compared to conventional method (35 h). PMID:26076619

  9. Surface and liquid-crystalline properties of FmHnFm triblock semifluorinated n-alkanes.

    PubMed

    Chachaj-Brekiesz, Anna; Górska, Natalia; Osiecka, Natalia; Makyła-Juzak, Katarzyna; Dynarowicz-Łątka, Patrycja

    2016-05-01

    A series of triblock semifluorinated n-alkanes of the general formula: F(CF2)m(CH2)n(CF2)mF, (in short FmHnFm), where m=10, 12, and n=6, 8, and 12 have been synthesized and employed for liquid crystalline studies and Langmuir monolayer characterization. Differential scanning calorimetry (DSC) measurements together with texture observation with polarizing microscope (POM) revealed the presence of liquid crystalline smectic phases for all the investigated homologs. The behavior of the studied molecules spread at the free water surface has also been investigated. Our results show for the first time that these unusual film-forming materials, which are completely hydrophobic in nature and do not possess any polar group in their structure, are surface active and form insoluble (Langmuir) monolayers at the air/water interface. Due to the fact that these molecules are chemically inert and, similar to the semifluorinated diblocks, are not toxic, they may be destined for biomedical uses as gas carriers and contrast agents, as well as in drug delivery systems.

  10. Processible Polyaniline Copolymers and Complexes.

    NASA Astrophysics Data System (ADS)

    Liao, Yun-Hsin

    1995-01-01

    Polyaniline (PANI) is an intractable polymer due to the difficulty of melt processing or dissolving it in common solvents. The purpose of the present investigation was to prepare a new class of conducting polyanilines with better solubility both in base and dope forms by (1) adding external salt to break aggregated chains, (2) introducing ring substituted units onto the backbone without disturbing the coplanar structure, and (3) complexing with polymeric dopants to form a soluble polymer complex. Aggregation of PANI chains in dilute solution was investigated in N-methyl-2-pyrrolidinone (NMP) by light scattering, gel permeation chromatography, and viscosity measurements. The aggregation of chains resulted in a negative second virial coefficient in light scattering measurement, a bimodal molecular weight distribution in gel permeation chromatography, and concave reduced viscosity curves. The aggregates can be broken by adding external salt, which resulting in a higher reduced viscosity. The driving force for aggregation is assumed to be a combination of hydrogen bonding between the imine and amine groups, and the rigidity of backbone. The aggregation was modeled to occur via side-on packing of PANI chains. The ring substituted PANI copolymers, poly(aniline -co-phenetidine) were synthesized by chemical oxidation copolymerization using ammonium persulfate as an oxidant. The degree of copolymerization declined with an increasing feed of o-phenetidine in the reaction mixture. The o-phenetidine had a higher reactivity than aniline in copolymerization resulting in a higher content of o-phenetidine in copolymers. The resulting copolymers can be readily dissolved in NMP up to 20% (w/w), and other common solvents, and solutions possess a longer gelation time. The highly soluble copolymer with 20 mole % o-phenetidine in the backbone has same order of conductivity as the unsubstituted PANI after it is doped by HCl. Complexation of PANI and polymeric dopant, poly

  11. 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.

  12. Poly(L-histidine) based copolymers: Effect of the chemically substituted L-histidine on the physio-chemical properties of the micelles and in vivo biodistribution.

    PubMed

    Zhang, Xiaojun; Chen, Dawei; Ba, Shuang; Chang, Jing; Zhou, Jiaying; Zhao, Haixia; Zhu, Jia; Zhao, Xiuli; Hu, Haiyang; Qiao, Mingxi

    2016-04-01

    Even though the Poly(l-histidine) (PHis) based copolymers have been well studied, the effect of the chemically substituted l-histidine on the physio-chemical and biological properties of the micelles has never been elucidated to date. To address this issue, triblock copolymer of poly(ethylene glycol)-poly(D,L-lactide)-poly(2,4-dinitrophenol-L-histidine)(mPEG-b-PLA-b-DNP-PHis) with DNP group substituted to the saturated nitrogen of l-histidine were synthesized. The pH sensitive properties of the copolymer micelles were characterized using an acid-base titration method, fluorescene probe technique, DLS observation, in vitro drug release and cytotoxicity against MCF-7 cells under different pH conditions, respectively. The results suggest that mPEG-b-PLA-b-DNP-PHis copolymers showed similar micellar stability for DOX loaded micelles, increased particle size, and similar pH responsive properties with mPEG-b-PLA-b-PHis copolymers. The subcellular distribution observation demonstrated that mPEG-b-PLA-b-DNP-PHis micelles showed a slightly compromised endo-lysosmal escape of doxorubicin as compared to mPEG-b-PLA-b-PHis micelles. The mPEG-b-PLA-b-DNP-PHis micelles showed higher cellular uptake by MCF-7 cells than mPEG-b-PLA-b-PHis micelles due to the different uptake pathways. Effect of DNP substitution on the in vivo distribution of the copolymer micelles was studied using non-invasive near-infrared fluorescence (NIRF) imaging with mPEG-b-PLA-b-PHis micelles as control. The results indicate that the mPEG-b-PLA-b-DNP-PHis micelles showed a reduced passive targeting to the tumor due to the larger particle size. These results suggest that saturated nitrogen of PHis may serve as a valuable site for chemical modification of the PHis based copolymers because of the little effect on the pH responsive properties. However, selection of the substitution group needs to be considered due to the possible increase of micellar particle size of the micelles, leading to compromised passive

  13. 21 CFR 177.1060 - n-Alkylglutarimide/acrylic copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false n-Alkylglutarimide/acrylic copolymers. 177.1060... Use Food Contact Surfaces § 177.1060 n-Alkylglutarimide/acrylic copolymers. n-Alkylglutarimide/acrylic...) Identity. For the purpose of this section, n-alkylglutarimide/acrylic copolymers are copolymers obtained...

  14. Shape Memory Performance of Thermoplastic Amphiphilic Triblock Copolymer poly(D,L-lactic acid-co-ethylene glycol-co-D,L-lactic acid) (PELA)/Hydroxyapatite Composites

    PubMed Central

    Kutikov, Artem B.; Reyer, Kevin A.

    2015-01-01

    Biodegradable polymer/hydroxyapatite (HA) composites are desired for skeletal tissue engineering. When engineered with thermal-responsive shape memory properties, they may be delivered in a minimally invasive temporary shape and subsequently triggered to conform to a tissue defect. Here we report the shape memory properties of thermoplastic amphiphilic poly(D,L-lactic acid-co-ethylene glycol-co-D,L-lactic acid) (PELA, 120 kDa) and HA-PELA composites. These materials can be cold-deformed and stably fixed into temporary shapes at room temperature and undergo rapid shape recovery (< 3 s) at 50 °C. Stable fixation (>99% fixing ratio) of large deformations is achieved at −20 °C. While the shape recovery from tensile deformations slows with higher HA contents, all composites (up to 20 wt% HA) achieve high shape recovery (>90%) upon 10-min equilibration at 50 °C. The permanent shapes of HA-PELA can be reprogramed at 50 °C, and macroporous shape memory scaffolds can be fabricated by rapid prototyping. PMID:26457046

  15. Subchronic toxicity and immunotoxicity of MeO-PEG-poly(D,L-lactic-co-glycolic acid)-PEG-OMe triblock copolymer nanoparticles delivered intravenously into rats

    NASA Astrophysics Data System (ADS)

    Liao, Longfei; Zhang, Mengtian; Liu, Huan; Zhang, Xuanmiao; Xie, Zhaolu; Zhang, Zhirong; Gong, Tao; Sun, Xun

    2014-06-01

    Although monomethoxy(polyethyleneglycol)-poly (D,L-lactic-co-glycolic acid)-monomethoxy (PELGE) nanoparticles have been widely studied as a drug delivery system, little is known about their toxicity in vivo. Here we examined the subchronic toxicity and immunotoxicity of different doses of PELGE nanoparticles with diameters of 50 and 200 nm (PELGE50 and PELGE200) in rats. Neither size of PELGE nanoparticles showed obvious subchronic toxic effects during 28 d of continuous intravenous administration based on clinical observation, body weight, hematology parameters and histopathology analysis. PELGE200 nanoparticles showed no overt signs of immunotoxicity based on organ coefficients, histopathology analysis, immunoglobulin levels, blood lymphocyte subpopulations and splenocyte cytokines. Conversely, PELGE50 nanoparticles were associated with an increased organ coefficient and histopathological changes in the spleen, increased serum IgM and IgG levels, alterations in blood lymphocyte subpopulations and enhanced expression of spleen interferon-γ. Taken together, these results suggest that PELGE nanoparticles show low subchronic toxicity but substantial immunotoxicity, which depends strongly on particle size. These findings will be useful for safe application of PELGE nanoparticles in drug delivery systems.

  16. 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.

  17. 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.

  18. Injectible bodily prosthetics employing methacrylic copolymer gels

    DOEpatents

    Mallapragada, Surya K.; Anderson, Brian C.

    2007-02-27

    The present invention provides novel block copolymers as structural supplements for injectible bodily prosthetics employed in medical or cosmetic procedures. The invention also includes the use of such block copolymers as nucleus pulposus replacement materials for the treatment of degenerative disc disorders and spinal injuries. The copolymers are constructed by polymerization of a tertiary amine methacrylate with either a (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) polymer, such as the commercially available Pluronic.RTM. polymers, or a poly(ethylene glycol) methyl ether polymer.

  19. Lipid modified triblock PAMAM-based nanocarriers for siRNA drug co-delivery.

    PubMed

    Biswas, Swati; Deshpande, Pranali P; Navarro, Gemma; Dodwadkar, Namita S; Torchilin, Vladimir P

    2013-01-01

    RNA interference by small interfering RNA (siRNA) holds promise to attenuate production of specific target proteins but is challenging in practice owing to the barriers for its efficient intracellular delivery. We have synthesized a triblock co-polymeric system, poly(amidoamine) dendrimer (generation 4)-poly(ethylene glycol)-1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (G(4)-D-PEG-(2K)-DOPE). G(4)-PAMAM dendrimer was utilized as a cationic source for efficient siRNA condensation; DOPE provided optimum hydrophobicity and compatible cellular interaction for enhanced cell penetration; PEG rendered flexibility to the G(4)-D for easy accessibility of siRNA for condensation; PEG-DOPE system provided stable micellization in a mixed micellar system. G(4)-D-PEG-(2K)-DOPE was incorporated into the self-assembled PEG-(5K)-PE micelles at a 1:1 molar ratio. Our results demonstrate that the modified dendrimer, G(4)-D-PEG-(2K)-DOPE and the micellar nanocarrier form stable polyplexes with siRNA, shows excellent serum stability and a significantly higher cellular uptake of siRNA that results in target protein down-regulation when compared to the G(4)-PAMAM dendrimer. Moreover, the mixed micellar system showed efficient micellization and higher drug (doxorubicin) loading efficiency. The G(4)-D-PEG-(2K)-DOPE has the higher efficacy for siRNA delivery, whereas G(4)-D-PEG-(2K)-DOPE/PEG-(5K)-PE micelles appear to be a promising carrier for drug/siRNA co-delivery, especially useful for the treatment of multi-drug resistant cancers. PMID:23137395

  20. Lipid Modified Triblock PAMAM-Based Nanocarriers for siRNA Drug Co-Delivery

    PubMed Central

    Biswas, Swati; Deshpande, Pranali P.; Navarro, Gemma; Dodwadkar, Namita S.; Torchilin, Vladimir P.

