AbstractPolycondensation of 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTDA) with 3,3′‐diaminobenzidine (DAB) and 3,3′4,4′‐tetraaminodiphenyl ether (TADPE), respectively, inN,N′‐dimethylacetamide (DMAc) at room temperature was found to produce high‐viscosity polybenzimidazobenzophenanthroline (PBIPA) precursors. The PBIPA films, exhibiting excellent thermal and mechanical properties, were conveniently prepared by the heat cure of precursors. UV‐vis spectra and IR spectra of PBIPA were measured. The permeability to H2, O2, and N2of these two polymer membranes was determined at 30°C and 1 atm. © 1995