Last but not least, chitin is a fascinating polysaccharide for a number of reasons. First, it is the second most abundant polycarbohydrate used by Mother Nature as a structural component both in the animal and in the plant kingdoms. Second, chitin has a chemical structure which is similar to that of cellulose except for a different functional group on the carbon atom number 2. Finally, from a practical point of view, chitin has been shown to have interesting useful properties. For instance, chitin exhibits biological activity (e.g. wound-healing, bacteriostatic effect) which makes it very attractive for medical applications.
Chitin can be easily converted into various physical and chemical forms when it is first partially deacetylated to chitosan. Chitosan’s structural uniqueness relies upon ionizable amino groups which make the polymer soluble in dilute acids. Without further derivatization one can then cross-link the deacetylated chitin and obtain a polycationic superabsorbent material which has very high absorbent capacity (Fig. 15).
Several technical solutions were disclosed with this regard [10]. Although technically sound, the main issue which still remains unresolved is the relatively high cost of the chitin raw material (Fig. 16). So far, the only practical origin of chitin is shellfish waste generated by the seafood industry. The logistics of collecting the waste in sufficient quantities in one place make it difficult to justify economic large-scale production of chitin and chitosan. Therefore, the use of these materials is restricted to specialty applications mainly in the pharmaceutical industry and in medicine.
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