College Park, Maryland      June 6 - 10 , 2004

M2-B4 (11:30 AM): Dispersing Single-Walled Carbon Nanotubes with Surfactants

H. Wang (Department of Materials Science and Engineering, Michigan Technological University, Houghton, MI 49931), W. Zhou, K. I. Winey, J. E. Fischer (Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia PA 19104), D. L. Ho, E. K. Hobbie, C. Glinka (National Institute of Standards and Technology)

We have investigated the dispersion of single walled carbon nanotubes (SWNTs) in heavy water with the surfactant Triton X-100 using primarily small angle neutron scattering. The data show that the SWNTs in this study have a large incoherent scattering cross-section, implying that they may be heavily hydrogenated due to acid treatment. The hydrogenation of SWNTs may play an important role in their dispersion with amphiphilic surfactants. The data also suggest an optimal surfactant concentration for dispersion, which we suggest results from competition between maximization of surfactant adsorption onto SWNT surfaces and a depletion interaction between SWNT bundles due to surfactant micelles. The latter effect drives SWNT reaggregation above a critical micellar volume fraction, leading to the general conclusion that the amount of surfactant, rather than its SWNT mass ratio, is the more relevant parameter in controlling dispersion. At optimal dispersion, the surfactant adsorption ratio is ca. 0.004 mol/g, comparable to previous findings.

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