    2012-01-01

    RNA interference by short interfering RNA (siRNA) holds promise to attenuate production of specific target proteins but is challenging in practice owing to the barriers for its efficient intracellular delivery. We have synthesized a tri-block co-polymeric system, poly(amidoamine) dendrimer (generation 4)-poly(ethylene glycol)-1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (G(4)-D-PEG-2K-DOPE). G(4)-PAMAM dendrimer was utilized as a cationic source for efficient siRNA condensation; DOPE provided optimum hydrophobicity and compatible cellular interaction for enhanced cell penetration; PEG rendered flexibility to the G(4)-D for easy accessibility of siRNA for condensation; PEG-DOPE system provided stable micellization in a mixed micellar system. G(4)-D-PEG-2K-DOPE was incorporated into the self-assembled PEG-5K-PE micelles at a 1:1 molar ratio. Our results demonstrate that the modified dendrimer, G(4)-D-PEG-2K-DOPE and the micellar nanocarrier form stable polyplexes with siRNA, shows excellent serum stability and a significantly higher cellular uptake of siRNA that results in target protein down-regulation when compared to the G(4)-PAMAM-dendrimer. Moreover, the mixed micellar system showed efficient micellization and higher drug (doxorubicin) loading efficiency. The G(4)-D-PEG-2K-DOPE has the higher efficacy for siRNA delivery, whereas G(4)-D-PEG-2K-DOPE/PEG-5K-PE micelles appear to be a promising carrier for drug/siRNA co-delivery, especially useful for the treatment of multidrug resistant cancers. PMID:23137395

  1. Synthesis Characterization and Electrospinning of Architecturally-Discrete Isotactic-Atactic-Isotactic Triblock Stereoblock Polypropene Elastomers

    SciTech Connect

    C Giller; G Gururajan; J Wei; W Zhang; W Hwang; D Chase; J Rabolt; L Sita

    2011-12-31

    Stereochemically homogeneous and architecturally discrete isotactic-atactic-isotactic triblock stereoblock PP (sbPP) thermoplastic elastomers in which the block lengths for each domain type can be varied in programmed fashion while keeping total molecular weight and molecular weight polydispersity the same has been achieved for the first time. Five sbPP materials were prepared: sbPP-1 (6iso-88a-6iso), total isotactic content, 12%; sbPP-2 (12iso-76a-12iso), 24%; sbPP-3 (18iso-64a-18iso), 36%; sbPP-4 (24iso-50a-26iso), 50%; and sbPP-5 (20iso-64a-33iso), 53%. All five sbPP materials were successfully processed by solution-based electrospinning to provide fiberous mats with feature sizes on the nanometer to micrometer length scale. Extensive characterization by analytical (SEM, AFM, tensile testing, DSC,), spectroscopic (FT-IR, FT-Raman), and synchrotron X-ray diffraction techniques of bulk samples, electrospun fibers and solvent cast films of the sbPP samples revealed well-defined trends in elastic properties, morphologies and crystallinity that are associated with a higher degree of crystallinity that emerges with higher isotactic contents. The results of these investigations serve to provide an important foundation that can be used to potentially identify the best combination of stereoerror level incorporation within the isotactic domains and total isotactic content for these architecturally discrete sb-PP materials for maximizing desirable elastomeric traits and solution-based (electrospinning) processing methodology with the goal of achieving the best possible structural forms for potential product applications.

  2. Curable polyphosphazene copolymers and terpolymers

    NASA Technical Reports Server (NTRS)

    Reynard, Kennard A. (Inventor); Rose, Selwyn H. (Inventor)

    1976-01-01

    Copolymers and terpolymers comprising randomly repeating units represented by the general formulae ##EQU1## wherein the R' radicals contain OH functionality and R being at least one member of the group of monovalent radicals selected from alkyl, substituted alkyl, aryl, substituted aryl and arylalkyl, and R' is represented by ##EQU2## wherein Q represents either --(CH.sub.2).sub. n or --C.sub.6 H.sub.4 X(CH.sub.2).sub. m, the --X(CH.sub.2).sub. m group being either meta or para and n is an integer from 1 to 6, m is an integer from 1 to 3, X is O or CH.sub.2, and R is H or a lower alkyl radical with up to four carbon atoms (methyl, ethyl, etc.). The ratio of R to R' is between 99.5 to 0.5 and 65 to 35.

  3. 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.

  4. 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

  5. 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).

  6. 21 CFR 173.65 - Divinylbenzene copolymer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    .... Divinylbenzene copolymer may be used for the removal of organic substances from aqueous foods under the following... are available from the Center for Food Safety and Applied Nutrition (HFS-200), Food and...

  7. 21 CFR 173.65 - Divinylbenzene copolymer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    .... Divinylbenzene copolymer may be used for the removal of organic substances from aqueous foods under the following... are available from the Center for Food Safety and Applied Nutrition (HFS-200), Food and...

  8. 21 CFR 173.65 - Divinylbenzene copolymer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    .... Divinylbenzene copolymer may be used for the removal of organic substances from aqueous foods under the following... are available from the Center for Food Safety and Applied Nutrition (HFS-200), Food and...

  9. Phase behaviors of cyclic diblock copolymers.

    PubMed

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

    2011-11-01

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

  10. Responsive Copolymers for Enhanced Petroleum Recovery

    SciTech Connect

    McCormick, C.; Hester, R.

    2001-02-27

    The objectives of this work was to: synthesize responsive copolymer systems; characterize molecular structure and solution behavior; measure rheological properties of aqueous fluids in fixed geometry flow profiles; and to tailor final polymer compositions for in situ rheology control under simulated conditions. This report focuses on the synthesis and characterization of novel stimuli responsive copolymers, the investigation of dilute polymer solutions in extensional flow and the design of a rheometer capable of measuring very dilute aqueous polymer solutions at low torque.

  11. 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.

  12. 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.

  13. Substrate effect on nanoporous structure of silica wires by channel-confined self-assembly of block-copolymer and sol-gel precursors

    DOE PAGES

    Hu, Michael Z.; Lai, Peng

    2015-09-22

    Nanoporous silica wires of various wire diameters were developed by space-confined molecular self-assembly of triblock copolymer ethylene/propylene/ethylene (P123) and silica alkoxide precursor (tetraethylorthosilicate, TEOS). Two distinctive hard-templating substrates, anodized aluminum oxide (AAO) and track-etched polycarbonate (EPC), with channel diameters in the range between 10 nm and 200 nm were employed for space-confinement of soft molecular self-assembly driven by the block-copolymer microphase separation. It was observed in the scanning and transmission electron microscope (STEM) studies that the substrate geometry and material characteristics had pronounced effects on the structure and morphology of the silica nanowires. A substrate wall effect was proposed tomore » explain the ordering and orientation of the intra-wire mesostructure. Circular and spiral nanostructures were found only in wires formed in AAO substrate, not in EPC. Pore-size differences and distinctive wall morphologies of the nanowires relating to the substrates were discussed. It was shown that the material and channel wall characteristics of different substrates play key roles in the ordering and morphology of the intra-wire nanostructures.« less

  14. Substrate effect on nanoporous structure of silica wires by channel-confined self-assembly of block-copolymer and sol-gel precursors

    SciTech Connect

    Hu, Michael Z.; Lai, Peng

    2015-09-22

    Nanoporous silica wires of various wire diameters were developed by space-confined molecular self-assembly of triblock copolymer ethylene/propylene/ethylene (P123) and silica alkoxide precursor (tetraethylorthosilicate, TEOS). Two distinctive hard-templating substrates, anodized aluminum oxide (AAO) and track-etched polycarbonate (EPC), with channel diameters in the range between 10 nm and 200 nm were employed for space-confinement of soft molecular self-assembly driven by the block-copolymer microphase separation. It was observed in the scanning and transmission electron microscope (STEM) studies that the substrate geometry and material characteristics had pronounced effects on the structure and morphology of the silica nanowires. A substrate wall effect was proposed to explain the ordering and orientation of the intra-wire mesostructure. Circular and spiral nanostructures were found only in wires formed in AAO substrate, not in EPC. Pore-size differences and distinctive wall morphologies of the nanowires relating to the substrates were discussed. It was shown that the material and channel wall characteristics of different substrates play key roles in the ordering and morphology of the intra-wire nanostructures.

  15. Polyhydroxyalkanoate copolymers from forest biomass.

    PubMed

    Keenan, Thomas M; Nakas, James P; Tanenbaum, Stuart W

    2006-07-01

    The potential for the use of woody biomass in poly-beta-hydroxyalkanoate (PHA) biosynthesis is reviewed. Based on previously cited work indicating incorporation of xylose or levulinic acid (LA) into PHAs by several bacterial strains, we have initiated a study for exploring bioconversion of forest resources to technically relevant copolymers. Initially, PHA was synthesized in shake-flask cultures of Burkholderia cepacia grown on 2.2% (w/v) xylose, periodically amended with varying concentrations of levulinic acid [0.07-0.67% (w/v)]. Yields of poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) [P(3HB-co-3HV)] from 1.3 to 4.2 g/l were obtained and could be modulated to contain from 1.0 to 61 mol% 3-hydroxyvalerate (3HV), as determined by 1H and 13C NMR analyses. No evidence for either the 3HB or 4HV monomers was found. Characterization of these P(3HB-co-3HV) samples, which ranged in molecular mass (viscometric, Mv) from 511-919 kDa, by differential scanning calorimetry and thermogravimetric analyses (TGA) provided data which were in agreement for previously reported P(3HB-co-3HV) copolymers. For these samples, it was noted that melting temperature (Tm) and glass transition temperature (Tg) decreased as a function of 3HVcontent, with Tm demonstrating a pseudoeutectic profile as a function of mol% 3HV content. In order to extend these findings to the use of hemicellulosic process streams as an inexpensive carbon source, a detoxification procedure involving sequential overliming and activated charcoal treatments was developed. Two such detoxified process hydrolysates (NREL CF: aspen and CESF: maple) were each fermented with appropriate LA supplementation. For the NREL CF hydrolysate-based cultures amended with 0.25-0.5% LA, P(3HB-co-3HV) yields, PHA contents (PHA as percent of dry biomass), and mol% 3HV compositions of 2.0 g/l, 40% (w/w), and 16-52 mol% were obtained, respectively. Similarly, the CESF hydrolysate-based shake-flask cultures yielded 1.6 g/l PHA, 39% (w

  16. Multifunctional polymer composites containing inorganic nanoparticles and novel low-cost carbonaceous fillers

    NASA Astrophysics Data System (ADS)

    Wu, Hongchao

    carbonaceous by-product of crude oil extraction, was studied as a novel and low-cost additives in polymer matrices. Two kinds of asphaltene were extracted and investigated using different analytical techniques for the comparison of their elemental composition, molecular structure, and morphology. One asphaltene underwent the successful molecular functionalization via two silane coupling agents prior to the preparation of epoxy composites. Another asphaltene was incorporated into poly(styrene-butadiene-styrene) copolymers (SBS) for the fabrication of hybrid composites using melt compounding technique. Based on it intrinsic rigid molecular structure, the reinforcement effect of asphaltene was recognized to be more pronounced in a softer matrix (SBS) than the rigid one (epoxy).

  17. The Effect of the Nonionic Block Copolymer Pluronic P85 on Gene Expression in Mouse Muscle and Antigen Presenting Cells

    PubMed Central

    Gaymalov, Zagit Z.; Yang, Zhihui; Pisarev, Vladimir M.; Alakhov, Valery Yu.; Kabanov, Alexander V.

    2008-01-01

    DNA vaccines can be greatly improved by polymer agents that simultaneously increase transgene expression and activate immunity. We describe here Pluronic P85 (P85), a triblock copolymer of ethylene oxide (EO) and propylene oxide (PO) EO26-PO40-EO26,. Using a mouse model we demonstrate that co-administration of a bacterial plasmid DNA with P85 in a skeletal muscle greatly increases gene expression in the injection site and distant organs, especially the draining lymph nodes and spleen. The reporter expression colocalizes with the specific markers of myocytes and keratinocytes in the muscle, as well as dendritic cells (DC) and macrophages in the muscle, lymph nodes and spleen. Furthermore, DNA/P85 and P85 alone increase the systemic expansion of CD11c+ (DC), and local expansion of CD11c+, CD14+ (macrophages) and CD49b+ (natural killer) cell populations. DNA/P85 (but not P85) also increases maturation of local DC (CD11c+CD86+, CD11c+CD80+, and CD11c+CD40+). We suggest that DNA/P85 promotes the activation and recruitment of the antigen-presenting cells, which further incorporate, express and carry the transgene to the immune system organs. PMID:19064283

  18. Initiator Effects in Reactive Extrusion of Starch Graft Copolymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Graft copolymers of starch with water-soluble polymers such as polyacrylamide have potential applications including hydrogels, superabsorbents, and thickening agents. Reactive extrusion is a rapid, continuous method for production of starch graft copolymers with high reaction and grafting efficienc...

