Influence of Optical Purity on Stability of Chiral Smectic-C Phase in Antiferroelectric Liquid Crystal under Pressure

Abstract

The complex dielectric constants of 4-(1-methylheptyloxycalbonyl) phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC) with different optical purities (R:S = 6:4, 9:1) were measured under pressure. In MHPOBC (R:S=6:4, 20%ee), the temperature width of the chiral smectic-C (SmC*) phase increased with pressure. On the other hand, the temperature width of the SmC* phase in MHPOBC (R:S=9:1, 80%ee) was almost independent of pressure at low pressures, but the SmC* phase vanished above 100 MPa. The chiral smectic-Cα (SmCα *) phase instead of the SmC* phase widened at 150 MPa. From these results, including those of previous studies, the SmC* phase widened with pressure when the optical purity was below 50%ee and vanished under pressure when the optical purity was above 80%ee. It is suggested that the disappearance of the SmC* phase under pressure is related to the appearance of the SmCα * phase at atmospheric pressure.