Design of a Mechanically Tough and Robust Lubricating Hydrogel via an Interpenetrating Hydrophilic–Hydrophobic Polymer Network

Hydrogels show great potential for mimicking human weight-bearing tissues due to their extremely high water content and desirable behavior, including softness and elasticity. However, developing joint cartilage-mimicking hydrogels with both superior mechanical properties and stable lubrication remains challenging. This study presents a self-assembled heterostructure hydrogel approach. A mechanically robust hydrogel with sustained lubrication properties is achieved by incorporating a hydrophilic network into a hydrophobic polyethyl acrylate (PEA) matrix. Two polymer networks interweave at the microstructural level, generating water-rich and water-poor phases. Outstanding load-bearing capacity is achieved by the flexible hydrophilic polymer network efficiently dispersing impact stress into the rigid hydrophobic network. Meanwhile, a hydrated lubricating layer forms on the hydrophilic network's surface, ensuring sustained lubrication. Moreover, the hydrophobic PEA network incorporation limits swelling in the hydrophilic network, imparting exceptionally stable antiswelling properties to the hydrogel. This study demonstrates that the heterostructure hydrogel maintains stable mechanical properties in aqueous solutions while providing lubricity, offering a novel approach to developing biomimetic materials with mechanical robustness and sustained lubricity.