  19. Hydrogen-bonded aggregates in precise acid copolymers

    SciTech Connect

    Lueth, Christopher A.; Bolintineanu, Dan S.; Stevens, Mark J. Frischknecht, Amalie L.

    2014-02-07

    We perform atomistic molecular dynamics simulations of melts of four precise acid copolymers, two poly(ethylene-co-acrylic acid) (PEAA) copolymers, and two poly(ethylene-co-sulfonic acid) (PESA) copolymers. The acid groups are spaced by either 9 or 21 carbons along the polymer backbones. Hydrogen bonding causes the acid groups to form aggregates. These aggregates give rise to a low wavevector peak in the structure factors, in agreement with X-ray scattering data for the PEAA materials. The structure factors for the PESA copolymers are very similar to those for the PEAA copolymers, indicating a similar distance between aggregates which depends on the spacer length but not on the nature of the acid group. The PEAA copolymers are found to form more dimers and other small aggregates than do the PESA copolymers, while the PESA copolymers have both more free acid groups and more large aggregates.

  20. Synthesis and in vitro study of cisplatin-loaded Fe3O4 nanoparticles modified with PLGA-PEG6000 copolymers in treatment of lung cancer.

    PubMed

    Nejati-Koshki, Kazem; Mesgari, Mehran; Ebrahimi, Eommolbanin; Abbasalizadeh, Farhad; Fekri Aval, Sedigeh; Khandaghi, Amir Ahmad; Abasi, Mozhgan; Akbarzadeh, Abolfazl

    2014-01-01

    In the field of cancer therapy, magnetic nanoparticles modified with biocompatible copolymers are promising vehicles for the delivery of hydrophobic drugs such as Cisplatin. The major aim of this effort was to evaluate whether Cisplatin-Encapsulated magnetic nanoparticles improved the anti-tumour effect of free Cisplatin in lung cancer cells. The PLGA-PEG triblock copolymer was synthesised by ring-opening polymerisation of d,l-lactide and glycolide with polyethylene glycol (PEG6000) as an initiator. The bulk properties of these copolymers were characterised using Fourier transform infrared spectroscopy. Cisplatin-loaded nanoparticles (NPs) were prepared by double emulsion solvent evaporation technique and were characterised for size, drug entrapment efficiency (%), drug content (% w/w), and surface morphology. In vitro release profile of cisplatin-loaded NP formulations was determined. Cytotoxic assays were evaluated in lung carcinoma (A549)-treated cells by the MTT assay technique. In addition, the particles were characterised by X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The anti-proliferative effect of Cisplatin appeared much earlier when the drug was encapsulated in magnetic nanoparticles than when it was free. Cisplatin-Encapsulated magnetic nanoparticles significantly enhanced the decrease in IC50 rate. The in vitro cytotoxicity test showed that the Fe3O4-PLGA-PEG6000 magnetic nanoparticles had no cytotoxicity and were biocompatible. The chemotherapeutic effect of free Cisplatin on lung cancer cells is improved by its encapsulation in modified magnetic nanoparticles. This approach has the prospective to overcome some major limitations of conventional chemotherapy and may be a promising strategy for future applications in lung cancer therapy. PMID:25090589

  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. Thermoreversible copolymer gels for extracellular matrix.

    PubMed

    Vernon, B; Kim, S W; Bae, Y H

    2000-07-01

    To improve the properties of a reversible synthetic extracellular matrix based on a thermally reversible polymer, copolymers of N-isopropylacrylamide and acrylic acid were prepared in benzene with varying contents of acrylic acid (0 to 3%) and the thermal properties were evaluated. The poly(N-isopropylacrylamide) and copolymers made with acrylic acid had molecular weights from 0.8 to 1.7 x10(6) D. Differential scanning calorimetry (DSC) showed the high-molecular-weight acrylic acid copolymers had similar onset temperatures to the homopolymers, but the peak width was considerably increased with increasing acrylic acid content. DSC and cloud point measurements showed that polymers with 0 to 3% acrylic acid exhibit a lower critical solution temperature (LCST) transition between 30 degrees and 37 degrees C. In swelling studies, the homopolymer showed significant syneresis at temperatures above 31 degrees C. Copolymers with 1 and 1.5% showed syneresis beginning at 32 degrees and 37 degrees C, respectively. At 37 degrees C the copolymers with 1.5-3% acrylic acid showed little or no syneresis. Due to the high water content and a transition near physiologic conditions (below 37 degrees C), the polymers with 1.5-2.0% acrylic acid exhibited properties that would be useful in the development of a refillable synthetic extracellular matrix. Such a matrix could be applied to several cell types, including islets of Langerhans, for a biohybrid artificial pancreas.

  3. Polyene photoisomerization rates: Are they distinct in aqueous block copolymer micellar solutions and gels?

    SciTech Connect

    Mali, K.S.; Dutt, G.B.; Mukherjee, T.

    2006-02-07

    Photoisomerization of 3,3{sup '}-diethyloxadicarbocyanine iodide (DODCI) has been investigated in water, 5% and 30% aqueous triblock copolymer, poly(ethylene oxide){sub 20}-poly(propylene oxide){sub 70}-poly(ethylene oxide){sub 20} (P123) by measuring the fluorescence quantum yields and lifetimes in the temperature range 293-318 K. Reports available in literature indicate that 5% aqueous P123 exists as micellar solution, whereas 30% aqueous P123 forms gel due to micelle-micelle entanglement. This study has been undertaken to find out how the polyene photoisomerization rates are influenced in the sol and gel phases. It has been observed that 60%-70% of DODCI is located in the palisade layer of the micelles in the sol as well as gel phases and the photoisomerization rate of this component is identical in both the phases at a particular temperature. The remainder of the probe is located in the interfacial region and isomerization rates of this fraction are slower by a factor of 1.4-1.1 in the gel phase compared with the micellar solution. The retardation of the isomerization rate in the gel phase has been explained on the basis of enhancement in the friction experienced by the probe due to micelle-micelle entanglement at the interface. Compared to the isomerization rates in water, the rates of photoisomerization of DODCI located in the palisade layer, interfacial region of micellar solution, and interfacial region of the micelles in the gel phase are slower by factors of 3.5, 1.5-1.9, and 2, respectively. The outcome of this study validates the point that in organized media photoisomerization rates are sensitive to the localized friction, which is not uniform unlike in a homogeneous solution.

  4. 21 CFR 181.32 - Acrylonitrile copolymers and resins.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Acrylonitrile copolymers and resins. 181.32...-Sanctioned Food Ingredients § 181.32 Acrylonitrile copolymers and resins. (a) Acrylonitrile copolymers and resins listed in this section, containing less than 30 percent acrylonitrile and complying with...

  5. pH-sensitive methacrylic copolymers and the production thereof

    SciTech Connect

    Mallapragada, Surya K.; Anderson, Brian C.; Bloom, Paul D.; Sheares Ashby, Valerie V.

    2006-02-14

    The present invention provides novel multi-functional methacrylic copolymers that exhibit cationic pH-sensitive behavior as well as good water solubility under acidic conditions. The copolymers are constructed from tertiary amine methacrylates and poly(ethylene glycol) containing methacrylates. The copolymers are useful as gene vectors, pharmaceutical carriers, and in protein separation applications.

  6. pH-sensitive methacrylic copolymers and the production thereof

    SciTech Connect

    Mallapragada, Surya K.; Anderson, Brian C.; Bloom, Paul D.; Sheares Ashby, Valerie V.

    2007-01-09

    The present invention provides novel multi-functional methacrylic copolymers that exhibit cationic pH-sensitive behavior as well as good water solubility under acidic conditions. The copolymers are constructed from tertiary amine methacrylates and poly(ethylene glycol) containing methacrylates. The copolymers are useful as gene vectors, pharmaceutical carriers, and in protein separation applications.

  7. 21 CFR 181.32 - Acrylonitrile copolymers and resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Acrylonitrile copolymers and resins. 181.32 Section... Ingredients § 181.32 Acrylonitrile copolymers and resins. (a) Acrylonitrile copolymers and resins listed in... of the vinyl chloride resin) resin—for use only in contact with oleomargarine. (iv)...

  8. 21 CFR 172.775 - Methacrylic acid-divinylbenzene copolymer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Methacrylic acid-divinylbenzene copolymer. 172.775... HUMAN CONSUMPTION Other Specific Usage Additives § 172.775 Methacrylic acid-divinylbenzene copolymer. Methacrylic acid-divinylbenzene copolymer may be safely used in food in accordance with the...

  9. 21 CFR 172.775 - Methacrylic acid-divinylbenzene copolymer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Methacrylic acid-divinylbenzene copolymer. 172.775... HUMAN CONSUMPTION Other Specific Usage Additives § 172.775 Methacrylic acid-divinylbenzene copolymer. Methacrylic acid-divinylbenzene copolymer may be safely used in food in accordance with the...

  10. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ethylene-acrylic acid copolymers. 177.1310 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid copolymers identified in paragraph (a) of this section may be...

  11. 21 CFR 172.775 - Methacrylic acid-divinylbenzene copolymer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Methacrylic acid-divinylbenzene copolymer. 172.775... Additives § 172.775 Methacrylic acid-divinylbenzene copolymer. Methacrylic acid-divinylbenzene copolymer may... produced by the polymerization of methacrylic acid and divinylbenzene. The divinylbenzene functions as...

  12. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-acrylic acid copolymers. 177.1310 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid copolymers identified in paragraph (a) of this section may be...

  13. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ethylene-acrylic acid copolymers. 177.1310 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid copolymers identified in paragraph (a) of this section may be...

  14. 21 CFR 172.775 - Methacrylic acid-divinylbenzene copolymer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Methacrylic acid-divinylbenzene copolymer. 172.775... HUMAN CONSUMPTION Other Specific Usage Additives § 172.775 Methacrylic acid-divinylbenzene copolymer. Methacrylic acid-divinylbenzene copolymer may be safely used in food in accordance with the...

  15. 21 CFR 181.32 - Acrylonitrile copolymers and resins.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) PRIOR-SANCTIONED FOOD INGREDIENTS Specific Prior-Sanctioned Food Ingredients § 181.32 Acrylonitrile copolymers and resins. (a) Acrylonitrile copolymers and... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Acrylonitrile copolymers and resins....

  16. 21 CFR 181.32 - Acrylonitrile copolymers and resins.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) PRIOR-SANCTIONED FOOD INGREDIENTS Specific Prior-Sanctioned Food Ingredients § 181.32 Acrylonitrile copolymers and resins. (a) Acrylonitrile copolymers and... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Acrylonitrile copolymers and resins....

  17. 40 CFR 721.484 - Fluorinated acrylic copolymer (generic name).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Fluorinated acrylic copolymer (generic... Specific Chemical Substances § 721.484 Fluorinated acrylic copolymer (generic name). (a) Chemical substance... fluorinated acrylic copolymer (PMN P-95-1208) is subject to reporting under this section for the...

  18. 40 CFR 721.484 - Fluorinated acrylic copolymer (generic name).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Fluorinated acrylic copolymer (generic... Specific Chemical Substances § 721.484 Fluorinated acrylic copolymer (generic name). (a) Chemical substance... fluorinated acrylic copolymer (PMN P-95-1208) is subject to reporting under this section for the...

  19. 21 CFR 177.1060 - n-Alkylglutarimide/acrylic copolymers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false n-Alkylglutarimide/acrylic copolymers. 177.1060... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1060 n-Alkylglutarimide/acrylic copolymers. n-Alkylglutarimide/acrylic copolymers identified in this section may be safely used as...

  20. 40 CFR 721.484 - Fluorinated acrylic copolymer (generic name).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Fluorinated acrylic copolymer (generic... Specific Chemical Substances § 721.484 Fluorinated acrylic copolymer (generic name). (a) Chemical substance... fluorinated acrylic copolymer (PMN P-95-1208) is subject to reporting under this section for the...

  1. 40 CFR 721.484 - Fluorinated acrylic copolymer (generic name).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Fluorinated acrylic copolymer (generic... Specific Chemical Substances § 721.484 Fluorinated acrylic copolymer (generic name). (a) Chemical substance... fluorinated acrylic copolymer (PMN P-95-1208) is subject to reporting under this section for the...

