Metal welding-inspired phase change self-healing strategy applied to high-modulus hydrogel composites

The self-healing efficiencies of polymers are inversely proportional to their modulus, as the recovery of the polymer network heavily relies on the mobility of polymer chains. Therefore, reinvigorated by the metal welding, we have developed S-PAM-SA-x supercooling hydrogels, consisting of polyacrylamide hydrogel networks and inorganic CH3COONa & sdot;3H2O phase change materials. Subsequently, rigid self-healing H-PAM-SA-x composites were achieved via self-actuated crystallization-related phase change from the supersaturated hydrogels, resulting in a significant enhancement in mechanical properties. Notably, Young's modulus experienced an astonishing increase from 0.07 to 387.1 MPa. The H-PAM-SA-130 % composites demonstrated satisfactory self-healing performance based on the phase change of melting and crystallization, as the dominant mechanical carrier was found to be the crystal lattice rather than the PAM network. Leveraging the reversible nature of melting and crystallization, the same position can undergo multiple healing cycles without compromising self-healing efficiencies. Moreover, this distinctive dynamic phase change process significantly expands the range of functional applications, encompassing self-healing, adhesion, and patterns' replication among others.