Ultra‐Stretchable and Low‐Temperature Adaptive Conductive Hydrogels Based on the Hofmeister Effect

Conductive hydrogels have attracted significant interest due to their potential applications in human motion monitoring, health diagnostics, and beyond. However, integrating ultra‐stretchability, strain sensitivity, and freeze resistance into hydrogel strain sensors remains a challenge. In this study, polyacrylamide/polyvinyl alcohol/quaternized chitosan (PAM/PVA/QCS, PPQ) hydrogel was fabricated via a one‐pot in situ free radical copolymerization process, followed by freeze–thaw treatment and immersion. The hydrogel matrix consists of acrylamide (AAm) chemically crosslinked by N, N′ ‐methylenebisacrylamide (MBA) and PVA, forming a physically crosslinked hydrogen‐bonded network, with QCS serving as the reinforcing phase. Under the Hofmeister effect, introduction of citrate ions (Cit 3− ) as salting‐out ions facilitates hydrogen bond formation through amino groups (‐NH 2 ) in PAM, while establishing electrostatic interactions with the quaternary ammonium groups in QCS. Concurrently, Cit 3− anions regulate the hydration chemistry of PVA by adsorbing water molecules within the polymer chains. The ionic hydrogel demonstrates a maximum elongation of 1,014% and ionic conductivity of 1.43 S/m while maintaining stable performance at −20°C. It exhibits exceptional mechanical properties, frost resistance, and electrical conductivity. Notably, when deployed as a flexible strain sensor, the hydrogel achieves outstanding tensile strain sensitivity (GF = 1.812), rapid response, and stable electrical signal output over 500 cyclic loading‐unloading tests.