Abstract Cationic ring-opening polymerization of substituted six-membered cyclic enol ethers offers a distinct route to vinyl polymers with head-to-head alternating side chains. However, poor control over the propagating chain-end—conventionally assumed to be a ring-opened oxocarbenium ion—has historically limited its development. Here, we report a chain-transfer-agent-free living cationic ring-opening polymerization enabled by the discovery and utilization of intrinsic chain-end stabilization.
