The synthesis and properties of host materials with fluoro substituents in the core and in a terminal chain for high dielectric biaxiality FLC mixtures

Abstract

Various liquid crystalline terphenyls with fluoro substituents strategically located in the core and the terminal chains have been synthesised and evaluated for a range of physical properties. The synthetic methods involved fluorinations to introduce fluoro substituents into the alpha and beta positions of the terminal chains, and low temperature metallations were used to prepare arylboronic acids which were employed in selective palladium-catalysed cross-coupling reactions to generate the final liquid crystals. The mesogens with fluoro substituents in the beta position of an alkyl chain tend to generate the S_C alt phase, which is an exciting development for this class of compound, whereas compounds with two fluoro substituents in the alpha position tend to exhibit the conventional S_C phase. The materials have been evaluated for a range of physical properties and enable the formulation of ferroelectric mixtures with a high dielectric biaxiality which is very important in TV minimum driving schemes.

Key Words:

• liquid crystals
• synthesis
• smectic C
• smectic C alt