Showing papers on "Copolymer published in 1991"
TL;DR: In this article, the concentration du copolymere de la variation des proprietes spectroscopiques du pyrene provoquee par son partage entre les phases micellaires et aqueuses permet de determiner les concentrations of critiques micellaire and les coefficients de partage.
Abstract: L'etude en fonction de la concentration du copolymere de la variation des proprietes spectroscopiques du pyrene provoquee par son partage entre les phases micellaires et aqueuses permet de determiner les concentrations critiques micellaires et les coefficients de partage
1,234 citations
TL;DR: Living polymerization techniques can be used to achieve a high degree of control over polymer chain architecture, which results in polymers with widely diverse physical properties, even though they are made from readily available low-cost monomers.
Abstract: Living polymerization techniques can be used to achieve a high degree of control over polymer chain architecture. Examples of the type of polymers that can be synthesized include block copolymers, comb-shaped polymers, multiarmed polymers, ladder polymers, and cyclic polymers. This control of structure, in turn, results in polymers with widely diverse physical properties, even though they are made from readily available low-cost monomers.
698 citations
Patent•
11 Oct 1991
TL;DR: In this paper, a biologically persistent, water-soluble, substantially non-immunogenic, and substantially nonantigenic conjugate of superoxide dismutase is prepared by coupling one to five strands of a polyalkylene glycol which is polyethylene glycol or polyethylenespecific polypropylene copolymer, having an average molecular weight of about 35,000-1,000,000.
Abstract: A biologically persistent, water-soluble, substantially non-immunogenic, substantially non-antigenic conjugate of superoxide dismutase is prepared by coupling one to five strands of a polyalkylene glycol which is polyethylene glycol or polyethylene-polypropylene glycol copolymer, wherein said polyalkylene glycol has an average molecular weight of about 35,000-1,000,000.
280 citations
TL;DR: In this paper, the shape selectivity of high-crosslinked polymers is discussed in detail, and the influence of the arrangement of functional groups within the cavities versus the spatial requirements (shape selectivity) on selectivity is discussed.
Abstract: Highly crosslinked polymers are prepared by radical copolymerization of β-D-fructopyranose 2,3:4,5-bis-O-((4-vinylphenyl)boronate) and α-D-galactopyranose 1,2:3,4-bis-O-((4-vinylphenyl)boronate) with a large amount of cross-linking agent. After splitting off the respective templates these polymers were used for racemic resolution of the racemates of the templates with separation factors α as high as α=2.36 in the batch procedures. The influence of the arrangement of functional groups within the cavities versus the spatial requirements (shape selectivity) on selectivity is discussed in detail. In the examples presented here, the orientation of the functional groups inside the cavity is the dominating factor; shape selectivity is only of secondary importance
255 citations
TL;DR: In this article, the diffusion and sorption of four long-chain hydrocarbons through four commercial polymer membranes has been studied in the temperature interval of 25-60°C by conventional weight gain experiments.
Abstract: Diffusion and sorption of four long-chain hydrocarbons, namely, 2,2,4-trimethylpentane, dodecane, tetradecane, and hexadecane, through four commercial polymer membranes has been studied in the temperature interval of 25-60°C by conventional weight gain experiments. The diffusion results have been analyzed in terms of the simple Fickian model. The slightly anomalous transport behavior of the polymer-solvent systems has been attributed to a slow leaching out of the indigenous elastomer compounds and/or additives during solvent immersion
214 citations
TL;DR: In this article, the styrene end blocks of a poly(styrene-(ethylene- co-butylene)-styrene) (SEBS) copolymer were sulphonated up to a concentration of 18 mol%.
209 citations
Book•
01 Apr 1991
TL;DR: In this article, the authors proposed a method for cross fractionation of polymers in the presence of a mixture of different molecular weights and showed the effect of the stockmayer distribution on the fractionation.
