Cross-linked polyurethane is widely used as a high-performance elastomer, owing to its excellent mechanical properties and superior durability. However, a critical challenge remains in integrating its in-use stability with dynamic behavior during recycling. Herein, supertough and multirecyclable cross-linked polyurethanes were developed through the cooperation of supramolecular chain extenders and noncovalent cross-linkers. This strategy, leveraging both a robust covalent network and a high-density hydrogen-bonded network, achieves enhanced mechanical strength and solvent resistance for in-use stability. The rapid and reversible dynamic exchange of the high-density hydrogen-bonded network endows polyurethane with excellent processability and recovery, exhibiting a distinct macroscopic flow at an elevated processing temperature. The resulting material exhibits a remarkable tensile stress of 50 MPa, an exceptional toughness of 300 MJ/m3, and maintains above 96% recycling efficiency after six recycling cycles, significantly outperforming conventional polyurethanes. Therefore, the integration of in-use durability and dynamic recyclability in cross-linked polyurethanes is successfully achieved, providing a promising pathway toward sustainability goals for cross-linked polymers with tailor-made mechanical properties.
Lai et al. (Thu,) studied this question.