Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 28: POSTERS Interfaces and Thin Films

CPP 28.26: Poster

Wednesday, March 25, 2009, 17:00–19:00, P3

Thickness dependence of diffusion in thin liquid crystalline films — •Benjamin Schulz, Jörg Schuster, and Christian von Borczyskowski — TU Chemnitz, Institut für Physik, 09107 Chemnitz

Liquid crystals are of high technical interest especially for the use in liquid crystal displays. As all applications are based on the orientational behaviour of the molecules, especially on surfaces, it is important to examine the molecular alignment and mobility in proximity to solid interfaces.

We are using single molecule microscopy to track the trajectories of dyes dissolved in the liquid crystal. This allows us to directly access to the molecular movement in the specimen. We are using specially tailored perylene dye molecules that align in the liquid crystal matrix and which are thus a good representation of the real behaviour of the liquid crystal molecules. The comparison with the diffusive behaviour of randomly aligning dye molecules gives us the chance to investigate the local structure on the surface. We find a drastic slowdown of diffusion as the film thickness decreases for both types of tracers, however, with a different thickness dependence. Film thickness is hereby varied from extremely thin quasi 2D films consisting of a single smectic double layer, up to quasi bulk material, where a crossover to 3D structured films (FCDs) is observed.

With our method we try to establish a model of the structure of extremely thin smectic liquid crystals, a question which is not yet resolved in literature, by relating the diffusive behaviour of the liquid crystals to the three dimensional patterning.