Effect of zinc ion concentration on crosslinking of carboxymethyl cellulose sodium-fumaric acid composite hydrogel

Anionic polysaccharides are known to react in unconventional patterns with di-valent metal ions to form 3D-structured hydrogels. However, little is known about the influence of divalent ions concentration on hydrogel formation. Herein, carboxymethyl cellulose based hydrogels crosslinked with zinc ions (Zn²⁺) and fumaric acid are synthesized and characterized for swelling, structure, morphology and thermal properties, and the effect of Zn²⁺ concentration on hydrogel properties is investigated. It was found that increasing Zn²⁺ to 0.5M enhances gel fraction and water absorbency, at which super-absorbent yet stable, crystalline (79% crystallinity index) FA-0.5 exhibiting water-absorbency (2259%) and stability toward water (51%) and heat (-3.17 mW and 0.9% degradation at 50 °C) is formed. The results reveal that crosslinking is influenced by Zn²⁺ concentration and interaction with other hydrogel components. The hydrolytic and thermal properties of FA-0.5 shows potential as a stable biomaterial.