Electro-Optical and Dielectric Investigations of Antiferroelectric and Ferrielectric Smectic Phases

Abstract

Dielectric and electro-optical properties of the various antiferroelectric and ferrielectric smectic phases of two compounds of the homologous series MHPnCBC (n = 8,9) have been investigated. MHP9CBC exhibits an unidentified chiral induced SmC subphase (denoted by SmC_x*) and shows the phase sequence Cr - SmI_A* - SmC_A* - SmC_γ* - SmC SmC_x* - SmC SmC_x* - SmA - I. The electro-optical and dielectric properties of the SmC SmC_x* phase of MHP9CBC differ distinctly from that of the SmC SmC_α* as well as the SmC SmC_γ* phase. The electric field - temperature phase diagram was obtained by two methods, measurement of the apparent tilt angle as well as the dielectric loss. The results of both methods are in good agreement. For both compounds a field induced ferrielectric state is observed in a broad temperature range (≊ 10 K) of the SmC SmC_A*−phase.

Key Words:

• Antiferroelectric liquid crystals
• SmC subphases
• electro-optical studies
• dielectric properties
• antiferroelectricity
• ferrielectricity