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Tip-Induced Orientational Order of Surfactant Micelles on Gold Hannes C. Schniepp, Dudley A. Saville, and Ilhan A. Aksay*
 

Summary: Tip-Induced Orientational Order of Surfactant Micelles on Gold
Hannes C. Schniepp, Dudley A. Saville, and Ilhan A. Aksay*
Department of Chemical Engineering, Princeton UniVersity, Princeton, New Jersey 08544
ReceiVed October 7, 2007. In Final Form: NoVember 29, 2007
Using liquid-cell atomic force microscopy, we investigate aqueous solutions of alkyltrimethylammonium halide
surfactants at the Au(111) surface. The long, micellar surfactant surface aggregates cover the gold surface completely
and exhibit two types of orientational order for chloride and bromide counterions, respectively. We observe lateral
forces perpendicular to the scanning direction, which we explain by anisotropic friction between the probe and the
oriented micelles. Conversely, we show that these friction forces can be employed to modify the spatial conformation
of the micellar adlayer. Where previous methods have failed to provide control over the orientation down to the level
of individual micelles, we use this technique to achieve a very high degree of order over more than 100 micelle
diameters.
Self-assemblyisapromisingfabricationtechnique1-8 providing
very high structural control and order on the nano- to micrometer
scale. A major shortcoming of this method, however, is that it
is not capable of providing deterministically defined structures
atmacroscopiclengthscales5,6,9,10 becauseamultitudeofdomains
are formed in an uncontrolled way as a result of the statistical
nature of domain nucleation and growth.5,6,11,12 To overcome
this problem, several approaches to guide self-assembly have

  

Source: Aksay, Ilhan A. - Department of Chemical Engineering, Princeton University

 

Collections: Materials Science