Preparation and Properties of Fiber Thermal Crosslinking - Metal coordination Synergistically enhanced dual-network Hydrogel

Conductive hydrogels have shown great potential in flexible sensor applications due to their excellent flexibility and conductivity. However, the widespread use of existing conductive hydrogels is severely limited by their insufficient mechanical strength. To address this issue, a novel hydrogel fabrication strategy was proposed. A polyvinyl alcohol-polyacrylic acid (PVA-PAA) composite fiber membrane, prepared via electrospinning, was employed as the matrix, and an ionic crosslinked network was constructed by introducing Fe³⁺ coordination. Additionally, glycerol, rich in hydroxyl groups, was incorporated to enhance the water retention capacity of the hydrogel. The resulting PVA-PAA-Fe³⁺ hydrogel comprised a first network of chemically crosslinked PVA and PAA and a second network of PAA coordinated with Fe³⁺ ions. The effects of PAA content and Fe³⁺ molar concentration on the mechanical properties of the hydrogel were systematically investigated, and the microstructure, mechanical properties, solid content, water retention, swelling ratio, and sensing performance of the composite fiber membrane were characterized. The results show that when the PAA mass fraction was 16wt.% and the Fe³⁺ molar concentration was 0.06 mol/L, the hydrogel exhibited optimal performance: a fracture stress of 4.13±0.80 MPa, fracture strain of 49.01±3.92%, toughness of 1.69±0.25 MJ/m³, and elastic modulus of 27.36±1.90 MPa. Moreover, the hydrogel demonstrated self-recovery capability (residual strain ~4.8%), high solid content (69±2%), low swelling ratio (21.8%, only an 18% degradation in mechanical properties was observed after swelling equilibrium), excellent water retention, and remarkable sensing performance (significant and repeatable resistance variation, GF = 0.726, conductivity = 0.7 S/cm). These properties indicate its potential as a highly sensitive and mechanically robust flexible sensor.