Preparation and characterization of carboxymethylated beta-chitins and their abilities of moisture absorption and retention.

Carboxymethyl chitins (CM-chitins) with a high degree of substitution (DS), a low degree of deacetylation (DD), and high molecular weight were prepared directly from beta-chitin and characterized using (1)H NMR, FT-IR, TA, potentiometric titration, and elemental analysis methods. CM-chitins with different molecular weight were prepared using ultrasonic degradation method. Their abilities of moisture absorption and retention were investigated. The moisture-absorption ratio and moisture-retention ratio of CM-chitins increased as their DS increased. The moisture-absorption ratio and moisture-retention ratio of CM-chitins with high DS were close to that of hyaluronic acid (HA). The effect of molecular weight (>10(6)) of CM-chitin on its moisture-absorption ratio and moisture-retention ratio is neglectable.