The concept of self-healing originates from the phenomenon of self-healing in biology. Organisms can self-heal from both the molecular level (such as DNA repair) to the macro level (such as the healing of small skin wounds). Inspired by nature, many self-healing polymer materials have been designed and synthesized. They can detect cracks by themselves, and re-fill and repair the cracks through a certain mechanism. Therefore, they can effectively prolong the service life of materials, improve material safety and reduce waste, which has important scientific significance and application value.
After more than twenty years of development, the research on the development of self-healing materials is no longer limited to exploring new types and mechanisms of self-healing materials, but should pay more attention to the industrial application of self-healing materials. To realize the application of self-healing materials, there are two key problems: one is to make the mechanical properties of self-healing materials meet the requirements of practical application. However, at present, the materials with high mechanical strength can not self-heal, while the materials with self-healing capability have low mechanical strength. How to design and synthesize materials with high mechanical strength and excellent self-healing properties is a challenging problem; Second, self-healing materials should have various functions in order to realize their indispensable application in real life and production.
Coordination bond is a special chemical bond. In supramolecular chemistry, coordination is considered to be one of the strongest supramolecular interactions. By selecting appropriate ligands and metals, we can get a moderate strength coordination bond, which is less than covalent bond, but much stronger than non-covalent weak interaction. This 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 coordination bond, the shortcomings of reversible covalent bond and non covalent weak interaction can be overcome. In addition, due to the diversity of coordination center ions and the variability of the number of ligands, the formed metal complexes and coordination cross-linked polymers have many special properties (such as nonlinear optical properties, magnetism, dielectric and catalytic activity). Therefore, through the combination of coordination chemistry and polymer chemistry, we work from two aspects: the design and synthesis of high-strength self-healing materials and the practical application of self-healing materials. Through the careful design of reversible chemical bonds, especially coordination bonds, a series of self-healing materials with high elasticity, rigidity or toughness were obtained. At the same time, self-healing materials are applied to national defense, aerospace, 3D printing, special adhesives, medical external fixation brackets and other fields, laying a good foundation for the further industrialized application of self repairing materials.
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