A poly[bis(trialkylammonium) 4,4’-oxydiphenylenepyromellitamate] film not containing residual solvents was prepared first as a polyimide precursor film. The preparative method is composed of three process steps involving (1) polymerization of pyromelitic dianhydride with 4,4’-oxydianiline in a mixed solvent of tetrahydrofuran/methanol, (2) addition of a mixture of methanol/trialkylamine to the resulting poly(4,4’-oxydiphenylenepyromellitamic acid) solution, and (3) casting onto glass plates and drying. The salt formation between the poly(amic acid) and trialkylamines was confirmed first by spectroscopic methods. The dried salt film is thermally cured to produce the polyimide film with a reduced coefficient of thermal expansion (CTE).