Thermo-reversible DA bonds-based polyurethanes with both excellent comprehensive mechanical property and remarkable room temperature self-healing capability

Thermal reversible Diels-Alder reaction (DA) is widely used to prolong the lifespan of polyurethane and cut down maintenance costs. However, it requires high temperature to repair damages with limited repair efficiency. In this study, a novel dual dynamic covalent bonds-based self-healing polyurethane (SPU-DA) with remarkable room temperature repair capability is fabricated by incorporating a custom-made chain extender containing disulfide bonds into DA bonds-based polyurethane. The resultant SPU-DA exhibits good comprehensive mechanical properties, and the tensile strength and elongation at break can reach 9.87 MPa and 636 %, respectively. Meanwhile, cracks emerged in SPU-DA can be repaired efficiently by the synergetic actions of the exchange of disulfide bonds, dissociation of hydrogen bonds, and the thermal reversible DA reaction. Furthermore, SPU-DA can be repaired multiply and the self-repair efficiency reaches 90.1 % at 120 degrees C and maintains a considerable 71 % even after three damage-repair cycles. More importantly, the as-prepared SPU-DA demonstrates the ability to heal at lower and room temperature. The repair efficiency of 41.3 % is achieved even at room temperature for 24 h without any additional treatment. Therefore, this research offers an ideal method to balance the rigidity provided by Diels-Alder bonds and the self-healing efficiency offered by the disulfide bonds. SPU-DA will be a potential functional material to be utilized in a wide range of engineering applications.