Untersuchung der elektrischen Leitfähigkeit im nematischen und smektischen Phasenbereich von 4-Alkyloxy-4'-cyanobiphenylen / Study of the Electrical Conductivity in the Nematic and Smectic Phases of 4-Alkyloxy-4''-cyanobiphenyls

The electrical conductivity of tetrabutylammonium picrate is measured in the liquid crystal phases of two 4-alkyloxy-4'-cyanobiphenyls as a function of the temperature and of the electrolyte concentration. The conductivity is corrected for the electrode polarization and the dielectric relaxation which are determined from the frequency dependence of the conductivity. The equivalent conductivity values in the nematic phase of a mixture of 4-pentyloxy-4'- cyanobiphenyl and 4-heptyloxy-4'-cyanobiphenyl are extrapolated to infinite dilution. The electrical conductivity in 4-octyloxy-4'-cyanobiphenyl is measured in the nematic and in the smectic phase. It changes continuously with the temperature in the region of the phase transition. The anisotropy ratio for both liquid crystals under investigation yields a strong dependence upon the concentration of the electrolyte. This behaviour is compared with results obtained for other liquid crystals

Anomalie der elektrischen Leitfähigkeitsanisotropie von 4,4' -Di-n-hexyloxy-azoxybenzol

The electric conductivity of 4,4'-di-n-hexyloxyazoxybenzene is studied as a function of temperature for parallel and perpendicular alignment. Below the clearing temperature the ratio of anisotropy V=x||/x⟂ is found to be higher than unity. Its value decreases below unity when approaching the transition to the smectic phase. Increasing the concentration of the electrolyte tetrabutylammonium picrate yields an unexpected increase of the ratio of anisotropy.

Bestimmung von Elastizitätskoeffizienten einer nematischen Flüssigkeit durch elektrische Leitfähigkeitsmessungen / Elastic constants of a nematic liquid crystal determined by electric conductivity measurements

The influence of a magnetic field of variable strength and direction on the deformations and the electric conductivity of a nematic liquid crystal is treated theoretically. The results are in good agreement with measurements of the electric conductivity of MBBA, doped with tetrabutylammonium picrate. The bend and the splay elastic constants of MBBA are found to be k33 = 8.62 · 10-7 dyn and k11 = 6.38 · 10-7 dyn at 22.1 °C.

Conductances of potassium chloride and tetrabutyl ammonium picrate in dioxan-water mixtures at pressures up to 2500 bars

The electrolytic conductance of solutions of potassium chloride and tetrabutyl- ammonium picrate over a range of concentrations have been measured in dioxan-water mixtures containing 0, 25, 50, 70, and 80% dioxan at 25� and pressures up to 1000 and 2500 bars respectively for the two solutes. The solvent concentration range corresponds to a range of dielectric constants of 78.3 (for water) to 11.98 (80% dioxan). The association of KCl in solutions of low dielectric constant is reduced by increasing pressure, so that the conductances of the solutions of finite concentration are not reduced as much by pressure as at infinite dilution. In contrast to this, the solutions of the tetrabutylammonium picrate are wholly dissociated even in very low dielectric constant solvents, as is shown by the limited concentration dependence of the conductance pressure characteristics.