Dithioesters in atom-transfer radical polymerization

Phenyl dithioacetates and bis(isobutyl) dithiocarbamates of Cu(II) and Ti(IV) were studied as chain-transfer agents in the controlled free-radical polymerization of methyl methacrylate and styrene. It was shown that the above compounds strongly decelerate the polymerization of at least one of the monomers. When Cu(II) bis(isobutyl) dithiocarbamate was used in an equivalent ratio with an initiator, the polymerization of MMA proceeded as a well-controlled process and yielded a monodisperse polymer. In other cases, when the concentration of the salt was reduced by two or more times, the most reliable feature of controlled polymerization was observed; that is, the molecular mass of the polymer increased linearly and progressively with an increase in the monomer conversion. The results obtained confirmed that dithiocarboxylate and dithiocarbamate groups can, similarly to halides, interact with transition-metal compounds through ligand-(atom)-transfer redox reactions.