Synthesis, properties and crystal structure of chiral semiperfluorinated liquid crystals with ferro and anticlinic smectic phases

A new chiral and semiperfluorinated series with ferro and anticlinic proper ties has been synthesized and characterized. The mesomorphic behaviour has been established on the grounds of both microscopic observations and DSC me asurements. The non-chiral intermediate ethyl 4-semiperfluorinated alkyloxy benzoates exhibit SmA phases, unusual for compounds with a single phenyl ri ng. The final derivatives display SmA, SmC* and in several cases SmCA* phas es. The longer fluorinated chains favour the SmA and SmC* phases at the exp ense of the SmCA* phase. Electro-optical measurements were carried out with the classical SSFLC geometry. The spontaneous polarization and tilt angle at saturation are higher than those of the hydrogenous homologues, around 1 40 nC cm(-2) at 40 degrees C. One compound of the series, the 4,4,5,5,6,6,7 ,7,8,8,8-nonafluoroheptyloxy derivative, C36H35O7F9, M-x = 750.6 g mol(-1) crystallizes in the triclinic system, space group P1, with four independent molecules in the asymmetric unit (Z = 4). The molecules are arranged in a head-to-tail fashion with two molecules oriented in the same direction and the two others in the opposite direction. They give rise to sheets with a s mectic C-like arrangement. The final reliability factors were R = 0.117 and w(R) = 0.134; the goodness of fit was S = 1.366.