  2. 21 CFR 177.1060 - n-Alkylglutarimide/acrylic copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true n-Alkylglutarimide/acrylic copolymers. 177.1060... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1060 n-Alkylglutarimide/acrylic copolymers. n-Alkylglutarimide/acrylic copolymers identified in this section may be safely used as...

  3. 21 CFR 177.1060 - n-Alkylglutarimide/acrylic copolymers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false n-Alkylglutarimide/acrylic copolymers. 177.1060... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1060 n-Alkylglutarimide/acrylic copolymers. n-Alkylglutarimide/acrylic copolymers identified in this section may be safely used as...

  4. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ethylene-acrylic acid copolymers. 177.1310 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid copolymers identified in paragraph (a) of this section may be...

  5. 40 CFR 721.484 - Fluorinated acrylic copolymer (generic name).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Fluorinated acrylic copolymer (generic... Specific Chemical Substances § 721.484 Fluorinated acrylic copolymer (generic name). (a) Chemical substance... fluorinated acrylic copolymer (PMN P-95-1208) is subject to reporting under this section for the...

  6. 21 CFR 177.1060 - n-Alkylglutarimide/acrylic copolymers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false n-Alkylglutarimide/acrylic copolymers. 177.1060... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1060 n-Alkylglutarimide/acrylic copolymers. n-Alkylglutarimide/acrylic copolymers identified in this section may be safely used as...

  7. Perfluorinated Moieties Increase the Interaction of Amphiphilic Block Copolymers with Lipid Monolayers.

    PubMed

    Schwieger, Christian; Blaffert, Jacob; Li, Zheng; Kressler, Jörg; Blume, Alfred

    2016-08-16

    The interaction of amphiphilic and triphilic block copolymers with lipid monolayers has been studied. Amphiphilic triblock copolymer PGMA20-PPO34-PGMA20 (GP) is composed of a hydrophobic poly(propylene oxide) (PPO) middle block that is flanked by two hydrophilic poly(glycerol monomethacrylate) (PGMA) side blocks. The attachment of a perfluoro-n-nonyl residue (F9) to either end of GP yields a triphilic polymer with the sequence F9-PGMA20-PPO34-PGMA20-F9 (F-GP). The F9 chains are fluorophilic, i.e., they have a tendency to demix in hydrophilic as well as in lipophilic environments. We investigated (i) the adsorption of both polymers to differently composed lipid monolayers and (ii) the compression behavior of mixed polymer/lipid monolayers. The lipid monolayers are composed of phospholipids with PC or PE headgroups and acyl chains of different length and saturation. Both polymers interact with lipid monolayers by inserting their hydrophobic moieties (PPO, F9). The interaction is markedly enhanced in the presence of F9 chains, which act as membrane anchors. GP inserts into lipid monolayers up to a surface pressure of 30 mN/m, whereas F-GP inserts into monolayers at up to 45 mN/m, suggesting that F-GP also inserts into lipid bilayer membranes. The adsorption of both polymers to lipid monolayers with short acyl chains is favored. Upon compression, a two-step squeeze-out of F-GP occurs, with PPO blocks being released into the aqueous subphase at 28 mN/m and the F9 chains being squeezed out at 48 mN/m. GP is squeezed out in one step at 28 mN/m because of the lack of F9 anchor groups. The liquid expanded (LE) to liquid condensed (LC) phase transition of DPPC and DMPE is maintained in the presence of the polymers, indicating that the polymers can be accommodated in LE- and LC-phase monolayers. These results show how fluorinated moieties can be included in the rational design of membrane-binding polymers. PMID:27442444

  8. Rheological study of the shape transition of block copolymer-nonionic surfactant mixed micelles.

    PubMed

    Löf, David; Schillén, Karin; Torres, Miguel F; Müller, Alejandro J

    2007-10-23

    A rheological study of mixed micelles formed by PEO-PPO-PEO triblock copolymer P123 and nonionic surfactant C12EO6 in aqueous solutions has been carried out with the purpose of investigating the time dependence of a shape transition of the mixed micelles and characterizing the shape before and after the transition. The rheology results presented in this report give clear evidence that the P123-C12EO6 mixed micelle grows and changes gradually in shape from spherical to elongated (rodlike) geometry with increasing temperature. These results are in accordance with the results found in the parallel dynamic and static light scattering and calorimetrical investigation.1,2 By using steady-state rheology, the time dependence of the sphere-to-rod transition of the mixed micelle system was carefully followed with time and temperature as simultaneously recorded variables in the experiments. This was performed by a designed novel experimental procedure. A temperature ramp was applied at a rate of 2.6 degrees C/min from a temperature below to a temperature above the shape transition at a constant shear rate while the viscosity of the solution was measured. The investigation was limited to two different compositions, surfactant-to-copolymer molar ratios (MR=nC12EO6/nP123) of 2.2 and 6.0 with varying total concentration from 1.5 to 21 wt % in comparison with the neat component. At low concentration, a slow transition was observed, which indicated that the mixed micelles are still growing into rods for several minutes after reaching the final temperature. At a total concentration of 4.0 wt % and above, the system reached equilibrium quickly. A concentration-dependent kinetic process is therefore anticipated, which was also found in the time-resolved static light scattering experiments previously performed (Löf, D.; Schillén, K.; Olofsson, G.; Niemiec, A.; Loh, W. J. Phys. Chem. B 2007, 111, 5911). At concentrations above 10 wt %, shear-thinning behavior was observed for the

  9. Biosolar energy generation and harvesting from biomolecule-copolymer hybrid systems

    NASA Astrophysics Data System (ADS)

    Chu, Bong-Chieh Benjamin

    Alternative energy sources have become an increasingly important topic as energy needs outpace supply. Furthermore, as the world moves into the digital age of portable electronics, highly efficient and lightweight energy sources will need to be developed. Current technology, such as lithium ion batteries, provide enough power to run portable electronics for hours or days, but can still allow for improvement in their power density (W/kg). Utilizing energy-transducing membrane proteins, which are by nature highly efficient, it is possible to engineer biological-based energy sources with energy densities far greater than any solid-state systems. Furthermore, solar powered membrane proteins have the added benefit of a virtually unlimited supply of energy. This work has developed protein-polymer hybrid films and nanoscale vesicles for a variety of applications from fuel-cell technology to biological-based photovoltaics. Bacteriorhodopsin (BR), a light-activated proton pump, and Cytochrome C Oxidase (COX), a protein involved in the electron transport chain in mitochondria, were reconstituted into biomimetic triblock copolymer membranes. Block copolymer membranes mimic the amphiphilic nature of a natural lipid bilayer but exhibit greater mechanical stability due to UV-polymerizable endgroups. In BR/COX functionalized nanovesicles, proton gradients generated by the light-activated proton pumping of BR are used to drive COX in reverse to generate electrons, providing a hybrid biologically-active polymer to convert solar energy to chemical energy, and finally to electrical energy. This work has found protein activity in planar membranes through the photoelectric current generation by BR and the proton pumping activity of BR-functionalized polymer membranes deposited onto proton exchange membranes, as well as the coupled functionality of BR and COX through current generation in cyclic voltammetry and direct current measurements. Current switching between light and dark

  10. Effect of Ternary Solutes on the Evolution of Structure and Gel Formation in Amphiphilic Copolymer Solutions

    NASA Astrophysics Data System (ADS)

    Meznarich, Norman Anthony Kang

    Aqueous solutions of polyoxyethylene-polyoxypropylene-polyoxyethylene (PEO-PPO-PEO) amphiphilic triblock copolymers (commercially known as Pluronic surfactants) undergo reversible and temperature-dependent micellization and arrangement into cubic ordered lattices known as "micelle gels". The macroscopic behavior of the ordering is a transition from a liquid to a gel. While the phase behavior and gel structure of pure Pluronic surfactant solutions have been well studied, less is known about the effects of added ternary solutes. In this dissertation, a comprehensive investigation into the effects of the added pharmaceutical methylparaben on solutions of F127 ranging from 10 to 30 wt% was conducted in order to better understand the behavior of F127 in multicomponent pharmaceutical formulations. The viscoelastic properties of F127 gel formation were studied using rheometry, where heating rates of 0.1, 1, and 10 degrees C/min were also used to probe the kinetics of the gel transition. In solutions containing methylparaben, F127 gelation occurred at up to 15 degrees C lower temperatures and was accelerated by a factor of three to four. Small angle x-ray scattering (SAXS) was used to characterize the structure of the ordered domains, and how they were affected by the presence of dissolved pharmaceuticals. It was found that ordered domain formation changed from heterogeneous nucleation and growth to possible homogeneous nucleation and growth. A roughly 2% reduction in the cubic lattice parameter was also observed for solutions containing methylparaben. Differential scanning calorimetry (DSC) experiments were performed on a series of different Pluronic surfactants in order to characterize the micellization behavior as a function of PPO center block length and PEO/PPO ratio. Added methylparaben suppressed the micellization endotherm, the degree of suppression depending linearly on the amount of added methylparaben, as well as the length of the PPO center block and PEO

  11. Nanoscale Ionic Aggregate Morphology in Zwitterionic Copolymers

    NASA Astrophysics Data System (ADS)

    Choi, Jae-Hong; Huyck, Rebecca; Salas-de La Cruz, David; Long, Timothy E.; Winey, Karen I.

    2009-03-01

    The morphology of two different zwitterionic copolymers, poly(sulfobetaine methacrylate-ran-butyl acrylate), and poly(sulfobetaine methacrylamide-ran-butyl acrylate) are investigated as a function of the mol % content of SBMA (7 and 9 mol %) and SBMAm (6, 10 and 13 mol %), respectively. In both copolymers, X-ray scattering results show a new structure in the material arising from ionic aggregates. The sizes of the ionic aggregates are obtained through the scattering model. The sizes of the ionic aggregates increase as the ion content increases. The application of scanning transmission electron microscopy to the study of ionomer morphology has enabled direct, model-independent visualization of the ionic aggregates. The correlation between X-ray scattering results and the real space imaging for morphology of these zwitterionic copolymers will be presented.

  12. Optical properties of coumarins containing copolymers

    NASA Astrophysics Data System (ADS)

    Skowronski, L.; Krupka, O.; Smokal, V.; Grabowski, A.; Naparty, M.; Derkowska-Zielinska, B.

    2015-09-01

    We investigate the optical properties such as absorption coefficient, refractive index, real and imaginary parts of dielectric function and energy band gap of coumarin-containing copolymers thin films by means of spectroscopic ellipsometry (SE) combined with transmittance measurements (T) and atomic force microscopy (AFM). We found that the optical properties of coumarin-containing copolymers strongly depend from length of alkyl spacer as well as the type of substitution in coumarin moiety. In our case the refractive index as well as the energy band gap of coumarin-containing copolymer decrease with increase the length of alkyl spacer. Additionally, the lengthening of the alkyl spacer brings the bathochromic shifts of the absorption spectra towards longer wavelengths.

  13. 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.

  14. Relaxations of light scattering in mixture of PEG-PDMS-PEG triblock polymer with water in oil nano-droplets

    NASA Astrophysics Data System (ADS)

    Sharifi, Soheil

    2015-05-01

    The effect of a triblock oil soluble polymer (PEG-PDMS-PEG) on the properties of water-in-oil (W/O) droplet microemulsion ( R ˜ 7.5 nm) has been studied as a function of the amount of added polymer. Macroscopically one observes a substantial increase of viscosity with increase of polymer concentration that it is surpassed and effective cross-linking of the droplets takes place. SAXS measurements show that the size of the droplets is not changed by the polymer addition but it induces repulsive interactions ones at high polymer content. One fast (alpha relaxation) and two slow relaxations (beta and gamma relaxations) were observed in mixture system by Quasielastic light scattering (QLS). At high polymer content the network formation leads to slowdown of beta and gamma relaxations in QLS and increase in the motion of alpha. Moreover, the increasing of midblock length of polymer in mixture systems can increasing the different between slow and fast relaxation.

