GAS-PERMEABILITY AND PERMSELECTIVITY IN HOMOLYIMIDES AND COPOLYIMIDES FROM 3,3',4,4'-BIPHENYLTETRACARBOXYLIC DIANHYDRIDE AND 3,3'-DIAMINODIPHENYLSULFONES AND 4,4'-DIAMINODIPHENYLSULFONES

The gas transport properties of homo- and copolyimides prepared from 3, 3′, 4, 4′-biphenyltetracarboxylic dianhydride (BPDA) and 3, 3′- and 4, 4′-diaminodiphenylsulfones (m-DDS and p-DDS, respectively) are investigated. With increasing fraction of m-DDS, the density of the polyimide films increased by 1.1% and the glass transition temperature decreased by 70 K. With increasing fraction of m-DDS, permeability coefficients P of H2 and CO2 in the film decreased to 1/3 and 1/15, while P ratios of H2 to CO and CO2 to CH4 increased by 4.1 and 1.8 times, respectively, as a result of decrease in the diffusion coefficient and increase in diffusivity selectivity. These observations are interpreted in terms of changes in free volume fraction, distribution of size of free volume, and segmental mobility. © 1990 The Society of Polymer Science, Japan.