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

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 discussed.