Abstract: 1 Introduction.- 1.1 About the Aims and Methods of Cross Fractionation.- 1.2 Classical Cross-Fractionation.- 1.3 Cross Fractionation Including Size Exclusion Chromatography.- 1.3.1 SEC Analysis of Fractions Obtained by Precipitation or Extraction.- 1.3.2 Preparative Thin-Layer Chromatography and SEC Analysis of the Fractions.- 1.3.3 Preparative SEC and TLC Analysis of the Fractions.- 1.4 Cross Fractionation by Coupled SEC Techniques.- 1.5 Elution Under Critical Conditions.- 1.6 References.- 2 Chemical Heterogeneity of Copolymers.- 2.1 Sequence Distribution.- 2.2 Instantaneous Heterogeneity.- 2.3 Modification of the Stockmayer Distribution.- 2.3.1 Generalization of the Marginal Composition Distribution.- 2.3.2 Generalization of Stockmayer's Distribution for Copolymers from Monomers of Different Molecular Weight.- 2.4 Conversion Heterogeneity.- 2.4.1 Integration of the Mayo-Lewis Equation.- 2.4.2 Distribution of Chemical Composition due to Conversion.- 2.4.3 Concluding Remarks.- 2.5 References.- 3 Size Exclusion Liquid Chromatography of Copolymers.- 3.1 Universal Calibration.- 3.2 Secondary Exclusion and Adsorption Effects.- 3.3 Detector Response.- 3.4 Fractionation by Hydrodynamic Volume.- 3.4.1 Intrinsic Viscosity Varying Linearly with Copolymer Composition.- 3.4.2 Nonlinear Composition Dependence of Intrinsic Viscosity without Extreme Values.- 3.4.3 Nonlinear Composition Dependence with Extreme Values.- 3.4.4 Concluding Remarks.- 3.5 References.- 4 Special Features of Polymer HPLC.- 4.1 Diffusion Coefficients of Macromolecules in Solution.- 4.2 Stokes Radii and Hydrodynamic Dimensions of Macromolecules.- 4.3 Retention by Multiple Attachment.- 4.4 Conformation of Synthetic Polymers.- 4.5 Solubility of Polymers.- 4.6 Gradient Elution of Polymers.- 4.7 Gradient Elution of Polymers on Small Pore Packings.- 4.8 The Martin Equation.- 4.9 Effect of Block Structure on Retention.- 4.10 References.- 5 Solubility and Adsorption Effects in Polymer HPLC.- 5.1 Dependence of Retention Time on Sample Size.- 5.2 Comparison Between Solubility and Elution Characteristics...- 5.2.1 Retention According to Molecular Weight.- 5.2.2 Retention According to Copolymer Composition.- 5.3 Correspondence Between Column Polarity and Gradient Orientation.- 5.4 Effect of Temperature.- 5.5 High-Performance Precipitation Liquid Chromatography.- 5.6 Normal-Phase Gradient Elution with Separate Adjustment of Polarity and Solvent Strength.- 5.7 References.- 6 Effect of Mobile and Stationary Phase in Polymer HPLC.- 6.1 Elution in the Critical Region.- 6.2 The Role of the Stationary Phase.- 6.3 Normal and Reversed Phase HPLC of Polymers.- 6.4 References.- 7 Detection in Gradient High-Performance Liquid Chromatography.- 7.1 Selective Detectors.- 7.1.1 UV/Visible Photometers and Spectrophotometers.- 7.1.2 Infrared Photometers.- 7.1.3 Amperometric Detectors.- 7.1.4 Reaction Detectors.- 7.2 Detection Subsequent to Eluent Vaporization.- 7.2.1 Transport Detectors.- 7.2.2 Evaporative Light-Scattering Detectors.- 7.3 References.- 8 Quantitative Evaluation and Calibration.- 8.1 Features of a Proper Run in Polymer HPLC.- 8.2 Quantitative Evaluation.- 8.3 Incomplete Retention and Elution.- 8.4 Signal Enhancement by Turbidity.- 8.5 Calibration of Polymer Gradient HPLC.- 8.5.1 Influence of Copolymer Composition and Molecular Weight on Elution Time.