Journal Article10.1021/LA9605448
Surface-Aggregate Shape Transformation
118
TL;DR: In this article, the authors used atomic force microscopy (AFM) to find that mixtures of DDAPS and dodecyltrimethylammonium bromide (DTAB) at the interface between mica and aqueous solution form aggregates which have a length dictated by the proportion of each surfactant in the mixture.
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Abstract: The structure of surfactant surface-aggregates can be controlled by mixing two surfactants which, individually, form different surface-aggregate structures. Using atomic force microscopy (AFM), we have found that mixtures of (dodecyldimethylammonio)propanesulfonate (DDAPS) and dodecyltrimethylammonium bromide (DTAB) at the interface between mica and aqueous solution form aggregates (“hemimicelles”) which have a length dictated by the proportion of each surfactant in the mixture. In pure DDAPS, the two axes of the aggregate parallel to the mica−solution interface are similar in length and similar to the diameter of a bulk micelle. As the mole fraction of DTAB in solution is increased, one axis of the surface aggregates increases while the other remains almost constant. In the limit of pure DTAB solutions, the aspect ratio is large (>10). The length of the mixed aggregates is not a linear function of the mole fraction of DTAB in bulk, but this can be partially rationalized on the basis of electrostatic inte...
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Citations
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Gemini Surfactants at Solid−Liquid Interfaces: Control of Interfacial Aggregate Geometry
S. Manne,Tilman E. Schäffer,Q. Huo,Paul K. Hansma,Dwain E. Morse,Galen D. Stucky,Ilhan A. Aksay +6 more
TL;DR: In this article, the authors report interfacial aggregate structures as a function of surfactant geometry by using gemini surfactants with varying tail and spacer lengths on the anionic cleavage plane of mica.
Adsorption of Hexadecyltrimethylammonium Bromide to Mica: Nanometer-Scale Study of Binding-Site Competition Effects
TL;DR: In this article, the authors investigated the influence of adsorption of the salts HBr, KBr, and N(CH2CH3)4Br on the adaption of hexadecyltrimethylammonium bromide (CTAB) to mica.
196
References
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TL;DR: In this paper, the authors used atomic force microscopy to obtain direct images of surfactant aggregates at solid surfaces in aqueous solutions, and the resulting structures were consistent with half-cylinders on crystalline hydrophobic substrates, full cylinders on mica, and spheres on amorphous silica.
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