Katsuyuki Murashiro

Ps inversion in three homologous series of ferroelectric 5-(2-fluoro-alkyloxy)-2-(4-n-alkylphenyl) pyrimidines

Abstract We synthesized members of four homologous series of the general formula Most of the compounds exhibit smectic phases with negative PS, at higher temperatures, changing the sign to give positive PS, at lower temperatures. The inversion temperatures and PS, at a reduced temperature show alternating behavior. The tilt angles measured by X-rays as well as by electrooptical investigation do not possess any anomaly at TPS, and in several cases are practically constant. We discuss the molecular arrangemeit in C and C* phases. In order to explain the PS behavior we use the molecular statistical theory developed by Osipov et al. In this theory Ps is determined by the chiral dipole, the steric dipole and the polarizability properties of the molecules; the interplay of these properties characterizes the binding site. By opposite signs of dipolar and quadrupolar coupling of the molecules and the temperature dependence of the steric dipoles, the Ps inversion can be explained.

Field-Induced Phase Transitions in Antiferroelectric Liquid Crystal

Cell thickness dependence and field impression rate dependence of field-induced phase transition in an antiferroelectric liquid crystal (MHPOBC) have been investigated by observing the optical transmittance hysteresis loop and texture of the cells. In thin cells, pseudo-triple hysteresis loops due to coexistence of ferroelectric and antiferroelectric domains have been observed. In thick cells, an antiferroelectric phase is stabilized near the zero-field region of a ferrielectric phase of a field-temperature phase diagram. A possible model for molecular orientational structure of the phases and field-induced transitions among them is discussed on the basis of these experimental results.

Submicrosecond Preliminary Process of Electric-Field-Induced Reorientation of a Ferroelectric Liquid Crystal, 5-(2-Fluoroalkoxy)-2-(4-n-Alkylphenyl)-Pyrimidine, Studied by Time-Resolved Infrared Spectroscopy:

Pulsed electric-field-induced reorientation of a ferroelectric liquid crystal (FLC), 5-(2-fluorooctyloxy)-2-(4-hexylphenyl)-pyrimidine, has been investigated by using a dispersive submicrosecond time-resolved infrared spectroscopic technique. The observed absorbance decay for a band at 1440 cm−1 due to a ring-stretching mode of the phenylpyrimidine group indicates that the FLC molecule reorients from a stationary state with a slight delay (less than 1 μs) just after the upswing of the electric field, while counter-reorientation occurs with a delay time of a microsecond after the reverse of the electric field. The delay time for the counter-reorientation changes with temperature, indicating that the viscosity has a strong influence on the delay time. It is also indicated in the present study that the whole FLC molecule reorients simultaneously as a rigid rod in both the preliminary and the counter-reorientation process.

The polymorphism of a new chiral compound with smectic C* AND CA* phases

Abstract In this paper we present the polymorphism of a new chiral substance. Evidence for two new low temperature phases is given. Special interest is focused on two smectic C phases, the transition beween both could be detected by means of texture observations and DSC measurements. X-ray measurements and density investigations point to a discontinuous change of the values. Miscibility studies with MHPOBC suppose the classification as smectic C and CA. The physical properties of the smectic C* phase are discussed.

Time-resolved FT-IR studyof 5-(2-fluoroalkoxy)-2-(4-n-alkylphenyl)-pyrimidine

Abstract The electric-field-induced reorientation of the C*phase of 5-(2-fluorooctyloxy)-2-(4-octylphenyl)-pyrimidine was investigated by using an asynchronous time-resolved FT-IR technique. The time-resolved study indicates that the liquid crystal (LC) molecule reorients from perpendicular (zero time of delay) to parallel (500μus delay) direction with respect to that of the polarized infrared light at 32°C while it does reversely at 41°C. It is also shown that the change in the voltage applied has little influence on the rate of reorientation in the region of the positive spontaneous polarization (Ps), while the rate in the region of the negative Ps strongly depends upon the voltage.

Coexistence of ferroelectric and antiferroelectric domains in chiral liquid crystals

Abstract Field-induced phase transition in an antiferroelectric liquid crystal (MHPOBC) have been investigated by observing optical transmittance hysteresis loops and microscopic textures. Pseudo-triple hysteresis loops due to coexistence of ferroelectric and antiferroelectric domains have been observed in an antiferroelectric temperature region in homogeneously aligned thin cells. The ratio of the coexisting domain area can be controlled by appropriate driving fields; the controllability leads to an application of antiferroelectric liquid crystal displays with gray scale.

Field dependence of helical structures in ferroelectric and antiferroelectric liquid crystals

Abstract Helical structures in ferroelectric and antiferroelectric liquid crystals and their changes by electric fields have been investigated by a simultaneous measurement of light diffraction intensities, transmitted light intensities and polarization reversal current of homogeneously aligned cells. The experimental results have been discussed on the basis of helix unwinding and polarization reversal process.