COLL 146 |
| Linda J. Magid1, Zhibin Li1, and Paul D. Butler2. (1) Department of Chemistry, University of Tennessee, 552 Buehler Hall, Knoxville, TN 37996-1600, (2) Solid State Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, MS 6393, P.O. Box 2008, Oak Ridge, TN 37831-6393 |
| Micellar morphology in aqueous solutions of cationic surfactants like cetyltrimethylammonium (CTAX) can be manipulated by changing the counterions, X-. Counterions that penetrate the micellar interface, especially substituted chloro- and hydroxybenzoates (salicylates) and tosylate, produce very large, semi-flexible wormlike micelles, whose solutions are often viscoelastic. Furthermore, adding high concentrations of the counterions’ sodium salt (NaX) causes reversion to a globular micellar shape; this occurs at an NaX concentration that is counterion-specific. We have determined by SANS the contour lengths, persistence lengths (flexibility) and cross-sectional radii of the worm-like micelles. Some aromatic counterions increase micellar flexibility; others decrease it. In addition, for the case of CTA 2,6-dichlorobenzoate, we have used micelles prepared with deuterated counterions and used SANS with external contrast variation to determine the role of counterion binding in the reversion to globular micelles. We have also used neutron spin-echo spectroscopy to study the dynamics of these discrete globular micelles. |
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Symposium in Memory of Arthur W. Adamson
2:00 PM-5:40 PM, Monday, March 29, 2004 Marriott -- Orange County 4, Oral
Division of Colloid and Surface Chemistry |