Antiferroelectric Behaviors of the SmCP Phase in Liquid-Crystalline Compounds with Achiral Bent-Core Liquid-Crystalline Molecules Containing Salicylaldimine-Based

摘要

A new series of bent-shaped mesogens has been synthesized and their mesomorphic properties studied. All compounds exhibit the B2 (SmCP) phase. Compounds with a 3,4′-biphenyldiol central core containing salicylaldimine-based and two terminal tetradecyloxy tails are reported. In addition, the effects of lateral substituent (R˭F and Cl) at the biphenyl core into 3′-position are examined. These substituents have a strong influence in reducing the clearing temperatures and increasing temperature range of the SmCP phase. The electro-optical switching characteristics have been investigated using both triangular-wave and DC electric fields. For several compounds, chirality switching from racemic to the homochiral state was seen after application of a low-frequency AC field. We studied spontaneous polarization, switching time, tilt angle, switching time, voltage-transmittance effect, and dielectric parameters (namely dielectric strength, relaxation frequency, distribution parameter) of a 7.5-µm-thick planar-oriented sample of a highly tilted anti-ferroelectric liquid-crystal material and investigated the correlation between their electro-optical properties and the chemical structures of these compounds.