Preparation of chitin and chitosan derivatives having mercapto groups

Chitin and its deacetylated derivative chitosan are natural copolymers composed of randomly distributed β-(1 → 4)-linked 2-acetamido-d-glucose and 2-amino-d-glucose units in variable proportions (Figure 5.1). Chitin occurs naturally in a wide variety of species from fungi to lower animals. However, chitosan only occurs in some fungi and it is normally prepared by the deacetylation of chitin (Muzzarelli 1977; Roberts 1998). Chitin is an abundant polymer and both chitin and chitosan exhibit very interesting properties, such as biocompatibility, biodegradability, and metal-binding ability among others (Aranaz et al. 2009). Therefore, both polymers have potential applications in many elds such as in biomedicine, waste water treatment, or cosmetics (Dodane and Vilivalam 1998; Rinaudo 2006).