Concurrent Cationic Vinyl-Addition and Coordination Ring-Opening Copolymerization via Orthogonal Propagation and Transient Merging at the Propagating Chain End

Controlled cationic vinyl-addition polymerization of an alkyl vinyl ether (VE) and ring-opening polymerization of epsilon-caprolactone (CL) simultaneously proceeded using HfCl4/Hf-(OBu)(4) as a dual-role catalyst for both mechanisms, yielding a graft copolymer consisting of a poly(VE) main chain and several poly(CL) side chains. The copolymer of conventionally incompatible monomers was generated via the unprecedented mechanisms consisting of orthogonal propagating reactions and transient merging. Specifically, the poly(CL) chains were incorporated into a poly(VE) chain through an exchange reaction between the VE-derived alkoxy group and the propagating poly(CL) chain at the acetal moiety of the propagating end of the poly(VE) chain. An appropriate ratio of HfCl4 and Hf(OBu)(4) was indispensable for both the simultaneous vinyl-addition and ring-opening polymerizations and the alkoxy group exchange reaction.