Atom transfer radical polymerization in the presence of a thiol: More evidence supporting radical intermediates

Octanethiol, a free-radical chain transfer agent, was added to the atom transfer radical polymerization of methyl methacrylate. The molecular weight and polydispersity data of the polymers produced were consistent with the known chain transfer behaviour of octanethiol in conventional free-radical polymerization. These results, which clearly indicate a radical nature of the propagating species, can be explained by a simple kinetic model, which describes an otherwise "living" polymerization system in the presence of an added chain transfer agent.