Static Permittivity and Electro-Optical Properties of Bi-Component Orthoconic Antiferroelectric Liquid Crystalline Mixtures Targeted for Polymer Stabilized Sensing Systems

Abstract

The behavior of two newly formulated bi-component orthoconic antiferroelectric liquid crystalline (OAFLC) systems, i.e., the Compound A + Compound B mixture system and Compound C + Compound B mixture system has been discussed in light of temperature and concentration dependencies of helical pitch length, spontaneous polarization, relaxation time, bulk viscosity, and the anchoring energy strength coefficient, together with static dielectric permittivity (ε) and dielectric anisotropy. Compound A + Compound B mixtures possess spontaneous polarization between 190–340 nC.cm−2 and fast relaxation times between 190–320 µs in the smectic antiferroelectric SmCA* phase at room temperature. Compound C + Compound B mixtures also have a spontaneous polarization in the range of 190–280 nC.cm−2 and relaxation times in the range of 190–230 µs at room temperature. Most of the mixtures have a helical pitch below one micrometer in the SmCA* phase. These advanced mixtures show a broad temperature range of the antiferroelectric SmCA* phase, fast switching of molecules under an applied electric field, negative dielectric anisotropy and a short helical pitch, confirming the advantage of designing new polymer-stabilized OAFLC that is targeted for novel application in sensing devices, utilizing the fast responsive electro-optical modulation elements.

The Influence of the Molecular Structure of Compounds on Their Properties and the Occurrence of Chiral Smectic Phases

“…The ferroelectric phase (SmC*) was predicted and then discovered by Meyer et al in 1975 [13], and antiferroelectricity in liquid crystals was discovered by Chandani et al in 1989 [14]. Practical applications have only liquid-crystalline mixtures [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] because the composition's tuning allows us to make the optimized ferro-or antiferroelectric mixtures. It is not easy to synthesize compounds with the desired properties.…”

Synthesis, Mesomorphic Properties and Application of (R,S)-1-Methylpentyl 4′-Hydroxybiphenyl-4-carboxylate Derivatives

“…[3][4][5]. Liquid crystalline mixtures are widely used in optical devices; therefore, new materials are constantly being developed for this purpose [6][7][8][9][10][11]. The use of the racemates also leads to a reduction in the preparation costs of the liquid crystalline The racemates can be used as dopants for the liquid crystalline mixtures, improving some of their properties, such as the antiferroelectric phase range, the helical pitch length, the reduction of the rotational viscosity, the decrease of the values of the spontaneous polarization, etc.…”

“…[3][4][5]. Liquid crystalline mixtures are widely used in optical devices; therefore, new materials are constantly being developed for this purpose [6][7][8][9][10][11]. The use of the racemates also leads to a reduction in the preparation costs of the liquid crystalline mixtures.…”