화학공학소재연구정보센터
Molecular Crystals and Liquid Crystals, Vol.437, 1343-1353, 2005
Revealing the structure of focal conics cores and their influence on the evolution with temperature: An x-ray study of ultra-thin 8CB films
We have studied by x-ray diffraction the deformations of thin smectic films induced by antagonistic anchorings, as a function of thickness and temperature. The structure of the cores is revealed for thicknesses of the order of 0.15 mu m when the deformations are dominated by the presence of the focal conics cores. In a cylindrical geometry imposed by the unidirectional anchoring on the substrate, the cores are tube-shaped rotating grain boundaries (RGB). The spatial extension is of the order of 0.14 x 0.22 mu m(2), larger than the ones usually proposed in the literature. A drastic evolution of the x-ray scans with temperature is also revealed. It corresponds to a variation of the location of the RGB and is analyzed as the result of a weak variation of the 8CB/air surface tension with temperature.