Topologically entangled zwitterionic hydrogels with reversible in situ transitions between ultraplastic and hyperelastic states

Elastoplastic materials with self-evolving ability can exhibit specific elastic or plastic responses to large strains, whereas hydrogels typically behave as elastomers with a low elastic range due to the nonuniform crosslinking structure and restrictions among cross-networks. Achieving both ultraplasticity and hyperelasticity within the same hydrogel has not been previously reported. In this study, a single-component hydrogel is developed that can reversibly transition in situ from ultraplasticity (ultralong plastic deformation, strain (λ) ~ 120000%) to hyperelasticity (λ = 1200%, with full recovery within 2–10 seconds after stretching) by modulating molecular chain conformation and network topology from free to entangled state through differences in electrostatic and hydrophobic interactions. The transformation can be regulated by adjusting internal system parameters, such as the in situ concentrations of polymers and ions. During the transformation process, the hydrogel exhibits a broad range of tuneable mechanical properties, including a modulus (E) ranging from 700 Pa to 2 MPa and a toughness (Γ) varying between 15 and 8000 kJ/m³. Additionally, this hydrogel demonstrated exceptional fatigue resistance and damage tolerance, with a fatigue threshold (Gi) reaching 1050 J/m². The hydrogel with self-evolving ultraplasticity-to-hyperelasticity can provide flexible mechanical responses, and can extensively simulate the mechanical properties of diverse biological tissue matrices, thereby offering a superior option for materials used in cell and tissue engineering.