Synthesis and characterization of N-vinylimidazole-ethyl methacrylate copolymers and determination of monomer reactivity ratios

Radical-initiated copolymerization of N-vinylimidazole (VIM) and ethyl meth acrylate (EMA) was carried out with 2,2 ' -azobisisobutyronitrile (AIBN) as an initiator in benzene at 70 degreesC in nitrogen atmosphere. Structure a nd composition of copolymers for a wide range of monomer feed were determin ed by elemental analysis (content of N for VIM-units) and by Fourier transf orm infrared spectroscopy through recorded analytical absorption bands for VIM (667 cm(-1) for C-N of imidazole ring) and EMA (1729 cm(-1) for C=O of ester group) units, respectively. Monomer reactivity ratios for VIM (M-1)-E MA (M,) pair were determined by Fineman-Ross and Kelen-Tudos (KT) methods. They are r(1) = 0.35 +/- 0.02 and r(2) = 3.47 +/- 0.2 as determined by KT m ethod. Parameters of Q(1) = 0.14 and e(1) = -0.61 for VIM monomer were calc ulated by using the Alfrey-Price scheme. Observed relatively high activity of EMA growing radical was explained by effect of complex formation between carbonyl group and imidazole fragments in chain growth reactions. Thermal behaviors of copolymers with various compositions were investigated by diff erential scanning calorimetry and thermogravimetric analysis. It was observ ed that glass transition temperature and thermal stability of copolymers in creased with increasing of VIM content in copolymers. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.