Influence of the Optical Purity on the Phase Sequence of an Antiferroelectric Liquid Crystal, MHPOBC, under Pressure

Abstract

The influence of the optical purity on the phase sequence of an antiferroelectric liquid crystal, MHPOBC, under pressure was studied by dielectric and switching current measurements. In the case of R:S = 75:25, the phase sequence is independent of pressure up to 150 MPa. As the pressure is increased, the temperature width of the ferroelectric SmC * phase widens slightly but that of the antiferroelectric SmC * A phase narrows a little. On the other hand, the ferroelectric SmC * phase in the case of R:S = 100:0 disappears at 100 MPa. The ferrielectric SmC * γ phase don't disappear and the temperature width of the phase widens. On the basis of the results under pressure, we discuss the strengths of the ferroelectric and antiferroelectric orderings in MHPOBC with different optical purities.

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

“…of SmC à phase and optical purity From the results, including those of previous studies, 15,16) the SmC à phase vanished under pressure above 80%ee and widened with pressure below 50%ee. To understand this difference, the relationship between the initial differential of the pressure for the temperature width of the SmC à phase, dðÁT SmC Þ=dp, and the optical purity is shown in Fig.…”

“…14) In previous papers, we reported that the SmC Ã phase in an AFLC, rectus 4-(1-methylheptyloxycalbonyl) phenyl 4 0 -octyloxybiphenyl-4carboxylate (R-MHPOBC, MHPOBC 100%ee), disappears under pressure, 15) but that it remains in MHPOBC (R : S ¼ 7:5 : 2:5, 50%ee). 16) Thus, there is no systematic change in these results. To clarify the reasons why any particular variety should be present, we measure the complex dielectric constants of two different optical purities of MHPOBC and report on the pressure-temperature (p-T ) phase diagrams and stability of the SmC Ã phase under pressure.…”