High-Strength Poly(vinyl alcohol) Hydrogels with Photo- and Metal-Ion-Induced Cross-Linking

Poly(vinyl alcohol) (PVA) hydrogels are frequently limited in biomedical applications mainly owing to prolonged preparation times, inadequate mechanical properties, and reliance on toxic chemical cross-linkers. Herein, a PVA hydrogel with high strength and cytocompatibility was prepared by a three-step method: the hydrogel was first formed by photo-cross-linking, then prestretched to achieve the molecular chain densification, and finally anchored by COO––Al3+ coordination. As expected, the hydrogel exhibits a 365-fold increase in tensile strength and a 762-fold increase in toughness compared to the original hydrogel with only photopolymerization, when the prestretching degree was 100% and the Al3+ concentration was 0.05 mol/L, respectively. This enhancement mainly comes from the synergistic effect of prestretching-induced molecular chain densification and subsequent aluminum–carboxylate coordination. Besides, the hydrogel is cytocompatible. Through the strategy of hydrogel network initial formation, prestretching, and metal ion coordination in sequence, the hydrogel can reach excellent strength and good cytocompatibility, which makes it potentially suitable for medical applications, e.g., wound dressing and wearable devices.