Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: Poster: Interfaces and Thin Films

CPP 19.9: Poster

Dienstag, 15. März 2011, 18:00–20:00, P2

Single Molecule Studies in Liquid Crystals — •Martin Pumpa and Frank Cichos — Molecular Nanophotonics Group, University of Leipzig

Liquid crystals show strong orientational order along a certain director, while lacking spatial order of their centers of mass. For uniaxial liquid crystals the orientational properties lead to anisotropy in the mobility and the optical properties of the material. Recent optical studies focus on their bulk behavior or the diffusion of microscopic particles, gaining only limited information on the microscopic dynamics in the liquid crystal. Single molecule fluorescence detection is in principle able to take a deeper look inside these systems, however, only few single molecule experiments have been published so far.

Here, we compare fluorescence depolarization experiments and single molecule tracking to get the anisotropic mobility of a fluorescent tracer molecule in LC samples. With polarization contrast images we are able to correlate findings from these experiments with the director orientation in the observed areas. Our results deviate strongly from recently published NMR results on the self-diffusion in liquid crystals. Thus we suggest based on additional FRAP measurements a strong influence of the fluorophore on the director structure in its immediate surrounding. This results in a smaller diffusion coefficient due to higher effective viscosities along and perpendicular to the macroscopic director orientation.