Synthesis and gas transport properties of novel hyperbranched polyimide–silica hybrid membranes

Abstract

AbstractPhysical and gas transport properties of hyperbranched polyimide (HBPI)—silica hybrid membranes prepared with a dianhydride monomer, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and triamine monomers, 1,3,5‐tris(4‐aminophenoxy)triazine (TAPOTZ), and 1,3,5‐tris(4‐aminophenyl)benzene (TAPB), were investigated and compared with those of 6FDA‐TAPOB HBPI system synthesized from 6FDA and 1,3,5‐tris(4‐aminophenoxy)benzene (TAPOB). Glass transition and 5% weight‐loss temperatures of the 6FDA‐based HBPI–silica hybrid membranes were increased with increasing silica content. 6FDA‐TAPOTZ HBPI system, however, showed relatively low 5% weight‐loss temperatures, suggesting thermal instability of triazine‐ring in the TAPOTZ moiety. CO2/CH4 permselectivity of the HBPI–silica hybrid membranes were increased with increasing silica content, tending to exceed the upper bound for CO2/CH4 separation. This result indicated that free volume elements effective for CO2/CH4 separation were created by the incorporation of silica for the HBPI–silica hybrid systems. Especially, 6FDA‐TAPB HBPI system had high gas permeabilities and CO2/CH4 separation ability, arising from high fractional free volume and characteristic size and distribution of free volume elements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013