Functionalization of single walled carbon nanotubes
Barron, Andrew R.
Doctor of Philosophy
Single walled carbon nanotubes (SWNTs) exhibit unique mechanical and physical properties and immediately after their discovery they were regarded as novel materials for future technologies. SWNTs are widely thought of as one of the basic building blocks to nanotechnology. However, they are very hard to disperse and dissolve in either water or organic solvent. The insolubility of nanotubes makes it very difficult to make composites of nanotubes with other materials. This limits nanotubes from the application for future technology. A feasible functionalization of nanotubes, i.e., the attachment of "chemical functional groups" provides a strategy for overcoming these barriers and has thus attracted synthetic chemists and materials scientists to contribute their efforts to making breakthrough. Functionalization can improve solubility and processibility, and will be able to link the unique properties of nanotubes to those of other types of materials. Through the chemical functional groups, nanotube may show improved solubility and compatibility with solvents, polymers, nanoparticles and other nanotubes. A functionalized SWNT may have mechanical or electrical properties that are different from those of the pristine SWNT, and thus may be used for fine-tuning the chemistry and physical properties of SWNTs. Fluorination of side walls of the SWNTs has been performed by using the technology developed for the fluorination of graphite, and then subsequent nucleophilic substitutions have been explored. It has been ascertained that in fluorination at the optimal temperature, C:F ratios of up to 2:1 can be achieved without disruption of the tubular structure. The fluorinated SWNTs proved to be much more soluble than pristine SWNTs in alcohols, N,N-dimethylformamide and some other selected organic solvents. This improved solubility and the high fluorine addition allow much more efficient solution-phase chemistry on the fluorinated SWNTs. The goals of this work were to examine novel type of reactions that one can do with fluorinated SWNTs and study the basic aspects of functionalization of SWNTs, i.e. the mechanism of functionalization, the structure of fluorinated SWNTs, and the distribution of functional groups in the functionalized SWNTs. In this thesis, an extensive NMR study of fluorinated SWNTs has been explored (Chapter 1) and this study gives us a deeper insight to the structure of fluorinated SWNTs and the mechanism of fluorination. A series of "hydroxyl nanotube" have been simply prepared by two types of one-step methods (Chapter 2). Amino-acid functionalized nanotubes with high water solubility and sensitive pH value dependence have been achieved, and the influence of different chain length of amino acid on the water solubility was detailed (Chapter 3). The nanotube-nanoparticle heterostructures have been prepared and used to investigate the distribution of functional groups along the axis of nanotubes (Chapter 4). Finally, a novel type of reaction, Diels-Alder cycloaddition to fluorinated nanotubes was successfully performed under a mild reaction conditions (Chapter 5).
Chemistry; Pure sciences; Fluorination; Nanotubes; Single-walled carbon nanotubes