Study On Chemical Functionalization Of Carbon Nanotubes And Their Sustained Releasing Pazufloxacin Mesilate

Purification, chemical functionalization of carbon nanotubes and using them as sustained-releasing drug carriers is one of the most important subjects in modern researches. The technologies of preparing carbon nanotubes, the methods of functionalizing them, the technologies of purifying them, and their application as drug carriers are reviewed in this thesis. Some new methods of purification of carbon nanotubes were studied. Carbon nanotube composite materials with excellent dispersibility by attaching polymers were prepared. Near edge X-rays absorption fine structure was used to analyze polymer modified carbon nanotubes. The ability of loading and releasing drugs of chitosan modified carbon nanotubes was preliminarily studied. The main topics of this thesis are as follows:Dichlorocarbene and dibromocarbene were used to functionalize multiple-walled carbon nanotubes by ring closure, the effect of catalysts was stidied. Elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy and other analytical methods were used to characterize the products. When preparing dibromocarbene modified multiple-walled carbon nanotubes, the amorphous carbon can be removed by post treatment, however, the defects of the modified products were still remained for further functionalizing.Dichlorocarbene was produced by a sonication treatment of magnesium and tetrachloromethane in anhydrous ethyl ether, then which reacted with multiple-walled carbon nanotubes to introduce dichlorocarbene. Energy dispersive x-ray spectroscopy analysis showed low content of chlororine in the products, and the procedure need to be optimized in the future.Three polycarbonates were used to functionalize multiple-walled carbon nanotubes: poly[(propylene oxide)-(carbondioxide)-(ε-carprolactone)], poly (butylene-co-ε-caprolactone carbonate), poly[(propylene oxide)-co-(carbon dioxide)-co-(maleic anhydride)]. And soluble poly[(propylene oxide)-(carbon dioxide)-(ε-carprolactone)] modified multiple-walled carbon nanotube composites and other three unsoluble polycarbonate modified multiple-walled carbon nanotube composites. Electron microscopy analysis showed that multiple-walled carbon nanotubes were coverd with polycarbonates. Thermal gravimetric analysis showed that soluble poly[(propylene oxide)-(carbon dioxide)-(ε-carprolactone)] modified multiple-walled carbon nanotube composites contain more amounts of polycarbonates.Octadecylamine and polycarbonate were simultaneously attached to carbon nanotubes and double modified single-walled carbon nanotubes were prepared. The solubility testing showed that different polycarbonate modified single-walled carbon nanotubes can disslove in different solvents: the poly (butylene-co-ε-caprolactone carbonate) and octadecylamine modified carbon nanotubes can dissolve in highly polar organic solvents such as dimethyl sulfoxide and dimethylformamide; the poly [(propylene oxide)-co-(carbon dioxide)-co-(maleic anhydride)] and octadecylamine modified carbon nanotubes can dissolve in normal polar organic solvents such as chloroform and dichloromethane. Here we also have prepared soluble methyl-β-cyclodextrins and octadecylamine double functionalized single-walled carbon nanoubes which can dissolve in dimethyl sulfoxide and N,N-dimethylformamide. We simultaneously attached octadecyl and chitosan to single-walled carbon nanotubes by double modification, the so obtained products can dissolve in normal polar organic solvents such as chloroform and dichloromethane.Multiple-walled carbon nanotubes were functionalized using liquid bromine. Negative octadecyl oxygen ions was obtained by reacting octadecanol with sodium hydride, which reacted with liquid bromine functionalized multiple-walled carbon nanotubes by nucleophilic substitution reaction to obtain octadecanol modified multiple-walled carbon nanotubes.Near-edge X-ray absorption fine structure was used to analyze pristine single-walled carbon nanotubes, oxidized single-walled carbon nanotubes, octadecylamine modified single-walled carbon nanotubes and three kinds of polycarbonate/octadecylamine modified single-walled carbon nanotubes. The results showed that the introduced elements from functionalization and their amouts can be obtained by constrast. Near-edge X-ray absorption fine structure is an effective method to characterize polymer modified carbon nanotubes.Chitosan (CS) modified multiple-walled carbon nanotubes (MWCNT-CS) were preoared under microwave irradiation. The final products were obtained by adjusting pH value of the solution. Three kinds of MWCNT-CS/CS semi-IPN hydrogels were prepared according different contents of MWCNT-CS in MWCNT-CS/CS. Pazufloxacin mesilate was chosen as a model drug, and semi-IPN hydrogels were used as drug carriers. Pazufloxacin mesilate was loaded to semi-IPN hydrogels by soaking method. The effect of the amount of MWCNT-CS in MWCNT-CS/CS and the pH value of the buffers to the loading and releasing ability of semi-IPN hydrogels were studied.