Synthesis of asymmetric tolane liquid crystals for display application

Abstract

Four series of trans-cyclohexyl-based tolanes, i.e., 4-(trans-4-alkylcyclohexyl)-4'-fluorotolanes, 4-(trans-4-alkylcyclohexyl)-3',4'-difluorotolanes, 4-[2-(trans-4-alkyl-cyclo-hexyl)ethyl]-4'-alkyltolanes and fluorinated 4-[2(trans-4-alkylcyclohexyl)ethyl] tolanes are prepared and characterized. All the obtained compounds display nematic liquid crystalline phases. The results demonstrate that incorporation of a cyclohexyl ring in the mesogen core structure leads to form a wide temperature range of mesophase. However it also increases the tendency to form a smectic phase. The dielectric anisotropy (Delta epsilon) and birefringence (Delta n) of some selected compounds were measured by a guest-host method. All of those compounds studied show relatively high dielectric anisotropy and birefringence.