Relationship between elasticity and orientational order in nematic liquid crystals

Abstract

The constants of the potential energy function deduced from the statistical theory of orientational order in nematic liquid crystals are given for a few compounds and their significance in relation to the molecular structure is discussed. The dependence of the free energy of elastic deformation and the intensity of light scattering on the orientational order parameters is then investigated theoretically. Calculations show that the elastic moduli should be greater and the scattering cross-section less in p-azoxyphenetole than in p-azoxyanisole. The results are in quantitative agreement with the available experimental data. The theory is also able to account for the observed fact that though the order parameters and the elastic moduli decrease rapidly with rise of temperature, the light scattering remains practically constant throughout the nematic range.