Study On Crosslinking And Degradation Of Polysaccharides

For the crosslinking and degradation of a polymer compound, there is a varietyof desirable methods, after crosslinking and degradation a significant change ofstructure and properties occurs, but for each of the polymer there is always a mostappropriate approach to change the molecular weight. People are constantly explorenew ways and combine with the original methods, in order to better adjust the changesin the molecular weight of a polymer, change the physical and chemical properties toadapt to a variety of producing and living needs.This thesis is divided into two parts, Part I Fenton reagent is used to combinewith ultrasonic to complete the degradation of chitosan and sesbania gum-two naturalpolysaccharides. Fenton reagent which contains Fe2+with H2O2, can produce strongoxidizing hydroxyl radicals which can be applied to the degradation ofpolysaccharides, ultrasonic cavitation instantly generate high-energy which can alsodamage the glycosidic bond in the polysaccharide long-chain, a combination of thesetwo has a synergistic effect to improve the efficiency of degradation of thepolysaccharide. The molecular average weight of degraded polysaccharide issignificantly reduced, the solubility changes for the better. This thesis explores theoptimal conditions using Fenton reagent combined with ultrasonic degradation todegrade chitosan and sesbania gum and proves that the synergistic effect of the twomethods. This part uses the intrinsic viscosity and viscosity average molecular weightchanges before and after degradation to explore optimum conditions for the Fentonreagent combination of ultrasonic degradation of two natural polysaccharide chitosanand Sesbania Gum. Some methods are used such as infrared spectroscopy, X-raydiffraction, scanning electron microscopy, thermal gravity analysis and other means oftesting for structural characterization of the former polysaccharide and the degradatedproducts. The infrared spectroscopy results show that the degradation process ofpolymer long-chain is just bond breaking without destroying the ring structure of thepolysaccharide, the X-ray diffraction pattern shows that the degradation of chitosancrystallization properties of crystalline properties of Sesbania Gum variation. Scanning electron microscopy results showed that chitosan degradation still havesome regular structure, loosely structured surface after sesbania gum degradation. Thethermal gravimetric analysis results showed that the chitosan degradation after weightloss between300℃-800℃slow Sesbania Gum initial decomposition temperatureafter degradation, which shows good thermal stability.Part Ⅱ The amino derivatives of sesbania gum crosslinked by Ethylenediamine isprepared and is used to crosslink natural hyaluronic acid. The solubility of naturalhyaluronic acid in water is very good, and it is easy to move or degradated byenzymes and soon excreted in the body content, but after crosslinking, hyaluronic acidderivatives will be able to overcome these deficiencies. This part uses the intrinsicviscosity and viscosity average molecular weight changes before and aftercrosslinking to explore optimum conditions for the crosslinking of hyaluronic acidusing amino derivatives of sesbania gum. Some methods are used such as infraredspectroscopy, X-ray diffraction, scanning electron microscopy, thermal gravityanalysis and other means of testing for structural characterization of hyaluronic acidand the crosslinked products. The infrared spectra indicates the formation of aminoderivatives of sesbania gum and crosslinked hyaluronic acid. The test results ofscanning electron microscopy show that sesbania gum cross-linked surfacemorphology did not change significantly. TGA results show that the crosslinkedhyaluronic acid shows good thermal stability between300℃-800℃.