Improved tough and conductive polyacrylamide/sodium alginate dual-network hydrogel by ionic liquid for flexible capacitor and multifunctional sensor

The utilization of hydrogels in the domain of flexible capacitors (FCs) and multifunctional sensors (MSs) has attained considerable prevalence. However, balancing the various properties of such versatile hydrogels remains a major challenge. In the present study, a novel xIL/PAM/SA dual-network hydrogel composed of polyacrylamide/sodium alginate (PAM/SA) and an ionic liquid (IL) 1-Butyl-3-methylimidazolium hydroxide ([BMIM][OH]) is proposed. The OH⁻ in the IL inhibits the protonation of -NH₂ groups on the polymer chain and avoids the reduction of the number of hydrogen bonds in the system due to the formation of -NH³⁺, thus enhancing the strength of the network. The results showed that the series of tough hydrogels had high tensile strength (386.64 kPa), elongation at break (338.16%), and toughness (670.83 kJ/m³). Moreover, the rich functionality such as capacitive performance (198.5 mF/cm²), water retention performance (LR = 25.4%), temperature sensitivity (GF = 2.12), and strain sensitivity (GF = 4.56), make it have broad application potential. This work improves the traditional dual-network hydrogels by ionic liquids (ILs) and provides a feasible idea for the design of multi-functional tough conductive hydrogels.