Keiichi Sakashita

Novel Ferroelectric Liquid Crystalline δ-Valerolactone Derivatives with Very Large Spontaneous Polarization

Abstract A series of new chiral compounds with a δ-valerolactone ring were synthesized and the physical properties of these compounds as well as the electrical properties of their ferroelectric liquid crystal (FLC) mixtures were investigated. The magnitude of spontaneous polarization (Ps) in the chiral smectic C phase (SmC*) was found to be as high as 384 nC/cm2 for (2R, 5R)-2-(4′-octyloxybiphenyl-4-carboxy)-5-butyl-δ-valerolactone at ΔT = Tc - T = 5°C, where Tc is the temperature of transition from the isotropic phase to the SmC* phase and T is the temperature at which the experiments were carried out. An FLC mixture containing 2% by weight of the optical isomer, (2S, 5R)-2-(4′-octyloxy-biphenyl-4-carboxy)-5-hexyl-δx-valerolactone exhibited a response time as fast as 96 μ seconds at 25°C, for an applied square-wave voltage of ± 10 volts. The relationship between the structural properties and the thermal properties, magnitude and polarity of Ps as well as the response times for their FLC mixtures are disc...

Novel Ferroelectric Liquid Crystals with Very Large Spontaneous Polarization

Several ferroelectric liquid crystals derived from a new optically active (2S, 5R)-2-hydroxy-5-hexyl-δ-valerolactone have been synthesized, and their mesomorphic and ferroelectric properties have been investigated. Very large spontaneous polarization (Ps) has been observed in these compounds, one of which shows an extremly large Ps value: as high as 320 nC/cm2.

2-Hydroxy-5,5-dialkyl-δ-valerolactone derivatives as chiral dopants for practical ferroelectric liquid crystals

Abstract 2-Hydroxy-5,5-dialkyl-δ-valerolactone derivatives have shown interesting properties as a chiral dopant for ferroelectric liquid crystals. In small amounts these compounds induce high magnitudes of spontaneous polarization and long helical pitches in the chiral nematic phase (N*). Alkyl chains attached at the C-5 position play an important role in these properties. Here we discuss the stereochemistry and ferroelectric properties of these lactones and compare them with those of 2-hydroxy-5-alkyl-δ-valerolactone derivatives reported previously. The ring structure of 5,5-dialkyl-δ-valerolactone is found to be a rigid ‘pseudo-chair’ conformation by *H NMR studies.

Synthesis and properties of new chiral dopants containing a δ-lactone ring for practical ferroelectric liquid crystal mixtures

Abstract A series of new optically active δ-lactones were synthesized as chiral dopants for ferroelectric liquid crystals (FLCs). The response time of an FLC mixture containing 4 mol% (S)-2,2-dimethyl-5-[2-fluoro-4-(5-n-octylpyrimidin-2-yl)-phenoxy[methyl-δ-valerolactone was 25 μs at 25°C. (0–90 per cent change in light transmission, 10 V μm−1). The synthesis and properties of these materials as practical chiral dopants are reported.

Stereochemical studies of optically active 2-hydroxy-5-alkyl-δ-valerolactone derivatives as chiral dopant for ferroelectric liquid crystals

Abstract Both (2S, 5R)- and (2R, 5R)-2-hydroxy-5-alkyl-δ-valerolactone derivatives, cis and trans, respectively, show almost the same magnitude of spontaneous polarization (P s) when added to a non-chiral smectic C mixture. The stereochemistry of these chiral dopants was studied using 1H NMR. Trans derivatives seem to have a half-chair conformation with the 2, 5-diequatorial substituents and the cis derivatives have rather a flat conformation in solution. However in the liquid-crystalline phase, the cis and trans derivatives appear to change their conformation or the distribution of their conformations as the alkyl chain length is varied. The difference in the effect as a chiral dopant depends upon lateral interactions between chiral molecules through the solvent liquid crystal phase.

Mesomorphic and ferroelectric properties of novel optically active compounds derived from (R)-3-hydroxynonanoic acid

Abstract Novel optically active compounds derived from (R)-3-hydroxynonanoic acid as shown in a general formula (I) have been synthesized and their mesomorphic and ferroelectric properties have been investigated. The kind of mesophases and the transition temperatures depend strongly on the linkage groups and the substituents in the core. The compounds with an unsubstituted core show non-titled smectic mesophases (smectic A or B). The chiral smectic C phase appears in the compounds having a central ester linkage and a chloro-substituent as the A 1 or B 1 position and in the compound having a central -OCH2- linkage and a chloro-substituent at the A 1 position. The maximum spontaneous polarization (500 μC/m2) was observed in 4-dodecyloxy-3-chlorobenzoyl-oxyphenyl (R)-3-hydroxynonanoate. The thermal stability of each mesophase and the ferroelectric properties have been discussed from the structural point of view.

Ferroelectric Liquid Crystal Mixtures Doped with Compounds Having Chiral Groups at Both Ends of the Core

The transition temperature from chiral smectic C (Sm*C) phase to smectic A (SmA) and the spontaneous polarization (Ps) of mixtures having two components of normal ferroelectric liquid crystal and a compound having two optical active 1-methylheptyl groups at both ends of the core have been investigated. The SmA-Sm*C transition temperature and the magnitude of Ps for the mixtures were found to depend on the absolute spatial configuration of both chiral groups. The maximum Ps (225 nC/cm2) was observed in a mixture doped with a compound whose chiral groups were classified into the same polarity as that of the host ferroelectric liquid crystal.

Relationship between Molecular Structure and Induced Spontaneous Polarization for Chiral Dopants Containing an Optically Active Lactone

Abstract A series of new optically active γ-lactones were synthesized. The relationship between molecular structures and induced spontaneous polarization of optically active γ-lactones and δ-lactones has been investigated. The molecular shapes of chiral dopants, especially the alkyl chains extending from a lactone ring, were found to play important roles in the generation of spontaneous polarization.

New Chiral Dopants with an Optically Active Six-membered Ring for Ferroelectric Liquid Crystals. Effect of Direction of the Dipole Moment on Spontaneous Polarization

Abstract New chiral dopants containing an optically active six-membered ring with a cyano group were synthesized. New chiral dopants containing an optically active six-membered ring with an epoxy group were also synthesized and the effect of the direction of the dipoles on spontaneous polarization were discussed using them. The spontaneous polarization is thought to be influenced by the direction of the dipoles of the chiral moiety.