Synthesis, characterisation and behaviour under a field of a chiral smectic liquid crystal

Abstract

The C12HH compound has been synthesised and the phase transition temperatures were obtained by combining several experimental techniques. This compound exhibits in volume all of the tilted smectic phases except the phase and presents a large SmC* range. The experimental results show unexpected behaviour in planar cell capacitors: (i) compared with the bulk, the SmC* range extends to lower temperature where it coexists with another phase; this demixing phenomenon is not due to a thickness effect but probably induced by a polarisation effect; (ii) the unwinding process of the ferroelectric SmC* phase occurs via two steps with an intermediate state (or phase). The E – T diagram of C12HH has been established except in the region where the coexistence occurs.

keywords:

• liquid crystal
• ferroelectric
• coexistence
• phase diagram

Acknowledgements

We wish to acknowledge the support of CMCU grant # 06/G 1311 and CNRS/DGRSRT grant # 18476. We thank Marie France Achard. We are also grateful to Anne Hochedez and Stéphane Gineste for synthesising the samples (R) and (S)12OF1M7.