Chemically Recyclable Alternating Poly(thioether<i>‐alt</i>‐ester)s with Tunable Properties Enabled by Substitution Effects and Stereochemistry

The development of innovative poly(ether-ester)s with perfectly alternating ether and ester functionalities to overcome the trade-offs between the polymer's depolymerizability and performance properties is in high demand for advanced material applications and sustainable development. Herein, we prepared a series of enantiopure cyclic thioether-ester monomers bearing various pendant substituents by a facile "polycondensation-depolymerization" strategy. The controlled ring-opening polymerizations of these enantiopure monomers will afford stereoregular poly(thioether-alt-ester)s with structural diversity. The varieties of substituent size, position and stereo-configuration provide the opportunity to systematically investigate polymerization kinetics and thermodynamics as well as structure-properties relationship for the resulting poly(thioether-alt-ester)s. The strategic positioning of α-, γ-, and δ-substituents coupled with stereoregular chain architectures and stereocomplex formation enables wide-range modulation of the polymer's thermal and mechanical properties. A(hard)-B(soft)-A(hard) triblock thermoplastic elastomers with good mechanical performance and elastic recovery were also created by sequential polymerization. Of note, these polymers can be chemically recycled by either ring-closing depolymerization or alcoholysis, with high monomer regeneration efficiency. The systematic investigation of substitution effects and structure-property relationships in this work provides a molecular blueprint for designing novel chemically recyclable polymers with high performance.