Preparation and performance of PVA/CNF/PB hydrogels based on dynamic borate ester bonds

A high-strength, tough, and self-healing hydrogel was fabricated using polyvinyl alcohol (PVOH) as the matrix, cellulose nanofibers (NFC) as the reinforcing agent, and sodium tetraborate (PB) as the crosslinking agent. The resulting PVOH/NFC/PB hydrogel has a dual-network structure formed by hydrogen bonds and dynamic borate ester bonds. The effects of NFC content on the hydrogel’s mechanical, self-healing, water retention, and electrical properties were systematically investigated. Results showed that NFC addition markedly increased tensile strength, with a maximum value of 47.2 kPa achieved at 1.2 wt% NFC. The elongation at break reached its peak (1038.5%) at 0.8 wt% NFC. Owing to the presence of dynamic borate ester bonds, the hydrogel exhibited outstanding self-healing capability, achieving a healing efficiency of 94.6% within 60 s at 1.2 wt% NFC. Moreover, NFC content influences the hydrogel’s water retention behavior and electrical conductivity, the latter reaching 0.345 S/m at 1.2 wt% NFC. The excellent plasticity and multifunctional properties of the PVOH/NFC/PB hydrogel highlight its promising potential for diverse applications.