The orientational order in nematic liquid crystals from birefringence measurements

Study of optical parameters of two fluorinated isothiocyanato nematic liquid crystals exhibiting high birefringence

“…Measure− ment of optical anisotropy, i.e., Dn provides not only the most simplest and convenient, but also yields direct and very precise results [13,21]. Thus, the optical methods are most frequently used for the calculation of order parameter of LCs [14,24]. Quite a few molecular structures with high Dn values have been investigated by using different methods [2][3][4]25].…”

“…However, assuming the validity of a local field model, the microscopic order pa− rameter can be determined from the knowledge of macro− scopic bulk tensorial properties [17,18]. Several methods have been developed for the measurement of macroscopic order parameter (Q) in a LC [13,14,16,[18][19][20][21]. Measure− ment of optical anisotropy, i.e., Dn provides not only the most simplest and convenient, but also yields direct and very precise results [13,21].…”

“…The effect of temperature on the refractive indices and birefringence is critically important for display devices. In order to establish a relationship of the temperature dependence of LC refractive indices, various theoretical models [6][7][8][9], as well as several experimental techniques [10][11][12][13][14] have been developed. From the study of refractive indices of liquid crystals, it is possible to obtain information on anisotropy of the light waves traversing through them [15].…”

Calculation of Optical Parameters of Liquid Crystals

“…As the temperature increases, the extraordinary refractive index decreases sharply while the ordinary refractive index decreases initially but gradually increases near the clearing temperature. Behavior of n e and n o for MLC-9200-000 and MLC-6608 is found to be similar as in the case of other organic liquids [12,15,16]. Figure 2 depicts the temperature dependence of experimental results and theoretical curves of birefringence ∆n.…”

“…Two procedures are discussed for the determination of order parameter. The first one is a simple procedure solely based on birefringence measurements [12]. This procedure consists in the following steps: measurements of birefringence ∆n, determination of ∆n o using extrapolation, and calculation of order parameter.…”