DesigningClosed-Loop Recyclable Thermosetting PolyurethanesUtilizing Polyfunctional Acetal-Containing Polyols

Polyurethane thermosets are a key component of high-performance plastics, renowned for their outstanding and customizable thermal and mechanical properties, making them ideal for a wide array of applications. Yet, existing recycling methods for conventional polyurethanes are based on harsh conditions that yield a complex mixture of molecules and oligomers, which are difficult to isolate, rendering chemical recycling unfeasible. This underscores the urgent need for innovative solutions to enhance recyclability of polyurethane materials, supporting the transition to a circular economy. To address these challenges, we have developed several polyfunctional acetal polyols, which were synthesized under solvent-free conditions using heterogeneous catalysts and incorporated into polyurethane thermosets. This integration yielded an array of recyclable thermosetting polyurethanes that exhibited a broad range of chemical and mechanical properties, matching the performance of traditional polyurethanes, including high thermal stability and excellent mechanical strength. Notably, these materials also displayed remarkable stability in water and various organic solvents. The depolymerization and recycling of thermosets were achieved through hydrolysis without utilization of organic solvents, allowing for the recovery of the original monomers and primary building blocks in high yield and purity. Our work presents a promising pathway toward more sustainable thermosetting materials, achieving recyclability without compromising thermal and mechanical performance.