Unlocking hexafluoroisopropanol as a practical anion-binding catalyst for living cationic polymerization

Abstract

Living cationic polymerization (LCP) is a classical technique for precision polymer synthesis; however, due to the high sensitivity of cationic active species towards chain-transfer/termination events, it is notoriously difficult to control polymerization under mild conditions, which inhibits its progress in advanced materials engineering. Here, we unlock a practical anion-binding catalytic strategy to address the historical dilemma in LCP. Our experimental and mechanistic studies demonstrate that commercially accessible hexafluoroisopropanol (HFIP), when used in high loading, can create higher-order HFIP aggregates to tame dormant-active species equilibrium via non-covalent anion-binding principle, in turn inducing distinctive polymerization kinetics behaviors that grant efficient chain propagation while minimizing competitive side reactions. This unique control mechanism delivers unprecedented polymerization activity and controllability across various electron-rich vinyl monomers under mild conditions, and provides easy access to high molecular weight polymers, block copolymers, and end-functionalized telechelic polymers. Also, the minimalistic structure of HFIP coupled with its convenient removal and recycle renders this approach easy to scale up, without concern for cost, sustainability and complicated work-up processes associated with previous systems. This study presents another universal and sustainable strategy for cationic macromolecular engineering, and will also stimulate further exploration of innovative non-covalent catalysis that enables more challenging living polymerization systems.