- 8.5.2 A General Remark.- 8.5.3 Influence of Copolymer Composition on Detector Response...- 8.6 References.- 9 Separation of Copolymers by Composition through Gradient High-Performance Liquid Chromatography.- 9.1 Statistical Copolymers from Styrene and Acrylonitrile.- 9.2 Statistical Copolymers from Styrene and Methyl Acrylate.- 9.3 Copolymers from Styrene and Methyl Methacrylate.- 9.3.1 Statistical Copolymers.- 9.3.2 Block Copolymers.- 9.4 Statistical Copolymers from Styrene and Ethyl Acrylate.- 9.5 Statistical Copolymers from Styrene and Ethyl Methacrylate..- 9.6 Copolymers from Styrene and t-Butyl Methacrylate.- 9.6.1 Statistical Copolymers.- 9.6.2 Block Copolymers.- 9.7 Alkyl Methacrylates and Acrylates with Different Side Groups.- 9.8 Copolymers from Methyl Methacrylate and Methyl Acrylate..- 9.9 Copolymers from Styrene and 2-Methoxyethyl Methacrylate...- 9.10 Copolymers of Styrene and Butadiene.- 9.11 Copolymers of Decyl Methacrylate and Methyl Methacrylate..- 9.11.1 Statistical Copolymers.- 9.11.2 Block Copolymers.- 9.12 Graft Copolymers of Methyl Methacrylate onto Copoly (Ethylene/Propylene/Diene Monomer) (EPDM).- 9.13 Epoxy Composite Formulations, Phenol-Formaldehyde Prepolymers, Macromonomers, and Telechelic Prepolymers.- 9.14 Ethylene/?-Olefm Copolymers.- 9.15 Copolymers of Styrene and Acrylic Acid.- 9.16 Separation of PMMA Isomers.- 9.17 References.- 10 Chromatographic Cross-Fractionation.- 10.1 Scope of this Chapter.- 10.2 Comparison of Calculated and Measured Curves of Chemical Composition Distribution.- 10.3 Chromatographic Cross-Fractionation of Model Mixtures 151 10.3.1 Model Mixtures of stat-Copoly(Styrene/Acrylonitrile).- 10.3.2 Model Mixtures of stat-Copoly(Styrene/2-Methoxyethyl Methacrylate) Samples.- 10.4 Chromatographic Cross-Fractionation of Real Copolymers...- 10.4.1 Investigation of stat-Copoly(Styrene/Acrylonitrile).- 10.4.1.1 Calibration.- 10.4.1.2 Investigation of a Commercial S/AN Sample.- 10.4.1.3 Reliability.- 10.4.2 Chromatographic Cross-Fractionation of a stat-Copoly(Styrene/Methyl Methacrylate) Sample in two Independent Ways.- 10.4.2.1 Calibration.- 10.4.2.2 CCF of S/MMA through Gradient HPLC Prefractionation and SEC.- 10.4.2.3 CCF by SEC Prefractionation and Subsequent Gradient HPLC.- 10.4.3 Investigation of stat-Copoly(Styrene/2-Methoxyethyl Methacrylate) Samples of Different Degree of Conversion.- 10.4.3.1 Calibration.- 10.4.3.2 Chromatographic Cross-Fractionation of S/MEMA Copolymers J and K.- 10.4.3.3 Reliability of S/MEMA Cross Fractionation.- 10.5 Cross Fractionation by Temperature-Rising Elution Fractionation and SEC Analysis of the Fractions.- 10.6 Chromatographic Cross-Fractionation of Graft Copolymers of Methyl Methacrylate onto Copoly(Ethylene/Propylene/Diene Monomer) (EPDM Rubber).- 10.7 Chromatographic Cross-Fractionation of Styrene/Vinyl Acetate Block Copolymers.- 10.8 References.- 11 Experimental Problems.- 11.1 THF as a Mobile Phase.- 11.2 Sample Solvent.- 11.3 Ghost Peaks.- 11.4 Sample Load and Column Blocking.- 11.5 Hazards Caused by Incompatible Sample Polymers.- 11.6 Column Flushing.- 11.7 Effect of Column Length.- 11.8 Peak Splitting.- 11.9 Column Conditioning by Sample Injection.- 11.10 Guidelines for Selecting Suitable Phase Systems for Copolymer HPLC.- 11.11 References.- 12 Glossary of Terms.- Author Index.
