Fabrication and Properties of Gelatin/Glycyrrhizic Acid Double-Network Hydrogels with High Freeze Resistance

Abstract

A series of double-network hydrogels are fabricated from gelatin and glycyrrhizic acid (GA), and the influence of GA content on the mechanical properties of hydrogels is investigated. It is shown that the hydrogel containing 5% GA possessed the best mechanical performance. Then this hydrogel is soaked in K₃Cit/ethylene glycol aqueous solutions and the effects of ethylene glycol concentration on the structure and properties of immersed hydrogels are explored. The results indicated that the as-obtained hydrogel demonstrated excellent freezing resistance due to the combination effects of ion hydration and hydrogen bonds. Moreover, the hydrophobic interactions between protein chains increased with an increase in ethylene glycol concentration. The strengthening of these interactions facilitated the formation of a triple helix structure in protein. As a result, the tensile strength and elongation at the break of the hydrogels are simultaneously improved. In addition, the long-term stability of the hydrogels is also enhanced by the introduction of ethylene glycol.