Aromatic polyimides derived from 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 3,3′‐ or 4,4′‐diaminodiphenylsulfone (m‐DDS or p‐DDS) have been synthesized with a chemical imidization. The disappearance of amic acid groups and the appearance of imide groups are determined by IR and 1H‐NMR spectroscopies. The obtained polyimides are amorphous and soluble in organic solvents. The gas transport properties of the polyimide membranes to CO2, O2, N2, and CH4 have been determined at 35°C and at a pressure up to 10 atm. The (PCO2/PCH4) and (PO2/PN2) selectivities of the membranes are augmented due to their large gas diffusivity selectivities. This is considered to be due primarily to the high packing density of polymer chain.
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Kawakami et al. (1995) studied this question.
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