A study of a ferroelectric organosiloxane liquid crystal with a high spontaneous polarisation

Abstract

The dielectric permittivity, the pyroelectric coefficient and the smectic layer thickness of a novel ferroelectric organosiloxane liquid crystalline material 12KN5DSi were measured as functions of the temperature and the bias electric field in the orthogonal and tilted phases of the material. It was found that this material has a very high spontaneous polarisation (∼240 nC/cm²) in the smectic C* (SmC*) phase and also demonstrates an unusual behaviour of the pyroelectric coefficient and the smectic layer thickness in a temperature range just below the phase transition from the smectic A* (SmA*) phase. This unusual behaviour is interpreted in terms of the new statistical theory based on order parameters of the SmC* phase.

Keywords:

• ferroelectric liquid crystals
• electroclinic effect
• pyroelectric coefficient
• smectic layer shrinkage
• de Vries materials
• dielectric permittivity
• freestanding films

Acknowledgements

We thank C. Blanc and V. Lorman for help with the X-ray measurements. N.M.S. acknowledges the support of the Russian Ministry of Science and Education Project No. P1430 and Project No. 02.740.11.5166. Work in Trinity College Dublin was funded by Science Foundation Ireland SFI Grant No. 02/IN.1/I031.