197 citations
Journal Article•
TL;DR: In this paper, a microporous gel of N-isopropylacrylamide was synthesized by increasing the solution temperature above the lower critical solution temperature of the polymer during the copolymerization/crosslinking reaction.
Abstract: A microporous gel of N-isopropylacrylamide was synthesized by increasing the solution temperature above the lower critical solution temperature of the polymer during the copolymerization/crosslinking reaction. In response to changes in temperature this gel expands 120 times faster and contrasts 3000 times faster than comparable homogeneous gels
197 citations
191 citations
Patent•
07 Feb 1991
TL;DR: In this paper, a process for the production of block copolymers of ethylene and an α-olefin such as propylene by using an ionic catalyst system including a metallocene component and a component having a cation capable of donating a proton and a compatible non-coordinating anion is described.
Abstract: A process for the production of block copolymers of ethylene and an α-olefin such as propylene by using an ionic catalyst system including a metallocene component and a component having a cation capable of donating a proton and a compatible non-coordinating anion. Novel block copolymers are produced.
188 citations
TL;DR: In this paper, a transition de phase is attributed to contrainte dans les domaines durs durs, soit d'un desordre des domains durs induit mecaniquement.
Abstract: Etude par dichroisme visible d'elastomeres urethanes contenant dans leurs segments durs des motifs diacetyleniques partiellement (<5%) polymerises. l'etirage des polymeres entraine l'orientation des chaines poly(diacetylene) dans la direction d'etirement ce qui implique l'orientation des domaines durs perpendiculairement a la direction d'etirement. Tous les elastomeres presentent un mecanochronisme attribue soit d'un desordre des domaines durs induit mecaniquement, soit a une transition de phase induite par la contrainte dans les domaines durs
TL;DR: In this article, the authors showed that macroscopic alignment of microstructure in a symmetric styrene-methyl methacrylate diblock copolymer can be induced by application of an electric field while cooling through the order disorder transition.
Abstract: SAXS measurements showed that macroscopic alignment of microstructure in a symmetric styrene-methyl methacrylate diblock copolymer can be induced by application of an electric field while cooling through the order-disorder transition.
Patent•
22 Aug 1991
TL;DR: A conjugated copolymer comprises at least two chemically different monomer units which, when existing in their individual homopolymer forms, have different semiconductor bandgaps as discussed by the authors.
Abstract: A semiconductive conjugated copolymer comprises at least two chemically different monomer units which, when existing in their individual homopolymer forms, have different semiconductor bandgaps. The proportion of said at least two chemically different monomer units in the copolymer is selected to control the semiconductor bandgap of the copolymer so as to control the optical properties of the copolymer. The copolymer is formed in a manner enabling it to be laid down as a film without substantially affecting the luminescent characteristics of the copolymer and is stable at operational temperature. The semiconductor bandgap may be spatially modulated so as to increase the quantum efficiency of the copolymer when excited to luminescence, to select the wavelength of radiation emitted during luminescence or to select the refractive index of the copolymer.
Patent•
09 Oct 1991
TL;DR: In this article, the authors proposed a method for treating patients with visual impairment using preformed silicone-containing acrylic copolymers and contact lenses made from acrylic star polymers, graft copolymer and macromonomers.
Abstract: The present invention relates to novel copolymers and contact lenses made from these copolymers comprising preformed silicone-containing acrylic star polymers, graft copolymers and macromonomers, preparation of these contact lenses and a therapeutic method for treating patients with visual impairment. Described is a composition comprising at least about 10% by weight of a preformed silicone-containing acrylic copolymer and no more than about 90% by weight of a matrix formed from the random polymerization of a mixture of monomers. The mixture of monomers comprises at least one hydrophilic monomer and optionally, monomers selected from the group consisting of silicone acrylates, esters of alpha, beta-unsaturated acids and crosslinking monomers. The preformed silicone-containing acrylic copolymer is preferably copolymerized throughout the matrix. The final compositions are hydrated to a final water content of at least about 10% by weight.
