Characterization of chitosan film and structure in solution

Abstract

Chitosan [(l-4)-2-amino-2-deooxy-β-D-glucan)] is one of a linear polysaccharides obtained by deacetylating chitin, which is extracted from the shells of crab, shrimp, and krill. Chitosan is insoluble in water but it becomes soluble and cationic when it is dissolved in organic acids such as acetic add, malic acid, citric acid, and formic acid. It is an excellent polymer to make a functional film. This chapter sheds light on a study conducted to determine the relation between molecular structure of chitosan in acidic aqueous solution and physical properties of chitosan films. In the experiment, the molecular weights (M(subscript)) of chitosan dissolved in acidic solutions were varied and depend on the type of acid used. M(subscript) of chitosan in acetic acid, citric acid, lactic acid and malic acid was 11.9 X 105, 5.64 X l05, 6.1 X 105, and 5.45 X 105, respectively. The Rg increased directly proportional to the increasing molecular weight. Tensile strength (TS), elongation (E), and water vapor p ermeability (WVP) of chitosan films depend on the type of acid used. The TS of acetic acid cast chitosan films is the highest (40.05MPa), and E of citric acid cast chitosan films is the highest (137%). In an acetic acid solution chitosan form dimer indicating that the intermolecular interaction is relatively strong WVP of malic acid cast chitosan films was 1.02 ngm/m2.sPa and was lower than those of the films dissolved in three other acidic solutions.