Salt Crystallization-InducingStrong and Tough Hydrogels

Research on salt-mediated hydrogel structure and property modulation often neglects the potential effects of salt crystallization. Here, we leverage the crystallization of sodium phytate during poly(vinyl alcohol) (PVA) hydrogel dehydration to induce the formation of dendritic crystals composed of PVA nanofibers. These crystals address network defects and act as robust “crosslinking blocks,” thereby strengthening the hydrogel matrix. Concurrently, enlarged secondary ordered domains bolster the amorphous phase, serving as buffers to optimize load transfer and distribution. This strategy yields a reinforced PVA hydrogel with high mechanical properties: a fracture strength of 29.12 ± 1.53 MPa, an elastic modulus of 58.91 ± 2.55 MPa, a toughness of 164.88 ± 1.96 MJ m–3, and a fracture energy of 97.45 ± 5.49 kJ m–2. Given the ubiquity of salt crystallization, this approach offers significant practical benefits and broad application potential for controlling hydrogel structure and properties.