Self-repairing materials are a new type of smart materials that have emerged in the past ten years. It can realize the detection of the material's own cracks and spontaneously complete the repair of the material, which can prevent the potential damage of the material due to the occurrence of cracks. It has important applications in the fields of aerospace, military industry, bridges, construction, and engineering. In order to pursue high strength and flexibility, traditional materials are usually constructed by irreversible covalent bonds. This covalent bond cannot be rebuilt after it is broken, so it is difficult to repair traditional materials after damage.
Scientists have synthesized a highly elastic self-healing material by designing and synthesizing coordination bonds. In supramolecular chemistry, coordination is generally regarded as one of the strongest supramolecular interactions. By choosing appropriate ligands and metals, a moderately strong coordination bond can be obtained, which is less strong than a covalent bond but much stronger than a non-covalent weak interaction. This kind of coordination bond will have physical (thermal) reversibility or chemical reversibility, so it can be used to construct self-healing materials. At the same time, due to the moderate strength of the coordination bond, it will be able to overcome the shortcomings of reversible covalent bonds and weak non-covalent interactions.
They introduced a ligand called 2,6-pyridinedicarboxamide into the polymethylsiloxane polymer. This ligand can provide multiple coordination sites to coordinate with the metal to obtain multiple different strengths. Coordination bond. The strong coordination bond is adjacent to the weak coordination bond. When subjected to stretching, the weak coordination bond breaks so that energy is dissipated, while the strong coordination bond can still be maintained so that the material does not break, so the material has very good properties. Stretchability, it can be stretched up to 45 times the original length, and it will not break even after the ratio of metal to ligand is changed to 100 times. On the other hand, due to the combination of strong coordination bonds and weak coordination bonds, the coordination structure is highly dynamic, and can be quickly formed spontaneously after being damaged. Therefore, the damaged material can be completely repaired without any external stimulation at room temperature. It can repair spontaneously even at low temperatures (-20 °C).