Difluorobiphenyl Dioxaborinanes for Ferroelectric Liquid Crystal Applications

Abstract

Six difluorobiphenyl dioxaborinanes, a new class of heterocyclic mesogen, have been synthesised. Compounds possessing lateral 2,3-difluorination of the end ring possess smectic C and nematic phases for the alkyl-alkoxy homologues. The smectic C phase is replaced by smectic A phase for the dialkyl homologues. While lateral 2,3-difluorination of the middle ring increase the nematic mesophase range, smectic phase stability is suppressed to such an extent that the smectic C phase appears only for longer chain length homologues. Compared to the analogous dioxanes, the transition temperatures of the dioxaborinanes are generally lower. Dioxaborinanes are more nematic in character with difluro substituents in the end phenyl ring, while they are more smectogenic when the difluorinated phenyl ring is in the middle of the core.