Polyacryloyl hydrazide incorporation into ionic hydrogels improves toughness, elasticity, self-healability, adhesive & strain sensing properties

Abstract

Development of hydrogels possessing toughness, extensibility, resilience, and self-healability together is challenging. Herein, we demonstrate that incorporation of polyacryloyl hydrazide (PAHz) substantially improves the mechanical properties and incorporates self-healing, adhesive and strain sensing properties in ionic hydrogels. For example, the compressive strength (80 MPa), tensile strength (0.7 MPa) and fracture energy (∼902 J m⁻²) values of polyacrylamido-2-methylpropanesulfonic acid (PAMPS)-based hydrogels prepared by adding ∼6.5 wt% of PAHz increased by 73, 18 and 451 times, respectively, compared to that of the control. The presence of PAHz in the PAMPS hydrogel matrix provided additional physical crosslinking in the form of SO³⁻⋯H₃N⁺–ionic interaction and created network reinforced zones that dissipated energy under stress and improved the toughness of the hydrogel system. At low water content (≤10 wt%), the compressive strength further increased to an unprecedented value of 0.4 GPa while maintaining adequate compressibility (92%). The PAHz incorporated-hydrogels exhibit an impressive adhesive strength value of up to 2.8 MPa on glass substrates, quick autonomous self-healing ability and strain sensing properties with a gauge factor value of up to 0.7. This general one-pot strategy may be extended to other ionic hydrogel systems for the improvement of mechanical properties.