Implementing a sulfur-substitution approach toward a high-performance recyclable polythioester

Developing new chemically recyclable polymers is highly demanded for a circular plastic economy. Herein, we implement a sulfur-substitution approach for improving the chemical recyclability and material performance of polycaprolactone (PCL). This thiocaprolactone (tCL) displayed excellent reactivity towards ring-opening polymerization, affording P(tCL) products with high thermal stability (T_d = 330 °C), high air stability, high crystallinity, and outstanding mechanical and transport properties (σ_B = ∼20 MPa, ε_B = ∼600%, PO₂ = 0.38 Barrer) comparable to commercial low-density polyethylene. Impressively, chemical recycling of P(tCL) to its monomer could be accomplished with excellent yield and purity, thus establishing its circular life cycle.