Thermal hysteresis at the phase transition in liquid crystalline materials

Abstract

Experimental results on antiferroelectric liquid crystalline materials are presented using techniques such as dielectric and electro-optical measurements. A demixing phenomenon has been observed for compounds exhibiting the ferroelectric SmC* phase in their phase sequence. This phenomenon is interpreted within the framework of a thermodynamic study. Large temperature hysteresis during cooling and heating has been observed and is discussed. The results of dielectric spectroscopy and electro-optical properties suggest that thermal hysteresis is related to the demixing phenomenon. The effect of cell thickness and spontaneous polarisation on the temperature range of this phenomenon has also been investigated.

Keywords:

• thermal hysteresis
• coexistence phases
• dielectric measurements
• liquid crystal

Acknowledgements

We are grateful to Mr Anis Tounsi (ISET Zaghouan) for proofreading this article.