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Characterization of 6FDA-based hyperbranched and linear polyimide–silica hybrid membranes by gas permeation and 129Xe NMR measurements

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Abstract

Physical and gas transport properties of novel hyperbranched polyimide–silica hybrid membranes were investigated and compared with those of linear-type polyimide–silica hybrid membranes with similar chemical structures. Hyperbranched polyamic acid, as a precursor, was prepared by polycondensation of a triamine, 1,3,5-tris(4-aminophenoxy)benzene (TAPOB), and a dianhydride, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). 6FDA-TAPOB hyperbranched polyimide–silica hybrids were prepared using the polyamic acid, water, and tetramethoxysilane (TMOS) by sol–gel reaction. 5% weight-loss temperature of the 6FDA-TAPOB hyperbranched polyimide–silica hybrids determined by TG-DTA measurement considerably increased with increasing silica content, indicating effective crosslinking at polymer–silica interface. CO2, O2, N2, and CH4 permeability coefficients of the 6FDA-based polyimide–silica hybrids increased with increasing silica content. In addition, CO2/CH4 selectivity of the 6FDA-TAPOB–silica hybrids remarkably increased with increasing silica content. From 129Xe NMR analysis, characteristic distribution and interconnectivity of cavities created around polymer–silica interface were suggested in the 6FDA-TAPOB–silica hybrids. It was indicated that size-selective separation ability is effectively brought by the incorporation of silica for the 6FDA-TAPOB hyperbranched polyimide–silica hybrid membranes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 291–298, 2006

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