Polyquinoxalines. II.

Abstract Five new high molecular weight polyquinoxalines have been prepared by the reactions of combinations of two tetramines, 3,3′‐diaminobenzidine (II) and 3,3′,4,4′‐tetraminodiphenyl ether (IV), with the three bisglyoxals, 1,4‐phenylenediglyoxal (I), 1,3‐phenylenediglyoxal (VI), and 4,4′‐oxydiphenylenediglyoxal (IX). Solution and melt polymerization techniques afford intermediate molecular weight polymers which can be converted to high molecular weight samples (η inh > 1.0) by heating at 375°C. under reduced pressure. All the polyquinoxalines have excellent thermal stability both in nitrogen and in air. Of these polymers, poly[2,2′‐(4,4′‐oxydiphenylene)‐6,6′‐oxydiquinoxaline] (XI) has the highest solubility in hexamethylphosphoramide (HMP), and films can be cast from intermediate molecular weight (η inh = 0.3–0.7) polymer solutions in HMP. Tough, insoluble films can be obtained by heating the cast films in nitrogen or under reduced pressure to 350–400°C.