On the Dielectric and Splay Elastic Constants of Nematic Liquid Crystals With Positive Dielectric Anisotropy

Abstract

The temperature dependence of dielectric constants, the Frederiks threshold voltage, and the splay elastic constant of three pure nematic liquid crystal (NLC) compounds and one binary mixture are reported. A four-parameter model explaining temperature dependency of dielectric constants is derived. The four-parameter model can be approximated as a three-parameter model for the liquid crystals (LCs) having low dielectric anisotropy, provided the operating temperature is far from the clearing point. To validate these models, the experimental data of four NLC compounds have been taken from the literature. The results obtained using the two models are compared. Applying the four-parameter model, temperature dependencies of the Frederiks threshold voltage (Vth) and the splay elastic constant (K11) are investigated. It is also discussed how the expression for the splay elastic constant can be written as a second-order polynomial under certain conditions. This prediction is also validated by comparing with the experimental results available in the literature. Using the dielectric anisotropy results, the orientational order parameter is also calculated. Satisfactory agreement between experimental data and fitting results is obtained.