Study On The Synthesis And Functionalization Of Polysaccharide-Based Derivatives

Polysaccharides,chitosan and cellulose are widely available,inexpensive and renewable natural polysaccharide polymers with highly ordered helical structures,and can be prepared as chiral stationary phase（CSP）with excellent enantioseparation capabilities for high performance liquid chromatography（HPLC）.The polysaccharide-based chiral stationary phases such as CDMPC and ADMPC have been commercialized previously and was widely used in enantiomeric separation and analysis processes in pharmaceutical industry and other fields.In recent years,CSPs prepared from chitosan derivatives have been reported extensively and they exhibited excellent the solvent tolerance in some organic solvents as well as strong chiral recognition.The chitosan exhibited many unique properties such as biocompatibility,cell affinity and antimicrobial properties,which make chitosan suitable for a wide range of applications in various fields,while showing great potential for corrosion resistance in metals.In this thesis,chitosan-based CSP was designed with high molecular weight chitosan as raw material,and mixed polysaccharide-based CSP with excellent resolution was also designed.At the same time,chitosan-based derivatives were used as corrosion resistance materials and the corrosion resistance of chitosan derivative composite coatings were investigated.In this thesis,chitosan of high molecular weight with high degree of deacetylation was obtained through a combined treatment of NaBH₄/NaOH.Isopropyl isothiocyanate was adopted to carry out regional substitution on the amino on the chitosan to synthesis the chitosan-2-isopropylthiourea derivative.Benzoyl chloride was subsequently used to react with the hydroxyl group on chitosan-2-isopropylthiourea derivatives to obtain the chiral selectors of chitosan-2-isopropylthiourea-3,6-benzoate derivatives（CS-2a～2c）.The structures of the derivatives were characterized by FTIR and ¹H NMR,and the results showed that the synthesized derivatives were in line with expectations.The chiral stationary phase CSP-2a～2c was prepared by coating method,and 13 enantiomers were separated by high performance liquid chromatography to evaluate the chiral recognition performance.2～3 enantiomers recognized by CSP-2a～2c,enantiomer 7 and enantiomer 12 achieving baseline separations.Chitosan derivatives/epoxy resin composite coatings were prepared by mixing chiral selectors CS-2a～2c with epoxy resin,and the performance of the composite coatings was analyzed by electrochemical impedance and polarization curve tests.The results showed that the corrosion resistance of the coating increased as the content of derivatives increased and then decreased.When the content of derivatives increased to 3 wt.%,the chitosan derivative composite coating exhibited better corrosion resistance compared to other concentrations.Chiral selectors（CS-3a,CS-3b,CS-4a,CS-4b）were synthesized using chitosan and cellulose derivatives.Their structures characterized by FTIR and ¹H NMR,and the results confirmed that the synthesized derivatives were in line with expectations.The polysaccharide derivative-based mixed chiral stationary phase（CSP-Mix-1～4）was prepared by coating method after equimixing the chiral selector.The results showed that CSP-Mix-1～4 was able to recognize 2～8 enantiomers,and three enantiomers achieving baseline separations.CSP-Mix-1～4 interacted strongly with the enantiomers,while it showed an extremely strong chiral splitting effect on specific enantiomers such as enantiomer 12 benzoin.