Synthesis and properties of liquid crystalline terphenyls containing a difluorophenoxymethyl moiety

The synthesis of a series of liquid crystals based on a p-terphenyl core, substituted with an aliphatic ester at one terminus (with tail length varying from 1 to 11 repeat units) and a dilfuorophenoxymethyl moiety on the other, is reported. All materials in the series display an enantiotropic nematic phase, and for aliphatic tails of two or more repeat units also exhibit an enantiotropic smectic C phase. Both the nematic and smectic phase stability decrease with increasing tail length. There is also evidence for the presence of multiple soft crystal phases upon cooling in several of the materials. The optical properties of the materials are reported, with all materials showing maximum absorption wavelengths in the region of 334–337 nm, together with modest average refractive indices (nav = 1.55) and birefringence values of around 0.28.