Mixed Spherical and Wormlike Micelles: A Contrast-Matching Study by Small-Angle Neutron Scattering
Small-angle neutron scattering studies were used to investigate the effect of adding an alcohol ethoxylate nonionic surfactant (d-C12E20) to aqueous solutions of a cationic surfactant, erucyl bis(hydroxyethyl) methylammonium chloride (EHAC), with and without salt (KCl). The systematic use of contras...
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Veröffentlicht in: | Langmuir 2004-11, Vol.20 (23), p.9978-9982 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Small-angle neutron scattering studies were used to investigate the effect of adding an alcohol ethoxylate nonionic surfactant (d-C12E20) to aqueous solutions of a cationic surfactant, erucyl bis(hydroxyethyl) methylammonium chloride (EHAC), with and without salt (KCl). The systematic use of contrast-matching, by alternately highlighting or hiding one of the surfactants, confirms that mixed micelles are formed. In salt-free solutions, mixed spherical micelles are formed and a core−shell model combined with a Hayter−Penfold potential was used to describe the data. The core radius is dominated by the EHAC tails and the outer radius determined by the ethoxylate headgroups of the nonionic surfactant. Addition of KCl promotes micellar growth; however, results of varying the solvent contrast revealed that when the nonionic surfactant is incorporated into the wormlike structure micellar breaking is promoted. Thus, mixed wormlike micelles with shorter contour lengths compared to the pure EHAC worms are formed. |
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ISSN: | 0743-7463 1520-5827 |
DOI: | 10.1021/la048355+ |