Dresden 2009 – scientific programme

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SYSO: Symposium Self-organizing Surfaces and Interfaces

SYSO 7: Self-Organizing Surfaces and Interfaces VI

SYSO 7.1: Talk

Thursday, March 26, 2009, 15:45–16:00, GÖR 226

Modulation of the free surface of smectic liquid crystals by focal conic domains — •Christian Bahr, Wei Guo, and Stephan Herminghaus — MPI for Dynamics and Self-Organization, Bunsenstr. 10, D-37073 Göttingen

If µ-thick films of smectic liquid crystals (LCs) on a solid substrate are subjected to antagonistic molecular anchoring conditions at the film/air and film/substrate interfaces, focal conic domains (FCDs) are generated in which the smectic layers are wrapped around two singular lines (a circle on the substrate surface and a straight line running from the circle center to the air interface).

FCDs often self-organize in regular two-dimensional arrays. They provide the LC film with a superstructure made up by a regular arrangement of defect lines and curved layers, and result in a deformation or modulation of the film/air interface: The curved arrangement of the smectic layers leads to a depression in the film/air interface above each FCD. The depth of these depressions amounts usually to a value between 50 nm and 2 µm and can be measured by AFM [1,2].

We report studies of several different LC/substrate systems and show, how the size and arrangement of FCDs—and thus the shape of the LC/air interface—can be controlled via the anchoring conditions on the substrate and the type of the smectic LC phase.

[1] V. Designolle, S. Herminghaus, T. Pfohl, and Ch. Bahr, Langmuir 22, 363 (2006).

[2] W. Guo, S. Herminghaus, and Ch. Bahr, Langmuir 24, 8174 (2008).