A mechanistic perspective on solvent effects in free-radical copolymerization

1. INTRODUCTION The ability of solvents to affect the homopropagation rate of many common monomers has been widely documented. For example, Bamford and Brumby [1] showed that the propagation rate kp of methyl methacrylate (MMA) at 25°C was sensitive to a range of aromatic solvents. Burnett, Cameron, and Joiner [2] found that the kp of styrene (Sty) was depressed by increasing concentrations of benzonitrile, bromobenzene, diethyl phthalate, dinonyl phthalate, and diethyl malonate, while in other studies [3, 4], they found that the kp for MMA was enhanced by halobenzenes and naphthalene. More recent work by Zammit et al. [5] has shown that solvents capable of hydrogen bonding, such as benzyl alcohol and N-methyl pyrrolidone, have a small influence on both the activation energy Ea and preexponential factor A in Sty and MMA homopropagation reactions. These are but a few of the many instances of solvent effects in the homopolymerization reactions of two typical monomers, Sty and MMA. For these monomers, solven...