The oxidative polymerization of methyl methacrylate

Methyl methacrylate has been shown to undergo a rapid polymerization above 100°C. in the presence of oxygen, but without other initiator, to yield a high molecular weight polymer free from peroxides. A study of the system has shown that the mean rate of polymerization at 120°C. is proportional to the initial partial pressure of oxygen. The catalysis is attributed to the initial formation of a low molecular weight oxygen‐methyl methacrylate copolymer (polyperoxide), decomposition of which yields initiating radicals and the observed oxidation products formaldehyde and methyl pyruvate. There is evidence that methyl pyruvate may itself initiate polymerization at higher temperatures. It is concluded that under the experimental conditions the distribution of oxygen throughout the reaction mixture is markedly non‐uniform, and that the high polymeric product is formed in regions of low oxygen content. Using 14 C‐labelled monomer we have shown that formaldehyde arises from the methylene and not the α‐methyl group of methyl methacrylate. Methyl acrylate and styrene have been found to polymerize under similar conditions, the rates of polymerization being related to the relative stability of the respective polyperoxides.