Physical properties and molecular behavior of chitosan films

Chitosan films, varying in molecular weight and degree of deacetylation, we re prepared by a casting technique using acetic acid as a dissolving vehicl e. The physicochemical properties of the films were characterized. Both mol ecular weight and degree of deacetylation affected the film properties. Pow der X-ray diffraction patterns and differential scanning calorimetry thermo grams of all chitosan films indicated their amorphous state to partially cr ystalline state with thermal degradation temperature lower than 280-300 deg reesC. The increase in molecular weight of chitosan would increase the tens ile strength and elongation as well as moisture absorption of the films, wh ereas the increase in degree of deacetylation of chitosan would wither incr ease or decrease the tensile strength of the films depending on its molecul ar weight. Moreover, the higher the degree of deacetylation of chitosan the more brittle and the less moisture absorption of films became. All chitosa n films were soluble in HCl-KCl buffer (pH 1.2), normal saline, and distill ed water. They swelled in phosphate buffer (pH 7.4), and cross-linking betw een chitosan and phosphate anions might occur. Finally, transmission infrar ed and C-13-NMR spectra supported that chitosan films prepared by using ace tic acid as a dissolving were chitosonium acetate films.