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)-<i>b</i>-poly­[poly­(ethylene glycol) methyl ethyl acrylate] was observed