Four members. of a homologous series of diary lethane ct-chloroester ferroelectric liquid crystals [1 J have been synthesized and chardcterized by polarizing optical microscopy and DSC measurements. Two of the compounds exhibit a twist grain boundary structure (TGB A* phase) or twisted smectic A* phase, shortly before reaching the smectic to cholesteric phase lransition. The temperature dependence of the optical tilt angle 0, the spontaneous polarization P s and the effective rotational viscosity Yq> were investigated for the ferroelectricSc. Sf andSt pha~es.1t was found that especially the spontaneous polarization and the rotational viscosity increased with decreasing length of the alkyl chain for all three ferroelectric phases. At the phase transition from St to sf. all material parameters determined showed a discontinuous change, giving evidence for a first order transition. At the transition from the Sf to the sf phase, the material parameters show only small. rather continuous changes.
Syntheses and Characterisation of Bisphenyl‐ and Biscyclohexyl‐4,4′‐bibenzyldicarboxylates
A one pot syntheses gives bisphenyl‐4,4′‐bibenzyldicarboxylates (2) or biscyclohexyl‐4,4′‐bibenzyldicarboxylates (3) from bibenzyl (4) and phenols (5) or cyclohexanols (6). 20 compounds 2 and 3 with substituents in the p‐position of the peripheric rings have been synthesized; liquid crystalline data are given.
Liquid Crystalline Bisphenyl-4,4'-bibenzyldi-thiocarboxylates anddithiocarboxylates, Syntheses and Characterization.-The title compounds (IVa), (IVf) and (VIa) do not show any liquid crystalline behavior indicating that a substituted aromatic group is necessary for this property. Compounds (VI) decompose below the clear point and are, in contrast to compounds (IV), useless as GC stationary phases. -(BOBERG, F.; KUSSEROW, J.; MUELLER, E.; REDDIG, W.; J. Prakt. Chem./Chem.
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