The copolymerization of N-(2-hydroxyethyl)ethyleneimine (HEEI) as nucleophilic monomer and maleic anhydride (MA) as electrophilic monomer in the absence of initiator in acetonitrile was investigated. Copolymers were characterized by IR, H-1-NMR and C-13-NMR spectroscopy. The copolymer composition depends on the monomer ratio in the feed, determined by H-1-NMR spectroscopy. The presence of MA bridges between copolymer chains was established by spectroscopic analysis. At lower temperature the yield and molecular weight of copolymers decrease as well as the MA unit content in the copolymer.