Influence of amide content on the crystal structure of chitin

Abstract

Abstract The crystalline structure of chitin and chitosan was investigated by X-ray diffraction (XRD). Chitosan filaments were prepared using a saturated solution of calcium chloride dihydrate in methanol (CaCl2-MeOH) as a mild solvent and the study focused on the interaction between the degree of acetylation (DA) and crystallinity. There were pronounced differences in the XRD patterns for specimens with DA values between 44.2% and 52.2%. We suggest that the crystalline structure changes from an anhydrous-type chitosan to an α-chitin type without any additives. CaCl2-MeOH is a good solvent for chitin and a poor solvent for chitosan and we found that it can regulate the distribution of N-acetyl glucosamine and glucosamine between amorphous and crystalline regions.