Zvetkow Twist Viscosity Measurements of Some Nematic Liquid Crystals

Abstract

Zvetkow twist viscosity measurements are reported for a series of cyanobiphenyl liquid crystals and their cutectic mixtures in the nematic phase. The values obtained exhibit a n odd-even variation. If the data are plotted against a reduced density, they divide into two groups, one corresponding to the odd and the other to the even series. This is attributed to effects of the configuration of the alkyl chain on the molecular packing density in the nematic phase. Using the Maier-Saupe theory, interaction energies are derived.

Viscosity coefficients of nematic liquid crystals: II. Measurements of some nematic liquid crystals†

“…Close agreement is observed between the measurements reported in this paper and those of Seidler et al [14] at the highest temperatures, but significant differences are observed as the temperature is lowered. Torsion angle [16]; -Seidler et al [14]; X Beens [17].…”

“…The constants obtained from the fitting of the data to Equation (3) are listed in Table 2 3.2 Viscosity coefficient measurements The principle viscosity coefficients; η 1 , η 2 , η 3, and η 45 were measured for all the liquid crystal materials using the oscillating plate viscometer method (OPV) following the procedures outlined in the previous paper [1]. The rotational viscosity coefficients γ 1 were measured using a modified version of the method described by Seidler et al [14] and described in the previous paper [1]. In this experiment the magnetic field is rotated relative to the suspended sample.…”

“…Oscillatory plate viscometer measurements used refinement of the method described by Seidler et al [14]. The current equipment uses a larger magnet which is suspended in a cradle, allowing rotation of the magnetic field axis and the plane of the plate oscillation and allowing measurement of the viscosity coefficients of the principle axes as described in the previous paper [1].…”

Time dependence of soliton formation in planar cells of nematic liquid crystals

“…Numerical calculations are performed with the parameters of the liquid-crystal mixture E7 from Merck, listed in Table I [17], [22]. …”

A field-cycling NMR study of nematic 4-pentyl-4′-cyanobiphenyl confined in porous glasses

“…However, because of the scatter in the values for elastic constant K reported in literature [41][42][43][44] only rough estimation can be made. For the typical average value K = 1 • 10-" N and with (Av) = 15 kHz and i = 0.1 Pa • s [42,[45][46][47][48] one obtains A = 2.0. 104 s -312 in agreement with experiment.…”