Free‐radical polymerization of methyl methacrylate in the presence of aluminium chloride

A study has been made of the influence of chloride on the free‐radical polymerization of methyl methacrylate at 25°C; the reaction was photoinitiated (λ = 3650 Å) by azo‐bis‐isobutyronitrile or benzoyl peroxide. At a concentration of 0.18 mole · l−1, aluminium chloride increases the velocity coefficient of propagation by 70%, approximately, but the increase in the overall rate of polymerization is less than this on account of retardation. Transfer reactions are important in the presence of aluminium chloride, and it is likely that the observed retardation arises from low reactivity of transfer radicals in reinitiation. It is suggested that the transfer agent is a complex between methyl methacrylate and aluminium chloride. In our experiments aluminium chloride had no significant effect on the rate of initiation.