Synthesis and properties of aromatic block copolyimides

Anhydride terminated polyamic acid prepolymer was prepared from pyromellitic dianhydride and a diamine (para-phenylene diamine/benzidine) in dimethyl formamide. The prepolymer was reacted with the other diamine to obtain (A_nB)_m block copolymic acid. The polyamic acid was converted to the polyimide by thermal cyclodehydration. The properties of block copolyimides were compared with those of random copolyimides prepared by conventional routes.