Synthesis and properties of new ferroelectric and antiferroelectric liquid crystals with a biphenylyl benzoate rigid core

Abstract

The aim of our research was the preparation of a family of 4'-(ω-perfluoroalkanoyloxy)alkoxybiphenyl-4-yl (S)-4-(1-methylheptyloxy)benzoates smectic liquid crystals. The synthesis has been designed in search of new compounds with a high-tilted smectic C* phase. Five homologous series of chiral esters have been obtained. Phase transition temperatures and enthalpies for all compounds, as well as tilt angle, spontaneous polarisation, helical pitch and layer thickness for some, have been measured. The shapes of the molecules were also simulated. Relationships between the chemical structure and the observed physical and chemical properties are discussed. Unexpectedly, the compounds show a low-tilt smectic C* phase, and sometimes also a smectic C*_A phase; an explanation of this feature is given.

Keywords:

• ferroelectric
• antiferroelectric
• liquid crystal
• smectic

Acknowledgements

The work was supported by grant No. PBW 933 and by grant No. 8/B/T02/2009/37 from Ministry of Science and Higher Education. Authors thank to Professor Piotr Kaszyński from Vanderbilt University in Nashville (USA) for the calculation of dipole moments of molecules and to Doctor Damian Pociecha for XRD measurements.