Synthesis Of New Ionic Liquids And The Application In The Degradation Of Chitosan

Chitin is the second most abundant natural biopolymer after cellose,which of the source is very broad.Chitosan is obtained after alkaline deacetylation of the chitin,which is the only natural cationic polysacchride in nature.Chitin and chitosan attracted much more attention on the biomedical,pharmacological,agricultual,and biotechnological fields.However,recent studies on chitin have attracted interest for converting chitin to it's oligosacchrides,because chitin oligosacchrides are not only water soluble,but also possess special fuctional properties such as antitumor activity,immunostimulating effects,and antimicrobial activity.The preparation of chitosan oligomers was limited because of poor warter-solubility of chitin and chitosan.New ionic liquids that dissolving for chitin and chitosan was synthesized to replace the traditional solvent(HAc) through a large number of experimental data,solving a large amount of defects of traditional solvents,for example large volatility,serious pollution and large consumption.So the clean preparation of chitosan oligomers could be completed in homogeneous system.The degree of deacetylation of chitosan was 85 % using acid-base titration.The viscosity calculated molecular weight of chitosan was 1,100,000 determined with Ubbelode viscometer.The moisture-absorption and retention capacity of chitin and chitosan was lower than glycerol by comparing the data.A series of ionic liquids was synthesized The ionic liquid that has good solubility for chitosan was selected,the solubility of [Gly]Cl for chitosan was well and the assistant degradation for chitosan was the best through experimental data.Various factors in oxidative degradation of chitosan were systematicly studied,for example,reaction medium,reaction temperature,reaction time and the amount of hydrogen peroxide.Under HAc system,the optimum condition for oxidative degradation was obtained as follows: chitosan 2 g,the aqueous of 2 %HAc 40 mL,n(ozogen):n(chitosan)3:1,reaction temperature 70-80℃and reaction time 2 h.Under the above condition,the yield of product was 70 % and the viscosity-average molar mass was 2200,and the moisture-absorption and retention capacity of low molecular weight chitosan was examined,the results showed the performance of moisture-absorption of chitosan oligomers(RH=43 %)was better than hyaluronic acid,residual ratio of water of chitosan oligomers (RH=43 %)was far larger than that of hyaluronic acid,the performance of moisture absoption and retention of chitosan oligomers was significantly superior to glycerol. Under ionic liquid system,the optimum condition for oxidative degradation was obtained as follows:chitosan 2 g,the aqueous of 2 %nionic liquid 40 mL,n(ozogen):n(chitosan)3:1,reaction temperature 80℃and reaction time 2 h.Under the above condition,the yield of product was 76 % and the viscosity-average molar mass was 2000,and having good-soluble,and the performance of moisture absoption and retention of product was significantly superior to hyaluronic acid and glycerol.The structure of the chitooligosacchrides of hydrolytic chitosan was determined by analysis of IR spectroscopy, and the polymerization degree was measured by HP-LC.This paper also investigated the moisture absorption and retention of chitosan oligomers.On contrast of the ratio of insoluble chitosan gotten by acetic acid degradation system,that obtained by ionic liquids degradation system with the chitosan oligomers was acutely decreasing.So the rate of the solubility chitosan oligomers got a raise. Finally,improved the micro-circumstance polarity of the reaction system,it helped hydrogen peroxide to attack the glycosidic C-O-C bonds.Therefore,the field of the soluble chitosan increased.By means of IR,we know that the positions of main peaks of chitosan are unchanged,and each peak strength changed while chitosan molecular weight ruduced,which we testified that the way of oxidizing is through dividingβ-1,4-glucoside band of chitosan,and identified the existence of monosacchrides- pentasaccharides using TLC.This study has great significance for better use of chitosan on the development of resource to promote the development of our marine biological products.