  15. Morphologies of poly(cyclohexadiene) diblock copolymers

    SciTech Connect

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

    2012-01-01

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

  16. 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.

  17. Co-polymer films for sensors

    NASA Technical Reports Server (NTRS)

    Ryan, Margaret A. (Inventor); Homer, Margie L. (Inventor); Yen, Shiao-Pin S. (Inventor); Kisor, Adam (Inventor); Jewell, April D. (Inventor); Shevade, Abhijit V. (Inventor); Manatt, Kenneth S. (Inventor); Taylor, Charles (Inventor); Blanco, Mario (Inventor); Goddard, William A. (Inventor)

    2010-01-01

    Embodiments include a sensor comprising a co-polymer, the co-polymer comprising a first monomer and a second monomer. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is polystyrene and the second monomer is poly-2-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium benzylamine chloride. Other embodiments are described and claimed.

  18. Co-polymer Films for Sensors

    NASA Technical Reports Server (NTRS)

    Ryan, Margaret A. (Inventor); Homer, Margie L. (Inventor); Yen, Shiao-Pin S. (Inventor); Kisor, Adam (Inventor); Jewell, April D. (Inventor); Shevade, Abhijit V. (Inventor); Manatt, Kenneth S. (Inventor); Taylor, Charles (Inventor); Blanco, Mario (Inventor); Goddard, William A. (Inventor)

    2012-01-01

    Embodiments include a sensor comprising a co-polymer, the co-polymer comprising a first monomer and a second monomer. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is polystyrene and the second monomer is poly-2-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium benzylamine chloride. Other embodiments are described and claimed.

  19. Syntheses and physical characterization of new aliphatic triblock poly(L-lactide-b-butylene succinate-b-L-lactide)s bearing soft and hard biodegradable building blocks.

    PubMed

    Ba, Chaoyi; Yang, Jing; Hao, Qinghui; Liu, Xiaoyun; Cao, Amin

    2003-01-01

    This study presents chemical syntheses and physical characterization of a new aliphatic poly(L-lactide-b-butylene succinate-b-L-lactide) triblock copolyester with soft and hard biodegradable building blocks. First, poly(butylene succinate) (PBS) prepolymers terminated with hydroxyl functional groups were synthesized through melt polycondensation from succinic acid and 1,4-butanediol. Further, a series of new PLLA-b-PBS-b-PLLA triblock copolyesters bearing various average PLLA block lengths were prepared via ring opening polymerization of L-lactide with the synthesized hydroxyl capped PBS prepolymer (Mn = 4.9 KDa) and stannous octanoate as the macroinitiator and catalyst, respectively. By means of GPC, NMR, FTIR, DSC, TGA, and wide-angle X-ray diffractometer (WAXD), the macromolecular structures and physical properties were intensively studied for these synthesized PBS prepolymer and PLLA-b-PBS-b-PLLA triblock copolyesters. 13C NMR and GPC experimental results confirmed the formation of sequential block structures without any detectable transesterification under the present experimental conditions, and the molecular weights of triblock copolyesters could be readily regulated by adjusting the feeding molar ratio of L-lactide monomer to the PBS macroinitiator. DSC measurements showed all single glass transitions, and their glass transition temperatures were found to be between those of PLLA and PBS, depending on the lengths of PLLA blocks. It was noteworthy that the segmental flexibilities of the hard PLLA blocks were found to be remarkably enhanced by the more flexible PBS block partner, and the PBS and PLLA building blocks were well mixed in the amorphous regions. Results of TGA analyses indicated that thermal degradation and stabilities of the PLLA blocks strongly depended on the average PLLA block lengths of triblock copolyesters. In addition, FTIR and WAXD results showed the coexistence of the assembled PLLA and PBS crystal structures when the average PLLA block

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  1. Fluctuation Effects on Phase Behavior of Gradient Copolymer Systems

    NASA Astrophysics Data System (ADS)

    Pandav, Gunja; Ganesan, Venkat

    2013-03-01

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

  2. 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.

  3. 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.

  4. 21 CFR 173.65 - Divinylbenzene copolymer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... with food only of Types I, II, and VI-B (excluding carbonated beverages) described in table 1 of... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Divinylbenzene copolymer. 173.65 Section 173.65 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED)...

  5. Copolymer sealant compositions and method for making

    NASA Technical Reports Server (NTRS)

    Singh, Navjot (Inventor); Leman, John Thomas (Inventor); Whitney, John M. (Inventor); Krabbenhoft, Herman Otto (Inventor)

    2004-01-01

    Condensation curable poly(fluoroorgano)siloxane-poly(silarylene)siloxane block copolymer compositions having a glass transition temperature not exceeding about -54.degree. C. and excellent solvent resistance have been found useful as sealants. Polyalkoxysilylorgano compounds, such as 1,4-bis[trimethoxysilyl(ethyl)]benzene have been found to be effective as cross-linkers.

  6. Copolymer sealant compositions and method for making

    NASA Technical Reports Server (NTRS)

    Singh, Navjot (Inventor); Leman, John Thomas (Inventor); Whitney, John M. (Inventor); Krabbenhoft, Herman Otto (Inventor)

    2003-01-01

    Condensation curable poly(fluoroorgano)siloxane-poly(silarylene)siloxane block copolymer compositions having a glass transition temperature not exceeding about -54.degree. C. and excellent solvent resistance have been found useful as sealants. Polyalkoxysilylorgano compounds, such as 1,4-bis[trimethoxysilyl(ethyl)]benzene have been found to be effective as cross-linkers.

  7. Copolymer sealant compositions and method for making

    NASA Technical Reports Server (NTRS)

    Singh, Navjot (Inventor); Leman, John Thomas (Inventor); Whitney, John M. (Inventor); Krabbenhoft, Herman Otto (Inventor)

    2002-01-01

    Condensation curable poly(fluoroorgano)siloxane-poly(silarylene)siloxane block copolymer compositions having a glass transition temperature not exceeding about -54.degree. C. and excellent solvent resistance have been found useful as sealants. Polyalkoxysilylorgano compounds, such as 1,4-bis[trimethoxysilyl(ethyl)]benzene have been found to be effective as cross-linkers.

  8. 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.

  9. 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

  10. 21 CFR 872.3500 - Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium...

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. 872.3500 Section 872.3500...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. (a) Identification... adhesive is a device composed of polyvinylmethylether maleic anhydride, acid copolymer,...

  11. 21 CFR 872.3500 - Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. 872.3500 Section 872.3500...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. (a) Identification. Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium (NACMC)...

  12. 21 CFR 872.3500 - Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium...

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. 872.3500 Section 872.3500...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. (a) Identification. Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium (NACMC)...

  13. 21 CFR 872.3500 - Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium...

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. 872.3500 Section 872.3500...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. (a) Identification. Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium (NACMC)...

  14. 21 CFR 872.3500 - Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium...

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. 872.3500 Section 872.3500...), acid copolymer, and carboxymethylcellulose sodium (NACMC) denture adhesive. (a) Identification. Polyvinylmethylether maleic anhydride (PVM-MA), acid copolymer, and carboxymethylcellulose sodium (NACMC)...

  15. Mechanism of Molecular Exchange in Copolymer Micelles

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  16. Multigraft Copolymer Superelastomers: Synthesis Morphology, and Properties

    SciTech Connect

    Uhrig, David; Schlegel, Ralf; Weidisch, Roland; Mays, Jimmy

    2011-01-01

    The synthesis of well-defined multigraft copolymers having a polydiene backbone with polystyrene side chains is briefly reviewed, with particular focus on controlling branch point spacing and branch point functionality. Use of living anionic polymerization and chlorosilane linking chemistry has led to the synthesis of series of materials having regularly spaced trifunctional (comb), tetrafunctional (centipede), and hexafunctional (barbwire) branch points. The morphologies of these materials were characterized by transmission electron microscopy and small-angle X-ray scattering, and it was found that the morphologies were controlled by the local architectural asymmetry associated with each branch point. Mechanical properties studies revealed that such multigraft copolymers represent a new class of thermoplastic elastomers (TPEs) with superior elongation at break and low residual strains as compared to conventional TPEs.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. Phase Behavior of Gradient Copolymer Solution

    NASA Astrophysics Data System (ADS)

    Pandav, Gunja; Gallow, Keith; Loo, Yueh-Lin; Ganesan, Venkat

    2012-02-01

    We study the behavior of amphiphilic linear gradient copolymer chains under poor solvent conditions. Using Bond Fluctuation model and parallel tempering algorithm, we explore qualitative behavior of this class of polymers with varying gradient strength; which is the largest difference in the instantaneous composition along the polymer chain. Under poor solvent conditions, the chains collapse to form micelles. We find a linear dependence of hydrophilic to hydrophobic transition temperature on gradient strength. Systematic analysis of these clusters reveals a strong dependence of micelle properties on gradient strength. Also, we discuss our results with reference to recent experiments on synthesis and cloud point depression in gradient copolymers confirming gradient strength as key parameter in tuning micelle properties.

  2. On the birefringence of multilayered symmetric diblock copolymer films

    SciTech Connect

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

    1993-09-27

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

  3. Reversible geling co-polymer and method of making

    DOEpatents

    Gutowska, Anna

    2005-12-27

    The present invention is a thereapeutic agent carrier having a thermally reversible gel or geling copolymer that is a linear random copolymer of an [meth-]acrylamide derivative and a hydrophilic comonomer, wherein the linear random copolymer is in the form of a plurality of linear chains having a plurality of molecular weights greater than or equal to a minimum geling molecular weight cutoff and a therapeutic agent.

  4. Gyroid nickel nanostructures from diblock copolymer supramolecules.

    PubMed

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

    2014-01-01

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

  5. Crystallization in Ordered Polydisperse Polyolefin Diblock Copolymers

    SciTech Connect

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

    2010-12-07

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

  6. 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.

  7. 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

  8. 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

  9. Block and Graft Copolymers of Polyhydroxyalkanoates

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

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

  10. Regulating block copolymer phases via selective homopolymers.

    PubMed

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

    2015-03-28

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

  11. Sulfur copolymers for infrared optical imaging

    NASA Astrophysics Data System (ADS)

    Namnabat, S.; Gabriel, J. J.; Pyun, J.; Norwood, R. A.; Dereniak, E. L.; van der Laan, J.

    2014-06-01

    The development of organic polymers with low infrared absorption has been investigated as a possible alternative to inorganic metal oxide, semiconductor, or chalcogenide-based materials for a variety of optical devices and components, such as lenses, goggles, thermal imaging cameras and optical fibers. In principle, organic-based polymers are attractive for these applications because of their low weight, ease of processing, mechanical toughness, and facile chemical variation using commercially available precursors. Herein we report on the optical characterization of a new class of sulfur copolymers that are readily moldable, transparent above 500 nm, possess high refractive index (n > 1.8) and take advantage of the low infrared absorption of S-S bonds for potential use in the mid-infrared at 3-5 microns. These materials are largely made from elemental sulfur by an inverse vulcanization process; in the current study we focus on the properties of a chemically stable, branched copolymer of poly(sulfur-random-1,3-diisopropenylbenzene) (poly(S-r- DIB). Copolymers with elemental sulfur content ranging from 50% to 80% by weight were studied by UV-VIS spectroscopy, FTIR, and prism coupling for refractive index measurement. Clear correlation between material composition and the optical properties was established, confirming that the high polarizability of the sulfur atom leads to high refractive index while also maintaining low optical loss in the infrared.

  12. Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

    PubMed Central

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

    2014-01-01

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

  13. 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

  14. 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.

  15. 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.

  16. 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?

