HCl.Et2O-Catalyzed Metal-Free RAFT Cationic Polymerization: One-Pot Transformation from Metal-Free Living Cationic Polymerization to RAFT Radical Polymerization

The metal-free RAFT cationic polymerization (MRCP) of vinyl ethers (VEs) mediated by HCl.Et2O and 1-isobutoxyethyl ethanedithioate (IDTA) as a RAFT cationogen was demonstrated. The IDTA was efficiently catalyzed and the cationic polymerization was initiated by the HCl.Et2O, allowing good control over the molecular weight, polydispersity, and chain end structure of the resulting polyVEs. The propagation step is considered to involve a reversible addition fragmentation chain transfer (RAFT) to the growing carbocationic species. Thus, the resulting polyVEs can exhibit high number-average end functionality at the RAFT terminal group, depending on the [IDTA](0)/[HCl](0) ratio. The polymers obtained by this process could be used as macro-chain transfer agents for the RAFT radical polymerization of radically polymerizable monomers such as (meth)acrylates and styrenes to synthesize novel block copolymers. Significantly, this MRCP system allows a one-pot transformation from MRCP to RAFT radical polymerization as a result of the metal-free nature of the processes. The syntheses of block copolymers were confirmed by GPC and the formation of novel thermoresponsive micelles in water by the amphiphilic block copolymer poly(2-ethoxyethyl vinyl ether)-b-poly[poly(ethylene glycol) methyl ethyl acrylate] was observed.