Polar 2‐alkoxyethoxy‐substituted nematic liquid crystals

Abstract

The synthesis is reported of a series of polar nematic liquid crystals incorporating an alkoxyalkoxy chain attached in a terminal position to a molecular core consisting of two aromatic rings. The dependence of the mesomorphism and phase transition temperatures on the nature of this terminal chain was studied. The shape anisotropy of the core is increased by the presence of an additional 1,4‐disubstituted phenyl unit in a number of p‐terphenyls. A number of highly polar esters with a terminal methoxyethoxy chain have been prepared as dopants to lower the threshold voltage of LCDs. The presence of the methoxyethoxy chain leads to an increase in the molecular dipole moment, the dielectric anisotropy and the dielectric constant perpendicular to the molecular long axis. Several compounds with a four‐unit diether central linkage were also prepared.

Acknowledgements

We express our thanks to Qinetiq for funding for a postgraduate studentship (NLC) and to Merck‐NBSC, Southampton, UK, for the supply of some reaction intermediates. We would also like to thank B. Worthington (¹H NMR) and K. Welham (MS) of the University of Hull for spectroscopic measurements. The referee is thanked for number of constructive and helpful comments.