The polymerization of isatoic anhydride (electrophilic monomer) with N-(2-hydroxyethyl)ethyleneimine (nucleophilic monomer) was studied in the absence of added initiator at different feed monomer concentrations, temperature, and time of copolymerization. The copolymers were characterized by FI-IR, H-1-NMR and C-13-NMR spectroscopy, and TGA. Based on spectroscopic data and copolymer composition, a copolymer structure was suggested.