Hydration-Controlled Charge Transport in Polymer Networks and Hydrogels

Water in soft electrochemical materials is far more than a passive solvent—it directly governs ionic transport, dielectric response, and structural stability. Unlocking the full potential of hydrogel electrolytes requires mastering the delicate interplay between polymer networks, confined water dynamics, and mobile ions. Classical models like Maxwell–Garnett fall short in capturing these complex interfaces; percolation-based frameworks like General Effective Medium (GEM) theory can describe transport transitions, though their parameters remain system-dependent. This review bridges molecular-level hydration phenomena, including non-freezing bound water, organohydrogel hybridization, and thermoresponsive phase behavior, with macroscopic performance metrics across bioelectronics, energy storage, and electronic skin. By integrating percolation physics, molecular design, and quantitative cross-system comparisons across material systems, we provide a roadmap to engineer resilient, high-performance soft electroactive architectures for next-generation technologies.