Controlling Structures and Properties of NaCl-Containing Alginate/Polyacrylamide Tough Hydrogels via a One-Pot...

Hydrogels have garnered significant interest as soft materials due to their flexibility, high water content, and biocompatibility. Alginate/polyacrylamide (Alg/PAAm) double-network (DN) hydrogels are particularly promising for wearable electronics, strain sensors, and soft electrolytes owing to their toughness and structural stability. However, the conventional soaking method for ion incorporation requires prolonged diffusion and often generates internal concentration gradients, leading to structural heterogeneity. This study introduces a one-pot strategy that incorporates NaCl directly into the precursor solution, enabling simultaneous gelation and ion integration. Elemental analyses indicate a more spatially consistent Na and Cl distribution across the examined surface regions of the one-pot hydrogel compared with the soaking-derived hydrogel. Furthermore, NaCl incorporation influences network formation primarily by modifying the ionic environment and hydration state rather than by creating new covalent bonds. The resulting hydrogels exhibit a composition-dependent trade-off between mechanical reinforcement and ionic transport. NaCl concentrations of 1.5-2.0 wt% provide a favorable balance among stiffness, strength, and deformability, whereas ionic conductivity reaches its maximum at 12.5 wt%. These findings indicate that no single NaCl concentration is optimal for all performance requirements and that the salt content should instead be tailored to the intended application.