An experimental study of a lyotropic nematic liquid crystal (CsPFO in a water solution) confined to a cylindrical tube is presented. The structure of the sample is controlled by a magnetic field. A small ac voltage is applied along the tube for conductivity measurements. Elastic constants and conductivity constants of the material are determined from static measurements at different magnetic fields. The method is also used to determine the rotational viscosity γ1 from dynamic response under sudden changes of the magnetic field. The dynamic measurements are analyzed in the framework of the Leslie–Ericksen theory. It is shown that although the dynamic behavior can be qualitatively explained with a single effective rotational viscosity γ1, back flow effects have to be taken into account should the analysis yield consistent values for γ1. The results obtained by this method agree well with other experimental studies.
Wood is transparent for microwaves and due to its anisotropic structure has anisotropic dielectric properties. A laboratory experiment that allows for the qualitative demonstration and quantitative measurements of linear dichroism and birefringence in the microwave region is presented. As the proposed experiments are based on the anisotropy (of wood), which is evident from the observable anisotropic structure of wood, they may serve as a demonstration for explaining the anisotropic properties in crystals in the optical region.
iquid crystal droplets, being L relatively easy to produce, have been of interest since the early days of liquid crystals. This interest is both scientific and practical. Scientifically, we would like to know how confinement can alter the macroscopic properties of materials previously understood only in the bulk. In the case of liquid crystal droplets, the boundary conditions are fundamentally incompatible with parallel orientation in the bulk, which leads to topological defects in the structure. By applying an electric field or increasing the chirality, the situation is further complicated and new textures with new defects may evolve. From a practical standpoint, an understanding of the above processes is necessary when using droplets for applications. Polymer-dispersed nematic liquid crystal
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