Construction of hydrogels based on the homogeneous carboxymethylated chitin from Hericium erinaceus residue: Role of carboxymethylation degree.

Carboxymethyl chitin hydrogels with different degree of substitution (DS) were prepared by the homogeneous carboxymethylation of chitin extracted from Hericium erinaceus residue. The effect of DS on gel structure and property were studied. Results showed that the DS of carboxymethyl chitin hydrogels can be increased by increasing the amount of sodium chloroacetate. The equilibrium swelling degree and pH swelling sensitivity of the hydrogels were enhanced as the increase of DS. Zeta potential, low-field nuclear magnetic resonance, contact angle and molecular dynamics simulation results suggested that the introduction of carboxymethyl functional group enhanced the negative charge, water mobility, surface hydrophilicity and the ability to form hydrogen bonds with water of the hydrogels, resulting in an increased swelling degree of the hydrogels. Moreover, the prepared hydrogels showed different adsorption capability to various dyes, and the adsorption performance of the prepared hydrogels for cationic dyes could be enhanced as the increase of DS.