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

Abstract

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 [CCl 4 ]/ I abs and rises monotonically with a limit of unity.