Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 21: POSTERS Colloids, Nanoparticles and Aggregates
CPP 21.1: Poster
Mittwoch, 27. Februar 2008, 16:00–18:30, Poster A
Tuning the Surface Field at Liquid/Liquid Interfaces: New Wetting Behaviours and Surface Phase Transitions — •Christian Bahr1, Erfan Kadivar2, Yasutaka Iwashita1, Holger Stark3, and Stephan Herminghaus1 — 1MPI for Dynamics and Self-Organization, 37073 Göttingen — 2Department of Physics, University of Isfahan, 81746 Isfahan, Iran — 3Institute of Theoretical Physics, Technical University Berlin, 10623 Berlin
We present experimental and theoretical results concerning the ordering and wetting behaviour at interfaces between thermotropic liquid crystals and aqueous phases. The addition of a surfactant to either of the two bulk media provides the interface with an ordering potential which strongly influences the behaviour in the vicinity of the liquid-crystal – isotropic phase transition.
At nematic – isotropic transitions, the observed behavior changes from surface-induced order at higher surfactant concentrations to surface-induced disorder at lower surfactant concentrations. The experimental behavior can be well described within the framework of Landau-de Gennes theory. Current measurements concentrate on the realization of prewetting transitions.
At smectic – isotropic transitions, the variation of the surfactant concentration enables the observation of new surface layering transitions and surface triple points which were predicted by theoretical models but have experimentally not been demonstrated so far.
[1] E. Kadivar, Ch. Bahr, and H. Stark, Phys. Rev. E 75, 061711 (2007); Ch. Bahr, Phys. Rev. Lett. 99, 057801 (2007).