Preparation Of Water-Soluble Carbon Nanotubes And Their Preliminary Applications

Carbon nanotubes (CNTs) have attracted great attentions, due to their intrinsic structures, outstanding physical and chemical properties as well as their promising potential applications in the area of material chemistry, biomedicine and catalyst carrier etc. However, CNTs cannot be dispersed in most solvents because of the strong Van der Waals force interactions, which hampers their potential utilities. It is of great significance to functionalize the CNTs in order to improve their dispersibility in solvents and matrics. Up to date, various functionalization methods have been reported, including noncovalent and covalent functionalization. The covalent functionalization can not only improve CNT's solubility, but also afford their novel properties. Water-solube CNTs show enticing potential in biomedical and Water treatment. The introducing of responsive chemical species affords responsibility to CNTs, which expands the application scope of CNTs. In this dissertation, carboxyls functionalized CNTs and hydroxyls functionalized CNTs were prepared through radical reaction and hydrothermal reaction. Utilizing the carboxyls and hydroxyls as targets, CNTs were functionalized with magnetic response and environmental response (pH and thermal) species. The applications of functionalized CNTs in water treatment and biomedicine were researched. The main research contents and results are shown as follow:1. Cyano groups functionalized CNTs were prepared throught radical reation between AIBN and CNTs, followed by hydrolyzing, carboxyls functionalized CNTs were obtained. Through amidation reaction, magnetic silica nanoparticle functionalized multi-walled carbon nanotubes (MS-MWNTs) were prepared. MS-MWNTs were used for the convenient, rapid and efficient separation of trace aromatic compounds.2. Through exfoliating the CNT bundles with sodium dodecylbenzene sulfonate (SDBS), individual CNTs have been obtained. Grafting polymerization of acrylonitrile was performed to produce polyacrylonitrile funtionalized CNTs (PAN-CNTs). After hydrolyzing PAN, polyacrylic acid functionalized CNTs (PAA-CNTs) were obtained. The amount of PAA grafted could be controlled by changing the feed ratio of initiator to monomer, and the maximum grafting amount could reach 40 wt%. The solubility of PAA-CNTs in water could be adjusted by pH, and the pH of critical dispersion is 5.0.3. CNTs bearing hydroxyl groups (CNTols) on the exterior surface have been synthesized by an alkaline-mediated hydrothermal treatment of CNTs. X-Ray photoelectron spectroscopy shows that the content of hydroxyl groups increases with the concentration of sodium hydroxide utilized. FT-IR spectroscopy shows that hemiketals were incorporated into the structure of MWNTols. The prepared MWNTols are highly soluble in polar solvents such as water, methanol, butanone and tetrahydrofuran, to give robust stable black solutions. Transmission electron microscopy reveals that the diameter, length and morphology of MWNTs are well retained in MWNTols.4. Utilizing the hydroxyls on the CNT surface as redox active center, redox polymerization of AA or NIPAM initiated by Ce(IV) ions was conducted at gental temperature (50℃or room temperature) in water. The amount of polymer (PAA or PNIPAM) grafted increased with the increase of feed monomers. The dispersibility of prepared PAA or PNIPAM functionalized CNTs can be controlled by varing the pH or temperature.5. Fe₃O₄ nanoparticles functionalied CNTs were prepared through chemical coprecipitation method, and showed good effect on application as dug carrier for lymphatic targeting.