Effect of Solvents and Dispersants on the Bundle Dissociation of Single-Wall Carbon Nanotube

Keywords:
dispersion nanotubes, polymers

Abstract:
Applications of single-wall carbon nanotubes (SWNT) are severely restricted, as they exist in rope-like bundles. It would be advantageous to have access to samples of dispersed individual nanotubes, or at the very least, to have some control over the bundle size. We have demonstrated a spectroscopic method to monitor bundle dissociation in low concentration NT-polymer composites. This method relies on the measurement of the ratio of free polymer to the nanotube-bound polymer in the SWNT-polymer solutions via luminescent spectroscopy. A theory has been developed to transform this data into bundle surface area, which is of course related to bundle size. This method clearly shows that individual, isolated SWNT are stable in low concentration dispersions. In addition, we have designed and synthesized different conjugated polymers, oligomers, as well as short-chain compounds in order to better understand the interactions of the nanotubes with the dispersant molecules. We have investigated the response of the different fluorescent molecules with single-wall, double-wall, and thin multi-wall nanotubes. We found a strong dependence of the concentration at which individual NTs become stable with the nature of the dispersant molecule, and with the diameter of the NTs. Finally we have used this technique to verify that certain amide solvents such as DMF and NMP can effectively solubilise and debundle SWNT. Our results are supported by extensive AFM and TEM data.

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Nanotech 2005 Conference Program Abstract