Fig. 4: Fracture and energy dissipation of hydrogels.

a The s-s curves of the as-prepared LC/MC/HC hydrogels and slightly-dehydrated LC hydrogels (\({\phi }_{w}\) = 70%) by pure shear tests. The slightly-dehydrated LC hydrogel exhibits larger modulus, fracture stretch, strength, and work of fracture. b The fracture toughness of LC/MC/HC hydrogels with various \({\phi }_{w}\) values measured by pure shear tests. Data are presented as mean values +/− SD (n\(\ge\)3). c The fracture stretches for uncut samples (the plain bars) and precut samples (the patterned bars) of LC/MC/HC hydrogels with various \({\phi }_{w}\) values. Data are presented as mean values +/− SD (n\(\ge\)3). d The snapshots of a slightly-dehydrated LC hydrogel (\({\phi }_{w}\) = 70%) under various deformation. The crack does not grow at a stretch ratio of 20. e The s-s curve in a loading-unloading cycle at a strain rate of \(\dot{\varepsilon }\) = 0.1 s⁻¹. The LC hydrogels show larger hysteresis loops. f The hysteresis ratios of LC/MC/HC hydrogels with various \({\phi }_{w}\) values measured by uniaxial tension tests. Data are presented as mean values +/− SD (n\(\ge\)3). g Four families of PAAm hydrogels are plotted on the toughness-modulus plane. The slightly-dehydrated LC hydrogels by the current strategy, with \({\phi }_{w}\) ranging from 65% to 87%, break the toughness-stiffness conflict, while the other strategies did not.