A number of experimental data on hexatic liquid crystal phases, namely the smectic I and F phases of various members of the TBnA family, are presented. They allow a better understanding of the respective structures and information of the smectic I and F phases.
The electrooptic response of the planar samples of TB 10A in book-shelf and chevron geometries has been measured in the frequency range 1 Hz -100 IrHz.In order to have a linear response 4% of ferroelectric liquid crystal DOBAlME'C has been admixed to the non-chiral TBlOA to create ferroelectricity in the mixture. In the Sc phase two low frequency relaxation processes have been found. The lower relaxation found in the region of several Hz corresponds to the deformation of the smectic layers, the higher one with the relaxation frequency of a few hundreds Hz corresponds to the azimuthal mode. These two relaxations give both positive resp. one positive and one negative contributions to the electrooptic response for the book-shelf resp. the chevron structures.
A new experimental technique is described for the measurement of local birefringence and molecular orientation in liquid crystals. This technique consists in analyzing the local channeled spectra obtained by optical polarising microscopy.
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