Effect of deacetylation time on the preparation, properties and swelling behavior of chitosan films

The effect of time during the deacetylation of chitin by hot alkali was studied to ascertain the film forming ability of chitosan. Five types of chitosan films were prepared in a single step deacetylation process by varying the alkaline treatment time from 2 to 10 h. The degree of deacetylation (DD) of chitosan and chitosan films were characterized using Fourier transform infrared spectroscopy (FT-IR) and elemental (CHN) analysis methods. The DD was found not to vary significantly beyond 2 h of deacetylation and the DD values by CHN analysis was higher than by FT-IR method. The degree of crystallinity (crystallinity index, CrI) of the chitosan films was also evaluated by X-ray powder diffraction method and the film prepared with 2 h deacetylation showed lower CrI. The morphology of this film by scanning electron microscopy (SEM) shows homogeneous and continuous structure. Swelling index of the films was measured in phosphate buffer solution at physiological conditions and film prepared with 2 h deacetylation showed maximum swelling index. However, the film formed with 6 h deacetylation process has the highest DD with higher CrI and low contact angle values. This film seems to be more suitable for biomedical applications.