Electronic Thesis and Dissertation Repository


Master of Engineering Science


Chemical and Biochemical Engineering


Dr. Jose Herrera


Obtaining stable aqueous dispersions is one of the main challenges hindering a widespread and effective use of single-walled carbon nanotubes (SWNT) in many applications. Although it has been recognized that their versatility makes them an extremely attractive material, the unique molecular structure that gives SWNTs their unmatched electronic, mechanical, and thermal properties is also responsible for strong van der Waals interactions. This, combined with extremely high aspect ratios and flexibility, causes SWNTs to adhere strongly into tightly bundled ropes. In these bundles, SWNTs are not as useful as their linearized unbundled equivalents. Thus, in order to take advantage of their properties effectively, SWNTs must be debundled. In this contribution we will report the characterization of a novel non-covalent system using the surfactant, cetyltrimethylammonium bromide (CTAB) and the polymer, polyvinylpyrrolidone (PVP) at different molecular weights. Initial tests using Vis-NIR spectroscopy showed that although individually these molecules are poor dispersers of SWNTs, they show a synergic effect when combined for all cases. We have probed for a mechanism using a battery of characterization techniques including Vis-NIR, atomic force microscopy (AFM), viscosity, dynamic light scattering (DLS), surface tension, and pH. Our data suggests that CTAB binds normally to nanotubes while PVP is augmenting dispersion through a physical mechanism specifically linked to its hydrodynamic radius. We propose our approach as a facile way of augmenting current nanotube dispersion techniques, potentially allowing for increased usage in the world today.