Catalytic chain transfer polymerization of methyl methacrylate in supercritical carbon dioxide: Evidence for a diffusion-controlled transfer process

The mechanism of catalytic chain transfer polymerization with methyl methac rylate was studied in a range of media. The chain transfer reaction in supe rcritical CO2 was found to be significantly enhanced compared with similar experiments in toluene or in bulk methyl methacrylate. The results are cons istent with a diffusion-controlled rate-determining step in the transfer pr ocess with cobaloxime catalysts. The gaslike viscosities in the supercritic al medium result in an approximate chain transfer coefficient (k(tr)) of 10 (8) L mol(-1) s(-1): an order of magnitude higher than values obtained in c onventional organic solvents.