Anionic Polymerization of Acrylic Monomers. 14. Carbon-13 and Lithium-7 NMR Characterization of the Complexation of Methyl .alpha.-Lithioisobutyrate with Various Lithium Cation-Binding Ligands in Tetrahydrofuran

The aggregation equilibrium and electronic structure of methyl alpha-lithioisobutyrate (MIBLi), a monomeric model structurally corresponding to a living poly(methyl methacrylate) chain end associated with a lithium countercation, has been examined by Li-7 and/or C-13 NMR spectroscopy in tetrahydrofuran (THF) in the presence of various lithium cation-binding ligands. The addition of dimethoxyethane (DME), triglyme (glyme-3),12-crown-4 (12-CE-4), and hexamethylphosphoric triamide (HMPA) to coexisting tetrameric and dimeric MIBLi in THF induces an increase in dimeric population in the order DME < glyme-3 < 12-CE-4 更多