DIFLUOROBIPHENYL DIOXABORINANES FOR FERROELECTRIC LIQUID-CRYSTAL APPLICATIONS

Six difluorobiphenyl dioxaborinanes, a new class of heterocyclic mesog en, have been synthesised. Compounds possessing lateral 2,3-difluorina tion of the end ring possess smectic C and nematic phases for the alky l-alkoxy homologues. The smectic C phase is replaced by smectic A phas e for the dialkyl homologues. While lateral 2,3-difluorination of the middle ring increase the nematic mesophase range, smectic phase stabil ity is suppressed to such an extent that the smectic C phase appears o nly for longer chain length homologues. Compared to the analogous diox anes, the transition temperatures of the dioxaborinanes are generally lower. Dioxaborinanes are more nematic in character with difluro subst ituents in the end phenyl ring, while they are more smectogenic when t he difluorinated phenyl ring is in the middle of the core.