Stereoregulation of Homogeneous Free Radical, Cationic and Anionic Polymerization Reactions

Abstract

The preceding discussions have been concerned almost entirely with the sterochemical control and the formation of stereoregular polymers by heterogeneous catalysts, presumably at chiral active sites on the catalyst surface. This chapter is concerned with the formation of stereoregular polymers by homogeneous reactions, primarily ionic polymerization reactions, in which the active endgroup is freely accessible in a matrix of solvent molecules. The solvent matrix is not necessarily passive, and indeed except for free radical polymerization reactions (for which specific solvent effects on the stereochemistry of polymerization reactions has not yet been convincingly demonstrated) and for polymerization reactions of free carbanions (but probably not for free carbenium ions), solvation can play a very important role in the stereochemistry of propagation.