Mechanically Robust, Environmentally Resistant, and Piezoionic Polyzwitterionic Composite Eutectogels Based on Polysaccharide Complexation Strategy for Stable Voltage Output, Energy Storage, and Strain Sensing

Polyzwitterionic gels with both positively and negatively charged groups have attracted attention because of their excellent biocompatibility and high water absorption. However, insufficient mechanical properties due to fragile cross-linked networks and low stability due to aqueous solvents are still prominent. In this study, a deep eutectic solvent (DES) was introduced into the sulfobetaine zwitterionic monomer DMAPS([2-(methacryloyloxy)ethyl]dimethyl-(3-sulphonatopropyl)ammonium hydroxide) system. Based on the complexation strategy of sodium alginate (SA) polysaccharide, a polyzwitterionic network skeleton was constructed to prepare a composite eutectogel with high strength, environmental resistance, and high conductivity. The presence of DES enables polyzwitterionic gels to obtain excellent environmental stability at high and low temperatures. Notably, the introduction of SA significantly enhanced the tensile strength, Young’s modulus, and toughness of the eutectogel without affecting the high transparency. This is attributed to the network of hydrogen bonding and electrostatic interactions within the matrix–filler constructed by the hydroxyl-rich and charged groups of SA in the presence of calcium ion complexation. At the same time, the polyzwitterionic network skeleton provides abundant binding sites for ion migration, which endows the eutectogels with excellent ionic conductivity (0.13–0.48 S·m^–1). Thanks to its internal porous structure, the composite eutectogel can provide a stable piezoionic output and be used for pressure response and powering LED lights. In addition, supercapacitors and strain sensors assembled on the basis of composite eutectogels proved their potential for applications in areas such as energy storage and human motion monitoring. In conclusion, this study provides important guidance for the construction of biomass ionic network skeletons and the development of high-performance ion-conducting materials.