Universal (Switchable) RAFT Agents

摘要

Radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization) is a reversible deactivation polymerization and one of the most versatile processes for conferring living characteristics on radical polymerization. The polymerization of most monomers that are polymerizable by radical polymerization can be controlled by the RAFT process. However, the RAFT agent [ZC(=S)S-R) must be selected according to the monomer(s) used. Thus, RAFT agents such as dithioesters (Z = aryl, alkyl) or trithiocarbonates (Z = alkylthio) suitable for controlling polymerization of "more-activated" monomers (MAMs), such as styrene, methyl acrylate (MA), and methyl methacrylate (MMA), inhibit or retard polymerizations of "less activated" monomers (LAMs), such as vinyl acetate (VAc), N-vinylpyrrolidone (NVP), and iV-vinylcarbazole (NVC). Similarly RAFT agents suitable for controlling polymerizations of LAMs, such as N,N-dialkyl- or N-alkyl-N-aryldithiocarbamates and xanthates, tend to be ineffective with MAMs.