Kinetics of copolymerization of acrylonitrile (AN) with ammonium itaconate (AI) initiated by azobisisobutyronitrile (AIBN) were investigated in a H2O/dimethyl formamide (DMF) mixture between 50 and 70degreesC under a N-2 atmosphere. The rate of copolymerization and particle size were measured. The kinetic equation of copolymerization system is obtained and the overall activation energy for the copolymerization system was computed. Values of monomer apparent reactivity ratios were calculated by the Kelen-Tudos method. It was found that in DMF-rich reaction medium (DMF/H2O > 80/20), monomer apparent reactivity ratios are similar to those in the solution polymerization system. Effect of hydroquinone and dioxane additives on copolymerization was discussed. The polymerization is retarded by hydroquinone and accelerated by dioxane, which confirms the free-radical copolymerization of AN with AI. (C) 2004 Wiley Periodicals, Inc.