Nature-inspired semi-IPN hydrogels with tunable mechanical properties and multi-responsiveness

Tough hydrogels with high mechanical properties and multi-responsiveness have attracted increasing attention in recent decades. Herein, we report a series of tough semi-interpenetrating hydrogels (poly(N-acryloyl-2-glycine)/polyvinyl alcohol hydrogels, PACG/PVA hydrogels, i.e., PAP hydrogels) comprised of natural amino acid-derived polymers PACG within physical crosslinked PVA. The PAP hydrogels demonstrated tunable mechanical properties, with tensile breaking stress (σb), breaking strain (εb), Young's modulus (E) and toughness (Wb) of 0.14–1.38 MPa, 420–530%, 15–106 kPa and 21–308 kJ m−3, respectively. Based on the ionizable side chains containing amino and carboxyl groups of PACG, the PAP hydrogels exhibited a significant response to salt and pH as well as self-healing, self-rolling, and reconstruction ability. Thus, the obtained hydrogels can act as promising candidates in soft actuators, flexible sensors, etc.