Novel Cationic Macromonomers by Living Anionic Polymerization of (Dimethylamino)ethyl Methacrylate

Water-soluble cationic macromonomers of (dimethylamino)ethyl methacrylate (DMAEMA) with terminal diallylmethylammonium or allylmethylphenylammonium group were synthesized by nitrogen anion (nitroanion) initiated living anionic polymerization of DMAEMA and subsequent quaternization. The initiators, lithium diallyamide and lithium allylphenylamide, were prepared by the reaction of corresponding N-substituted allylamine with butyllithium. The substituents on the nitroanion had a significant effect on the initiation efficiency. The initiator efficiencies of lithium allylamide, diallylamide, and allylphenylamide increased by the order 0 < 25% < 79% at −78 °C. The low initiator efficiency of lithium diallylamide was due to the reaction of the nitroanion with carbonyl groups in the monomer and polymer and could not be improved by optimizing polymerization conditions. A capping method using dimethylacrylamide (DMA) or tert-butyl methacrylate (tBMA) was then developed to modify the lithium diallylamide and thereby increased initiator efficiency. The DMA or tBMA capped lithium diallylamide had an initiator efficiency higher than 0.90, producing polymers with predicted molecular weight and nearly monodispersed polydispersity. Subsequent quaternization with CH3I and dimethyl sulfate converted the polymer into cationic macromonomers with diallylmethylammonium or allylmethylphenylammonium terminal groups, which are readily copolymerizable with other vinyl monomers such as acrylamide and vinylformamide.