Synthesis and characterization of soluble polymides from 2,5‐bis(4‐aminophenyl)‐3,4‐diphenylthiophene and aromatic tetracarboxylic dianhydrides

Abstract

Abstract 2,5‐Bis(4‐aminophenyl)‐3,4‐diphenylthiophene, a polyimide‐forming monomer, was prepared in three steps starting from benzyl chloride and sulfur. Novel polyimides were synthesized from the diamine and pyromellitic dianhydride or 3,3′, 4,4′‐benzophenonetetracarboxylic dianhydride (BTDA). Polymerization was carried out either by the usual two‐step procedure that included ring‐opening polyaddition giving polyamic acids, followed by cyclodehydration to polyimides, or by the direct one‐pot procedure involving cyclodehydration in situ . The polyimide derived from the diamine and BTDA, especially that prepared by the one‐pot procedure in m ‐cresol containing isoquinoline, is soluble in various organic solvents and gave a yellow, transparent, tough, and flexible film. Solubility of this polyimide varied by the preparative method and by the copolymerization with bis(4‐aminophenyl) ether. All the polyimides are highly thermally stable and exhibited no appreciable decomposition up to 450°C in air and nitrogen atmospheres.