Perspectives on the contributions of Michael Szwarc to living polymerization

The review starts with a short historical introduction (Sections 1 and 2), followed by the famous work of Michael Szwarc on electron transfer to styrene and related monomers in THF and similar solvents (Section 3), forming the basis of most of his subsequent work. Section 4 describes his now classical work on the effects of ion pairing, ion pair solvation and triple ion formation on styrene anionic polymerization kinetics, as well as exploratory work on several related monomers and a brief description of work by others on related systems, such as the effects of LiCl and lithium alkoxides on the polymerization of styrene, and the mediation of styrene polymerizations by divalent Ba2. Section 5 starts with a summary of solvation studies of fluorenyl ion pairs that allowed a better understanding of the role of ion pairs in styrene polymerizations. The effects of solvent and carbanion structure on ion pair solvation and dissociation and their role in initiation equilibria are discussed. Finally a study of the dynamics of ion pair dissociation and triple ion formation based on the second Wien effect is discussed. Section 6 reviews anionic copolymerization studies by Szwarc and collaborators. This is followed by subsequent work on the Hammet relationships involving the addition of 1,1-diphenylethylenes to polystyrenelithium in hydrocarbon/THF. Studies by others on the role of Li-pi donors coordination in butadiene/styrene and isoprene/styrene copolymerizations in hydrocarbon media are also reviewed in this section, as is the role of this coordination in the LiOH mediated isotactic polymerization of styrene.