PTMSP aging studies

It has been reported recently that flux and even selectivity of PMP and PTMSP can be enhanced by the addition of nanoparticles (285, 286]. Merkel et al. [285] added fumed sihca to PMP and observed a simultaneous increase of butane flux and butane/methane selectivity. This unusual behavior was explained by fumed-silica-induced disruption of polymer chain packing and an accompanying increase in the size of free volume elements through which molecular transport occurs. Gomes et al. [286] incorporated nanosized sihca particles by a sol-gel technique into PTMSP and found also for this polymer a simultaneous increase in flux and selectivity. It has to be studied, if physical aging of the polyacetylenes is reduced by the addition of nanoparticles. 

One of the authors reported decreases in J-spacing (13) and Ch (12) of PTMSP membranes upon aging. Upon aging, based on density measurements, wide-angle X-ray diffraction, and positron annihilation lifetime spectroscopy studies, YampoFskii and co-workers also inferred a decrease in the free volume of PTMSP(75). 

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. 

In general, the permeability can be represented as the product of gas solubihty and gas diffiisivity. In previous studies of light gases (4,11), the reduction in gas permeability of PTMSP upon aging depended on gas ffusivity more than gas... 

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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