Naphthalene-based bent-shaped liquid crystals with a semifluorinated terminal chain

Novel non-symmetrical bent-shaped liquid crystals based on a laterally substituted naphthalene central core and a semifluorinated terminal chain in one arm are presented. The non-substituted (X=H), methyl- (X=CH₃) and chloro-substituted compounds (X=Cl) exhibit formation of a B₂ phase, the antiferroelectric character of which was proved by electrooptic, dielectric and X-ray studies. In the cyano-substituted materials, the B₇ phase appeared. Increasing the length of the polyfluorinated unit leads to an increase of the transition temperatures and broadening of the temperature interval of the B₂ and B₇ phases, respectively. The length of the perfluorobutyl unit in the terminal chain is sufficient to support the formation of lamellar phases.