Physical and gas transport properties of hyperbranched polyimide-silica hybrid membranes were investigated. 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), and subsequently modified a part of end groups by 3-aminopropyltrimethoxysilane (APTrMOS). The hyperbranched polyimide-silica hybrid membranes were prepared by sol-gel reaction using the polyamic acid, water, and alkoxysilanes. 5% weight-loss temperature of the hybrid membranes increased with increasing silica content, indicating effective crosslinking at polymer-silica interface mediated by APTrMOS moiety. On the other hand, glass transition temperature of the hybrid membranes prepared with methyltrimethoxysilane (MTMS) showed a minimum value at low silica content region, suggesting insufficient formation of three-dimensional Si-O-Si network compared to the hybrid membranes prepared with tetramethoxysilane (TMOS). CO2, O-2, N-2, and CH4 permeability coefficients of the hybrid membranes increased with increasing silica content. Especially for TMOS/MTMS combined system, the hybrid membranes showed simultaneous enhancements of gas permeability and CO2/CH4 separation ability. It was concluded that the 6FDA-TAPOB hyperbranched polyimide-silica hybrid membranes have high thermal stability and excellent CO2/CH4 selectivity and are expected to apply to high-performance gas separation membranes. (C) 2008 Wiley Periodicals, Inc.