Mechanistic aspects of catalytic chain transfer polymerization

A range of experiments has been conducted with the aim of elucidating the mechanism of catalytic chain transfer in methacrylic and styrenic polymerizations. Evidence for a diffusion-controlled transfer step in methacrylate polymerization is presented. The measured chain transfer constant, Cs, for styrene is relatively low when compared with the methacrylates. This low C_s in styrene systems can be (partly) attributed to the formation of Co-C bonds reducing the concentration of active Co(II) catalyst. The precise identification of the elementary steps in catalytic chain transfer remains elusive. The experimental observation that the molecular weight distribution of the polymer formed in catalytic chain transfer remains constant with conversion is at present inexplicable.