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ABSTRACT Random and block sulfonated poly( meta-phenylene isopthalamide)s as proton exchange membranes were synthesized through the Higashi-Yamazaki phosphorylation method. Polymers with different degrees of sulfonation from 40 to 100 mol percent were prepared by adjusting the molar feed ratio of 5-sulfoisophthalic acid sodium salt (SIPA) and isophthalic acid (IPA) in the reaction with meta-phenylene diamine. Creasable polymer films were obtained by casting DMSO polymer solutions and the membrane films could be exchanged to the proton form in strong acid. 1H NMR spectroscopy and titration confirmed the degree of sulfonation. Thermogravimetric analysis demonstrated good thermal stabilities with 5% weight loss greater than 380 °C. The copolymers with low degrees of sulfonation (DS = 40 mol %) exhibited low water uptake (water uptake < 17 wt %) at room temperature. A segmented multiblock copolymer prepared by preforming a sulfonated block showed lower water uptake at high temperatures than the random polymer with the same DS of 40 mol % and displayed stability in water up to 80 °C. Both random and block copolymers showed higher proton conductivities at high temperature than that of Nafion-117 under 95% relative humidity. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2582-2592 [ABSTRACT FROM AUTHOR]

Polylactides (PLAs) have been known for several decades but have only recently gained commercial significance as a leading environmentally benign plastic available from renewable resources. Accordingly, it is highly desirable to understand the optical properties of these materials. Optical properties are important in dyeing operations for textile applications and in various packaging applications where coloring or clarity is desirable, however, a description of optical properties is not available in the literature. In this study, ellipsometric measurements were made on a well-characterized set of homopolymers and copolymers spanning a wide range of stereoisomer proportions ( L-content). Data were collected and analyzed within the framework of the well-known Cauchy model for the index of refraction. No statistical difference is found for the Cauchy parameters for the various optical compositions. The data for all samples can be accurately described using values of Cauchy coefficients of A=1.445±7.529×10−4 and B=4.8916×103±1.426 × 102 nm. It was found that over the light wavelengths from 300 to 1300 nm, the index of refraction for PLA decreased from 1.499 to 1.448. The uncertainty in the index of refraction calculated from the Cauchy coefficients increases with increasing wavelength, and ranges from 1.1% at 300 nm to 0.1% at 1300 nm. The final useful result of the study is that the index of refraction of PLA within the range of wavelengths from 300 nm to 1300 nm may be described by n(λ)=(1.445±0.00075)+(4892±143) nm2/λ 2. [ABSTRACT FROM AUTHOR]

Using a unique one-pot convergent anionic polymerization strategy, 18 (polystyrene)star-b-(polyisoprene)linear-b-(polystyrene)star (SnISn) pom-pom triblock copolymers were synthesized varying a range of architectural parameters including PS arm molecular weight (Mn,star), the number of arms contained in the star (n), and the PI midblock molecular weight (Mn,PI). A selected series of five of these 18, in which Mn,star was held approximately constant between 14.3 and 16.5 kDa, but with the numbers of arms in the star and PI midblock molecular weight varied, were selected for detailed characterization using rheology, AFM, and SAXS. The five selected all shared PS as the minority component, with star volume fractions (fPS) varying between 0.11 and 0.22. All samples showed clear phase separation, with three of the five adopting a highly ordered hexagonal packing of cylinders (HPC) confirmed through SAXS and AFM. The remaining two systems were limited to liquid-like packing of cylindrical domains (LLP). Longer midblock molecular weights and increased numbers of arms in the star both showed a propensity to hinder formation of a highly ordered hexagonal lattice. Increasing the number of arms in the star also favored transitions to a disordered phase at lower temperatures when overall SnISn molecular weight was held constant. The behavioral trends identified suggest interfacial packing frustration plays a prominent role in determining the ability of the system to develop highly ordered periodic structures. The chain crowding produced by the PS star architecture intrinsically favors interfacial curvature toward the majority PI component, contrary to that intrinsically favored by the block composition alone. In the two systems in which the frustration was architecturally most severe (largest n of 7.1, highest Mn,PI of 191 kDa), evolution of a hexagonal lattice could not be induced, even after significant thermal annealing. The pom-pom architecture itself also appears to have a significant impact on entanglement relaxation dynamics, with development of HPC morphologies only possible at elevated temperatures. [ABSTRACT FROM AUTHOR]