The polymerization of pyromellitic dianhydride with diphenylmethane diisocyanate

Abstract

Abstract A novel polyimide forming reaction is reported. Pyromellitic dianhydride undergoes a condensation polymerization with diphenylmethane diisocyanate in solution or under melt‐fusion conditions to give polydiphenylmethanepyromellitimide (II) and carbon dioxide. Polymer II was characterized by inherent viscosity, infrared spectrum, and thermogravimetric analysis. An intermediate Polymer I was isolated which appeared to contain seven‐membered rings in the backbone. It is postulated that these rings eliminate carbon dioxide to form polyimide II.