The effect of imidization on gas-separation properties of membranes based on poly(4,4'-oxydiphenylene)pyromellitimide

Transport properties of composite membranes with a selective skin layer of poly(4,4'-oxydiphenylene)pyromellitimide were studied, The skin layer was prepared from the corresponding polyamic acid an a support made of poly(2,6-dimethyl-1,4-phenylene oxide). To convert the polyamic acid to polyimide, two low-temperature solid-phase imidization procedures were applied: chemical imidization using pyridine and acetic anhydride and catalytic imidization in he presence of benzimidazole. Composite membranes prepared by catalytic imidization showed higher gas permeation for Ile, N-2, O-2, and CO2 and retained high selectivity. This pattern is the result of a more uniform supermolecular organization of the polymer because of the complex formation between the polyamic acid and benzimidazole.