The effect of morphology on sorption and transport of carbon dioxide in poly(4,4'‐oxydiphenylene pyromellitimide)

Abstract

AbstractSorption and transport of carbon dioxide were investigated for poly(4,4'‐oxydiphenylene‐pyromellitimide) films (PI‐1, PI‐2, and PI‐3) imidized at 160, 200, and 400°C, respectively, as well as for a chemically identical commercial polyimide film, Kapton‐H. The solubility, permeability, and diffusion coefficients (S, P, and \[ \overline D \] , respectively) at 80°C and 20 atm in PI‐3 were 67, 25, and 37%, respectively, as large as those in PI‐2. These significant reductions are attributed to a higher degree of segmental aggregation in PI‐3 caused by a 1.7% increase in the density (d) as compared with PI‐2. The differences in S, P, \[ \overline D \] , and d between PI‐3 and Kapton‐H were rather small as compared with those between PI‐3 and PI‐2, suggesting that the in‐plane orientation has a minor effect on the sorption and transport in Kapton‐H as compared with the aggregation. Influence of the morphology on the dual‐mode sorption and transport parameters was also investigated. With increasing density, the Langmuir capacity constant and the diffusion coefficients for the Henry's law and Langmuir populations decreased by higher rates than the Henry's law solubility constant, being contrary to the results reported for a typical semicrystalline glassy polymer, polyethylene terephthalate. This may suggest that the nonaggregated or less‐aggregated regions taking an important part in the sorption and transport are denser for the sample having a higher overall density.