  17. Multicomponent Nanomaterials with Complex Networked Architectures from Orthogonal Degradation and Binary Metal Backfilling in ABC Triblock Terpolymers

    PubMed Central

    2015-01-01

    Selective degradation of block copolymer templates and backfilling the open mesopores is an effective strategy for the synthesis of nanostructured hybrid and inorganic materials. Incorporation of more than one type of inorganic material in orthogonal ways enables the synthesis of multicomponent nanomaterials with complex yet well-controlled architectures; however, developments in this field have been limited by the availability of appropriate orthogonally degradable block copolymers for use as templates. We report the synthesis and self-assembly into cocontinuous network structures of polyisoprene-block-polystyrene-block-poly(propylene carbonate) where the polyisoprene and poly(propylene carbonate) blocks can be orthogonally removed from the polymer film. Through sequential block etching and backfilling the resulting mesopores with different metals, we demonstrate first steps toward the preparation of three-component polymer–inorganic hybrid materials with two distinct metal networks. Multiblock copolymers in which two blocks can be degraded and backfilled independently of each other, without interference from the other, may be used in a wide range of applications requiring periodically ordered complex multicomponent nanoarchitectures. PMID:25836760

  18. Kinetics of temperature response of PEO-b-PNIPAM-b-PAA triblock terpolymer aggregates and of their complexes with lysozyme

    DOE PAGES

    Papagiannopoulos, Aristeidis; Meristoudi, Anastasia; Hong, Kunlun; Pispas, Stergios

    2015-12-18

    We present the kinetics of temperature response of a PEO-b-PNIPAM-b-PAA triblock terpolymer and of its complexes with lysozyme in aqueous solution. It is found that during the coil-to-globule transition of PNIPAM new bonds within the polymer aggregates are created, making the transition of the aggregates partially irreversible. This effect is also found for the protein loaded PEO-b-PNIPAM-b-PAA aggregates whereas in this case protein globules appear to enhance the formation of bonds, making the transition totally irreversible. The internal dynamics of both aggregates and complexes are “frozen” once the temperature is increased upon PINIPAM's LCST in water and remain so evenmore » when the temperature drops below LCST. As a result, we investigate the complexation kinetics of lysozyme and PEO-b-PNIPAM-b-PAA and observe that it occurs in two stages, one where protein globules adsorb on single pre-formed aggregates and one where protein globules cause inter-aggregate clustering.« less

  19. Kinetics of temperature response of PEO-b-PNIPAM-b-PAA triblock terpolymer aggregates and of their complexes with lysozyme

    SciTech Connect

    Papagiannopoulos, Aristeidis; Meristoudi, Anastasia; Hong, Kunlun; Pispas, Stergios

    2015-12-18

    We present the kinetics of temperature response of a PEO-b-PNIPAM-b-PAA triblock terpolymer and of its complexes with lysozyme in aqueous solution. It is found that during the coil-to-globule transition of PNIPAM new bonds within the polymer aggregates are created, making the transition of the aggregates partially irreversible. This effect is also found for the protein loaded PEO-b-PNIPAM-b-PAA aggregates whereas in this case protein globules appear to enhance the formation of bonds, making the transition totally irreversible. The internal dynamics of both aggregates and complexes are “frozen” once the temperature is increased upon PINIPAM's LCST in water and remain so even when the temperature drops below LCST. As a result, we investigate the complexation kinetics of lysozyme and PEO-b-PNIPAM-b-PAA and observe that it occurs in two stages, one where protein globules adsorb on single pre-formed aggregates and one where protein globules cause inter-aggregate clustering.

  20. Triblock polyphiles through click chemistry: self-assembled thermotropic cubic phases formed by micellar and monolayer vesicular aggregates.

    PubMed

    Tan, Xiaoping; Kong, Leiyang; Dai, Heng; Cheng, Xiaohong; Liu, Feng; Tschierske, Carsten

    2013-11-25

    Three series of triblock polyphiles consisting of a rigid 4-phenyl-1,2,3-triazole or 1,4-diphenyl-1,2,3-triazole core with three lipophilic and flexible alkoxyl chains at one end and a polar glycerol group at the opposite end were synthesized by copper-catalyzed azide-alkyne click reactions. Their mesophase behavior was studied by polarizing optical microscopy, differential scanning calorimetry, and XRD. Depending on alkyl chain length and core length, a transition from hexagonal columnar to Pm3n-type cubic phases was observed. In the cubic phases, the molecules are organized as spherical objects. Remarkably, compounds with a longer core unit have a higher tendency to form these cubic phases, and their stability is strongly enhanced over those of the compounds with a shorter core, despite longer cores having a smaller cone angle and therefore being expected to disfavor the formation of spherical objects. There is a large difference in the number of molecules involved in the spherical aggregates formed by compounds with long and short cores. Whereas the aggregates in the cubic phases of the compounds with short rod units are small and could be regarded as micellar, the long-core compounds form much larger aggregates which are regarded as a kind of monolayer vesicular aggregate.

  1. In vitro anticancer activity of docetaxel-loaded micelles based on poly(ethylene oxide)-poly(epsilon-caprolactone) block copolymers: Do nanocarrier properties have a role?

    PubMed

    Ostacolo, Luisanna; Marra, Monica; Ungaro, Francesca; Zappavigna, Silvia; Maglio, Giovanni; Quaglia, Fabiana; Abbruzzese, Alberto; Caraglia, Michele

    2010-12-01

    In this paper we have investigated the behavior of core-shell poly(ethylene oxide)-poly(epsilon-caprolactone) (PEO-PCL) micelles derived from copolymers with linear triblock (TR) and 4-arm star-diblock (ST) architectures for the delivery of docetaxel (DTX). DTX was loaded inside micelles (DTX-TR(m) and DTX-ST(m)) with high efficiency and released slowly for more than two weeks. DTX-loaded micelles based on both copolymers had very similar properties in terms of mean size, zeta potential, loading ability and release rate in buffered saline. However, the stability of DTX-ST(m) was very poor in aqueous media with proteins resulting in a strong and progressive aggregation. We studied the effect of increasing concentrations of free DTX or DTX-loaded micelles on growth inhibition of human breast MCF-7 and MDA-MB468 and prostate PC3 and DU145 adenocarcinoma cell lines. DTX-loaded TR micelles induced cell growth inhibition similarly to free DTX whereas DTX-ST(m) showed lower cytotoxicity. On the other hand, by normalizing IC(50) values for the actual amount of DTX released from micelles in the medium, DTX-loaded ST micelles became more active than free DTX in all cell lines tested. Both free DTX and DTX-loaded TR micelles displayed a significantly lower cytotoxic activity in G(2)/M phase synchronized cells, whereas cytotoxicity of DTX-loaded ST micelles did not change. Cytotoxicity was related to micelle stability, uptake and release rate in cell culture media. Our results suggest that for a correct interpretation of cytotoxicity of nanocarriers, the evaluation of their behavior in biologically relevant conditions is of utmost importance to select proper systems for further in vivo testing.

  2. Preparation and Characterization of Ultralow-Dielectric-Constant Porous SiCOH Thin Films Using 1,2-Bis(triethoxysilyl)ethane, Triethoxymethylsilane, and a Copolymer Template

    NASA Astrophysics Data System (ADS)

    Fu, Shuang; Qian, Ke-Jia; Ding, Shi-Jin; Zhang, David Wei

    2011-10-01

    Ultralow-dielectric-constant ( k) porous SiCOH films have been prepared using 1,2-bis(triethoxysilyl)ethane, triethoxymethylsilane, and a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer template by means of spin-coating. The resulting films were characterized by cross-section scanning electron microscopy, small-angle x-ray diffraction, atomic force microscopy, Fourier-transform infrared spectroscopy, nanomechanical testing, and electrical measurements. Thermal treatment at 350°C for 2 h resulted in the formation of ultralow- k films with k of ˜2.0, leakage current density of 3 × 10-8 A/cm2 at 1 MV/cm, reduced modulus ( E r) of ˜4.05 GPa, and hardness ( H) of ˜0.32 GPa. After annealing between 400°C and 500°C for 30 min, the resulting films showed fluctuant k values of 1.85 to 2.22 and leakage current densities of 3.7 × 10-7 A/cm2 to 3 × 10-8 A/cm2 at 0.8 MV/cm, likely due to the change of the film microstructure. Compared with 350°C annealing, higher-temperature annealing can improve the mechanical strength of the ultralow- k film, i.e., E r ≈ 5 GPa and H ≈ 0.56 GPa after 500°C annealing.

  3. Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

    DOE PAGES

    Han, Youngkyu; Ahn, Suk-kyun; Zhang, Zhe; Smith, Gregory S.; Do, Changwoo

    2016-06-01

    We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous solution In a carbon nanotube/PEO105-PPO70-PEO105 (poloxamer 407) aqueous solution, the amphiphilic poloxamer 407 adsorbs onto the carbon nanotube surfaces and self-assembles into continuous layers, driven by intermolecular interactions between constituent molecules. The addition of 5-methylsalicylic acid changes the self-assembled structure from spherical-micellar to a cylindrical morphology. The fabricated poloxamer 407/carbon nanotube hybrid particles exhibit thermo-responsive structural features so that the density and thickness of poloxamer 407 layers are also reversibly controllable by varying temperature. The detailed structural properties of the poloxamer 407/carbon nanotubemore » particles in suspension can be characterized by small-angle neutron scattering experiments and model fit analyses. The distinct curve shapes of the scattering intensities depending on temperature control or addition of aromatic additives are well described by a modified core-shell cylinder model consisting of a carbon nanotube core cylinder, a hydrophobic shell, and a hydrated polymer layer. In conclusion, this method can provide a simple but efficient way for the fabrication and in-situ characterization of carbon nanotube-based nano particles with a structure-tunable encapsulation.« less

  4. 40 CFR 721.4700 - Metalated alkylphenol copolymer (generic name).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Metalated alkylphenol copolymer (generic name). 721.4700 Section 721.4700 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.4700 Metalated alkylphenol copolymer (generic name). (a)...

  5. 21 CFR 177.1312 - Ethylene-carbon monoxide copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from the American Society for... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ethylene-carbon monoxide copolymers. 177.1312... Use Food Contact Surfaces § 177.1312 Ethylene-carbon monoxide copolymers. The ethylene-carbon...

  6. Imide/arylene ether copolymers with pendent trifluoromethyl groups

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.; Havens, Stephen J.

    1992-01-01

    A series of imide/arylene ether block copolymers were prepared using an arylene ether block containing a hexafluoroisopropylidene group and an imide block containing a hexafluoroisopropylidene and a trifluoromethyl group in the polymer backbone. The copolymers were characterized and mechanical properties were determined and compared to the homopolymers.

  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. 21 CFR 177.1320 - Ethylene-ethyl acrylate copolymers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... percent by weight unless it is blended with polyethylene or with one or more olefin copolymers complying with § 177.1520 or with a mixture of polyethylene and one or more olefin copolymers, in such... prescribed for polyethylene in § 177.1520. (1) Specifications—(i) Infrared identification....

  9. 21 CFR 177.1320 - Ethylene-ethyl acrylate copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... percent by weight unless it is blended with polyethylene or with one or more olefin copolymers complying with § 177.1520 or with a mixture of polyethylene and one or more olefin copolymers, in such... prescribed for polyethylene in § 177.1520. (1) Specifications—(i) Infrared identification....

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Beckingham, Bryan; Register, Richard

    2013-03-01

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

  13. 40 CFR 721.10213 - Polyether polyester copolymer phosphate (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... phosphate (generic). 721.10213 Section 721.10213 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10213 Polyether polyester copolymer phosphate (generic). (a) Chemical... as polyether polyester copolymer phosphate (PMN P-09-253) is subject to reporting under this...

  14. 21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ethylene-acrylic acid copolymers. 177.1310 Section... Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid... for use in contact with food subject to the provisions of this section. (a) The ethylene-acrylic...

  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. 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.

  17. 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

  18. First-principles investigation of PVDF and its copolymers

    NASA Astrophysics Data System (ADS)

    Ranjan, V.; Yu, Liping; Buongiorno Nardelli, Marco; Bernholc, J.

    2009-03-01

    Recently, PVDF and its copolymers have generated significant interest due to their electroactive properties [1] and potential for ultra-high energy-storage applications [2]. In this talk, we present the results of first-principles calculations of stable phases and dielectric properties of different copolymers and terpolymers of PVDF at varying concentrations. Our results show that at very high concentrations of Chloro-trifluoroethylene (CTFE), PVDF/CTFE displays sharp transitions between non-polar (α) and polar (β) phases. On the contrary, the same transitions in copolymers with trifluoroethylene (TrFE) and tetrafluoroethylene (TeFE) are not sharp and happen at lower concentrations. We discuss the interplay of copolymer admixture on the dielectric properties of PVDF and discuss the suitability of copolymers for energy storage and electroactive applications. [1] S. G. Lu et al., App. Phys. Lett. 93, 042905 (2008). [2] V. Ranjan et al., Phys. Rev. Lett. 99, 047801 (2007).

