Improving the mechanical and thermal properties of gelatin hydrogels cross-linked by cellulose nanowhiskers

This study demonstrates the preparation of a renewable and biocompatible hydrogel with superior mechanical properties consisting of a gelatin matrix cross-linked with oxidized cellulose nanowhiskers. We found an increased degree of chemical cross-linking (0.14-17%) between gelatin and nanowhiskers with the increased amount of aldehyde contents (0.062-0.230 mmol g^-1). ¹H nuclear magnetic resonance (NMR) T₂ relaxation experiments on D₂O swollen hydrogels demonstrated systems consisting of both gelatin and cellulose nanowhiskers displayed a higher percentage of "ridge" protons, attributed in part to increasing chemical cross-linking junction points between gelatin and nanowhiskers. This increase in hydrogel rigidity not only modified local chain dynamics but also influenced gel swelling, showing relatively reduced water uptake ability than that of the neat gelatin. Rheological measurements confirmed a 150% improvement in storage modulus (G′) of the cross-linked hydrogels compared to neat gelatin. Chemical cross-linking also increased the resistance of the gels towards thermal degradation above the melting temperature of gelatin as observed by thermal scanning experiments.