MECHANISM OF ALTERNATING COPOLYMERIZATION

In the studies using the spin-trap method, it was demonstrated that during the copolymerization of various electron donor monomers with SO2 or maleic anhydride, the radical of electron-accepting monomer is the only active center in the process; the copolymerization proceeds via the mechanism involving complex formation. The donor monomers with an active double bond (styrene, N-vinylpyrrolidone) present an exception; copolymerization of these monomers with SO2 and maleic anhydride reveals the occurrence of cross-propagation reactions, which involve radicals of both acceptor and donor monomers. Various cases of alternating copolymerization are treated from the uniform grounds on the basis of the concepts assuming the decisive role of donor-acceptor interactions between the monomers and the chain propagation radicals (the mechanism of Pravednikov and Hirooka). The mechanism and kinetics of spontaneous initiation and of inhibition and chain transfer in alternating copolymerization are discussed.