Lithium-Salt-Driven Lewis Pair Polymerization for Chemically Recyclable and Ion-Conductive Polyester Elastomers

Herein, we report a lithium-salt-driven Lewis pair polymerization (LPP) strategy to accomplish controlled polyester synthesis, ionic conductivity, and closed-loop recyclability within a single platform. The combination of commercial lithium salts (LiTFSI or LiCF₃SO₃) and a novel bifunctional N-heterocyclic olefin (NHO) enables rapid and living ring-opening polymerization of diverse lactones (ε-caprolactone, δ-valerolactone, and rac-lactide) under mild conditions, affording well-defined block copolymers with predictable molecular weights and narrow molecular weight distributions. Kinetic and mechanistic studies reveal a nonclassical zero-order dependence on the concentrations of both monomer and Lewis acid, governed by the multi-coordination capability of lithium cations. Distinct from traditional polymerizations, the residual lithium salts are retained in situ to impart competitive ionic conductivity, which enables the fabrication of ion-conductive polyester elastomers with highly tunable mechanical properties (ε∼229%‒2111% and σ∼1.6‒37.4 MPa) and room-temperature ionic conductivities (up to 10^-5 S/cm) through a one-step protocol. A comprehensive evaluation of the strain sensitivity, electrical hysteresis, response/recovery behavior, and cyclic sensing performance supports their potential for applications in reliable, real-time flexible strain sensing. Furthermore, both the polyester matrix and lithium salts can be efficiently recovered, realizing full closed-loop recycling. This catalyst-to-function paradigm provides a general blueprint for integrating catalysis, functionality, and circularity in polymer design.