Alfred Germann

Polar nematic methyl (E)-[trans-4-cyclohexyl-substituted]allyl ethers: Synthesis, liquid crystal transition temperatures and some physical properties

Abstract We have introduced an oxygen atom and a carbon-carbon double bond with a trans-configuration (E) into the terminal alkyl chain attached to the cyclohexyl ring of a variety of two- and three-ring nematic liquid crystals of positive dielectric anisotropy. The new polar two-ring methyl (E)-allyl ethers often possess low melting points, but are not mesomorphic in general. The related three-ring methyl (E)-allyl ethers exhibit high clearing points and wide nematic ranges. Comparisons with the corresponding derivatives incorporating either just an oxygen atom or just a carbon-carbon double bond in the same position indicate that synergetic effects lead to broader nematic phases than would otherwise have been expected. This is partially due to the low smectic transition temperatures observed for the methyl (E)-allyl ethers. Selected physical properties of three binary mixtures of a weakly polar standard nematic liquid crystal and three difluoro-substituted (polar) liquid crystals (including the new ethe...

New Liquid Crystals: The Mesomorphic Properties of Mono-and Bisalkenyl(oxy)substituted Esters

Abstract 61 mono- and 16 bisalkenyl(oxy)substituted bi- and tricyclic esters have been synthesized by systematically varying both the position of the isolated C, C-double bonds and the nature of the central core ring system. The influences of the various structural parameters on the mesomorphic properties are discussed and the observed nematic and/or smectic thermal stabilities are compared with those of the corresponding saturated alkyl(oxy) analogs.

New Liquid Crystals: The Synthesis and Mesomorphic Properties of Alkenylsubstituted Cyanophenylethylcyclohexanes and Cyanobiphenylylcyclohexanes

Abstract Nineteen alkenylsubstituted cyanophenylethylcyclohexanes and cyanobiphenylycyclohexanes have been synthesized by systematically varying both the position and the configuration of the isolated C, C-double bond. The influences of such structural changes on the mesomorphic properties are discussed and the observed nematic thermal stabilities (cf. Table I) are compared, where possible, with those of the corresponding saturated alkyl analogs.

The Synthesis and Mesomorphic Properties of Liquid Crystals Containing Three-membered Ring Systems

Abstract Various mesogenic benzonitriles containing trans-epoxy-or trans-cyclopropane rings at different positions have been synthesized. The influence of these three-membered ring elements on the mesomorphic properties is discussed and the observed nematic thermal stabilities (cf. Table 1) are compared with those of the corresponding trans-ethenyl-and dimethylene-linked analogs.