By diminishing the energy barrier between SC; and SC*, antiferroelectricity has become thresholdless in a threecomponent mixture. It shows V-shaped switching, realizing attractive display characteristics: extremely wide viewing angle with very large contrast ratio, high speed response and ideal analogue grey scale with no hysteresis. A simplified model of the phase with this property is presented.
Neutron diffraction and Mossbauer measurements have been used to determine the strurtures of a series of Co(GaVFe) alloys having a constant electron concentration.Despite wide variations in composition the alloys exhibit a similar structure with the V and Fe site occupations appearing to follow a similar pattern to that observed for the simpler Co(GaV) and Co(GaFe) alloy systems. For the latter systems previous measurements have indicated that Fe atoms occupy equivalent Ga sites identically whereas V atoms develop a preference for one type of Ga site leading to L2, order as the concentration increases beyond a critical value.
The transition behavior in the (R)- and (S)-mixtures of 4-(1-trifluoromethylheptyloxycarbonyl)phenyl 4-(5-dodecyl-oxypyrimidin-2-yl)benzoate (TFMHPDOPB) has been studied by X-ray diffraction. Two important findings were made. In all the mixtures, the transition is of the first order irrespective of the spontaneous polarization and the transition sequences; SmA-SmC*
A (pure enantiomers), SmA-SmC* (R:S=3:1) and SmA-SmC (racemate). The layer thickness depends on the optical purity even in the SmA phase, although the overall profiles of the temperature dependence are almost the same in all the mixtures.
Novel antiferroelectric liquid crystals having phenylalkanoate and phenylalkenoate moieties were synthesized and their mesomorphic properties were studied. 4-[2-{1-(Trifluoromethyl)heptyloxycarbonyl}ethyl]phenyl 4'-decyloxybiphenyl-4-carboxylate l b exhibited the chiral smectic C, phase at a temperature below the chiral smectic C .phase. Biphenyl-cinnamate derivatives of the three-ring system exhibited a stable mesomorphic phase and enantiotropic smectic C, phase, with the carbon-carbon double bond acting as a mesogenic core.
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