COLL 152 |
| P Somasundaran1, Rui Zhang1, Xi-Yuan Hua2, and K. P. Ananthapadmanabhan2. (1) NSF IUCUR Center for Advanced Studies in Novel Surfactants, Columbia University, 500 W120th Street, 911 Mudd, New York, NY 10027, (2) Unilever Research US, Edgewater, NJ 07020 |
| In order to develop an understanding of the structure-performance relationships that control adsorption, solubilization and micellization properties in mixed surfactant systems, it is necessary to acquire information on micellar shape. Lack of such information has been a major barrier for major advances in this area. Effects of mixing and surfactant molecular structures on the micellar shape are correlated in this work with packing parameter in the binary mixtures of anionic-nonionic, cationic-nonionic, and nonionic-nonionic (nonyl phenol ethoxylated decyl ether-n-dodecyl-¦Â-D-maltoside) surfactants. The packing parameters of the mixtures calculated by assuming that the hydrophilic groups are spheres do not agree with the literature results. For the first two mixtures, modifications have been made to include the electrostatic repulsions between ionic surfactants and the results are in reasonable range. To explain the disagreement between the the predicted micellar shapes for nonionic mixtures with experimental results from FT-PGSE-NMR, a study using analytical ultracentrifuge and cryo-TEM was conducted and thus showed co-existence of primary and elongated micelles in the same solutions. The ultrafiltration results suggested polyethylene oxide surfactant to be responsible for micellar growth. Flexibility of polyethylene chain assists to minimize the cross-sectional area and in turn to form large micelles and even network structures. |
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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 |