Gas Permeability and Characterization of Novel Thermally Rearranged Polymers Based On 3,3'-Diamino-4,4'-Dihydroxy Biphenyl (AHB) and 2,2'-Bis-(3,4-decarboxyphenyl) Hexafluoropropane Dianhydride (6FDA)

摘要

Thermally rearranged (TR) polymers, which are typically polybenzoxales with a rigid-rod structure, have recently gained interest in gas separation application due to their excellent gas transport and separation performance, particularly for CO2/CH4 mixtures. Another attractive feature is their apparent strong resistance to plasticization. In this study, the permeabilities of H2, N2, O2, CH4, and CO2 were measured over pressure ranging from 3 atm to 17 atm at 35°C for aromatic polyimides based on 3,3'-diamino-4,4'-dihydroxy biphenyl and 2,2'-bis-(3,4-decarboxyphenyl) hexafluoropropane dianhydride (AHB-6FDA). Thermally rearranged (TR) polybenzoxazoles (PBO) were obtained by thermally treating the polyimides between 350 and 450°C. Upon 79% TR conversion, AHB-6FDA bearing acetate ortho-functional groups showed high CO2 permeability (369 Barrer) and a pure gas CO2/CH4 selectivity of 25, which surpassed the upper bound. Free volume also increased with extent of TR conversion.