In this research, the anionic polymerization of epsilon-caprolactam was carried out in the presence of small amounts of several different polyimides to generate polyimide-g-nylon 6 copolymers. The polyimides, which were prepared from 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride and commercially available diamines with a one-step method, were first dissolved in molten epsilon-caprolactam. Phenylmagnesium bromide was then added at 120 degrees C. Under these conditions, caprolactam anions were formed that attacked the five-membered imide rings to form N-acyllactam moieties, which activated the anionic polymerization of caprolactam. In essence, nylon 6 chains grew from the polyimide backbones. Probably because of a high activation energy, the process was relatively slow, requiring 1 h at 120 degrees C. The introduction of 5 wt % polyimide into the graft copolymers produced significant increases in the tensile modulus and tensile strength in comparison with those of low- and high-molecular-weight nylon 6. The elongation to break, however, was reduced. (c) 2005 Wiley Periodicals, Inc.