| In this paper, the following five parts have been studied in detail.1. The preparation of chitosan in a mixed medium of water and alcohol has been studied. The influence of reaction conditions on chitosan characteristics (degree of deacetylation and molecular weight) is investigated, such as reaction medium, alkaline kind and concentration, reaction time and temperature, solid-liquid ratio, multi-step alkaline treatment process and the application of oxygen scavenger. A new preparative method has been developed. In the method, the optimum conditions of deacetylation of chitin are as follows: 95% alcohol as reaction medium, temperature of 90 , 18.7% (m/V) NaOH concentration and intermittent alkaline treatment. This new technology needs lower NaOH concentration, shorter reaction time and less water washing than that of conventional NaOH aqueous solution method. The produced chitosan is of high degree of deacetylation (%D.D>90) and molecular weight (9.3 105).2. A new one-pot preparation route to N,O-carboxymethylchitosan from chitin in water-ethanol media has been studied. The optimum preparation conditions have been obtained by monofactorial experiment. Chitin is deacetylated to produce chitosan in sodium hydroxide water-ethanol solution of 90 for two hours, and then reaction temperature is fell to 40~50 . The produced chitosan is directly reacted with monochloroacetic acid for three hours without being separated. This continuous preparative procedure for N,O-carboxymethylcitosan can reduce consumption of NaOH and reaction time. The oxidative degradation can be avoided also. The N,O-carboxymethylcitosan with high viscosity (viscosity of 4% aqueous solution for 1660mPa-s) and degree of substitution (SD for 1.16) can be obtained by the method. The yield is 115%. The properties of N,O-carboxymethylchitosan obtained by the method have been studied also, such as solubility, humidity-retaining ability, anti-acidity and anti-alkaline.3. Chitosan is converted to dry, free-flowing and water-soluble chitosan salts by grinding between particulate chitosan and organic or inorganic acid containing properamount of water, without environment pollution and weight loss. Five kinds of chitosan salts have been produced, i.e. chitosan hydrochloride, chitosan acetate, chitosan formate, chitosan lactate and chitosan succinate, yield for 126%, 134%, 120%, 143% and 130% respectively. The structures of solid chitosan salts are affirmed by IR spectroscopy, X-ray diffraction and potentiometric titration. Chitosan occurs protonation with acid during the process of grinding. The experimental results show that the solid chitosan salts are soluble in acidic, neutral and weak alkaline aqueous solution and their solubility and viscosity of solution can remain for four months at least. The solid chitosan salts obtained by a simple method are water-soluble, stable and convenient in the application, transportation and store.4. Two kinds of methods for the determination of degree of deacetylation of chitosan on the base of previous literatures are established, i.e. improved first derivative UV spectrophotometry and multi-wavelength liner regression UV spectrophotometry. By these methods, light adsorption in the reference system can be decreased and the interference of coexistent substance can be removed. The multi-wavelength liner regression UV spectrophotometry can be simply carried out by different spectrophotometers. The experimental results show that the methods are more accurate, precise and simple. The relative standard derivation is 0.21~ 1.36% and the recovery is 99.8% ~ 101.4% for the unproved first derivative UV spectrophotometry. The relative standard derivation is 0.20~0.52% and the recovery is 100.2-101.6% for multi-wavelength liner regression UV spectrophotometry.5. The determination of substitution degree of N,O-carboxymethylchitosan by potentiometric titration has been studied in detail. The end points of N,O-carboxymethylchitosan groups in a titrati...
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