The thresholdless, hysteresis-free V-shape electro-optical switching in surface-stabilized ferroelectric liquid crystals, observed usually with a triangular voltage form, has been shown to be rather an apparent and not a real effect. Strictly speaking, it is observed only at one characteristic frequency f(i) and is accompanied by an inversion of the electro-optical hysteresis direction from the normal to the abnormal one. The switching of the director in a liquid crystal layer at f(i), in reality, has a threshold and a normal hysteresis. Even the optical transmittance shows a hysteresis at f(i) when it is plotted as a function of the voltage on the liquid crystal layer and not as a function of the total voltage on the liquid crystal cell which always includes the inner insulating layers. Due to these layers, a voltage divider is formed which includes the capacitance of the insulating layers and the dynamic impedance (capacitance and resistance) of the ferroelectric liquid crystal layer. The new explanation has been confirmed by experiments with different ferroelectric liquid crystal cells combined with external resistors and capacitors and by measurements of a strong dependence of f(i) on the liquid crystal resistance which was varied over three orders of magnitude. A theoretical analysis of the problem has also been made using certain approximations for material parameters and the space dependence of the sine form of the electric field in the liquid crystal layer. The conclusions are qualitatively consistent with the experimental results. Finally, the dynamic problem has been solved numerically by taking into account of all the relevant parameters (in the absence of flow and irregularities in the cell plane) and the obtained results are in excellent correspondence with the experiment. This has been demonstrated for sets of material and cell parameters providing the best V-shape performance.
The influence of the gold nanorods (GNRs) diameter on the electro-optic and dielectric properties of the ferroelectric liquid crystals (FLCs) was investigated. It was shown that dispersing of GNRs in FLCs could lead to an increase of the internal electric field inside the liquid crystalline layer. This effect results in a significant decrease of the switching time and the rotational viscosity of the FLC/GNRs nanodispersions independently on the GNRs diameter. Oppositely, the relaxation frequency and the dielectric strength of the Goldstone mode strongly depend on the GNRs diameter, which can be explained by the charge transfer between the GNRs and FLC molecules.
The motion of dielectric microparticles induced by external ac electric field, E, was investigated in the cell with in-plane stripe electrodes and filled with homeotropically aligned nematic liquid crystal. It was demonstrated that the average velocity of the microparticles depended on the third power of the electric field strength (v=μ(3)E3). The experimental results were explained by the induced charge electrophoresis.
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