1C21 Analysis of layer structure of bent-shaped dimer liquid crystals by X-ray microdiffraction

Abstract

Layer structure of bent-shaped achiral dimers, having two rod-like mesogens connected with a methylene spacer, designated as m (O) AMnAM (O) m, was investigated using x-ray microdiffraction. It was found that the structure changes from single layer to frustrated layer and bilayer with the increase of the terminal chain length (m) in compounds with a fixed spacer length (n). In mOAM5AMOm (m=8, 10, 12), (101) diffraction spots characteristic to frustrated structure were observed. On the other hand, in the homologous series with m=14 and 16, diffraction pattern depends on the irradiated position ; In one domain, only (001) indicating double layer structure was observed, and in the other domain, (001) and (101) diffractions were observed. These results suggest that the competition between frustrated and double layer structure occurs in these compounds, and critical correlation length of frustation is about 200Å.