Proton transfer anionic polymerization (PTAP) of 2-vinylpyridine
Living anionic polymerization is a powerful tool for precision polymer synthesis, but typically requires highly reactive organometallic initiators and stringent conditions. Recently, we developed proton transfer anionic polymerization (PTAP) of acrylic monomers, which proceeds via reversible proton transfer reactions between growing anionic species and dormant C–H bonds, offering a milder and more user-friendly alternative. Herein, we report PTAP of 2-vinylpyridine (2VP), an aromatic vinyl monomer with a lower reactivity than acrylic monomers, to expand the scope of PTAP systems. Controlled anionic polymerization of 2VP was achieved using compounds with weakly acidic C–H bonds as initiators or chain-transfer agents (CTAs) in the presence of potassium tert -butoxide as base catalysts with cryptand 222 or 18-crown-6 as ligands. Systematic investigations revealed that appropriate CTAs and slow monomer addition were effective for achieving precise molecular weight control. Additionally, this system also exhibited tolerance to tert -butyl alcohol, which functioned as a reversible terminator to rapidly regenerate dormant C–H species and to enable more precise molecular weight control. Furthermore, the facile synthesis of poly( N , N -diethylacrylamide)- b -poly(2VP) block copolymers was successfully achieved by sequentially conducting PTAP of acrylic and aromatic vinyl monomers on the basis of common dormant C–H bonds.