Electroconductivity study of active centers of polar vinyl monomers in the anionic polymerization

Ion equilibria in THF solutions of organolithium compounds are studied at −30°C. The extremely low values of the dissociation constants (from 10−11 to 10−13M) and the formation of ion triples of the types A−, B+, A− prove that active centers exist in THF mainly as contact ion pairs with very small interionic distance (∼ 2.5 Å) and tend to form higher associates. A comparison is made between the physicochemical characteristics of active centers of vinyl nitriles, ketones, and esters. A planar structure is proposed for the anion of methyl methacrylate. The results indicate that the intramolecular chelate complexation between the polar group and the counterion of the active center decreases in the order . A greater participation of ion triples in the propagation reaction is proposed.