Syuichi Tatemori

SmCα* domains in SmCβ* phase of antiferroelectric liquid crystals

Abstract The ferrielectricity and domain structures of the chiral smectic Cβphase (SmCCβ*) in antifer-roelectric liquid crystals were investigated. The real part of complex dielectric constant ε′ in SmCβ* shows two-step decrease with increasing DC bias field. Each decrease corresponds to the suppression of relaxational two modes: one is the ferroelectric Goldstone mode and the other is a new mode induced by DC bias field. The relaxational frequency of the latter mode is nearly the same as that of chiral smectic Cαphase (SmCα*). Another mode was observed at the field strength where ε′ shows steeply decrease. This mode may be attributed to the boundary motion between domains or phases. Three peaks of the switching current were observed in SmCβ* and also in the lower-temperature region of SmCα*. The peak positions are continuously linked to those of SmCα*. It can be said that the antiferroelectric ordering of SmCα* may appear as domains even in SmCβ* by electric bias field.

Antiferroelectricity of a Chiral Smectic Liquid Crystal Having Three Isolated Phenyl Rings in the Core

Abstract Phase sequence and helicoidal structure of a chiral smectic liquid crystal and its binary mixtures with a well-known antiferroelectric liquid crystal MHPOBC were studied by dielectric electro-optic and circular dichroism measurements. Structural difference between this material and MHPOBC is an ester group introduced into the biphenyl core. The fundamental phases of antiferroelectric liquid crystals, SmC* and SmCA*, do not appear in this pure material, but, by doping a small amount of MHPOBC, SmCA* is stabilized in a wide temperature range. This material may be categorized as a potential antiferroelectric liquid crystal.

Deflection of Light at the Boundaries between Ferroelectric and Antiferroelectric States in Chiral Smectic Liquid Crystals

A light deflection phenomenon was observed at a field-induced phase transition point between an antiferroelectric state and ferroelectric one in antiferroelectric liquid crystals. The dependence of the angle of deflection on the angle of incidence was numerically analyzed, and it was concluded that the light deflection is due to refraction and reflection at the boundaries between the states coexisting at the field-induced phase transition point. A similar deflection phenomenon was also observed in the ferroelectric and ferrielectric phases at zero electric field. Possible phases or domains coexisting in this condition were discussed.

Reflection and refraction of light at the boundaries between ferroelectric and antiferroelectric phases in chiral smectic liquid crystals

Abstract Light deflection phenomena in antiferroelectric chiral smectic liquid crystals were investigated. Characteristic deflected lights were observed at electric field induced phase transitions between antiferroelectric (AF) state to ferroelectric (F) one. On the basis of a numerical analysis of Huygens construction at the phase boundaries between coexisting AF and F states, it is concluded that the light deflection is not due to diffraction but due to refraction and reflection at the phase boundaries. The characteristic dependence of the deflection angle on the angle of incidence was proposed as a possible evidence of coexistence of phases or domains in materials.

Field Induced Domains in Antiferroelectric Liquid Crystals.

Domain structures at field induced phase transitions of antiferroelectric liquid crystals were investigated by dielectric, electrooptic and light deflection experiments under electric bias fields. Characteristic light deflection phenomena indicating the co-existence of different refractive index domains were observed in antiferroelectric, ferroelectric and ferrielectric phases. Above all, in the chiral smectic Cβ* phase (SmCβ) being considered ferroelectric, the light deflections appeared at zero field after removing the bias and also in two field ranges at which the dielectric constant and the apparent molecular tilt angle showed the step-wise changes. Possible models for the coexisting domains at these induced phase transitions were discussed.

Light deflection by antiferroelectric liquid crystals under electric bias field

Abstract Domain structures of a chiral smectic phase, Cβ, of antiferroelectric liquid crystals were investigated by dielectric, electro-optic and light deflection experiments under electric bias fields. Characteristic light deflection indicating the coexistence of domains of different refractive index were observed in two regions of bias field where the electric constant show steep decrease, and also in the absence of field after removing the bias. A possible model for the molecular orientation and helical structure in each domain were dicussed.

Dielectric Relaxation Behavior of Ferroelectric Phase in Antiferroelectric Liquid Crystals

The ferroelectric phase in optically pure samples and racemized ones of an antiferroelectric liquid crystal were studied by a dielectric dispersion experiment. In the optically pure samples, in addition to the Goldstone mode, a new relaxation mode was found, which is related to a molecular motion within the plane parallel to the cell surface. A model based on a field-induced conformation change of molecules was proposed for the ferrielectric-like behavior of SmCβ*.

Polarized FT-IR study on SmCβ* and SmC* of antiferroelectric liquid crystals

Abstract Alignment of molecules and hindered rotation of molecular segments in SmCp* and SmC* of antiferroelectric and ferroelectric liquid crystals were studied by the polarized infrared absorption spectroscopy. The experimental results show that the apparent molecular tilt angle in SmCβ* increases not monotonously but as a two-step staircase with increasing dc bias field, and the characteristics of hindered rotation of carbonyl groups in unwound state of helix are the same as that of SmC*.