Kinetic Studies on the Radical Polymerization of Butadiene Derivatives

Abstract

A kinetic study on the radical polymerization of diene compounds was carried out at 25±0.001°C. The diene compounds were ethyl pentadienoate and its derivatives CH2=CX–CH=CHCOOCH2CH3 (EP:X=H, EMP:X=CH3, and EEP:X=OCH3) and 1-acetoxybutadiene (AB). Elementary rate constants of these diene compounds were determined by the rotating sector method; the values of kp and kt for EP, EMP, EEP, and AB were 30.9 and 1.9×107, 29.7 and 2.3×107, 9.9 and 0.93×107, and 18.0 and 28.1×107 M−1 s−1, respectively. These kp values are lower than those reported for styrene, MMA, methyl acrylate, and vinyl acetate. Cross-propagation rate constants (k12 and k21) were estimated from the kp values and monomer reactivity ratios in the copolymerizations of these dienes (M2) with styrene (M1). Reactivity of the monomers and the propagating radicals was compared with vinyl compounds and other dienes by using k12 and k21, respectively. Lower kp values of these dienes are primarily ascribed to the fact that the decrease in the reactivity of the propagating radical is larger than the increase in that of monomer. Change in radical reactivity among dienes is larger than that in their monomer reactivity. Effects of the resonance stabilization of the propagating radicals on kt were not clearly evident in these radical polymerizations which are discussed on the basis of the preexponential factor.