Controlled reversible addition-fragmentation chain-transfer polymerization: ESR spectra and structure of radical intermediates

The formation of radical intermediates in the course of polymerization of diverse monomers (styrene, its deuterated derivatives, n-butyl acrylate, N-vinylpyrrolidone, etc.) in the presence of reversible chain-transfer agents (tert-butyl dithiobenzoate and di-tert-butyl trithiocarbonate) and various initiators was studied by ESR spectroscopy. The spectra of these intermediates were interpreted. The intensity of the spectra was shown to be strongly dependent on the nature and concentration of reversible chain-transfer agents, the concentration and activity of radical initiators, temperature, and the monomer nature. A technique providing separate determination of the concentration of intermediates arising in the course of polymerization was suggested.