Dresden 2003 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 20: POSTER A

CPP 20.36: Poster

Montag, 24. März 2003, 19:00–21:00, ZEU/250

Isotropic droplets in thin smectic films — •Heidrun Schüring and Ralf Stannarius — Universität Leipzig, Institut für Experimentelle Physik I, Linnéstr. 5, 04103 Leipzig

Stable freely suspended films of a few molecular layers can be prepared from smectic liquid crystals. At temperatures near the smectic/isotropic phase transition, inner layers of the material start to melt. The molten material is either expelled into the meniscus, leading to a stepwise film thickness reduction, or collected in isotropic droplets in the films.

After some initial dynamics of droplet formation, their shapes remain unchanged at constant temperature. Analysis of the droplet shape allows to determine the difference of surface tensions of isotropic and smectic phase as well as interface tensions between both phases [1].

The system behaves in some aspects like a two dimensional colloid. Capillary forces can be investigated from droplet dynamics. Whereas in films of homogeneous thickness, droplets move only randomly (Brownian) within the film plane, a directed motion toward thicker film regions, driven by capillary forces, is observed in inhomogeneous films.

[1] H. Schüring, R. Stannarius; Langmuir 18 9735 (2002).