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

Conventional hydrogels typically exhibit limited elastic ranges due to heterogeneous crosslinking and restricted chain mobility. Achieving both ultraplasticity and hyperelasticity within the same hydrogel is challenging. Herein, we developed a zwitterionic hydrogel (PSM) based on a single poly ([2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide) (PSBMA). The hydrogel exhibits a reversible in situ transition from an ultraplastic state (PSM2M, manual tensile strain (λ) ~ 120000%) to a hyperelastic state (PSM6M, λ = 1200%, with full recovery within 2–10 s) by modulating chain conformation from free to entangled states through electrostatic and hydrophobic interactions. During the process, the PSM exhibits broadly tuneable mechanical properties with modulus of 700 Pa – 2 MPa and toughness of 15 – 8000 kJ/m3. Thus, this hydrogel provides adaptable mechanical responses and can accurately replicate the diverse mechanical properties of biological tissues, offering an option for materials used in cell and tissue engineering. It is useful to be able to determine the changes a material has undergone, but this is challenging in synthetic systems. Here, the authors report the development of a hydrogel materials conditioned by swelling, allowing determination of exposure to heat and salt by nucleation changes.