An assessment of carborane-containing liquid crystals for potential device application

Two 4-alkoxyphenyl 12-pentylcarborane-1-carboxylate nematic liquid crystals have been synthesized. The materials are found to exhibit ideal mixing of nematic phases in their binary mixtures with analogous bicycle [2.2.2] octane derivatives and with the polar nematogen 4-(4-isothiocyanatophenyl)-1-(trans-hexyl)cyclohexane. The smectic phases for the bicycle [2.2.2] octanes are destabilized by addition of the carborane derivative. For carborane compound 5BC5 the extrapolated dielectric anisotropy and measured optical anisotropy are -1.3 and 0.057 respectively at 20 degrees C. The refractive indices have been correlated with the calculated electronic polarizabilities and the low birefringence measured for 5BC5 can, at least in part, be attributed to the carborane cylindrical symmetry.