2,2-Bis[4-(3,4-Dicarboxyphenoxy) Phenyl] Propane Dianhydride (BPADA)-Based Polyimide Membranes for Pervaporation Dehydration of Isopropanol : Characterization and Comparison with 4,4/-(Hexafluoroisopropylidene) Diphthalic Anhydride (6FDA)-Based Polyimide Membranes

摘要

Polyimides were synthesized from one-step polycondensation of BPADA and various diamines and were characterized with GPC, FTIR, NMR, DSC, and TGA. Polyimide membranes were prepared, and their hydrophilicity was estimated by contact angles and the free energies of interfacial interactions. Pervaporation properties were investigated for the dehydration of isopropanol, and comparisons were made between BPADA-based membranes and 6FDA-based membranes. The concentration coefficients of BPADA-based membranes were calculated from the linear moiety contribution method based on the results from 6FDA-based membranes, and they were compared to understand the effects of the feed concentration on pervaporation properties. The effects of temperature on permeation flux were Studied with permeation activation energies for total AM and water flux in permeates. Moiety contribution factors for activation energies were used to correlate permeation flux and monomer moieties in the polymers, and reasonable results were obtained for BPADA. It is revealed that steric effects of monomers may change the diffusion properties, while functional groups are favorable to the changes in sorption properties. (C) 2008 Wiley Periodicals, Inc.