A capping method for nitrogen anion initiated living anionic polymerization for synthesizing alkyl methacrylate macromonomers

Lithium alkylamides are important functional initiators for anionic polymer ization of methacrylates, but only sterically hindered ones can initiate a successful living polymerization. A capping method is reported here to modi fy nitrogen anion initiators (capping reaction) for living anionic polymeri zation of alkyl methacrylates. Dimethylacrylamide (DMA) and tert-butyl meth acrylate ((t)BMA) were found to be effective capping agents for lithium dia llylamide. After capped with DMA or tBMA, the initiator efficiency of lithi um diallylamide was increased from 0.1 to 0.9 for various monomers. Monosub stituted lithium alkylamides (vinyloxypropylamide and allylamide) could not directly initiate the polymerization of methacrylates due to severe reacti on with the carbonyl groups in the monomers. After capped with DMA, the ini tiators polymerized methacrylates with initiator efficiency about 0.4-0.6, depending on the monomer type. tBMA was not suitable as capping agent for t he monosubstituted lithium amides. Using these capped initiators, we subseq uently synthesized block copolymers. H-1 NMR demonstrated that all the poly mers prepared had terminal unsaturated groups from the initiators.