Gas Transport Properties of ODPA-TAPOB Hyperbranched Polyimide-Silica Hybrid Membranes

Abstract

Physical and gas transport properties of novel hyperbranched polyimide-silica hybrid membranes were investigated. Hyperbranched polyamic acid as a precursor was prepared by polycondensation of a triamine monomer, 1,3,5-tris(4-aminophenoxy)benzene (TAPOB), and a dianhydride monomer, 4,4′-oxidiphthalic anhydride (ODPA), and subsequently modified the end groups by 3-aminopropyltrimethoxy-silane (APTrMOS). Hyperbranched polyimide-silica hybrid membranes were prepared using the polyamic acid, water, and tetramethoxysilane (TMOS) by the sol-gel method and thermal imidization. The 5% weight-loss temperature and glass transition temperature of the hybrid membranes determined by TGDTA measurements considerably increased with increasing silica content, indicating effective cross-linking at polymer-silica interface mediated by APTrMOS. CO₂, O₂, N₂, and CH₄ permeability coefficients of the hybrid membranes increased with increasing silica content. In addition to the increased permeability, CO₂/CH₄ selectivity of the hybrid membranes increased with increasing silica content. It was concluded that the ODPA-TAPOB hyperbranched polyimide-silica hybrid membranes have high thermal stability and good gas selectivity, and are expected to apply to a high-performance gas separation membrane.