Novel Copolymers with an Improved Combination of High Permeability and High Selectivity for Use in Making Membranes for Gas and Vapor Separations

本研究致力于合成具有高渗透性和高选择性的新型气体分离用聚合物膜。PI集中在取代聚乙炔膜上，并指出这类化合物PtMSP(聚(三甲基硅丙炔)：ı(C(CH3)=C(Si(CH3)3)n！)在所有已知的聚合物中对大多数气体具有最高的渗透性。然而，它的选择性很差，例如它的O2/N2选择性只有1.8。高渗透性是由于骨架僵硬，以及附着的三甲基硅基非常大的事实。这两个因素都限制了聚合物链的有效堆积，导致了较大的自由体积，这是渗透性的原因。为了提高选择性，PI打算以牺牲一定的渗透率为代价，减小自由体积大小以增加选择性。为了减少游离量，本研究将遵循两个策略；(A)第一种是开发热退火程序，使膜中的链条在更放松的状态下，促进更好的包装和更低的自由体积。(B)第二种策略是将高渗透性、低选择性的聚合物与具有高选择性的芳基取代聚乙炔共聚。我们的想法是，芳基应该促进聚合物链的凝聚力，热退火后的共聚物可以在渗透率和选择性之间达到所需的平衡。

This study is concerned with synthesizing, for gas separations, new polymeric membranes which will have both high permeability and selectivity. The PI focuses on substituted polyacetylene membranes, and notes that of this class PTMSP (poly(trimethylhysilylpropyne): ı(C(CH3) = C(Si(CH3)3)n!) has the highest permeability to most gases of any known polymer. However, its selectivity is very poor; for example its O2/N2 selectivity is only 1.8. The high permeability is due to the stiff backbone, and to the fact that the attached trimethysilyl group is very bulky. Both factors limit efficient packing of the polymer chains, resulting in a large free volume which accounts for the permeability. To improve the selectivity, the PI intends to reduce the free volume size to increase the selectivity at the expense of some permeability. To decrease the free volume, this study will follow two strategies; (a) The first is to develop thermal annealing procedures which result in membranes in which the chains are in a more relaxed state that promotes better packing and a lower free volume. (b) The second strategy is to copolymerize high permeability low selectivity polymers with aryl substituted polyacetylenes that have high selectivity. The idea is that the aryl groups should promote polymer chain cohesion, and that thermally annealed copolymers can be developed with the desired balance of values of permeability and selectivity.