Anionic Polymerization of 2-Vinylpyridine: A Computational Study of Solvent Effects on Polymerization Stereochemistry

摘要

Stereoreguiar poiy(2-vinylpyridines) have been prepared by anionic polymerizations with magnesium, lithium, and other alkali metal counterions1'4. The counterions, solvent systems, and steric effects have all been found to affect the stereochemistry of polymerization. Indirect evidence has suggested that the polymerization of sterically unhindered monomers by alkyllithium initiators in THF results in an isotactic polymer due to coordination of the lithium counterion by the nitrogen atom of the repeat unit penultimate to the growing chain end. It has long been known that aggregation and solvation affects the stereochemistry and regiochemistry of reactions involving organolithium compounds. Studies by Sakurai, Fraser, and coworkers have demonstrated the effects of solvent on the alkylation of lithio azaallylic enolate equivalents.5'7