Advances in Switchable RAFT Polymerization

This paper reviews recent developments in RAFT Polymerization with proton switchable RAFT agents. We report on the successful use of N-methyl-N-(4-pyridinyl) dithiocarbamates RAFT agents for controlling the polymerization of N,N-dimethylacrylamide (DMAm) in aqueous media, the dependence of the RAFT agent activity on acid type and acid strength (for best results a stoichiometric amount of a strong acid should be used), and the synthesis of block copolymers such as poly(DMAm)-block-poly(N-vinylpyrrolidone). We describe a new class of switchable RAFT agents, the N-aryl-N-(4-pyridinyl) dithiocarbamates. These RAFT agents are more active with more activated monomers (MAMs) in protonated (switched) form and more active with less activated monomers (LAMS) in non-protonated (unswitched) form. Finally we examine the dependence of RAFT polymerization of N-vinylcarbazole (NVC) on the type of RAFT agent used (dithiobenzoate, trithiocarbonate, xanthate, switchable dithiocarbamate). Contrary to popular belief, NVC does not behave as a typical LAM, its polymerization is best controlled with a trithiocarbonate RAFT agent, and NVC should be described as an intermediate activity monomer (IAM).