Orientational Response to Applied Fields

The response of liquid crystal molecular orientation to an electric field is another major characteristic utilised for many years in industrial applications [44] and more recently in studies of electrically-induced phase transitions [45]. The ability of the director to align along an external field again results from the electronic structure of the individual molecules. 

In most devices the liquid crystal molecules are confined between two thin walls which act as capacitor plates. This allows the determination of the dielectric properties of the liquid crystalline material through the simple relations 

It is evident that the sign of the dielectric anisotropy is not fixed by the form of this expression and that it depends on the magnitude of Aa as well as on the 

From a practical perspective a high dielectric anisotropy leads to a low operating voltage according to 

In this expression k represents an average elastic constant. 

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