Extreme Toughening of Conductive Hydrogels Through Synergistic Effects of Mineralization, Salting-Out, and Ion Coordination Induced by Multivalent Anions.

Developing conductive hydrogels with both high strength and fracture toughness for diverse applications remains a significant challenge. In this work, an efficient toughening strategy is presented that exploits the multiple enhancement effects of anions through a synergistic combination of mineralization, salting-out, and ion coordination. The approach centers on a hydrogel system comprising two polymers and a cation that is highly responsive to anions. Specifically, polyvinyl alcohol (PVA) and chitosan quaternary ammonium (HACC) are used, as PVA benefits from salting-out effects and HACC undergoes ion coordination with multivalent anions. After just 1 h of immersion in an anionic solution, the hydrogel undergoes a dramatic improvement in mechanical properties, increasing by more than three orders of magnitude. The optimized hydrogel achieves high strength (26 MPa), a high Young's modulus (45 MPa), and remarkable fracture toughness (67.3 kJ m), representing enhancements of 860, 3200, and 1200 times, respectively, compared to its initial state. This breakthrough overcomes the typical trade-off between stiffness and toughness. Additionally, the ionic conductivity of the hydrogel enables reliable strain sensing and supports the development of durable supercapacitors. This work presents a simple and effective pathway for developing hydrogels with exceptional strength, toughness, and conductivity.