Time-Dependent Ambient Aging and Rehydration of PVA-MA Hydrogels: Correlating Water Loss with Electromagnetic Recovery

Poly(vinyl alcohol-methacrylate) (PVA-MA) hydrogels are emerging as reusable testbed for bio-electromagnetic applications, but their long-term stability under ambient conditions remains unclear. We report a quantitative study of time-dependent dehydration and rehydration in PVA-MA hydrogels and its impact on their dielectric and rheological behavior. Samples maintained in deionized water over six weeks showed minimal variation in permittivity and, in three weeks, the mechanical modulus, indicating negligible intrinsic aging. In contrast, hydrogels exposed to ambient air exhibited mass loss and dielectric relaxation consistent with water evaporation and network densification. Remarkably, rehydration in deionized water restored dielectric spectra and viscoelastic moduli to within the standard deviation of continuously hydrated controls after one week. These findings demonstrate that PVA-MA hydrogels undergo reversible physical aging dominated by water-content dynamics rather than chemical degradation, supporting their use as robust, reconditionable polymer systems for long-term electromagnetic and soft-tissue applications.