Strengthening and stiffening in swollen polyampholyte hydrogels

(Size: 5 cm height × 13 cm width). [Display omitted] •Developing a modified polyampholyte hydrogel with a swelling-strengthening behavior.•Hydrogel exhibiting high elastic modulus (18.5 MPa) and tensile strength (1.85 MPa).•Providing a simple pathway for achieving strong and stiff swollen hydrogels. Hydrogel networks are usually diluted upon swelling, weakening their mechanical performance. The mechanical weakness limits their practical applications. Herein, we report a modified polyampholyte (PA) hydrogel with a swelling-strengthening behavior via a secondary equilibrium strategy, based on the synergy of ionic and metal–ligand bonds in the network by introducing Zr4+ ions. Swelling and mechanical properties of the hydrogels are investigated, and the structure–property relationship is discussed. The modified PA gel possesses 18.5 MPa Young’s modulus and 1.85 MPa tensile strength, highly surpassing the original PA gel. This work provides a simple route to achieve strong and stiff swollen hydrogels.