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, O-2, N-2, 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 Xe-129 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. (c) 2005 Wiley Periodicals, Inc.