High-Strength, Transparent, and Freeze-Resistant PVA Hydrogel Enabled by Microcrystal Regulation

Hydrogels hold promising potential in biomedical and flexible electronics applications, yet their practical utilization is constrained by insufficient mechanical strength. This study successfully fabricated high-performance transparent anti-freezing polyvinyl alcohol (PVA) hydrogels using a synergistic freeze-thaw/solvent exchange strategy. The hydrogel synthesis involved a two-stage process: utilizing DMSO as the solvent for PVA to promote molecular chain extension, followed by freeze-thaw cycling to induce microcrystalline formation; and structural reinforcement through osmotic pressure-driven bidirectional water-sorbitol exchange in saturated sorbitol solutions. Sorbitol not only acts as a physical crosslinker but also promotes PVA microcrystal formation, both of which enhance the strength of PVA hydrogels. Meanwhile, its strong hydrogen bonding with water suppresses ice crystallization, conferring exceptional freeze resistance to the hydrogel. The optimized hydrogel achieved excellent properties: high tensile strength (16.1 MPa), elongation (767%), toughness (64.9 MJ m -3 ), visible transmittance (80%), freeze resistance (-60°C), and excellence biocompatibility (L929 cells viability >83%). This hydrogel system exhibits remarkable application potential in scenarios demanding both exceptional mechanical robustness and superior environmental adaptability. • Freeze-thaw process with DMSO more effectively promotes PVA microcrystal formation. • Sorbitol promotes PVA microcrystal formation while suppressing ice crystallization. • PVA hydrogel possess 16.1 MPa strength, 80% transmittance and 83% cell viability.