The free-radical copolymerization of methyl acrylate with styrene initiated by triphenylstibonium 1,2,3,4-tetraphenylcyclopentadienylide under nitrogen blanket at (60 +/- 0.1)degrees C in 1,4,dioxane for 2 h has been carried out. The kinetic expression is R-p proportional to [I](0.14) [MA](0.70) [Sty](0.75). The system follows nonideal kinetics due to primary radical termination as well as degradative chain transfer reactions. The overall activation energy is 42 kJ mol(-1). The reactivity ratios calculated from Kelen-Tudos method for r(1) (MA) and r(2) (Sty) are 0.16 +/- 0.01 and 0.028 +/- 0.005 respectively. These values suggest the alternating nature of the copolymer. The ylide dissociated to form a phenyl radical, which brings about copolymerization of methyl acrylate with styrene. (c) 2006 Wiley Periodicals, Inc.