  19. Cell protective, ABC triblock polymer-based thermoresponsive hydrogels with ROS-triggered degradation and drug release.

    PubMed

    Gupta, Mukesh K; Martin, John R; Werfel, Thomas A; Shen, Tianwei; Page, Jonathan M; Duvall, Craig L

    2014-10-22

    A combination of anionic and RAFT polymerization was used to synthesize an ABC triblock polymer poly[(propylenesulfide)-block-(N,N-dimethylacrylamide)-block-(N-isopropylacrylamide)] (PPS-b-PDMA-b-PNIPAAM) that forms physically cross-linked hydrogels when transitioned from ambient to physiologic temperature and that incorporates mechanisms for reactive oxygen species (ROS) triggered degradation and drug release. At ambient temperature (25 °C), PPS-b-PDMA-b-PNIPAAM assembled into 66 ± 32 nm micelles comprising a hydrophobic PPS core and PNIPAAM on the outer corona. Upon heating to physiologic temperature (37 °C), which exceeds the lower critical solution temperature (LCST) of PNIPAAM, micelle solutions (at ≥2.5 wt %) sharply transitioned into stable, hydrated gels. Temperature-dependent rheology indicated that the equilibrium storage moduli (G') of hydrogels at 2.5, 5.0, and 7.5 wt % were 20, 380, and 850 Pa, respectively. The PPS-b-PDMA-b-PNIPAAM micelles were preloaded with the model drug Nile red, and the resulting hydrogels demonstrated ROS-dependent drug release. Likewise, exposure to the peroxynitrite generator SIN-1 degraded the mechanical properties of the hydrogels. The hydrogels were cytocompatible in vitro and were demonstrated to have utility for cell encapsulation and delivery. These hydrogels also possessed inherent cell-protective properties and reduced ROS-mediated cellular death in vitro. Subcutaneously injected PPS-b-PDMA-b-PNIPAAM polymer solutions formed stable hydrogels that sustained local release of the model drug Nile red for 14 days in vivo. These collective data demonstrate the potential use of PPS-b-PDMA-b-PNIPAAM as an injectable, cyto-protective hydrogel that overcomes conventional PNIPAAM hydrogel limitations such as syneresis, lack of degradability, and lack of inherent drug loading and environmentally responsive release mechanisms.

  20. Small domain-size multiblock copolymer electrolytes

    DOEpatents

    Pistorino, Jonathan; Eitouni, Hany Basam

    2016-09-20

    New block polymer electrolytes have been developed which have higher conductivities than previously reported for other block copolymer electrolytes. The new materials are constructed of multiple blocks (>5) of relatively low domain size. The small domain size provides greater protection against formation of dendrites during cycling against lithium in an electrochemical cell, while the large total molecular weight insures poor long range alignment, which leads to higher conductivity. In addition to higher conductivity, these materials can be more easily synthesized because of reduced requirements on the purity level of the reagents.

  1. 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.

  2. Self-Assembly and Chain-Folding in Hybrid Coil-Coil-Cube Triblock Oligomers of Polyethylene-b-Poly(ethylene Oxide)-b-Polyhedral Oligomeric Silsesquioxane

    SciTech Connect

    Miao,J.; Cui, L.; Lau, H.; Mather, P.; Zhu, L.

    2007-01-01

    Self-assembly and chain-folding in well-defined oligomeric polyethylene-block-poly(ethylene oxide)-block-polyhedral oligomeric silsesquioxane (PE-b-PEO-b-POSS) triblock molecules were studied by small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and transmission electron microscopy (TEM). The triblock oligomers were synthesized by attaching two kinds of functional POSS molecules, namely, isocyanatopropyldimethylsilylisobutyl-POSS (Ib-POSS) and isocyanatopropyldimethylsilylcyclopentyl-POSS (Cp-POSS), to a hydroxyl-terminated PE-b-PEO-OH diblock oligomer (denoted as E{sub 39}EO{sub 23}) via urethane reactions. In these triblock oligomers, both PE and POSS were crystalline, whereas PEO became amorphous due to tethering of its both ends to other two blocks. In the crystalline state, PE chains tilted 32{sup o} from the lamellar normal, and both Ib-POSS and Cp-POSS molecules stacked into four-layer (ABCA) lamellar crystals, having the same trigonal (R{bar 3}m) symmetry as in pure POSS crystals. Because the cross-sectional area for a PE chain in the PE crystals (0.216 nm{sup 2}/chain) at the interface was much smaller than that for a POSS molecule in POSS crystals (1.136 nm{sup 2}/molecule), the self-assembly and PE chain-folding were substantially affected by the sequence of PE and POSS crystallization when crystallizing from the melt. For example, PE crystallization induced the POSS crystallization in the bulk E{sub 39}EO{sub 23}-Ib-POSS, and thus extended-chain PE crystals were observed. The grains of crystalline lamellae again were small with often highly curved lamellar crystals. This could also be attributed to the unbalanced interfacial areas for POSS and PE blocks (the interfacial area ratio being 2.6 for interdigitated PE crystals, i.e., two PE chains per POSS molecule). For the E{sub 39}EO{sub 23}-Cp-POSS triblock oligomer, POSS molecules crystallized before PE crystallization, forming a well-defined lamellar structure. The preexisting

  3. 21 CFR 177.1340 - Ethylene-methyl acrylate copolymer resins.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ethylene-methyl acrylate copolymer resins. 177...-methyl acrylate copolymer resins. Ethylene-methyl acrylate copolymer resins may be safely used as... prescribed conditions: (a) For the purpose of this section, the ethylene-methyl acrylate copolymer...

  4. 21 CFR 177.1360 - Ethylene-vinyl acetate-vinyl alcohol copolymers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Ethylene-vinyl acetate-vinyl alcohol copolymers... acetate-vinyl alcohol copolymers. Ethylene-vinyl acetate-vinyl alcohol copolymers (CAS Reg. No. 26221-27-2... accordance with the following prescribed conditions: (a) Ethylene-vinyl acetate-vinyl alcohol copolymers...

  5. 21 CFR 177.1360 - Ethylene-vinyl acetate-vinyl alcohol copolymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-vinyl acetate-vinyl alcohol copolymers... acetate-vinyl alcohol copolymers. Ethylene-vinyl acetate-vinyl alcohol copolymers (CAS Reg. No. 26221-27-2... accordance with the following prescribed conditions: (a) Ethylene-vinyl acetate-vinyl alcohol copolymers...

  6. 21 CFR 177.1360 - Ethylene-vinyl acetate-vinyl alcohol copolymers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Ethylene-vinyl acetate-vinyl alcohol copolymers... acetate-vinyl alcohol copolymers. Ethylene-vinyl acetate-vinyl alcohol copolymers (CAS Reg. No. 26221-27-2... accordance with the following prescribed conditions: (a) Ethylene-vinyl acetate-vinyl alcohol copolymers...

  7. 21 CFR 177.1360 - Ethylene-vinyl acetate-vinyl alcohol copolymers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Ethylene-vinyl acetate-vinyl alcohol copolymers... acetate-vinyl alcohol copolymers. Ethylene-vinyl acetate-vinyl alcohol copolymers (CAS Reg. No. 26221-27-2... accordance with the following prescribed conditions: (a) Ethylene-vinyl acetate-vinyl alcohol copolymers...

  8. 21 CFR 177.1340 - Ethylene-methyl acrylate copolymer resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-methyl acrylate copolymer resins. 177.1340... copolymer resins. Ethylene-methyl acrylate copolymer resins may be safely used as articles or components of...) For the purpose of this section, the ethylene-methyl acrylate copolymer resins consist of...

  9. 21 CFR 177.1340 - Ethylene-methyl acrylate copolymer resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Ethylene-methyl acrylate copolymer resins. 177... Repeated Use Food Contact Surfaces § 177.1340 Ethylene-methyl acrylate copolymer resins. Ethylene-methyl... section, the ethylene-methyl acrylate copolymer resins consist of basic copolymers produced by...

  10. Kinetic assembly of block copolymers in solution helical cylindrical micelles and patchy nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhong, Sheng

    There is always an interest to understand how molecules behave under different conditions. One application of this knowledge is to self-assemble molecules into increasingly complex structures in a simple fashion. Self-assembly of amphiphilic block copolymer in solution has produced a large variety of nanostructures through the manipulation in polymer chemistry, assembly environment, and additives. Moreover, some reports suggest the formation of many polymeric assemblies is driven by kinetic process. The goal of this dissertation is to study the influence of kinetics on the assembly of block copolymer. The study shows kinetic control can be a very effective way to make novel polymeric nanostructures. Two examples discussed here are helical cylindrical micelles and patchy nanoparticles. Helical cylindrical micelles are made from the co-assembly of amphiphilic triblock copolymer poly(acrylic acid)-block-poly(methyl acrylate)- block-polystyrene and organoamine molecules in a mixture of tetrahydrofuran (THF) and water (H2O). This system has already shown promise of achieving many assembled structures. The unique aspects about this system are the use of amine molecules to complex with acid groups and the existence of cosolvent system. Application of amine molecules offers a convenient control over assembled morphology and the introduction of PMA-PS selective solvent, THF, promotes the mobility of the polymer chains. In this study, multivalent organoamine molecules, such as diethylenetriamine and triethylenetetramine, are used to interact with block copolymer in THF/water mixture. As expected, the assembled morphologies are dependent on the polymer architecture, selection and quantity of the organoamine molecules, and solution composition. Under the right conditions, unprecedented, multimicrometer-long, supramolecular helical cylindrical micelles are formed. Both single-stranded and double-stranded helices are found in the same system. These helical structures share

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Vanderwoude, Gordon; Shi, An-Chang

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

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  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. Polysaccharide based Copolymers as Supramolecular Systems in Biomedical Applications.

    PubMed

    Célia Monteiro de Paula, Regina; Andrade Feitosa, Judith Pessoa; Beserra Paula, Haroldo César

    2015-01-01

    Polysaccharides are natural polymers, obtained from a large variety of sources ranging from fungi to more complex organisms such as birds and whales. Their use for pharmaceutical and biomedical applications has been the subject of numerous researches by the world´s academia. Polysaccharide chemical/physical modifications leading to graft copolymers are discussed in this review, focusing on those nanosystems that are potential candidates for drug delivery applications. Therefore, this review focuses on the biomedical application of polysaccharide based copolymers, particularly as nanocarriers. Copolymer of polysaccharides such as alginate, cellulose, chitosan, dextran, guar, hyaluronic acid, pullulan and starch as drug delivery nanocarriers will be discussed. PMID:26424388

  20. 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.

  1. Photocrosslinkable copolymers for non-linear optical applications

    SciTech Connect

    Kawatsuki, N.; Pakbaz, K.; Schmidt, H.W.

    1993-12-31

    New photocrosslinkable copolymers have been synthesized and applied as non-linear optical materials. The copolymers are based on methyl methacrylate, a photo-excitable benzophenone monomer, a non-linear optical active 4`-[(2-hydroxyethyl)ethylamino]-4-nitro-azobenzene (disperse red 1) side chain monomer and a crosslinkable 2-butenyl monomer. These copolymers can be crosslinked by UV light at 366 nm in the poled state and show a stable alignment of NLO chromophore by monitoring the adsorption spectra. The crosslinked and poled film did not change its alignment after storing 4 weeks at room temperature.

  2. 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

  3. [Emulsification experiments with dimethylsiloxane/phenylmethylsiloxane copolymer].

    PubMed

    Ikeda, T; Nakamura, K; Sakagami, K; Iwahashi, H; Sugimoto, K; Matsuda, T; Tano, Y

    1997-02-01

    We compared the emulsification tendency of dimethylsiloxane/phenylmethylsiloxane copolymer (DPC; 5%-phenylated, specific gravity 0.984) with that of silicone oil (dimethylsiloxane; SO, specific gravity 0.966) and fluorosilicone oil (methyl-3,3,3-trifluoropropylsiloxane; FSO, specific gravity 1.256), which are clinically used as an intraocular tamponade. After SO, DPC and FSO were placed in a glass container with an equal amount of albumin solution (1 mg/ml) or gamma-globulin solution (1 mg/ml), and shaken SO and DPC, with their specific gravities being closer to water, showed less emulsification than FSO. Following vitrectomy, DPC was injected into the rabbit vitreous cavity, but did not seem to show any severe histological damage. Highly-phenylated DPC, which is slightly heavier than water, may be useful to treat inferior retinal detachment in place of FSO.

