Design of self-healing and self-restoring materials utilizing reversible and movable crosslinks

Self-healing materials have attracted attention due to their ability to regain their structure and function after damage. In recent years, significant progress has been made in achieving various functions through supramolecular chemistry. This review describes an overview of the strategies used to prepare self-healing and self-restoring materials utilizing reversible and movable crosslinks. Reversible crosslinks, consisting of noncovalent bonds, can reversibly undergo repeated cleavage and reformation. Therefore, self-healing can be achieved by effectively regenerating reversible crosslinks between polymeric chains. Reversible crosslinks exploit many kinds of dynamic covalent bonds and noncovalent bonds, such as hydrogen bonds, metal coordination bonds, ionic interactions, π-π stacking, van der Waals forces, and hydrophobic interactions. Movable crosslinks exhibit self-restoring properties. Self-restoring materials can regain their original shape and mechanical properties after a cycle of loading and unloading external stress. Movable crosslinks consist of polymer chains that penetrate macrocyclic units and have self-restoring properties due to their sliding motion along the polymeric chains. In addition, multiple reversible cross-links produce synergistic effects to simultaneously achieve high toughness and effective self-healing. We believe that self-healing and self-restoring materials will play a substantial role in realizing a sustainable society.