RAFT Polymerization of N-Methyl-N-vinylacetamide and Related Double Hydrophilic Block Copolymers

Bulk reversible addition-fragmentation chain-transfer polymerization (RAFT) of N-methyl-N-vinylacetamide (NMVA) was explored with four different RAFT agents, which are two xanthates and two dithiocarbamates. Working at 35 degrees C with an unusually high [V-70](0)/[RAFT agent](0) ratio, cyanomethyl O-ethyl carbonodithioate and cyanomethyl diphenylcarbamodithioate allowed the synthesis of poly(N-methyl-N-vinyl acetamide) (PNMVA) with predetermined M-n and relatively low dispersities (D < 1.5). A good thiocarbonylthio end-group fidelity was revealed by H-1 nuclear magnetic resonance (NMR), mass spectrometry, chain-extension experiment, and block copolymer synthesis. Two double hydrophilic poly(ethylene oxide)-b-poly(N-methyl-N-vinylacetamide) (PEO-b-PNMVA) and poly(N-isopropylacrylamide)-b-poly(N-methyl-N-vinylacetamide) (PNIPAAm-b-PNMVA) diblock copolymers were successfully synthesized, the latter of which exhibits a lower critical solution temperature (LCST) with the reversible formation of colloidal aggregates in water.