  4. 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.

  5. 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

  6. Cationic vinyl pyridine copolymers and products thereof

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor)

    1978-01-01

    Quaternized, cross-linked, insoluble copolymers of unsubstituted and substituted vinyl pyridines and a dihalo organic compound are spontaneously formed at ambient temperature on mixing the two monomers in bulk, in solution or in suspension. The amount of cross-linking may be varied according to the composition and reaction conditions. The polymer product exhibits ion exchange capacity and undergoes a reversible color change from black at a pH above 7 to yellow at a pH below 7. The polymer may be formed in the presence of preformed polymers, substrates such as porous or impervious particles or films to deposit an ion exchange film in situ or on the surface of the substrate. The coated or resin impregnated substrate may be utilized for separation of anionic species from aqueous solution.

  7. 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.

  8. Multicompartmental Microcapsules from Star Copolymer Micelles

    SciTech Connect

    Choi, Ikjun; Malak, Sidney T.; Xu, Weinan; Heller, William T.; Tsitsilianis, Constantinos; Tsukruk, Vladimir V.

    2013-02-26

    We present the layer-by-layer (LbL) assembly of amphiphilic heteroarm pH-sensitive star-shaped polystyrene-poly(2-pyridine) (PSnP2VPn) block copolymers to fabricate porous and multicompartmental microcapsules. Pyridine-containing star molecules forming a hydrophobic core/hydrophilic corona unimolecular micelle in acidic solution (pH 3) were alternately deposited with oppositely charged linear sulfonated polystyrene (PSS), yielding microcapsules with LbL shells containing hydrophobic micelles. The surface morphology and internal nanopore structure of the hollow microcapsules were comparatively investigated for shells formed from star polymers with a different numbers of arms (9 versus 22) and varied shell thickness (5, 8, and 11 bilayers). The successful integration of star unimers into the LbL shells was demonstrated by probing their buildup, surface segregation behavior, and porosity. The larger arm star copolymer (22 arms) with stretched conformation showed a higher increment in shell thickness due to the effective ionic complexation whereas a compact, uniform grainy morphology was observed regardless of the number of deposition cycles and arm numbers. Small-angle neutron scattering (SANS) revealed that microcapsules with hydrophobic domains showed different fractal properties depending upon the number of bilayers with a surface fractal morphology observed for the thinnest shells and a mass fractal morphology for the completed shells formed with the larger number of bilayers. Moreover, SANS provides support for the presence of relatively large pores (about 25 nm across) for the thinnest shells as suggested from permeability experiments. The formation of robust microcapsules with nanoporous shells composed of a hydrophilic polyelectrolyte with a densely packed hydrophobic core based on star amphiphiles represents an intriguing and novel case of compartmentalized microcapsules with an ability to simultaneously store different hydrophilic, charged, and hydrophobic

  9. Counit Inclusion in Hydrogenated Polynorbornene Copolymer Crystals

    NASA Astrophysics Data System (ADS)

    Burns, Adam; Showak, Michael; Stella, Andrew; Register, Richard

    2014-03-01

    Crystallization in poly(A-co-B) random copolymers, where homopolymer A is crystalline but B is not, is dictated by the degree to which crystals of A can include B units. Typically, B units are strongly excluded from the A crystals, drastically reducing the degree of crystallinity wc and crystal thickness tc even at modest comonomer contents. However, in some cases, B units can be incorporated into the crystals as defects, significantly diminishing the counits' impact on wc and tc. The extent and consequences of counit inclusion have been investigated in hydrogenated polynorbornene (hPN) with alkylnorbornene counits, synthesized by living ring-opening metathesis polymerization followed by hydrogenation. In the case of 5-hexylnorbornene (HxN) counits, a steep decline in wc and tc with counit content is found, indicative of strong exclusion. In contrast, when the counits are 5-methylnorbornene (MeN), extensive inclusion of MeN units into the crystals is observed. hP(N-co-MeN) copolymers maintain appreciable crystallinity above 30 mol% MeN, and the dependence of the melting point Tm on tc tracks that of the hPN homopolymer. Four times as much MeN as HxN (molar basis) is required to produce a comparable drop in wc. Therefore, copolymerization with MeN can be used to tune Tm without drastically reducing wc. Additionally, hPN exhibits a polymorphic transition to a rotationally disordered (RD) crystal at temperature Tcc

  10. Insensitive explosive composition of halogenated copolymer and triaminotrinitrobenzene

    DOEpatents

    Benziger, Theodore M.

    1976-01-01

    A highly insensitive and heat resistant plastic-bonded explosive containing 90 wt % triaminotrinitrobenzene and 10 wt % of a fully saturated copolymer of chlorotrifluoroethylene and vinylidene fluoride is readily manufactured by the slurry process.

  11. Surface Characterization of Aliphatic Polyester -g- Phosphorylcholine Copolymers

    NASA Astrophysics Data System (ADS)

    Zhang, Xiongfei; Emrick, Todd; Hsu, Shaw L.

    2007-03-01

    In order to control biodegradation behavior of a class of polyesters, hydrophilic functional groups were grafted onto the main chains. Phosphorylcholine (PC) molecules with azide attached at the end were synthesized. Due to their excellent biocompatibility and hydrophilicity, they have been covalently coupled to biodegradable aliphatic polyesters via a ``click'' cycloaddition reaction to produce amphiphilic graft copolymers. A series of copolymers were prepared by varying the molar incorporation of PC groups. Surface properties of the copolymers were examined to further explore their applications in drug delivery systems. Grazing angle reflection infrared spectroscopy was employed to determine segmental orientation at the film surface. XPS was used to verify surface composition. A water adsorption experiment was carried out to determine the water permeation rate. The improvement in hydrophilicity was confirmed by a water contact experiment. Results indicate that the graft copolymers were promising in drug delivery systems.

  12. 21 CFR 173.60 - Dimethylamine-epichlorohydrin copolymer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... solution of the copolymer has a minimum viscosity of 175 centipoises at 25 °C as determined by LVT-series... analytical method entitled “The Determination of Epichlorohydrin and 1,3-Dichloro-2-Propanol in...

  13. 21 CFR 173.60 - Dimethylamine-epichlorohydrin copolymer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... weight percent on a dry basis. (2) A 50-percent-by-weight aqueous solution of the copolymer has a minimum... epichlorohydrin and 1,3-dichloro-2-propanol content is determined by an analytical method entitled...

  14. Self-Consistent Field Theory of ABn Miktoarm Copolymer Melts

    NASA Astrophysics Data System (ADS)

    Grason, Gregory; Kamien, Randall

    2004-03-01

    Using self-consistent field theory (SCFT) techniques we investigate the phase behavior of AB_n, miktoarm copolymer melts. In particular, we examine how the molecularasymmetry stabilizes morpholgies with highly curved interfaces. While strong-segregation theory tends to overestimate this effect for asymmetric molecules, the SCFT results are in strong agreement with experiments on PI-PS miktoarm copolymer melts. In addition, we report the stability of a new cubic phase of one-component block copolymer melts, with Pm bar3 n symmetry. This phase, the A15 phase of spherical micelles, is stable in melts of ABn copolymers for n ≥ 2. We interpret the relative stability of the sphere phases in terms of well-studied, geometric moments of the candidate sphere lattices.

  15. Microdomain contraction in microphase-separated multiblock copolymers

    SciTech Connect

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

    1993-06-01

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

  16. Crystalline Morphology of Propylene 1-Octene Random Copolymers

    NASA Astrophysics Data System (ADS)

    Jeon, Keesu; Alamo, Rufina G.

    2008-03-01

    The morphology of isotactic propylene 1-octene random copolymers has been studied by AFM, DSC, WAXS, and FTIR in an octene range of 10-20 mol %. Different morphologies were observed below and above 15 mol %. The morphological components in the higher counit copolymers are not of the lamellae-type, thicker than lamellae observed below 15 mol %, connected and isotropic in their orientation. Their global morphology is developed via nucleation and growth (NG) of spherulitic aggregates. The evolution of heat of fusion with time is also sigmoidal shape, typical of NG-type crystallization mechanism. WAXS diffractograms for the higher counit copolymers are devoid of crystalline reflections, except for small and broad peaks suggesting mesomorphic-like structures, which by FTIR show small contents of the 840 cm-1, 12 and higher units regularity bands, and hence formed of short helical sequences. The PO morphology is additionally compared with copolymers with ethylene, 1-butene and 1-hexene counits at matched contents.

  17. 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.

  18. Thermal analytical study of polyamide copolymer/Surlyn Ionomers Blends

    SciTech Connect

    Qin, C.; Ding, Y.P.

    1993-12-31

    Thermal analytical technique was used as a screening method to study polyamide(Nylon)/ethylene-co-methacrylic acid copolymer-based ionomer(Surlyn)blends. The retardation of crystallization process from molten state of Nylon-12 by the existence of the ionomer was observed, but the crystallization of Nylon-12 can not be thwarted even at high concentration of ionomers. Zinc ionomers shows stronger effect than sodium ionomers. A Nylon copolymer, polyamide-6,6-co-polyamide-6,10, was used to blend with different ionomers and the crystallization process from molten state of Nylon copolymer could be thwarted at high concentration of zinc ionomer even at very cooling rate. Interesting cold crystallization behavior of polyamide copolymer was observed during second DSC heating cycle in the temperature range of the melting process of ionomer.

  19. Melt structure and self-nucleation of ethylene copolymers

    NASA Astrophysics Data System (ADS)

    Alamo, Rufina G.

    A strong memory effect of crystallization has been observed in melts of random ethylene copolymers well above the equilibrium melting temperature. These studies have been carried out by DSC, x-ray, TEM and optical microscopy on a large number of model, narrow, and broad copolymers with different comonomer types and contents. Melt memory is correlated with self-seeds that increase the crystallization rate of ethylene copolymers. The seeds are associated with molten ethylene sequences from the initial crystals that remain in close proximity and lower the nucleation barrier. Diffusion of all sequences to a randomized melt state is a slow process, restricted by topological chain constraints (loops, knots, and other entanglements) that build in the intercrystalline region during crystallization. Self-seeds dissolve above a critical melt temperature that demarcates homogeneity of the copolymer melt. There is a critical threshold level of crystallinity to observe the effect of melt memory on crystallization rate, thus supporting the correlation between melt memory and the change in melt structure during copolymer crystallization. Unlike binary blends, commercial ethylene-1-alkene copolymers with a range in inter-chain comonomer composition between 1 and about 15 mol % display an inversion of the crystallization rate in a range of melt temperatures where narrow copolymers show a continuous acceleration of the rate. With decreasing the initial melt temperature, broadly distributed copolymers show enhanced crystallization followed by a decrease of crystallization rate. The inversion demarcates the onset of liquid-liquid phase separation (LLPS) and a reduction of self-nuclei due to the strong thermodynamic drive for molecular segregation inside the binodal. The strong effect of melt memory on crystallization rate can be used to identify liquid-liquid phase separation in broadly distributed copolymers, and offers strategies to control the state of copolymer melts in ways of

  20. Photooxidative degradation of clear ultraviolet absorbing acrylic copolymer surfaces

    NASA Technical Reports Server (NTRS)

    Gupta, A.; Liang, R. H.; Vogl, O.; Pradellok, W.; Huston, A. L.; Scott, G. W.

    1983-01-01

    Photodegradation of copolymer of methyl methacrylate and 2(2'-hydroxy 5'vinyl-phenyl) 2H-benzotriazole has been investigated in order to determine the changes in the chemical composition of the surface of the copolymer on photooxidation. An electronic energy transfer mechanism has been postulated in order to interpret the observed photochemical changes in the polymer. Preliminary examination of the photophysical properties of the chromophore provides support for such a mechanism.