A Polycondensation–depolymerization strategy enables closed-loop recyclable polyoxalates <i>via</i> ring-opening polymerization of six-membered cyclic oxalates

Developing a simple and efficient strategy for the scalable production of closed-loop recyclable polymers from abundant and low-cost feedstocks remains highly desirable. Here, we present a facile "polycondensation-depolymerization" approach for the large-scale synthesis of cyclic 1,2-alkylene oxalates, which undergo controlled ring-opening polymerization to yield high-molecular-weight polyoxalates. The influence of alkyl substituents on the polymerization kinetics, thermodynamics, and material properties was systematically investigated. Remarkably, these polyoxalates can be chemically recycled to their pristine monomers with high purity and yield using sodium glycolate as a catalyst. Furthermore, the polyoxalates exhibit excellent marine degradability, providing a promising strategy to tailor the seawater degradation behavior of polyesters through copolymerization.