Studies in polymerization - XV. The photosensitized initiation of vinyl polymerization by manganese carbonyl

It has been found that a system consisting of manganese carbonyl and a low concentration of carbon tetrachloride can act as an efficient photoinitiator of vinyl polymerization. This paper describes a kinetic study of the mechanism of photoinitiation at λ = 4358 Å, in which methyl methacrylate was the monomer. Trichloromethyl radicals are shown to be the initiating species. The main observations are consistent with a reaction scheme in which a primary product F of the photolysis of the carbonyl forms an adduct with carbon tetrachloride. This adduct may either dissociate into trichloromethyl radicals or be destroyed by reaction with F. Suggestions are made as to the chemical nature of F. Other mechanisms are considered which explain certain of the kinetic features observed. The quantum yield of photoinitiation is a function of [CCl4]/Iabs and rises monotonically with a limit of unity.