Synthesis And Characterization Of Dialkoxy Phosphoryl Chitooligosaccharide/Chitosan

In this research, using low molecular weight chitooligosaccharide (The molecular weight is about 5 kDa) and dialkyl phosphite as raw material, a series of novel dialkoxy phosphoryl chitooligosaccharide were prepared. Among those dialkoxy phosphoryl chitooligosaccharide, N-diisopropyl phosphoryl chitooligosaccharide and N-diethoxy phosphoryl chitooligosaccharide were the most satisfactory in term of good 31P NMR spectra and high phosphorus content. Their optimal conditions were investigated. When the optimal conditions of N-diethoxy phosphoryl chitooligosaccharide were studied, it was rather surprising and interesting that the locus of graft of diethoxy phosphoryl group can be controlled through varying the experiment conditions (namely the molar ratio of chitooligosaccharide to triethlamine). Then, N, O, O-diethoxy phosphoryl chitooligosaccharide and O,O-diethoxy phosphoryl chitooligosaccharide were obtained. At last, the optimum reaction conditions of N-diethoxy phosphoryl chitooligosaccharide and N, O, O-diethoxy phosphoryl chitooligosaccharide were determined by single factor variable method. The optimum reaction conditions of N, O, O-diethoxy phosphoryl chitooligosaccharide were applied to more molecular weight chitosan (the molecular weight was about 200 kDa). It was surprising found that the solubitity of N, O, O-diethoxy phosphoryl chitosan was quite good. The preparation of this new chitosan derivative provides a new approach to soluble chitosan derivative.1. In the system of water-ethanol, a simple and efficient method for the preparation of a novel dialkoxy phosphoryl chitooligosaccharide/chitosan was proposed though the reaction of chitosan with dialkyl phosphite.2. It was found that the 31P NMR of those N-dialkoxy phosphoryl chitooligosaccharide were satisfying and their peaks were emerging in the range from 0 to 10 ppm. Chemical shifts were determined by kinds of dialky group.3. The optimal conditions of N-diisopropyl phosphoryl chitooligosaccharide were studied by orthogonal test, and the optimum reaction conditions were determined as follow:nCS:nTEA= (1:4)～(1:6); ncs:nDIPPH= (1:2)～(1:4); the time of dropwise was 2 h; the time at the low temperature was 4 h; the reaction time at the room temperature of 8～16 h; The maximum phosphorus content (P%) achieve 0.84% under the optimum conditions;4. The FT IR,13C NMR and 31P NMR results showed that N-diethoxy phosphoryl group was grafted onto the amino group of chitosan. XRD indicated that the incorporation of diethoxy phosphoryl group into chitosan increased the crystalline structure of the polymer. TG demonstrated that diethoxy phosphoryl chitosan was more thermal stable than chitosan. The optimal conditions of N-diethoxy phosphoryl chitooligosaccharide were studied by single factor variable method, and the optimum reaction conditions were determined as follow:nCS:nTEA=1:6; ncs:nDEPH= 1:3; the time at the low temperature of 2 h; the time of dropwise was 2 h; the reaction at the room temperature was not carried out. The maximum phosphorus content (P%) achieves 1.50% under the optimum conditions.5. The optimum reaction conditions of N, O, O-diethoxy phosphoryl chitooligosaccharide were determined as follow:ncs:nTEA=1:6; nCS:nDEPH= 1:5; the time at the low temperature was 4 h; the time of dropwise was 2 h; the reaction time at the room temperature was 8 h. The maximum phosphorus content (P%) achieves 3.42% under the optimum conditions.6. The optimum reaction conditions of N, O, O-diethoxy phosphoryl chitooligosaccharide were applied to chitosan (the molecular weight was about 200 kDa) which had more molecular weight than chitooligosaccharide. The product was characterized by FT IR, NMR, ICP, XRD, TG and SEM, respectively. FT IR,1H NMR,13C NMR and 31P NMR results unequivocally demonstrated that diethoxy phosphoryl groups were grafted onto on the amino and hydroxyl groups of chitosan. The results of XRD indicated that a distinct change taken place with the crystalline structure of chitosan due to graft of the diethoxy phosphoryl group. The analysis of TG stated that N, O, O-diethoxy phosphoryl chitosan was less thermal stable than chitosan.