Research Of Carbon Nanotubes Functionalized By Water Soluble Chitosan

Carbon nanotubes have attracted strong attention since their discovery by S. Iijima in 1991 owing to the combination of such features as their high stiffness, high strength, excellent electronic and chemical properties. A major drawback in the use of MWNT is the difficulty of processing them, as they are immiscible with most media because of their great tendency to establish strong van der Waals andπ-πinteractions, which cause them to form tight bundles. Dispersing MWNT and ensuring a good stability of MWNT have proved especially challenge for aqueous systems.Chitosan has attracted a great deal of interest due to good biocompatibility, biodegradability, low toxicity, low cost, good film forming character and antiviral properties. Although chitosan has been shown to be a good polymeric dispersant for MWNT in acetic acid, it is normally insoluble in water at neutral or high pH region because of its rigid crystalline structure which limited its application. Therefore, chemical modification of chitosan by controlled covalently attaching molecules to its amino and/or hydroxyl groups to provide water-soluble materials is a prime problem. Some work has been carried out in this thesis which is associated with chitosan and carbon nanotubes.Firstly, N-palmitoyl chitosan (p-CS) has been synthesized by a non-toxicity and good biocompatibility EDC/NHS mediated reaction through the formation of amide linkages between chitosan and palmitic acid. FT-IR and 1H NMR reveal that EDC/NHS couplant can graft palmitic acid to the amido of chitosan successfully. XRD shows that when hydrophobic palmitoyl groups are graft onto the amine groups of chitosan, the inter- and extra-molecular hydrogen bonds are destroyed, the crystalline structures of chitosan are changed. The solubility of chitosan and p-CS in acid solution and deionized water has been measured, the solubility of p-CS depends on the degree of substitution of amine groups of chitosan, the initial ratio of 0.3 is the most appropriate one for good solubility in acid solution and deionized water.Secondly, p-CS non-covalent functionalized multi-walled carbon nanotubes (p-CS/MWNT) has been prepared by disperse MWNT to the water solution of p-CS, ultrasonic cavitate method is used as a stimulus. Compared with MWNT the p-CS/MWNT has a slight blue shift on the UV-vis absorption spectra which can be ascribed to the interaction between p-CS and MWNT. FT-IR,XRD,Raman and XPS further confirm the changes of MWNT before and after interaction with p-CS. In the HRTEM images, a p-CS layer lying around MWNT in varying thicknesses has been observed. CD measurement has been used to characterize the structure change of p-CS before and after interaction with MWNT by non-covalent functionalization at different temperature and pH values.Thirdly, UV-vis and CD measurement have been used to characterize the performance of p-CS and p-CS/MWNT as BSA carrier.