In-Situ Direct Mechanistic Transformation from RAFT to Living Cationic Polymerization for (Meth)acrylate−Vinyl Ether Block Copolymers

Abstract

In-situ direct mechanistic transformation from living radical to cationic polymerization was investigated using a trithiocarbonate-type reversible addition−fragmentation chain-transfer (RAFT) agent and an azo-initiator for RAFT polymerization of (meth)acrylates followed by the addition of a Lewis acid catalyst for the sequential living cationic block polymerization of vinyl ethers. Prior to the mechanistic transformation reaction, the possibility of living cationic polymerization was examined via activation of the thioester bond by Lewis acids, such as SnCl4, EtAlCl2, and ZnCl2. The CH3CH(OiBu)SC(S)SEt/SnCl4-initiating system induced living cationic polymerization of isobutyl vinyl ether (IBVE) in the presence of ethyl acetate (EtOAc) as an additive in toluene at 20 °C to give polymers with controlled molecular weights and narrow molecular weight distributions (MWDs) (Mw/Mn = 1.18). The RAFT copolymerization of methyl acrylate (MA) or methacrylate (MMA) and IBVE was then first carried out using (CH3)2C(CN...