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Gemini Surfactants at Solid-Liquid Interfaces: Control of Interfacial Aggregate Geometry
 

Summary: Gemini Surfactants at Solid-Liquid Interfaces: Control of
Interfacial Aggregate Geometry
S. Manne,*, T. E. Scha¨ffer, Q. Huo,§ P. K. Hansma, D. E. Morse,|
G. D. Stucky,§ and I. A. Aksay
Princeton Materials Institute and Department of Chemical Engineering, Princeton
University, Princeton, New Jersey 08544-5263, and Departments of Physics, Chemistry,
and Molecular, Cellular and Developmental Biology, University of California,
Santa Barbara, California 93106
Received January 22, 1997. In Final Form: June 2, 1997X
Recent work has shown that conventional surfactants form ordered aggregates of well-defined shape
and size at solid-liquid interfaces.1,2 Here we 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, aggregates tend to favor a lower curvature than in solution but follow the same
generalvariationwithsurfactantgeometry(i.e.,withlargerheadgroupareasresultingingreatercurvature).
These morphologies on mica correlate well with those observed in surfactant-silicate mesophases, where
electrostatic binding of headgroups also plays a dominant role. In addition, interfacial sphere-to-rod
transitions are induced on mica (as in free solution) by binding with a headgroup-specific counterion. In
contrast to mica, the hydrophobic cleavage plane of graphite interacts with surfactant tailgroups, giving
rise to interfacial aggregates that are surface-controlled and relatively independent of surfactant geometry.
This interaction is used to heterogeneously nucleate a surfactant-silicate mesophase which is interfacially

  

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

 

Collections: Materials Science