TL;DR: The adsorption kinetics of polystyrene (PS)-poly(ethylene oxide) (PEO) diblock copolymer were measured in situ by ellipsometry as mentioned in this paper.
Abstract: The adsorption kinetics and adsorption isotherm of a polystyrene (PS)-poly(ethylene oxide) (PEO) diblock copolymer onto a silicon wafer from toluene solution was measured in situ by ellipsometry. PS-PEO behaves like an end-adsorbed chain. The adsorption kinetics shows two processes on a clearly separated time scale. The repulsion between the nonadsorbing PS blocks determines the maximal adsorbed amount. The adsorbed monolayer can be rapidly and completely displaced by PEO oligomer with a length comparable to the PEO block in the block copolymer
TL;DR: The morphology of a system consisting of a bisphenol A digrycidylether (DGEBA) based epoxy, cured with a cycloaliphatic diamine (4,4'-diamino-3,3'-dimethyldicyclohexylmethane, 3DCM), in the presence of an epoxy-terminated butadiene-acrylonitrile random copolymer (ETBN), was studied as a function of the cure schedule and the initial rubber concentration.
Abstract: The morphology of a system consisting of a bisphenol A digrycidylether (DGEBA) based epoxy, cured with a cycloaliphatic diamine (4,4'-diamino-3,3'-dimethyldicyclohexylmethane, 3DCM), in the presence of an epoxy-terminated butadiene-acrylonitrile random copolymer (ETBN), was studied as a function of the cure schedule and the initial rubber concentration
Patent•
05 Jun 1991TL;DR: An improvement in the process for the continuous copolymerization of ethylene with certain polar comonomers having reactive double bonds was proposed in this paper, where a single phase is maintained in the reactor by means of methanol introduced concurrently with the reactants, whereby reactor fouling is significantly reduced or eliminated.
Abstract: An improvement in the process for the continuous copolymerization of ethylene with certain polar comonomers having reactive double bonds, wherein a single phase is maintained in the reactor by means of methanol introduced concurrently with the reactants, whereby reactor fouling is significantly reduced or eliminated.
TL;DR: In this article, the effect of a small addition of poly(styrene-b-2-vinylpyridine) block copolymer on the microstructure and mechanical properties of phase-separated blends of polystyrene (PS) and poly(2vinyl pyridine), was investigated.
Abstract: The effect of a small addition of poly(styrene-b-2-vinylpyridine) block copolymer on the microstructure and mechanical properties of phase-separated blends of polystyrene (PS) and poly(2-vinylpyridine) (PVP) was investigated. Only copolymers whose PVP block degree of polymerization was above 200 were found to be effective in preventing failure at the interface. This critical value corresponds roughly to the molecular weight between entanglements M e , suggesting therefore that at least one average «entanglement» between the PVP bhlock and the PVP homopolymer is necessary to have good stress transfer at the interface
TL;DR: In this article, a comprehensive 13C-NMR method for the analysis of composition in the most common commercial polyethylene copolymers has been established, which covers ethene copolymer with propene, butene, hexene-1, octene, and 4-methyl pentene, in the composition range of 1-10 mol %.
Abstract: A comprehensive 13C-NMR method for the analysis of composition in the most common commercial polyethylene copolymers has been established. The method covers ethene copolymers with propene, butene-1, hexene-1, octene-1, and 4-methyl pentene-1 in the composition range of 1–10 mol %. The chemical shift assignments and T1 values of the resonances of the copolymers are presented. Results of precision studies and interlaboratory analyses showed that the molar composition could be determined with a relative precision at 2δ of about 6%. This method is being proposed to ASTM as Method X70-8605-2.
TL;DR: In this paper, high molecular weight copolymers of L-lactide and e-caprolactone have been synthesized by ring opening copolymerization with stannous octoate as catalyst.
