Molecular motion PTMSP

Molecular Motion of PTMSP/PTBA Blends Before and After Aging. The... 

Figures 14 and 15 show the relationship between PTB A content and carbon spin-lattice relaxation time (Ti) of the PTMSP side-chain and backbone carbon atoms, respectively. The effect of PTBA content on Ch is also shown in these figures. Ti of the methyl group carbon atoms (a) in the side-chain of PTMSP became longer with increases in PTBA content. This result indicates that the molecular motion of the trimethylsilyl groups became slower. On the other hand, Ti values for the carbon atoms of the other methyl group (b) and the backbone chain show a maximum at 20 vol % PTBA, which suggests perfect mixing of PTMSP and PTBA. These results coincide with the maximum stability of the gas permeability coefficient (c/. Figure 10).

The catalyst used for polymerization influences several properties such as the solubility of PTMSP in various solvents (7). Even though the cis-trans content of PTMSP has not been quantitatively determined, Costa et al (5) and Izumikawa et al. (6) reported that the polymerization catalyst NbClj produced a more regular chain confi ation than TaClj. In addition, PTMSP synthesized using NbClj had a cis-rich structure relative to that prepared with TaClj. In this study, Sie effects of physical aging on gas permeability and molecular motion of PTMSP membranes synthesized using various catalysts are reported. 

Molecular Motion. Spin-lattice relaxation times, T, determined using solid-state NMR provide a practical method to characterize molecular motion of polymers in the solid state. In diis regard. Figure 4 presents Si T, values for as-cast and aged PTMSP membranes. Based on the results in this table, the spin lattice relaxation time is not sensitive to aging for PTMSP synthesized with the thrw catalysts considered in this study. 

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