Salting-enhanced polyvinyl alcohol hydrogel: synergistic effects of sodium acetate and ammonium citrate on structural and mechanical properties

Abstract

Non-covalently cross-linked polyvinyl alcohol (PVA) hydrogels potentially function as promising biomaterial candidates for diverse biomedical applications. However, conventional PVA hydrogels have inherent limitations in mechanical strength that constrain their practical applications. This study develops a high-performance polyvinyl alcohol (PVA) hydrogel through dual-salt-regulation strategies involving sodium acetate (NaAc) and ammonium citrate (CAS). The in situ addition of NaAc (0.7 mol/L) induces PVA protonation, enhancing intramolecular/intermolecular hydrogen bonds (H-bonds), which elevates toughness to 1.3 MJ/m³ (10 × improvement). Subsequent CAS salting-out (3 mol/L) further strengthens H-bond network and reduces crystalline domains, achieving exceptional mechanical properties: tensile stress (4.26 MPa), strain (760%), toughness (20.98 MJ/m³), and fracture energy (765.72 kJ/m²). Structural analyses confirm that NaAc disrupts PVA–water interactions, while CAS promotes dense chain packing via salting-out, collectively reducing water content from 88 to 26% and creating a hierarchical porous structure. Cyclic compression tests demonstrate outstanding fatigue resistance. The synergistic Hofmeister effect and dynamic ionic cross-linking enable energy dissipation, making this hydrogel promising for soft robotics and biomedical applications requiring robust, deformable materials.