Research On The Preparation Of The Low Molecular Weight Chitosan

In this work, the mechanism and the process of chitosan degradation with hydrogen peroxide in the simple homogeneous media was investigated. The temperature,time and concentration of hydrogen peroxide were influence function. On the base of realization on that mechanism, we put forward and proved the special degradation mechanism of complex homogeneous media with inorganic compounds. The viscosity calculated molecular weight of chitosan was determined with Ubbelode viscometer. The degraded chitosan were characterized by TG,DSC,FT-IR,Fluorescence probe.Firstly, the present study showed that the simple homogeneous hydrogen peroxide solution treating is an effective method for chitosan degradation. The increase of the concentration of hydrogen peroxide in reaction media leaded to a rapid decrease in degradation of chitosan. Temperature rise also accelerated this process. In conclusion, hydrogen peroxide concentration range 3.5%~7%(w/v) and temperature range 50℃~60℃ seemed to be the optimal condition for chitosan degradation, the viscosity calculated molecular weight can be lowered to about 8000.Secondly, the relative curves of ln[Nn/(Nn-1)] versus reaction time(t) in degradation process showed linearity, and the reaction kinetic is first order. It was also proved that the oxide degradation of chitosan in the simple homogeneous media was accomplished in first 2h.Thirdly, on contrast of the radio of insoluble chitosan gotten by simple homogeneous degradation system, that obtained by complex homogeneous degradation system with inorganic compounds was acutely decreasing (from 56% to 2%). So the rate of the solubility low molecular weight chitosan 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.