Dielectric and High Pressure Studies of Liquid Crystals

  • R. Shashidhar
Part of the NATO ASI Series book series (NSSB, volume 290)


Dielectric studies probe the response of molecules to the application of an external electric field. In liquid crystals, the situation is quite complex: The materials exhibit anisotropy of dielectric permittivity while maintaining their fluidity. Also, the frequency response of the dielectric constants depends strongly on the relative direction of the electric field with respect to the long axis of the molecules. An investigation of the static permittivities gives important information on the dielectric anisotropy in relation to the molecular structure and dipole-moment. On the other hand, a study of the dielectric dispersion enables us to understand the different relaxation processes associated with the dipolar molecules of liquid crystals. However the interpretation of the dielectric dispersion data is difficult in view of the fact that the effects due to the nematic potential and viscosity are difficult to separate. Also, the activation energy calculated by the Arrehnius plots of the dielectric dispersion frequencies appear to be strongly influenced by short range order effects. This is particularly so when the range of the liquid crystalline phase is narrow and it is somewhat difficult to define a unique activation energy for a given liquid crystalline phase. In the present chapter, we shall discuss the behavior of static dielectric permittivity for different types of liquid crystals composed of nonpolar, weakly polar and strongly polar molecules. We shall also discuss how dielectric properties enable us to probe the nature of dipole-dipole interactions in liquid crystals.


Liquid Crystal Nematic Phase Dielectric Anisotropy Single Component System High Pressure Study 
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Copyright information

© Springer Science+Business Media New York 1992

Authors and Affiliations

  • R. Shashidhar
    • 1
    • 2
  1. 1.Naval Research LaboratoryCenter for Bio/Molecular Science & EngineeringUSA
  2. 2.Geo-Centers, Inc.Fort WashingtonUSA

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