An Amphiphilic Entangled Network Design Toward Ultratough Hydrogels.

Hydrogels find important roles in biomedicine, wearable electronics, and soft robotics, but their mechanical properties are often unsatisfactory. Conventional tough hydrogel designs are based on hydrophilic networks with sacrificial bonds, while the incorporation of hydrophobic polymers into hydrogels is less well understood. In this work, a hydrogel toughening strategy is demonstrated by introducing a hydrophobic polymer as reinforcement. Semicrystalline hydrophobic polymer chains are "woven" into a hydrophilic network via entropy-driven miscibility. In-situ-formed sub-micrometer crystallites stiffen the network, while entanglements between hydrophobic polymer and hydrophilic network enable large deformation before failure. The hydrogels are stiff, tough, and durable at high swelling ratios of 6-10, and the mechanical properties are tunable. Moreover, they can effectively encapsulate both hydrophobic and hydrophilic molecules.