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

Various liquid crystalline terphenyls with fluoro substituents strategicall y located in the core and the terminal chains have been synthesised and eva luated for a range of physical properties. The synthetic methods involved f luorinations to introduce fluoro substituents into the alpha and beta posit ions of the terminal chains, and low temperature metallations were used to prepare arylboronic acids which were employed in selective palladium-cataly sed cross-coupling reactions to generate the final liquid crystals. The mes ogens 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 cl ass of compound, whereas compounds with two fluoro substituents in the alph a position tend to exhibit the conventional S-C phase. The materials have b een evaluated for a range of physical properties and enable the formulation of ferroelectric mixtures with a high dielectric biaxiality which is very important in tau V minimum driving schemes.