Radical Substitution of the Dithiocarbonyl Group of Poly(methyl methacrylate) Obtained by Reversible Addition–Fragmentation Chain Transfer Polymerization

Abstract The authors perform a systematic study of the reaction of radical replacement of the dithiocarbonyl group of poly(methyl methacrylate) (PMMA) obtained by reversible addition–fragmentation chain transfer polymerization upon interaction with a radical azo initiator in an inert solvent at 80°C. It is shown that, for a polymer with a dithiobenzoate group, an increase in the molar ratio of the concentrations of the initiator and macromolecules with a terminal dithiobenzoate group to 100 equivalents promotes fast and quantitative replacement of the dithiobenzoate group by the initiator fragment and suppression of side chain termination reactions with the participation of radical intermediates. To replace the trithiocarbonate group, milder conditions are required, namely, a 20-fold molar excess of the initiator and a short reaction time of 2–5 h. The stability of the radical intermediates plays the decisive role in choosing the replacement reaction conditions. The reversible chain transfer agent formed during the replacement reactions, a low-molecular-weight compound containing a dithiocarbonyl fragment, can be repeatedly used for PMMA synthesis.