Some rubbers and gels self-repair.If the two fracture surfaces are pressed against each other, they will be fused and reused.Within the tissues of these self-healing materials, high molecular weight substances, in which small molecules are connected for a long time in one dimension, are actively thermally moving.Therefore, the polymer chains intrude into each other and become entangled between the pressed fracture surfaces to regenerate the tissue indistinguishable from the undamaged site.In contrast, polymer chains that make up hard materials such as glass are so slow in thermal motion that they cannot reconstruct their pre-breakage texture.

　The glass developed this time is made of a polymer material called "polyether thiourea".This polymer substance was designed as an intermediate for synthesizing a polymer substance named "molecular glue" that strongly adheres to the surface of biomolecules.In the process, I noticed that while having a hard, silky-feeling surface, they exhibit a special property of fusing when the fracture surfaces are pressed against each other.When the repair ability of this material was evaluated using a device capable of precisely controlling the temperature and compressive stress, the mechanical strength recovered to the same value as before the breakage after several hours of crimping at room temperature.

　We synthesized multiple polymer substances with a self-repairing structure and evaluated their mechanical strength and repair ability.As a result, it is necessary to use a relatively short polymer chain for high-density cross-linking with hydrogen bonds, and the structure does not induce crystallization and facilitates hydrogen bond exchange. Was found to be important for achieving local motility and high mechanical strength.

Paper information:[Science] Mechanically robust, readily repairable polymers via tailored noncovalent cross-linking