Radical-initiated solution copolymerization of N-vinylimidazole (VIM) and acrylonitrile (AN) was carried out with 2,2-azobisisobutyronitrile (AIBN) as an initiator in benzene at 70 degreesC in nitrogen atmosphere. The structure and composition of synthesized copolymeres for a wide range of monomer feeds were determined by FTIR, H-1 and C-13 NMR spectroscopy with the aid of recorded analytical absorption bands for VIM (667 cm(-1), C-N of imidazole ring) and AN (2242 cm(-1), CN group), as well as by using the areas of proton and carbon atom signals from corresponding functional groups of monomer units. Monomer reactivity ratios for VIM (M-1)-AN (M-2) pair were determined by nonlinear regression (NLR), Kelen-Tudos (KT) and Fineman-Ross (FR) methods. They were found to ber r(1) = 0.24 and r(2) = 0.12 for the FR method, respectively. The relatively high activity observed of VIM growing macroradical and the results of FTIR and H-1 NMR structural analysis of copolymers suggest the formation of complexed linkages between monomers and growing radicals in chain propagation reactions. Similar complexation between monomer-comonomer units in the structure of formed macromolecules showed an increase in isotactic triad fractions in the copolymer.