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 K2CO3, respectively. The diamines were utilized as co-monomers with BPDA and PDA to synthesize poly (amic-acids.) Films were cast and cured (350-degrees-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-degrees-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.