Self-healing and recyclable polymer materials are being developed through extensive investigations on noncovalent bond interactions. However, they typically exhibit inferior mechanical properties. Therefore, the present study is aimed at synthesizing a polyurethane–urea elastomer with excellent mechanical properties and shape-memory-assisted self-healing behavior. In particular, the introduction of coordination and hydrogen bonds into elastomer leads to the optimal elastomer exhibiting good mechanical properties (strength, 76.37 MPa; elongation at break, 839.10%; toughness, 308.63 MJ m⁻³) owing to the phased energy dissipation mechanism involving various supramolecular interactions. The elastomer also demonstrates shape-memory properties, whereby the shape recovery force that brings damaged surfaces closer and facilitates self-healing. Surprisingly, all specimens exhibite clustering-triggered emission, with cyan fluorescence is observed under ultraviolet light. The strategy reported herein for developing multifunctional materials with good mechanical properties can be leveraged to yield stimulus-responsive polymers and smart seals.

Smart materials that integrate multiple functions into one system broaden the application range of materials, but there are still challenges to obtaining a material with excellent shape memory, toughness, and self-healing. Herein, we prepared a high-strength and high-toughness thermosetting shape memory polyurethane with the aid of a chain extender containing dual dynamic covalent bonds, which showed excellent self-healing effects. Compared with PUs that contain only disulfide bonds or imine bonds, elastomers with dual dynamic covalent bonds possess superior mechanical properties. The maximum tensile strength and breaking elongation of elastomer PU-SS-CN-12.5% are 33.70 ± 4.25 MPa and 1137.72 ± 81.29%, respectively, and it also presents a high toughness of 197.35 ± 35.33 MJ m⁻³. Surprisingly, PU-SS-CN-12.5% demonstrates excellent low-temperature flexibility, and can deform arbitrarily at −50 °C. In addition, all PUs exhibit shape memory properties, which can be fixed at −60 °C. The shape fixation rate is approximately 90%, and they can recover immediately at 60 °C; the shape recovery rate is approximately 95%. The elastomers also have the capacity of self-healing resulting from the existence of dynamic covalent bonds. The healing efficiency of PU-SS-CN-15% is close to 100%, and it can also be recycled by hot-pressing at 120 °C and 3 MPa for 24 h. Due to its excellent properties, it might have significant potential as a low-temperature smart material.

Recently, the focus of materials research has shifted towards intelligent materials and structures with customizable properties and stimulus-responsive functions. Here, A recyclable thermosetting epoxy resin with self-reported wear and customizable friction is achieved through the dynamic and reversible molecular structure design. The epoxy vitrimer displays exceptional mechanical properties with young's modulus of 2.3 GPa, elongation at break of 7.1%, and tensile strength of 79.25 MPa. Based on the reversible exchange of dynamic covalent bonds, the epoxy vitrimer can be fully recovered through hot pressing without the need for additional adhesives or catalysts, and even self-healing can be achieved. Furthermore, by utilizing the reversibility of dynamic covalent bonds, nanofillers (GO and PTFE) with specific tribological properties are incorporated into the recovery process to achieve customizable friction coefficients and wear rates. The self-reporting characteristics of wear based on sulfur radical are realized through exploiting the dynamic nature of disulfide bond. The correlation between wear time and wear state is investigated. Molecular structure design of epoxy based on dynamic covalent bonds has resulted in a versatile thermosetting material with self-reporting and customizable friction properties, ideal for sustainable engineering and friction fields. This enables intelligent manufacturing while reducing resource waste.