The free-radical copolymerization of 4-vinyl pyridine (4-VP) with methyl acrylate (MA) initiated by p-acetylbenzylidene triphenylarsonium ylide at 60 +/- 0.1 degrees C with dioxane as an inert solvent yielded random copolymers. The kinetic equation was R-p proportional to [Ylide](0.83)[4-VP](0.33) [MA](0.40) (where R-p is the rate of polymerization); in other words, the system followed nonideal kinetics. The values of the energy of activation and k(p)(2)/k(t) (where k(p) is the rate constant of propagation and k(t) is the rate constant of termination) were 23.21 kJ/mol and 1.212 x 10(-5) mol L-1 s(-1), respectively. The reactivity ratios calculated with the Kelen-Tudos method were 0.14 +/- 0.0075 for 4-VP and 0.56 +/- 0.0078 for MA. The copolymers were characterized with Fourier transform infrared, proton nuclear magnetic resonance, differential scanning calorimetry, and electron spin resonance methods. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 3354-3359, 2009