Abstract: High molecular weight copolymers of L-lactide and e-caprolactone have been synthesized by ring opening copolymerization with stannous octoate as catalyst. The good mechanical properties of the 50/50 copolymers make it a suitable material for biomedical applications such as nerve guides etc., where degradation of the elastomeric implant is required. In contrast to the frequently used MDI containing polyurethanes, degradation products of the P(LLA-e-CL) are non toxic. The use of such a material is therefore preferable.
Patent•
17 Sep 1991TL;DR: In this paper, a process for producing a vinyl acetate-ethylene copolymer emulsion is described, which consists of an emulsifying dispersant in an amount of from 2.5 to 3.0 parts by weight of polyoxyethylene nonionic surface active agent having an average polymerization degree of from 300 to 1,000.
Abstract: A vinyl acetate-ethylene copolymer emulsion is disclosed, comprising a vinyl acetate-ethylene copolymer composed of from 10 to 40% by weight of an ethylene unit and from 90 to 60% by weight of a vinyl acetate unit and an emulsifying dispersant in an amount of from 2.5 parts by weight or more but less than 5.0 parts by weight per 100 parts by weight of the vinyl acetate unit, and having a mean particle size of not larger than 0.9 μm and a solids content of from 65 to 75% by weight, wherein the emulsifying dispersant contains from 1.0 to 1.9 parts by weight of partially saponified polyvinyl alcohol prepared so as to have an average polymerization degree of from 300 to 1,000 and from 1.0 to 3.0 parts by weight of a polyoxyethylene nonionic surface active agent having an HLB of from 16.5 to 17.5 per 100 parts by weight of the vinyl acetate unit. A process for producing the vinyl acetate-ethylene copolymer is also disclosed.
TL;DR: In this paper, it was shown that the average monomer sequence length has a large effect on the thermal and mechanical properties of these copolymers, and that copolymer with different average sequence lengths and molecular weights can be synthesized by varying the polymerization temperature.
Abstract: The large difference in reactivity of L-lactide and e-caprolactone in ring opening polymerization with stannous octoate, leads to the formation of copolymers with blocky structures. By varying the polymerization temperature, copolymers with different average sequence lengths and molecular weights can be synthesized. It is shown that the average monomer sequence length has a large effect on the thermal and mechanical properties of these copolymers.
TL;DR: In this article, the relation between stoechiometry and droplet size is described by a simple geometrical model which can be generalized to other nonpolar monomers such as methyl methacrylate (MMA) and even copolymerization with MMA.
Abstract: Polystyrene latices with 10nm < R < 60 nm were prepared via microemulsion polymerization. The size of the particles was controlled only by the ratio of styrene to surfactant. Within a certain range, the relation between stoechiometry and droplet size is described by a simple geometrical model which can be generalized to other nonpolar monomers. By contrast, the microemulsion polymerization of polar monomers such as methyl methacrylate(MMA) and even copolymerization with MMA become more complex and the simple model fails.
TL;DR: In this paper, the equilibrium blend morphologies were studied by transmission electron microscopy and small angle x-ray scattering, and the type of ordered morphology observed in each blend was generally dictated by the overall polystyrene volume fraction in the blend, i.e., the homopolymer concentration.
Abstract: Binary blends of a lamellar poly(styrene‐b‐isoprene) diblock copolymer and homopolystyrenes of various molecular weights self‐assembled into highly ordered morphologies upon solvent evaporation. The equilibrium blend morphologies were studied by transmission electron microscopy and small angle x‐ray scattering. The type of ordered morphology (lamellae, the ordered bicontinuous double diamond morphology, cylinders on a hexagonal lattice, and spheres on a cubic lattice) observed in each blend was generally dictated by the overall polystyrene volume fraction in the blend, i.e., the homopolymer concentration. The blend morphology also depended on the homopolymer molecular weight at a single fixed composition. The intermaterial dividing surface between the polystyrene and the polyisoprene microdomains was characterized by the interfacial mean curvature (H) and the average area per copolymer junction (σj). H and σj increased as the homopolymer concentration increased and/or as the homopolymer molecular weight d...
TL;DR: The ability of the triblock copolymer micelles in water/1,4-dioxane mixtures to solubilize and release hydrophobic species was studied in this article.
