Robust Hydrogel with Significant Swelling Resistance via the Synergy of Hydrogen Bond Regulation and Ionic Cross-linking

The development of high-performance hydrogels has received much attention, but the simple and cost-effective preparation of hydrogels with high mechanical strength and excellent swelling resistance remains a challenge. In this study, a facile and green strategy was proposed to construct a polyvinyl alcohol/chitosan-based (PVA/CS-based) hydrogel with high mechanical strength and superior swelling resistance. By introducing tannic acid (TA), a natural polyphenol, and forming hydrogen bonding cross-linking with the polymer chains through solvent regulation, as well as by ionic cross-linking and salting-out effects further induced through sodium citrate solution immersion, a strong and homogeneous multiple physical cross-linking network was formed, which endowed the resulting hydrogel with excellent mechanical and swelling resistance performance. For the hydrogel with PVA, CS, and TA in the mass ratio of 5:1:5, the tensile strength was up to 8.22 MPa, and the tensile strength retention was up to 96% of the original value after swelling equilibrium. In addition, our hydrogel can be attached in situ to various substrates and enabled wet adhesion. The easy scale-up and energy-saving features made our method highly promising for the preparation of high-performance hydrogels for many advanced applications.