Chitosan by widespread nature of chitin (chitin) obtained after deacetylation, the chemical name for polydextrose amine (1-4) -2 - amino-BD glucose, since 1859, the French Rouget first obtain chitosan, the biological function of this natural polymer and compatibility, blood compatibility, security, microbial degradation and other excellent properties is widespread concern in all walks of life, in medicine, food, chemical, cosmetics, water treatment, metal extraction and recovery, biochemical and biomedical engineering and many other fields of applied research has made significant progress. For patients, chitosan fat, lowering blood sugar has been study.

Chitosan is the N-deacetylation of chitin product, in general, N-acetyl-off of more than 55% can be called chitosan, or, in 1% acetic acid or 1% hydrochloric acid dissolved in 1% of deacetylation of chitin, the deacetylation of chitin is called chitosan. Alias ​​for "chitin", "deacetylation of chitin," "deacetylation of chitin," "soluble chitin", "soluble chitin", "shell glycosaminoglycans", "chitosan", "crustaceans sugar," " amino polysaccharide "," Crustacean polysaccharide "," chitosan ", etc., chemical called β-(1 → 4) -2 - amino - 2 - deoxy-D-glucose, structure shown in Fig. Deacetylation degree (DD) determines the macromolecular chain amino (NH2) the amount of content, and DD increased, due to the protonated amino acid solution of chitosan in leaving charged groups increased, polyelectrolyte charge density increase, the result will inevitably lead to its structure, properties and performance changes since the nature of chitosan in dilute solution studies have ignored the value of the Equation of DD. VANDUM, who has studied the different ionic strength on the chitosan molecules in dilute solution size and viscosity. Concluded that the ionic strength will change in different random coil expansion of degree and then change the molecular size and intrinsic viscosity, through the different DD chitosan MARK-HOUWINK equation constants measured results show that K, A value with changes in the value of DD . Thus by the MARK-HOUWINK equation constants K, A regularly rely on degree of deacetylation of chitosan changes, but also in the same molecular weight, with the increase of degree of deacetylation of chitosan molecules in dilute solution size, intrinsic viscosity factors such as degree of increase and expansion, while the characteristic ratio and steric factors as the degree of deacetylation increases. Thus within the scope of any of the chitosan sample by comparing the simple measurement of intrinsic viscosity, you can calculate the average molecular weight, which can accumulate some basic data for further research.

As the chitosan and chitin with a high chemical reactivity and ease of modification by some chemical reagents, so research in this area of work more, but also achieved gratifying results. Through a variety of ways to make the nature of the modified chitosan. Such as chitosan porous beads, chelation of heavy metals can also be used for the immobilization of biological materials. Halogenated iodide was prepared by graft copolymer of chitosan. Halide and the main methods for chitosan iodide functional group transformation, which iodide under mild conditions, and can produce a variety of reaction precursors. The reaction easily occurred in the C6-bit value, the other for the preparation of cationic graft copolymers. The reaction conditions at room temperature and UV 308NM Department. Various functional groups of chitosan transformation also includes preparation of hydroxy-chitosan.