Autonomous self-healing and superior tough polyurethane elastomers enabled by strong and highly dynamic hard domains

Abstract

Self-healing materials show exceptional application potential for their high stability and longevity. However, a great challenge of the application of self-healing materials is the tradeoff between mechanical robustness and room temperature self-healing. In order to address this tradeoff, inspired by the characteristic that small molecules of living organisms self-assemble into large protein molecules by non-covalent interactions, we constructed polyurethane with highly dynamic and strong hard domains composed of dense hydrogen bonds and π–π interactions between the phenylurea groups at the end of the side chain. The prepared elastomer (PU-HU₂-60) exhibits exceptional tensile performance (tensile strength is 18.27 MPa and ultimate elongation is 904.6%) and crack tolerance (fracture energy is 57.78 kJ m⁻²), surpassing those of most room temperature self-healing materials. After being damaged, the dynamic change process of hydrogen bonds and π–π interactions enables the elastomer to show a high self-healing efficiency of 92.15% at room temperature. Using molecular dynamics (MD) simulations and experiments, we verified that hydrogen bonds and π–π interactions promote the formation of hard domains and the autonomous self-healing of elastomers. The prepared elastomers can also be recycled and they showed ultra-high and restorable adhesion between metals. This work demonstrates a new strategy to balance the mechanical and self-healing properties of elastomers to expand their practical applications such as metal adhesives.