Optical determination of viscoelastic properties of nematic OHMBBA

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Abstract
Experimental values are reported for the splay/twist viscoelastic ratios of OHMBBA in the nematic region as a function of temperature. In the experiments the homodyne self-beat technique was used to detect noise intensity spectra of laser light scattered by the nematic liquid crystal. The measured rotational viscosity can be described as a function of the temperature, the order parameter and an activation energy. The splay/twist ratio of the elastic constants was determined by measuring the scattered cross section as a function of the scattering wave vector and by making a noise analysis in the mixture region. The results obtained with each method are in agreement, but differ from Freedericksz transition data. This discrepancy is discussed