Salt-Induced Sphere-to-Disk Transition of Octadecyltrimethylammonium Bromide Micelles
| Autor: | Martin Swanson-Vethamuthu, Eloi Feitosa, Wyn Brown |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Hydrodynamic radius
Stereochemistry Chemistry technology industry and agriculture Analytical chemistry Surfaces and Interfaces Condensed Matter Physics Micelle Light scattering Surface tension Differential scanning calorimetry Dynamic light scattering Transmission electron microscopy Critical micelle concentration Electrochemistry General Materials Science Spectroscopy |
| Zdroj: | Langmuir. 14:1590-1596 |
| ISSN: | 1520-5827 0743-7463 |
| DOI: | 10.1021/la9608167 |
| Popis: | We have used surface tension measurements, differential scanning calorimetry (DSC), dynamic light scattering (DLS), and cryo-transmission electron microscopy (cryo-TEM) to investigate the dynamic and structural behavior of octadecyltrimethylammonium bromide (C18TAB) micelles in water and NaBr solution. The surface tension data for fixed C18TAB concentrations of 25 mM and varied NaBr additions (0−50 mM) shows that the critical micelle concentration (cmc) increases after an initial decrease at 0.5 mM NaBr. This unusual effect has been explained using results from DSC and DLS. At low salt concentrations (below ca. 25 mM) the relaxation time distribution is bimodal with a dominant fast mode due to spherical micelles. Above ca. 35 mM NaBr disklike structures are favored and the relaxation time distribution is more closely unimodal. The postulated sphere-to-disk transition is supported by cryo-TEM micrographs. A pronounced increase in the micellar effective hydrodynamic radius (RH) is observed as the NaBr conce... |
| Databáze: | OpenAIRE |
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