Mechanically Robust, Biocompatible and Durable Phema-Based Hydrogels Enabled by the Synergic Effect of Strong Intermolecular Interaction and Suppressed Phase Separation

While the poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel is highly biocompatible and stable, its actual application for soft-tissue replacement is severely limited due to the poor mechanical properties. Herein, we develop a facile strategy to construct PHEMA-based hydrogels with the highest strength and toughness ever reported. Our strategy relies on introducing robust coordination interactions to suppress phase separation of PHEMA chains from aqueous solution, thereby inducing a homogeneous network. The homogeneous network can avoid stress concentration, and the robust coordination crosslinking can effectively dissipate energy and maintain network elasticity simultaneously. The synergistic effect of these two factors imparts the hydrogels with exceptionally high tensile strength (3.44 MPa), elastic modulus (14.22 MPa) and toughness (4.17 MJ/m 3 ), which are 22.7, 43.1 and 24.2 folds higher than those of pure PHEMA hydrogels, respectively. Such mechanical properties are comparable to human nasal and auricular cartilages. Moreover, the hydrogels manifest outstanding self-recovery properties and fatigue resistance, which is a prerequisite for long-term and sustainable use. Importantly, our strategy does not sacrifice excellent biocompatibility and stability of PHEMA hydrogels, as demonstrated by in vitro cell experiments and in vivo animal experiments. These PHEMA-based hydrogels with the combination of excellent mechanical properties, fatigue resistance and biocompatibility can therefore be considered a promising candidate material for replacement of diseased or damaged nasal and auricular cartilages