Composite hydrogels based on deep eutectic solvents and lysine for pressure sensors and adsorption of Fe³

This study explored the preparation of a novel composite hydrogel based on deep eutectic solvent (DES) with lysine (Lys) and its application in pressure sensing and Fe³⁺ adsorption. DES was synthesized from acrylamide (AM) and urea (U) as hydrogen bond donors (HBD) with choline chloride (ChCl) as hydrogen bond acceptor (HBA), and Lys was used as a functional filler, and Lys/P(AM-U-ChCl) composite hydrogels were successfully prepared by frontal polymerization (FP) method. The structure of the hydrogels was characterized in depth using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The effects of Lys content on the mechanical properties, pH-responsive behavior, pressure-sensitive properties, and Fe³⁺ adsorption capacity of the hydrogels were further analyzed. It was found that the introduction of Lys significantly improved the compressive and pressure-sensitive properties of the hydrogels. The composite hydrogels exhibited excellent swelling equilibrium rates at different pH values. The capacitance change of the hydrogel with 0.5 wt% Lys at 200 g pressure was 2.12-fold higher than that of the hydrogel without Lys addition, and the adsorption efficiency of the hydrogel for Fe³⁺ was greatly enhanced. This study provides a new idea for the functionalized design of composite hydrogels and demonstrates their great application prospects in high-performance pressure sensors and heavy metal ion adsorption.