Polyimides based on 2,5-bis(4-aminophenoxy)biphenyl

A diamine monomer II, 2,5-bis(4-aminophenoxy)biphenyl, was prepared through a nucleophilic substitution reaction of phenylhydroquinone and p-chloronitrobenzene in the presence of potassium carbonate in N,N-dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. A series of all-aromatic, organosoluble polyimides bearing pendent phenyl groups were synthesized from the diamine with six kinds of commercial dianhydrides via a conventional two-stage process. For improving solubility of polypyromellitimide, copolypyromellitimides with arbitrary solubilities were prepared from 11 and a pair of dianhydrides, which were mixed at certain molar ratios. These polymers showed good solubilities in N-methyl-2-pyrrolidone and m-cresol. The softening temperatures of these polyimides were recorded between 206 and 269 degreesC. Polymers had glass-transition temperatures at 230-286 degreesC and 10% weightloss temperatures above 521 degreesC in air or nitrogen atmospheres, Their films had high tensile moduli and strengths. Excellent properties of these polyimides are attributed to the incorporation of the pendent phenyl group in diamine II. (C) 2002 John Wiley Sons, Inc.