Characterization of half N-acetylated chitosan powders and films

The simple homogeneous N-acetylating reaction was developed for preparation of chitosans with various degree of deacetylation (DDA). Water-soluble half N-acetylated chitosan powders were characterized by IR, CP/MAS-13CNMR, XRD and thermal analysis. The results show the half N-acetylated chitosan presents higher water hold capacity, lower crystallinity and thermal stability in contrast to the original chitosan with 91% DDA, which may be explained by the differences of intermolecular hydrogen bonding. The influences of DDA on crystalline properties, mechanical and the swelling of chitosan films were studied by XRD, Dynamic Mechanical Analyzer and swelling test, respectively. The results confirm the swelling index of chitosan films increase with decreasing DDA, especially for half N-acetylated chitosan film showing instant water solubility. The tensile strength and elongation at failure of chitosan films are found to have correlation with DDA, and half N-acetylated chitosan films show better elongation at failure. XRD results show the half N-acetylated chitosan film has higher crystallinity with possible layered crystalline structure. Special crystalline structure, water solubility of half N-acetylated chitosan powders and films would be helpful for developing modification and application methods in medicine, packaging industry, or food processing.