Characterization and Solution Properties of Chitosan and Chitosan Derivatives

This chapter describes mainly the methods to prepare water-soluble chitosan derivatives and to characterize the different products. Chitosan is the fully deacetylated chitin, i.e., a pure d-glucosamine polymer, but also polymers with low degree of acetylation such as to become soluble in acidic conditions. For grafting hydrophobic alkyl chains, reductive alkylation is chosen as an easy and versatile method to form a covalent bond between an alkyl substituent and the amine function of chitosan. One of the most important chitin derivatives results from the carboxymethylation of chitosan. This reaction allows to get a water-soluble polymer in a large range of pH and especially over pH 6 where chitosan is no longer soluble. The acetylation degree can also be determined from conductimetric titration: the chitosan sample is dissolved in water with a known quantity of HCl and titrated using a sodium hydroxide solution.