Regensburg 2010 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 14: Poster: Interfaces and Thin Films

CPP 14.19: Poster

Montag, 22. März 2010, 16:30–18:00, Poster C

Temperature-dependent structure transitions in thin smectic liquid crystalline films — •Benjamin Schulz, Christian Bahr, and Stephan Herminghaus — MPI for Dynamics and Self-Organization, Bunsenstraße 10, 37073 Göttingen

Thin films of smectic liquid crystals are known to show the formation of self-organized structures if they are subjected to antagonistic boundary conditions [1]. Such structure formations are promising systems as templates for the lithography of photonic crystals [2]. For this reason, a deeper understanding of the conditions that evoke different types of such structures is necessary for further applications of liquid crystal films.

We study films of about 300 nm in thickness of the liquid crystal 8CB near its transition between the smectic-A and the nematic phase using AFM and optical microscopy/polarized light microscopy. Below the actual phase transition temperature, we find structural changes in both the internal structure of the film and the surface topography. Depending on the film thickness, we can identify up to three different structures in the smectic phase. The liquid nature of our system should allow for a straightforward minimization of the free energy. However, near the second-order transition to the nematic state this seems to be a delicate process as we observe different structures. This behaviour could result from major changes of the elastic properties of the film in the vicinity of the transition.