AbstractCopolymers were prepared by reacting a prepolymer consisting of an anhydride terminated polymeric acid from pyromellitic anhydride and a diamine (p‐ orm‐phenylenediamine), with the second diamine. The resulting polymeric acids were converted into polyimides by thermal cyclodehydration. The corresponding random copolyimides were prepared by a conventional procedure and their properties were compared with those of three step copolyimides of similar composit