C-13 kinetic isotope effects in the copper(I)-mediated living radical polymerization of methyl methacrylate

Carbon-13 kinetic isotope effects (KIEs) have been determined for free-radical and copper-mediated living radical polymerizations of methyl methacrylate at 60degreesC. While free-radical polymerization shows only one primary C-13 KIE, on the least-substituted double bond carbon (k(12)/k(13) = 1.045), two significant KIEs are observed, one on each double bond carbon, for copper-mediated polymerization (k(12)/k(13)(H2C) = 1.050, k(12)/k(13)(=C<) = 1.010), showing that copper-mediated living radical polymerization does not propagate via a simple free radical process.