| Chitosan is obtained by deacetylation of chitin, which is a natural polysaccharide. It is theonly alkaline polysaccharide in nature, with special physical and chemical properties andbiological characteristics. In recent years, more and more attention is paid to chitosan. Sincethe molecules of chitosan have abundant active groups on the long chains, such as hydroxyand amino, a variety of chemical modification can be conducted in order to preparederivatives of chitosan that have different properties and uses, which imparts chitosan somenovel performance. In this thesis, an amino, a reactive group of chitosan is regarded as anentry point. Brief narration shows the close relationship between solubility property,adsorption property, colloidal-forming property (chemical crosslinking method) as well as itsantibacterial characteristics and amino groups, thus proposing idea about preparation of multi-amino chitosan and preparing6-amino ethylamino-6-deoxy chitosan derivatives inaccordance with this idea. The paper is divided into three parts:The first chapter mainly describes the physical characteristics and chemical properties ofchitin and chitosan. Descriptions of the physical nature contain solubility and molecularstructure. Descriptions of the chemical nature contains the chemical modification methods ofchitin and chitosan, such as hydrolysis, alkylation modification, acylation modification,carboxyl modification, hydroxyl modification, and other conventionally chemicalmodification such as silylation. Based on these conventional modifications, this chapterintroduces relatively novel chemical modification methods in recent years, such as sugarmodification, enzymes modification, cyclodextrins modification and crown modification, etc.In the end, synthesis of idea is proposed and compared with the conventionally chemicalmodification methods, summing up three advantages.The midbody, tosylate of chitin (6-OTs-Chitin) is prepared from chitin. Experimentaldesign accords to the control variable method. Structure of the synthesized product ischaracterized, such as the solubility characteristic of the product which indicates a benzene ring is introduced on the molecule chain of chitin. Furthermore, X-ray diffraction spectroscopyand Thermogravimetric Analysis are conducted in order to study the crystal structure andthermal stability of the compound, providing a theoretical basis for the solubility property ofthe product. By infrared spectrum analysis, there have been a benzene ring and a sulfone (S=O) characteristic absorption peaks, identifying the generating of a tosylate, and identifychemical modification sites by analyzing the change in absorption of the primary hydroxylgroup C-O. The degree of substitutio of the product referring to the method about infraredspectroscopy quantitative analysis of chitosan is analyzed, and the optimal reaction conditionsare as follows: the reaction temperature is20℃, the ratio of reactants is1:15(nchitin: nTsCl).In the third part, ammonia ethylamino chitin is prepared firstly, then aminolysised anddeacetylated. Conditions of control in reaction process are also in accordance with the variablecontrol method. The final product is used XRD, TGA, IRand elemental analysis detectionmethods to analyze. The polymorphs graph and thermal stability of product are determinedfrom the XRD and TGA, while determining the generation of the product by analyzing theinfrared spectra, drawing the optimal reaction conditions via comparing the ratio of theinfrared spectra A1310and A1420: the optimum temperature is50℃, and the best volume ratiois1:1(n6-OTs-Chitin: nethanediamine), and the reaction time is10h.After characterizing the structure of the product, properties of the product, such assolubility, hygroscopic property, hydrating property and protonation degree are researched.Acid-base potentiometric titration is adopted in protonating research process and the extent ofits protonated is determined through the analysis of double sudden change points. |
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