Direct Synthesis of Well-Defined Epoxide-Terminated Telechelic Polymers via an Alcohol-Mediated Self-Switching Strategy.

The one-step synthesis of well-defined telechelic polymers represents a highly attractive approach, providing an efficient alternative to conventional stepwise synthetic protocols. However, achieving such control remains challenging due to the competitive nature of chain propagation and end-group functionalization, which often leads to uncontrolled chain-end structures and broad dispersities. Here, we report an alcohol-mediated self-switching strategy, in which the dominant chain-end reaction shifts from propagation to end-group functionalization upon consumption of one monomer component within a single reaction system. Using epichlorohydrin, a multisite monomer, as a model for the ring-opening alternating copolymerization with cyclic anhydrides, we obtained well-defined epoxide-terminated telechelic polyesters with narrow dispersities (Đ ∼ 1.1), high end-group fidelity (>99%), and controllable linear, three-arm, and four-arm architectures under alcohol-mediated conditions. Mechanistic studies reveal that monomer activation and stabilization of the living species through hydrogen-bonding interactions, combined with the zero-order kinetics of cyclic anhydride, facilitate rapid propagation while suppressing premature functionalization. Subsequent intramolecular cyclization of β-chlorohydrin living chain ends, along with proton-transfer-induced dehydrochlorination of β-chlorohydrin dormant chain ends, collectively ensure quantitative epoxide end-group formation. These results elucidate the catalyst-like roles of alcohol and establish self-switching of competing chain-end reactions as a practical strategy for the direct synthesis of well-defined telechelic polymers.