K. Kenig

Bicomponent Systems with Induced or Enhanced Antirerroelectric SmCA* Phase

Abstract A new method of the formulation of liquid crystalline antiferroelectric (CA*) materials from smectic C* and smectic A components is demonstrated. The phase diagrams of the induced CA* systems and the temperature dependence of their smectic layer spacings and switching behavior are shown.

Synthesis and Some Physical Properties of Unsymmetrical 4,4′-Dialkylazoxybenzenes

Abstract Two series of unsymmetrical 4,4′-dialkylazoxy compounds: have been obtained, where K = C m H2m+l with m = 2 to 10. The method of their synthesis and the results of measurements of the phase transition temperatures, dielectric constants, refractive indices and densities are presented. Compounds I and in a lesser degree compounds II are low-melting nematics with a small positive anisotropy of the dielectric constant. In both series a strong alteration was observed of clearing point, dielectric constant anisotropy Δe and birefringence Δn with the number in ofcarbon atoms in the alkyl radical.

Synthesis and mesomorphic properties of esters with swallow type terminal chain and their ability to enhance or induce anticlinic phases

Compounds with the terminal swallow tailed chain have been synthesized. The prepared compounds were studied by thermomicroscopy, differential scanning calorimetry, miscibility and X-ray diffraction methods.

Systems with Enhanced Antiferroelectric Phase. Phase Diagrams, Dielectric and Electro-Optic Studies

Abstract The phase diagrams, dielectric permittivity, electro-optic response for field induced antiferroelectric-ferroelectric transition of mixtures containing compounds with a partially fluorinated terminal chain are shown. V-shaped switching is observed in such mixtures.

Electro-optical properties of mixtures with the induced antiferroelectric phase

In some mixtures composed of ferroelectric components the induced antiferroelectric phase was observed. Two mixtures of this kind, both exhibiting antiferroelectric order in a broad concentration range, were investigated. The effect of electric field of various strengths on optical properties of these mixtures was studied. In small electric fields the modulation of light intensity occurred, which amplitude in ferroelectric phase was much higher than in the antiferroelectric one. In mixtures with induced antiferroelectric phase we detected a large hysteresis of the transition temperature between ferroelectric and antiferroelectric sates. In high electric fields thresholdless switching was observed in the hysteresis range. The presence of the thermal hysteresis of the CA* - C* phase transition can be considered as a mark of the V-shaped switching. In bulk samples the C*- phase is stable in, this temperature region, where the V- shaped switching was observed in thin samples.

Terphenyls and ketons as dopants for ferroelectric mixtures

Abstract Two host smectic C mixtures with the phase sequence SC*-N were doped with compounds not-having the smectic C phase chosen from biring ketons and/or triring terphenyls and dioxane derivatives. It was shown that these compounds may be useful as components for smectic C mixtures, especially when they are used simultaneously. When introduced in small amounts to smectic C mixtures they involve a change of a SC*-N(N) phase sequence to SC*-SA*-N(N) one, without depressing the thermal stability of the smectic C phase of the host mixtures and allow to adjust the tilt angle of molecules in the smectic C layers.

Viscosity, thermal and ultraviolet stability of liquid crystalline isothiocyanato compounds and their mixtures

Abstract The thermal stability of 4-(isothiocyanatophenyl)-1-(4-trans-alkyl)cyclohexane (CHBT) purified by treating with different sorbents and doped with polar and non-polar compounds was tested. The doping effect of various compounds on the bulk viscosity, optical and dielectric anisotropy and clearing point of CHBT mixtures was studied. The most advantageous components for obtaining these mixtures have been chosen.