Dehydration-Induced Chain Entanglement for Tough, Low-Hysteresis, Double-Network Hydrogels

Highly entangled hydrogels achieve outstanding mechanical properties via dense physical entanglements as cross-links. However, their fabrication usually relies on processing concentrated precursor solutions, which limits their scalability and practical application. This study introduces a facile dehydration-induced entanglement approach to fabricating double-network hydrogels with programmable entanglement density. Initially, a single-network hydrogel is synthesized via UV polymerization of a precursor solution containing acrylamide (AAm), carboxymethyl chitosan (CMCS), cross-linkers, and a photoinitiator. Subsequent controlled dehydration of the hydrogel drives spontaneous polymer chain condensation, enabling dense intermolecular entanglements that are stabilized through secondary cross-linking of CMCS chains. The resulting hydrogel achieves a tensile strength of 798 kPa and a toughness of 1.98 × 10³ J·m^-2, representing 11-fold and 10-fold enhancements over conventional double-network hydrogels, respectively. These properties stem from the synergistic interplay of covalent networks and physical entanglements, that enables an optimal balance between high modulus and low hysteresis. This optimized stiffness-toughness profile renders the hydrogel an attractive candidate for applications in flexible electronics, advanced wound dressings, and controlled drug delivery systems. This methodology provides a robust platform for designing high-performance hydrogels without complex processing constraints.