POLYIMIDES CONTAINING QUINOXALINE AND BENZIMIDAZOLE UNITS

Two new aromatic dianhydrides containing 2,3-quinoxaline and 5,5'-bis( benzimidazole) units were synthesized and used to prepare polyimides. The aromatic nucleophilic substitution reaction of either N-phenyl-4-f luorophthalimide or N-phenyl-4-nitrophthalimide with the disodium salt s of 2,3-bis(4-hydroxyphenyl)quinoxaline or 5,5'-bis[2-(4-hydroxypheny l)benzimidazole], respectively, in DMSO at 80-degrees-C provided the i ntermediate-4-substituted N-phenylphthalimides. The N-phenylphthalimid es were hydrolyzed with aqueous sodium hydroxide and subsequently acid ified to yield the bis(1,2-dicarboxylic acid)s. Reaction of these comp ounds with acetic anhydride provided the dianhydrides. Polyimides prep ared from these new dianhydrides with various diamines exhibited relat ively high glass transition temperatures and good thermal stability. S ome of the polyimides formed tough, creasible films with good mechanic al properties. Several of the polyimides containing the 5,5'-bis(benzi midazole) group were soluble in DMAc and NMP.