Pressure and temperature dependences of ferroelectricity in liquid crystals

Abstract

Based on Landau-de-Gennes type free-energy density expansion, we study the influence of pressure and temperature on the spontaneous polarisation, tilt angle and smectic A (Sm A) – chiral smectic C (Sm C*) transition temperature () of ferroelectric mesogen p-(n-decyloxybenzilidene)-p′-amino-(2-methylbutyl) cinnamate (DOBAMBC). The pressure dependence of the ferroic properties is incorporated through the pressure dependent Landau coefficients associated with the order parameters coupling terms of the free-energy density expansion. It is found that the application of pressure reduces the stability of Sm C* phase, while the stability of Sm A phase increases. The order parameter coupling terms play an important role and the ferroelectric properties are in good agreement with the available experimental data of DOBAMBC.

Keywords:

• liquid crystal
• ferroelectricity
• phase transition
• free-energy density

Acknowledgement

The financial support received from UGC, New Delhi, and DST, New Delhi, is thankfully acknowledged.