Block Copolymer Synthesis through the Use of Switchable RAFT Agents

The use of "switchable" RAFT agents in expanding the use of RAFT polymerization in block copolymer synthesis is decsribed. N-(4-pyridinyl)-N-methyldithiocarbamates provide excellent control over polymerization of less activated monomers (LAMs) (e.g., vinyl acetate, N-vinylcarbazole), and, after addition of one equivalent of a protic or Lewis acid, become effective in controlling polymerization of more activated monomers (MAMs) (e.g., styrene, methyl methacrylate). They thus allow a convenient synthesis of polyMAM-block-polyLAM with narrow molecular weight distributions. Advantages, limitations and factors effecting the scope of the process are discussed.