Synthesis of polyimide and poly(imide‐benzoxazole) in polyphosphoric acid

Abstract

Abstract A polyimide made from 4,4′‐diaminodiphenyl ether (ODA) and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) was synthesized in polyphosphoric acid. Although the polymerization proceeded heterogeneously, a polyimide with an inherent viscosity of 0.90 was obtained, and a tough and flexible film was made from this polyimide. This polymerization was a one‐step reaction including polycondensation and imidization; this was also confirmed by a model reaction between aniline and phthalic anhydride. Utilizing this polymerization method, 3,3′‐dihydroxy‐4,4′‐diaminobiphenyl and 2 mol of 4‐aminobenzoic acid were reacted in PPA, then BPDA was reacted to obtain an alternate copolymer containing imide and oxazole rings. This reaction gave a homogeneous solution of the poly(imide‐benzoxazole). © 1993 John Wiley & Sons, Inc.