Structural modifications in imide‐aryl ether phenylquinoxaline random copolymers

A rigid rod polyimide derived from biphenyldianhydride (BPDA) and p‐phenylenediamine (PDA) was modified by the incorporation of diamines containing performed phenylquinoxaline and aryl ether linkages, and the morphology and mechanical properties of the resulting imide‐aryl ether phenylquinoxaline copolymers were investigated. These phenylquinoxaline containing diamines, 1, 4‐bis[6‐(3‐aminophenoxy)‐3‐phenyl‐2‐quinoxalinyl] benzene and 1, 4‐bis[6‐(4‐aminophenoxy)‐3‐phenyl‐2‐quinoxalinyl] benzene, were prepared by a novel nucleophilic aromatic substitution reaction of 1,4‐(6‐fluoro‐3‐phenyl‐2‐quinoxalinyl) benzene with either 1, 3‐ or 1, 4‐aminophenol in the presence of K 2 CO 3 , respectively. The diamines were utilized as co‐monomers with BPDA and PDA to synthesize poly(amicacids.) Films were cast and cured (350°C) to effect imidization, affording films which showed high elongations and moduli. The copolymers with high phenylquinoxaline compositions displayed T g 's in the 300°C range, and the thermal stability of the copolymers was comparable to that of the parent polyimide. The copolymers also showed improved auto‐ or self‐adhesion, particularly those which showed a T g , allowing sufficient molecular motion for interdiffusion. Copyright © 1992 John Wiley & Sons, Inc.