Dresden 2009 – wissenschaftliches Programm

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SYSO: Symposium Self-organizing Surfaces and Interfaces

SYSO 3: Self-Organizing Surfaces and Interfaces - Posters

SYSO 3.5: Poster

Mittwoch, 25. März 2009, 17:30–19:30, P3

Observation of prewetting transitions at surfactant-laden liquid-crystal/water interfaces — •Christian Bahr — MPI for Dynamics and Self-Organization, Bunsenstr. 10, D-37073 Göttingen

Fundamental arguments [1,2] predict for systems possessing a first-order wetting transition at coexistence, that first-order surface transitions should exist also off coexistence. These prewetting transitions are characterized by a discontinuous finite change of the thickness of the wetting film.

We have recently studied [3,4] the wetting behavior of thermotropic liquid crystals at surfactant-laden interfaces to aqueous phases. The wetting film at the interface consists in this case of a thin ordered (nematic or smectic) film which exists at temperatures where the bulk phase is in the disordered (isotropic) state. A significant advantage of the liquid-crystal/water systems is, that the strength of the ordering surface field can be controlled via the concentration of the surfactant. Careful tuning of the surfactant concentration should enable the experimental realization of prewetting transitions. In this study, we report first measurements confirming the existence of prewetting transitions in a nematic wetting film at such interfaces.

[1] J. W. Cahn, J. Chem. Phys. 66, 3667 (1977).

[2] H. Nakanishi and M. E. Fisher, Phys. Rev. Lett. 49, 1565 (1982).

[3] Ch. Bahr, Phys. Rev. Lett. 99, 057801 (2007).

[4] E. Kadivar, Ch. Bahr, and H. Stark, Phys. Rev. E 75, 061711 (2007).