Eur. Phys. J. E 25, 385-393 (2008)
DOI: 10.1140/epje/i2007-10302-5

Probing the material properties and phase transitions of ferroelectric liquid crystals by determination of the Landau potential

P. Archer¹, I. Dierking¹, V. Görtz² and J. W. Goodby<sup>2

1</sup>  School of Physics and Astronomy, University of Manchester, Schuster Building, Oxford Road, M13 9PL, Manchester, UK
²  Department of Chemistry, University of York, YO10 5DD, Heslington, York, UK

ingo.dierking@manchester.ac.uk

(Received 7 November 2007 / Published online 21 April 2008)

Abstract

The full Landau potential of several, widely varying ferroelectric liquid-crystalline materials has been experimentally determined. Tilt angle and polarisation data is analysed across the SmA ^* to SmC ^* transition for varying applied electric-field amplitudes, allowing the determination of all the coefficients of the generalised Landau model of ferroelectric liquid crystals. The materials investigated encompass different materials, including low-polarisation mixtures to high-polarisation single-component materials. The materials also possess a variation in the order of the SmA ^* to SmC ^* phase transition from strongly first order to strongly second order. The effects of both the polarisation and order of phase transition of the system are discussed with respect to the various terms of the generalised Landau model. Further, the mechanisms behind the difference between a first- and second-order phase transition are discussed with respect to the Landau potential and the second Landau coefficient b .

PACS
64.70.M- - Transitions in liquid crystals.
64.70.mj - Experimental studies of liquid crystal transitions.
77.80.Bh - Phase transitions and Curie point.

Correspondence: ingo.dierking@manchester.ac.uk


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2008