ABSTRACT:Thermal behaviors of syndiotactic polystyrene (SPS) gels in SPS-xylene isomer system were investigated to get information on the isomer effect of xylene on ability of complex formation with SPS. The melting temperature of the crystalline complex of p-xylene with SPS in SPS--p-xylene system was higher than that in SPS m-xylene system. The weight of the gel sample in each thermogravimetric curve decreased by two step in both systems. This might suggest that there were two spaces in which xylene molecules could be located. The weight of p-xylene in the second step decreased more largely and at higher temperature than that of m-xylenc. We could conclude that p-xylene exhibited higher ability of complex formation with SPS than m-xylene from thermal analyses. Infrared results on the process of gelation showed that the content of TTGG conformation was larger and the completion of gelation was faster in SPS p-xylene system. The difference of sorption behaviors at 25-C of the annealed atactic polystyrene film were not observed between xylene isomers, but the p-and m-xylene sorption isotherms of the annealed SPS film showed sigmoid-type isotherms and were diiTerent between xylene isomers. Sorption amount of p-xylene was larger than that of 111-xylene at low activity, but smaller at high activity, which resulted in the preferential sorption of p-xylene into a meso phase at low activity and the decrease of an amorphous part by complex formation of p-xylene with SPS at high activity.
ABSTRACT:C02 permeation and diffusion behaviors ofpoly(4-methyl pentene-1) (PMP) with three different degrees of crystallinity were examined at -I 0 to 45°C. Permeation and diffusion coefficients in crystalline and amorphous parts of PMP were obtained by an extrapolation to 100 and 0% degrees of crystallinity, respectively. The inflection corresponding to the glass transition temperature of PMP was observed in Arrhenius plot of both the permeability and diffusion coefficients only for the amorphous part of PMP. The non zero values of permeation and diffusion coefficients of crystalline part of PMP indicated that the permeation and diffusion of C02 occurred even in the crystalline part of PMP. The permeation and diffusion of C02 for the crystalline part of PMP were Arrhenius type within experimental scatter.KEY WORDS Poly(4-methyl pentene-1) I Gas Permeation / Gas Diffusion I Degree of Crystallinity IThe sorption, diffusion, and permeation of small molecules such as gas and vapor do not occur in and through a crystalline part of the crystalline polymers, in contrast to the amorphous part and amorphous polymers. 1.2 Therefore, the sorption, diffusion, and permeation of crystalline polymers are, in general, corrected by the degree of crystallinity using their quantities of purely amorphous phase. 3 -5 We recently reported that change of C02 sorption for the polystyrenejpolycarbonate blend membranes prepared by casting can be mainly explained from the amount of crystallite of the polycarbonate component, assuming that the crystallite cannot sorb C0 2 • 6 Poly(4-methyl pentene-1) (PMP; Scheme 1) is used in chemical experiments, medical appliances, electronic microwave tableware, heat stable wire, etc. with good light, transparent, heat stable, and solvent resistant properties. It has higher density for an amorphous part and lower density for a crystalline part. 7 -9 This indicates a negative volume change of melting at melting point. This polymer is also known to demonstrate characteristic thermodynamic properties of the pressure dependence of the melting temperature. 10 These facts suggest that a crystalline part of PMP is in a coarse packing of the PMP regular chain molecule compared with a random coiled amorphous part. Kusanagi et at. reported the crystal lattice structure of PMP, and concluded that the low density is due to the loose packing of the crystal. 11 There is coarse packing between PMP chains, i.e., the molecular cavity or micro void of approximately 4A exists between the chain segments in this model. This is a probable merit for the gas separation membranes with both high permeability and high selectivity which are expected from the crystalline part of PMP.Paul et a!. confirmed gas sorption and transport of a crystalline part of PMP. 12 They used the PMP with crystallinity levels ranging from 20 to 75%, including the crosslinking PMP to obtain low crystallinity, and reported that the solubilities for C0 2 and CH 4 in the t To whom all correspondence should be addressed. crystalline part of PMP ar...
Interface properties of nano-silica/thermotropic liquid crystalline polyesters (TLCP) composites were investigated by X-ray diffraction analysis and differential scanning calorimetory. The crystallinity of TLCP in the composites drastically decreased with an increase of nano-silica content, depending on the surface area of the silica particles. Little size effects (40-400 nm) in the particles and strong interaction between silica surface and the C=O moieties of TLCP were observed by IR analysis. The glass transition temperature of TLCP (<20 nm) in silica surface increased about 20˚C higher than that in bulk.
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