Sorption and transport of carbon dioxide in a polyimide from 3,3′4,4′‐biphenyltetracarboxylic dianhydride and 4,4′‐diaminodiphenyl sulfone

CO2 sorption and transport were investigated for the polyimide prepared from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐diaminodiphenyl sulfone (DDS). The morphology of films did not change on annealing above the glass transition temperature and remained amorphous unlike the polyimide prepared from BPDA and 4,4′‐oxydianilline (ODA). This seems to be due to the strong hindrance to rotation of the sulfonyl linkage. Sorption and transport data were analyzed according to the dual‐mode model. Solubility, diffusion, and permeability coefficients at 20 atm and 80°C for BPDA‐DDS polyimide were substantially equal between as‐cast and annealed films and were 1.7, 2.2, and 3.7 times greater, respectively, than for the as‐cast films of the BPDA‐ODA polyimide. The higher solubility was due to larger values of the Henry's law solubility constant kD, Langmuir capacity constant C , and the Langmuir affinity constant b. The sorption and transport properties were compared with those for amorphous glassy aromatic polymers including other polyimides. The relation of k, C , b, and the diffusion coefficients in the Henry's law population and the Langmuir population (DD and DH) with other properties of the polymers were discussed. Values DD and DH for BPDA‐DDS polyimide were much larger than expected from the estimated free‐volume fraction.