Stretchable Hydrogels with Low Hysteresis and High Fracture Toughness for Flexible Electronics.

Stretchable materials, especially hydrogels, are emerging in various fields recently. Many applications demand low hysteresis and high fracture toughness of the materials to be used under dynamic mechanical loads. Herein, the authors report a hydrogel with high fracture toughness and low hysteresis through using a strong metal coordination bond and relatively high crosslinking density. This design allows the sacrificial bond to remain intact under normal operation, while fracturing to dissipate mechanical energy in the fracture zone to prevent propagation of the cracks. The obtained hydrogel exhibits a low hysteresis (≈1.5%) and a high fracture toughness (≈2,164 J m -2 ). Moreover, the hydrogel possesses a high fatigue threshold of ≈141 J m -2 and a reasonable conductivity. This study provides a worth-adopted approach to synthesize hydrogels with low hysteresis and high fracture toughness.