Antiferroelectric phase in liquid crystalline compounds containing an azo group in their molecular core

Abstract

Novel lactic acid derivatives containing an azo group in their molecular core have been synthesised and their mesomorphic properties established. Compounds with a short aliphatic non-chiral chain exhibited the SmA* phase and ferroelectric (FE) SmC* phase. The monotropic antiferroelectric (AF) phase was found in the homologues with a longer terminal chain. Spontaneous polarisation and tilt angle were measured for the FE and AF phases. Dielectric spectroscopy in the frequency range 1 Hz–10 MHz was carried out and dielectric properties established within the temperature range of the smectic phases. Two high frequency modes were detected in the AF phase. Small-angle X-ray measurements were conducted, and the temperature dependence of layer spacing values is established and discussed.

Keywords:

• antiferroelectric liquid crystals
• ferroelectricity
• dielectric properties
• lactate group
• photosensitivity
• azo linkage

Acknowledgements

This work was supported by the German–Czech bilateral programme, DAAD No. D4–CZ5/ 2010–2011, between the German Academic Exchange Service and the Academy of Science of the Czech Republic (ASCR), by means of grants IAA100100911, 202/09/0047 and SVV–2010–261303.