Crystallization/Precipitation Driven Nonequilibrium Ring‐Opening Polymerization of Thiovalerolactone Toward Closed‐Loop Recyclable Polythioester with Excellent Barrier Properties

Abstract The development of closed‐loop recyclable polymers with comparable performances with commodity plastics remains as a challenge to establish a circular plastic economy. In this contribution, we propose a precipitation/crystallization driven nonequilibrium ring‐opening polymerization of δ‐thiovalerolactone (δTVL) to produce high‐molecular‐weight PTVL in the presence of a strong base/urea binary catalyst. The obtained PTVL exhibits good thermal and mechanical performances as well as superior barrier properties comparable with some commodity plastics. Remarkably, the obtained PTVL can be depolymerized to recover pristine monomer with a high yield and purity by distillation from a commodity plastic waste mixture without tedious separation, highlighting its great potential as a closed‐loop recyclable packaging material.