Abstract: The ability of the triblock copolymer micelles in water/1,4-dioxane mixtures to solubilize and release hydrophobic species was studied.
TL;DR: In this article, the authors studied diffusion and sorption of n-alkanes through commercial polymer membranes such as neoprene, styrene butadiene rubber, ethylene propylene diene terpolymer, Nitrile Butadiene Rubber, and natural rubber.
Abstract: Diffusion and sorption of n-alkanes (C6–C10) through commercial polymer membranes such as neoprene, styrene butadiene rubber, ethylene propylene diene terpolymer, nitrile butadiene rubber, and natural rubber have been studied from 25 to 60°C. The diffusion results have been explained in terms of the size of liquid molecules and the diffusion mechanism was found to follow the Fickian trend. Nitrile butadiene rubber and neoprene showed much smaller values of diffusivities and sorption constants than the other polymer membranes. Arrhenius parameters for the activated diffusion process and the thermodynamic quantities for the process of equilibrium sorption have been estimated.
TL;DR: In this article, the amount of copolymers of various molecular weight and composition adsorbed on oxidized silicon and mica is measured. And a dimensionless surface density σ* is found to be a unique function of a copolymer block size asymmetry radio.
Abstract: The amounts of copolymers of various molecular weight and composition adsorbed on oxidized silicon and mica are measured. A dimensionless surface density σ* is found to be a unique function of a copolymer block size asymmetry radio. Within this correlation, two regimes of behavior are found. For copolymers of moderate asymmetry, the surface density σ is influenced more strongly by the molecular weight of the adsorbing PVP block. These results agree well with a model by Marques et al. For copolymers with large PS blocks (high asymmetry), the surface density is determined primarily by the molecular weight of the PS block
TL;DR: It is concluded that piezoelectrically active vinylidenefluoride-trifluoroethylene copolymer tubes significantly enhance nerve regeneration as compared to chemically identical, unpoled tubes and that the polarity of the corona poling procedure used to fabricate piezOElectric materials may play a role in determining biological responses.
TL;DR: In this article, the UV spectra suggest charge transfer complex formation between the polymeric and monomeric donors with electron-acceptor tetracyanoethylene (TCNE) and the equilibrium constants were estimated to be in the sequence of ethylbenzene > PSt > copolymer of St with methylmethacrylate.
Abstract: Polystyrene (PSt) exhibits a new UV absorption band at around 290nm in comparison with ethylbenzene, which is attributed to associative interaction between pendant phenyl groups. Similar absorption bands are also observed for polymers of styrene derivatives. The UV spectra suggest charge-transfer complex formation between the polymeric and monomeric donors with electron-acceptor tetracyanoethylene (TCNE) and the equilibrium constants were estimated to be in the sequence of ethylbenzene > PSt > copolymer of St with methylmethacrylate.
Patent•
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TL;DR: In this paper, films or sheets comprising an olefin polymer composition which is comprised of (a) from about 10 to 50 parts of a propylene homopolymer having an isotactic index greater than 80, or (b) a copolymer of propylene with ethylene and/or an another alpha-olefin, containing over 80% propylene and having anisotropic index higher than 80.
Abstract: Disclosed are films or sheets comprising an olefin polymer composition which is comprised of (a) from about 10 to 50 parts of a propylene homopolymer having an isotactic index greater than 80, or a copolymer of propylene with ethylene and/or an another alpha-olefin, containing over 80% propylene and having an isotactic index greater than 80; (b) from about 5 to 20 parts of a semi-crystalline copolymer fraction, which copolymer is insoluble in xylene at room or ambient temperature; and (c) from about 40 to 80 parts of a copolymer fraction of ethylene with propylene and/or another alpha-olefin, and optionally with minor amounts of a diene, said copolymer fraction containing less than 40% ethylene and/or other alpha-olefin, being soluble in xylene at room temperature, and having an intrinsic viscosity from 1.5 to 4 dl/g. Coextruded films or sheets and laminates wherein at least one layer is a film or sheet as described above, and films or sheets of blends of the olefin polymer composition and another olefin polymer are also disclosed.