Viscosity of Nematic Liquid Crystals

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The book gives a systematic account of the hydrodynamic properties of anisotropic liquids (nematic liquid crystals) and describing methods for measuring the anisotropic viscosity and experimental dependence of the viscosity of nematic liquid crystals on all thermodynamic parameters, compared with empirical approaches developed earlier, molecule-statistical and molecule-dynamic theories. The author offers a highly accurate calculation method for predicting the level of viscosity. The structure of modern liquid crystal materials for optoelectronic devices is analysed in detail form the standpoint of preparation of mixtures with optimum viscosity and flow rate. Topics include Concepts of hydrosynamics of liquid crystals Methods for measuring the viscosity of liquid crystals Theory of temperature dependence of the viscosity of liquid crystals Dependence of the viscosity of liquid crystals on temperature and pressure Effect of molecular structure on viscosity of liquid crystals About The Author Dr V V Belyaev is currently affiliated to Central Research Institute, Moscow. He graduated from Moscow Institute for Physics and Technology and did his PhD in the area electro optic effects in liquid crystals. His recent research is in the area of physical properties of nematic, cholesteric, smectic A and smectic C liquid crystals. Table of Contents Concepts of the hydrodynamics of liquid crystals Anisotropy of the viscosity coefficients of liquid crystals Relationships of the processes of the shear flow of liquid crystals and rotation of the liquid crystal director Methods for measuring the viscosity of nematic liquid crystals The shear flow method Ultrasound methods of measuring the viscosity of nematic liquid crystal The method of the rotating magnetic field The methods associated with the examination of the dynamics of reorientation of the liquid crystal in the magnetic or electrical field The method of light scattering on thermal fluctuations of the director of liquid crystals Theory of the temperature dependence of the viscosity of nematic liquid crystals Activation mechanism The free volume model The Diogo-Martins theory Calculation of the viscosity coefficient of nematic liquid crystals using the kinetic equation Calculation of the internal friction and rotational viscosity coefficients by the method of the nonuniform statistical operator Description of the viscosity of nematic liquid crystals by the molecular dynamics methods Dependence of the viscosity of nematic liquid crystals on temperature and pressure Activation nature of the temperature dependence of rotational viscosity Relationship of viscosity with molecular packing and free volume Comparison of the experimental data with the results of the molecular-statistical approach to describing the viscosity of the nematic liquid crystal Pressure dependence of the viscosity of nematic liquid crystals Temperature dependence of dynamic viscosity and Mesovich and Leslie viscosity coefficients Effect of the molecular structure on the viscosity of nematic liquid crystals Effect of the dimensions and form of the molecule and of its fragments on viscosity and its temperature dependence Effect of the polarity of the molecule and its fragments on the viscosity of liquid crystal substances Viscosity of mixtures of nematic liquid crystals Viscosity of mixtures of mesogens The viscosity of liquid crystal solutions of non-mesogenic compounds Viscosity of mixtures of nematic liquid crystals with optically active additions Viscosity of liquid crystal materials Calculation of the viscosity of the developed materials Approaches to the development of liquid crystal materials for various applications from the viewpoint of their viscosity properties.