Toughening of anti-freezing ionic hydrogels with Zr4+-dicarboxylic acid coordination complex for low temperature sensing applications

[Display omitted] •Zr4+-dicarboxylic acid coordination complexe-crosslinked hydrogels with enhanced mechanical properties are prepared.•The ionic hydrogels show excellent anti-freezing properties and high ionic conductivity with 8.45 S/m.•The hydrogel sensors can realize continuous and stable monitoring of grasping objects at low temperature of −30 °C. Conductive hydrogels are widely used in electronic skin, wearable sensing devices, human–machine interfaces, and soft robots because of their high elasticity, biocompatibility, and conformability in interfacial contact. However, hydrogels lose electrical conductivity and flexibility due to water crystallization at low temperatures, which severely limits their applications in the frigid regions. In this study, we propose to design a metal–ligand ionic hydrogel (PAASP-Zr-LiCl) through the formation of a stable coordination bond between the dicarboxylic acid group monomer poly(N-acryloyl aspartic acid) (PAASP) and zirconium ion (Zr4+). Zr4+–COO- metal-coordination complex as physical cross-linking points of the network can effectively improve the mechanical properties of hydrogels. By introducing lithium chloride (LiCl), the hydrogel obtained excellent anti-freezing properties (crystallization temperature