Temperature-dependent characterization of optical parameters in novel high birefringence nematic liquid crystal mixtures: an empirical investigation

Abstract

Abstract
This study investigates the temperature-dependent behaviors of three novel high-birefringence (Δn) nematic liquid crystals (NLCs) with varying clearing temperatures (TNI). The high birefringence of the studied novel nematic liquid crystals is advantageous for LCD applications. It ensures fast response times, wide viewing angles, enhanced color reproduction, and reduced cross-talk, optimizing display performance and image quality. The goal is to characterize their order parameters (S(T)), effective geometry parameters (αeg), normalized polarizabilities, and crossover temperatures (Tco). Utilizing a modified four-parameter model for temperature-dependent refractive indices, we extract adjustable parameters and analyze their impact on Tco and S(T). Three approaches, including the Vuks model, Haller approximation model, and an effective geometry parameter-based model, are employed to assess S(T). The study focuses on four unknown parameters (A, B, (Δn)0, and β) derived from the modified model, along with the nematic-isotropic transition temperature (TNI). Findings reveal that a higher absolute value for the B parameter, a smaller β parameter value, elevated TNI values, and increased (Δn)0 values enhance the Tco value.

Effect of different surface alignment layers and temperature changes on bandwidth of Bragg reflection in chiral nematic liquid crystal

“…Since the central reflection wavelength is directly related to the data obtained from the transmission spectrum measured with a spectrophotometer, the cholesteric pitch is not explicitly considered in this equation. On the other hand, according to the Haller approximation [35,36], for nematics, the temperature dependence of birefringence follows the following relationship:…”

“…The temperature-dependent orientational alignment of Nematic Liquid Crystals (NLCs) is intricately connected and effectively elucidated by the Modified Four-Parameter model. The model takes into account the temperature variations and predicts the behavior of NLCs with high accuracy, making it a valuable tool in the study of liquid crystal systems [36]. Based on Vuk's model and Haller's approximation, Li developed a four-parameter model [15] to describe the effect of temperature on ordinary and extraordinary refractive indices of NLCs as follows [8]:…”