| Because the fossil resources such as petroleum, coal and so on, are being exhausted increasingly, and the problem of environmental pollution from the waster and litter of nondegradable polymer materals that are mainly derived from petrolrum resources becomes more and more serious. Therefore the polymer science and technology faces a new challenge. Nowdays, research and exploitation of new materials based on natural polymers have become the front of polymer science. Konjac Glucomannan(called KGM for short), is the special resource in China, which is a kind of natural polymers. It is innocuous and biodegradable, which has the similar structure to cellulose, but has the water solubility that is not embodied by cellulose. The abundant hydroxyl groups in KGM molecules are highly active, and it contains certain amount of acetyl groups, so that KGM is ease to be chemically modified by green technology.Generally speaking, the molecular weight of KGM can reach to the order of magnitude of 10~6. The high molecular weight, on one hand, has excellent properties of thickening and gelling, on the other hand limites KGM's application. If we can control the degradation triumpHantly, and get Konjac Oligo-Glucomannan at expected molecular weight, the KGM will have extensive applications.In this article, firstly according to the method of enzyme-catalyze and acid-catalyze, we obtained different molecular weights of KGM, then changed the reaction conditions to find out the various influences to the degradation of KGM's molecular weight. Compared the molecular weight and solubility, the process of acid degradation and enzyme degradation have been improved. Finally the KGM at expected molecular weight were obtained.Secondly, according to the degree of sulfonic esterification and intrinsic viscosity that represented molecular weight size, the sulpHonate process was optimized.The preferable laboratory preparation technological conditions to sulfonated Konjac Oligo-Glucomannan with different molecular weights, in purpose of getting familiar substituting degree has been confirmed. The structure has been characterized by FTIR, elementary analysis, viscosity measurements and their bioactivity was investigated by means of anticoagulant time test , antitumor test in vitro, antimicrobial activity test etc. It is indicated that the bioactivity is the best when the sulfonated KGM has a molecular weight between 100 000 and 300 000, which not only has anticoagulant activity, but also can resist on the neoplasm's activity.Thirdly, according to the techniques of cyanoethyl cellulose and cyanoethyl Starch, and the synthetical technics of cyanoethyl konjac glucomannan was optimized and cyanoethyl konjac glucomannan with higher substituting degree was obtained. The structure and lyotropic liquid crystalline behavior of cyanoethyl konjac glucomannan were investigated by FTIR, elemental analysis, viscosity measurements, light-scattering analysis, rheological measurements respectively. It shows that the liquid crystal action of cyanoethyl konjac glucomannan is not only related to substituting degree, but also has a certain relation to the concentration of cyanoethyl konjac glucomannan. In the works, the liquid crystal behavior has been studied and found that the cyanoethyl konjac glucomannan forms liquid crystal in m-Cresol when its concentration reaches to 8.62wt%.In this article, we researched the degradation of KGM, and chemical modifications on the basis of different molecular weights, which will provide novel avenues and theory data to prepare various use of new materials so as to make full use of special resources in our country, realize agricultural product science and technology added value purpose and improve economic and social benefits.
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