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 methacrylate was studied in a range of media. The chain transfer reaction in supercritical CO 2 was found to be significantly enhanced compared with similar experiments in toluene or in bulk methyl methacrylate. The results are consistent with a diffusion-controlled rate-determining step in the transfer process with cobaloxime catalysts. The gaslike viscosities in the supercritical 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 conventional organic solvents.