Ph. D. Thesis

Reactivity and handling of single-wall carbon nanotubes : surface functionalization through covalent grafting and the use as a structural directing agent

ABSTRACT

This thesis work is concerned with the use of single-walled carbon nanotubes (SWNTs) as structural directing agent, and with the covalent grafting of SWNTs in order to modify their surface properties.

In the first part, we discuss the use of SWNTs as structural directing agent in the synthesis, in the hydrothermal way, of mesoporous aluminosilicates. Some composites presenting the MCM-41 structure are thus formed. They are characterized by electronic microscopy, Raman diffusion, X-ray diffraction and adsorption-desorption of N₂. Isolated nanotubes in the mesopores were observed with transmission microscopy, but the structure of the composites is not yet well defined.

The second part deals with the fluorination of SWNTs with F₂. The spectroscopic evolutions of fluorinated buckypapers are discussed as a function of growing amounts of grafted fluorine. The good solvation properties of C₂F fluorotubes in isopropanol is highlighted by atomic force microscopy (observation of a majority of isolated tubes, and not bundles). The defluorination reaction, using hydrazine, has been studied with Raman diffusion, first upon solvated fluorotubes, then upon isolated fluorotubes deposited on a surface. The evolution of the radial breathing modes, observed after defluorination, are explained by the bundle effect.

The last chapter is focused on the grafting of aryl groups on SWNTs, using the electrochemical reduction of diazonium salts. Thin films made of nanotubes are utilized as a work electrode in a constant potential device. The grafting of 4-bromophenyl, 4-carboxyphenyl and 4-chloromethylphenyl groups are characterized with Raman diffusion and X-ray photoelectron spectroscopy. The possibility of coupling some grafted aryls and other groups has been explored upon nanotubes functionalised with 4-chloromethylphenyls (nucleophilic substitutions with amines and diamines).

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