Accurate Determination of K1/ηsplay, K2/ηtwist and K3/ηbend in Nematic Liquid Crystalsby Using Photon Correlation Spectroscopy

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Abstract
A system based on photon correlation spectroscopy has been constructed using a microcomputer to measure the spectral width of Rayleigh light scattered from nematic liquid crystals. Maps in the (α, φ, θ=0° ) space have been devised to find the most suitable scatterinu geometries for the determination of K 1/ηsplay, K 2/ηtwist and K 3/ηbend, where α, φ and θ specify the scattering angle and the director direction. The ratios have been obtained as a function of T NI–T for 4'-alkyl-4-cyanobiphenyls (n=5∼8).