Gas separation properties of 6FDA-based polyimide membranes with a polar group

6FDA-based polyimides were prepared from the thermal imidization reaction of 6FDA with diamines of BAPAF, DAP, and DABA having a polar group of hydroxyl or carboxyl. Properties of the dense polyimide membranes were characterized and their gas permeation properties for H-2, CO2, O-2, N-2, and CH4 were investigated. Permeabilities, diffusion coefficients and diffusivity selectivities of polar group-containing polyimide membranes including 6FDA-BAPAF, 6FDA-DAP, and 6FDA-DABA polymer for the gases did not change largely. The separation properties of 6FDA-TrMPD polyimide membrane used as a reference polymer were compared with those of the polyimide membranes mentioned above. It was found that the polyimides of 6FDA-BAPAF, 6FDA-DAP, and 6FDA-DABA, which were soluble in alcohol or/and 2-methoxyethanol, could be applicable to the preparation of a dense composite membrane by dip-coating method.