Dielectric Properties in Ferroelectric Liquid Crystal Mixtures with Ultrashort Pitch

Abstract

The dielectric propereties of smectic liquid crystal mixtures containing chiral dopants derived from trifluoromethylated pyranose were studied. In every mixture, a large dielectric response due to the Goldstone mode was observed, indicating the smectic C* phase, although two switching current peaks indicative of the smectic CA * phase were observed in the mixtures with high dopant ratios. With increasing the chiral dopant ratio, the dielectric strength becomes smaller and the relaxation frequency becomes larger. This behavior was qualitatively explained by the chiral dopant ratio dependence of the spontaneous polarization and the helicoidal pitch. It was also found that a higher dc bias field was required to suppress the Goldstone mode in the mixture with a higher dopant ratio, suggesting the helicoid-stabilized state.

Current Topics in Smectic Liquid Crystal Research

“…If, however, the pitch is very short (typically below 300 nm) and the cell gap is not too small, it is possible to obtain the double current peak and three-state electro-optic response characteristic of antiferroelectric switching even from an SmC* phase. [38,159,160] An example of how the electro-optic response of an extremely short-pitch SmC* mixture changes from mainly ferroelectric to antiferroelectric as the cell gap is increased is shown in Figure 28.…”

Influence of ZnO nanostructures in liquid crystal interfaces for bistable switching applications

“…Earlier work reported this difference in dielectric and electro-optical rotational viscosity values for different LCs [64,65]. The reason is that polarization reversal measurement is a large signal method requiring full switching of the hydrogen bonded benzoic acid LC.…”

A Chameleon Chiral Polar Liquid Crystal: Rod-Shaped When Nematic, Bent-Shaped When Smectic

“…At small amplitude analogue deformed-helix-mode response is detected and at large amplitude ferroelectric switching directly between the two uniform nonhelical states are seen, both response types clear indications of the phase being synpolar. At intermediate amplitude, in the range where the helix is unwound and rewound during every switching cycle, the response is quite complex, having a component of ferroelectric switching as well as of the helix unwinding/rewinding process, effectively antiferroelectric. ,, This gives the current response three peaks per half cycle at this amplitude, a response which one may mistakenly interpret as a sign of the phase being ferrielectric. The strong influence of the cell surfaces in the 0.8 μm sample strongly favored supercooling of the SmC s P F * phase which made investigations of the SmC a P A * phase very difficult but had the advantage that the spontaneous polarization could be measured at temperatures far below the melting point of the material.…”