The synthesis and electro-optic properties of liquid crystalline 2-(2,3-difluorobiphenyl-4′-yl)-1,3-dioxanes

Fifty-six novel alkyl and/or alkoxy disubstituted 2-(2,3-difluorobiphenyl-4'-yl)-1,3-dioxanes (DFBPD) were prepared. Smectic C and nematic mesophases were exhibited by most of the alkyl-alkoxy homologues. Conversely, most of the dialkyl compounds exhibited smectic C, smectic A and nematic phases. The birefringence (Delta n), dielectric anisotropy (Delta epsilon), spontaneous polarisation and response times of two ferroelectric mixtures formulated from the dioxanyl systems were determined. The birefringence results were compared with eight other groups of mixtures where the materials were based on different core systems. The overall electro-optic properties of the DFBPDs were found to be comparable to the best of the eight most commonly used materials in ferroelectric display devices.