| Konjac glucan-mannan chitosan(KGM)is a water-soluble non-ionic polysaccharide and natural polymer resource which extracted from konjac tuber.KGM has high affinity that it can absorb water automatically and swell sol formation.the water soluble gel has been general studying because of high viscosity which could be thickening,gel,emulsify and film forming.But during the process of studying KGM gel water,many problems appeared such as gel filtration,unstable strength and elastic function that hindered the KGM application in industrial production.In order to improve the application scope of KGM gel water,this paper,by using the Material Studio software and related experimental method by using molecular inter-atomic forces analysis,molecular dynamics simulation,study about network structure of KGM in different solution system from the molecular level,study the KGM respectively,in a solution of metal ions,in water environment system and the interaction of sulfuric acid esterification reaction in sulfuric acid solution,reveal the factors affecting the stability of KGM water gel structure,discusses the formation mechanism of gel and stability influence factors,in order to produce KGM gel in the lowest energy and stability state.The main research contents and results are as follows:(1)In this paper,we do the job as list,firstly,we study the interaction force among the molecules in aqueous solution and build the 3D model of KGM with the aid of Material Studio software.Secondly we founded the amorphous model and analysis hydrogen bonding of KGM in different concentration,thirdly we simulate the interaction process about the different concentrations of KGM molecular gel with water by using the simulation method of the DPD mesoscopic scale module.By doing the works mention above,we draw the conclusion that hydrogen bond is the main force in different concentrations of the konjac glucan-mannan chitosan solution in water environment.with the increasing of KGM concentration,the number of hydrogen bonds increase,gel reaction between konjac glucan-mannan chitosan in aqueous solution enhance,due to react with water to the start of the interface stress is small,with the increase of simulation steps,with water to form a stable system,with the increase of concentration,the interface stress increase.(2)By creating the amorphous model,we use the theory of Gaussian3 to analyze the hydrogen bonds of konjac glucan-mannan formation under the action of the iron ion.With the help of the molecular dynamics simulation theory,this paper combine the lennard-Jones and Boys-Shavitt multi-parameters model to analyze KGM in iron gel formed under the action of the RMSd.Result can be drawn that the system formed by ion with glucan-mannan formation complexes contains a large number of hydroxyl groups metal,the formation of polymer are connected by hydrogen bonding,acetyl hasn't any change,the system of KGM beta glycosidic bond is not destroyed,assorted system contain pyran ring,hydrogen bond is still the largest influence factor in the KGM conformation,followed is the electrostatic potential,van der Waals force is little effect,interaction of different hydrogen bonding loci and the number of hydrogen bonds make the stability of single KGM conformation in aqueous solution change,molecules form double chain structure,intermolecular stability improved.With the analysis of RMSd and model,KGM in iron ion solution formed by the structure has certain stability.Ferric chloride solution which could form a stable structure is a good solvent.(3)To study the molecular inter-atomic forces and dynamics analysis of the konjac glucan-mannan chitosan(KGM)in sulfuric acid system,we found the amorphous model of KGM in sulfuric acid solution and analyze the distribution of hydrogen bond.In addition,we research the gel formed by KGM in sulfuric acid solution and make dynamics analysis respectively from the energy,the interface stress,gel strength and viscosity.Studies have shown that KGM set off sulfuric acid esterification reaction in sulfuric acid solution,acid acidification occurs mainly on the C3,and C2,C6 of KGM,the modification of KGM main chain primary structure has little change,the structure of KGM single in sulfuric acid solution with different sites of hydrogen bonding and hydrogen bond number influence the stability of single KGM conformation in aqueous solution.When hydrogen bond number increase,after the esterification of polysaccharide sulfate its structure more order than before.By means of molecular dynamics analysis to KGM in sulfuric acid solution,the energy continually reduce and tends to a stable value,and more lower compared to the pure KGM,which shows that the higher the degree of substitution is,the lower the energy shows,the stability the system gets.In sulfuric acid solution,the interface stress is smaller at the start,but with the increase of simulation steps,material end of reaction,new material quickly formed a stable system,the viscosity and strength of KGM gel after sulfuric acid esterification is bigger than that in aqueous solution.Finally through the model analysis of the reaction of KGM in sulfuric acid solution to form a stable system of sulfuric,we can get the verdict that acid is a good solvent for KGM. |
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