Polyimide-g-nylon 6 copolymers were prepared by the polymerization of phenyl 3,5-diaminobenzoate with several diamines and dianhydrides with a one-step method. The polyimides containing pendant ester moieties were then used as activators for the anionic polymerization of molten epsilon-caprolactam. Nylon 6-b-polyimide-b-nylon 6 copolymers were prepared by the use of phenyl 4-aminobenzoate as an end-capping agent in the preparation of a series of imide oligomers. The oligomers were then used to activate the anionic polymerization of epsilon-caprolactam. In both the graft and copolymer syntheses, the phenyl ester groups reacted quickly with caprolactam anions at 120 degrees C to generate N-acyllactam moieties, which activated the anionic polymerization. All the block copolymers had higher moduli and tensile strengths than those of nylon 6. However, their elongations at break were much lower. The graft copolymers based on 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride and 2,2'-bis[4-(4-aminophenoxy)phenyl]propane displayed elongations comparable to that of nylon 6 and the highest moduli and tensile strengths of all the copolymers. The thermal stability, moisture resistance, and impact strength were dramatically increased by the incorporation of only 5 wt % polyimide into both the graft and block copolymers. The graft and block copolymers also exhibited improved melt processability. (c) 2005 Wiley Periodicals, Inc.