Experimental Confirmation of Angular Dependence of Rayleigh Line Spectral Width in Nematic Liquid Crystals

概要

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We compared calculated results with experimental data on the scattering angular dependence of the relaxation time corresponding to the Rayleigh line spectral width obtained by using a homeotropically- and homogeneously-aligned cell to check the validity of the Orsays formulas for the dynamic behavior of the director modes and the accuracy of scattering measurements. However, to increase the strength of the scattered intensity, we tilted the cell, thus changing the angle φ' between the incident light and the director over a range of -30°≤φ'≤30°and 60°≤φ'≤120°, while keeping the director in the scattering plane. All measurements were made using the homodyne technique. The obtained experimental data were within an accuracy of 0.1 % for the refractive index, 5% for the elastic constant ratio and 3 % for the relaxation time. Experimental results indicate that the Leslie viscosity coefficients μ_1 and μ_3 of MBBA are very small in comparison with the four other coefficients. By using the twist elastic constant K_2, other Leslie viscosity coefficients can be given as μ_2/K_2=-26×10^9, μ_4/K_2=20×10^9, μ_5/K_2=16×10^9 and μ_6/K_2=-10×10^9 in kgm^<-1>s^<-1>/N at a temperature T-T_<NI>= -21℃ (nematic-isotropic transition temperature T_<NI>=46.2℃). Temperature variations in the relaxation time for splay, twist and bend deformation are also described.
社団法人応用物理学会の論文
1986-06-20