SOLVATION EFFECTS IN ANIONIC-POLYMERIZATION OF POLAR VINYL MONOMERS

The anionic polymerization (AP) of polar vinyl monomers (PVM) is strongly affected by additives with electron donor and electron acceptor properties. For the purpose of estimating the interactions of the active centers (AC) of chain growth with different ligands, the approach of studying a reference system was adopted, viz. lithium picrate (LiPi) in dioxane (DO). Three types of interaction were distinguished: with electron pair donors (EPD), with Li salts and alkoxides, and with Lewis acids. Spectral evidence was found of charge transfer complexation with Li alkoxides and enolates, leading to modified dianionic Meisenheimer adducts. The experimental procedure was employed in studies of competitive solvation of LiPi by two ligands. The results were related to reviewed literature data on the kinetics and stereochemistry of methyl methacrylate (MMA) and 2-vinylpyridine (2VP) polymerizations by lithium initiators.