Chiral Smectics: As Observed through Dielectric Spectroscopy

Abstract

Chiral compounds show rich variety of smectic phases viz. SmC a à , SmC b à , SmC c à , SmC à , SmC A à due to different correlation between adjacent layers and various TGB phases due to different orientation of blocks of layers. Dielectric spectroscopy has proven as an important tool for the characterization of various smectic phases posses by chiral compounds. Dielectric spectra of these phases are sometimes complex but rich in information and are very helpful in the determination of the structure of these phases. Dielectric spectroscopy of the above phases observed in the recently synthesized materials is discussed with regards to their structure property relationship.

Experimental evidence of soft mode in the smectic C*α phase of chiral ferroelectric liquid crystals

“…Similar results were obtained during the dielectric spectroscopy studies of other chiral smectics. [19][20][21][22] If assumed that the relaxation times characterising the SmC * a phase describe the azimuthal mode, then according to that principle it might be considered that the helix pitch p in the SmC * a phase is three times shorter than that in the SmC* phase. Thus, the shortening would be limited to the range of typical changes observed during heating of the ferroelectric smectic C* phase to the paraelectric SmA* one.…”

Changes in the Dielectric Parameters of an Antiferroelectric Material (Racemic Mixture) Due to Electron Beam Irradiation

“…The temperature of the sample was controlled with the help of a hot stage (Instec model HS-1) having an accuracy of AE0.1 C and temperature resolution of 3 mK. To analyze the measured data, the dielectric spectra have been fitted with the generalized Cole-Cole equation [16][17][18]. Further details about the experimental techniques used for the dielectric measurements are described in some other publications [11-13, 17,18].…”

Dielectric and switching properties of a highly tilted AFLC material (S)-(+)-4-(1-methylheptyloxycarbonyl)-2,3-difluorophenyl 4′-[3-(2,2,3,3,4,4,4-heptafluorobutoxy)prop-1-oxy]biphenyl-4-carboxylate

“…orthoconic AFLC) material. [10,11] Studies of AFLCs are important not only from application point of view but for the basic studies as well because many of these materials are very rich in mesomorphism. In AFLC, spontaneous polarisation emerges perpendicular to the tilt plane, reflecting the polar properties of the liquid crystal.…”