Study of Dielectric Properties of Two Mesogenic Mixtures as a Function of Temperature

Abstract

Dielectric studies as a function of temperature have been conducted on two liquid-crystalline mixtures: mixture 1, containing phenyl cyclohexane, biphenyl cyclohexane, and cyclohexane carboxylate (code name: ZLI 1701); and mixture 2, containing phenyl cyclohexane, cyano cyclohexane, and cyclohexane carboxylate (code name: ZLI 1800-000).

Each of the mixtures exhibits only the nematic phase with a similar temperature range. Both the mixtures contain phenyl cyclohexane and cyclohexane carboxylate groups. However, mixture 1 contains biphenyl cyclohexane, whereas mixture 2 contains cyano cyclohexane. Until now, no systematic study on the two mixtures have been reported. Our interest is to compare the macroscopic properties of the two mesogenic mixtures and to study the effect of replacing the biphenyl cyclohexane group in mixture 1 by a cyano cyclohexane group in mixture 2. With this aim, the variation of the dielectric permittivities ϵ_⊥ and ϵ_∥ with temperature has been determined for both the samples in an aligning magnetic field at frequencies of 1 kHz, 10 kHz, and 100 kHz, and the dielectric properties of the two mixtures have been compared. We have also calculated the variation of angle of inclination β of the molecular dipole moment with the director for both the samples as a function of temperature.

Keywords:

• angle of inclination
• dielectric constant
• mesogen

ACKNOWLEDGMENTS

We are thankful to Merck Ltd. for supplying the sample. Thanks are due to P. Nandy, Department of Physics, Jadavpur University, for allowing us the use of her laboratory for texture studies. The authors thankfully acknowledge a University Grants Commission (U.G.C.) research project grant. Saswati Chakraborty is thankful for the U.G.C. Research Associate fellowship under this project.