The Dielectric Properties of Nematic MBBA in the Presence of Electric and Magnetic Fields

Abstract

The dielectric-properties of liquid crystalline mesophases have been the subject of numerous investigations,1,2,3 and it has been observed that nematic mesophases become dielectrically anisotropic when subjected to electric or magnetic fields. This induced dielectric anisotropy is associated with a high degree of molecular alignment within the mesophase, although the precise molecular mechanism of the alignment process is still not known. The high degree of molecular alignment that may be induced in liquid crystalline mesophases by electric fields, magnetic fields or suitably treated glass surfaces forms the basis of many technological applications. These usually require thin films of the oriented mesophase, and so most dielectric studies have been made on such films. To avoid the surface effects associated with thin films, we have made dielectric measurements on bulk samples of nematic mesogens. In this paper we report measurements of the low frequency electric permittivity of bulk samples of p-methoxy-benzylidene-p-n-butyl aniline (MBBA) oriented by both static electric and magnetic fields. The dependence of the electric permittivity components on magnetic and electric field strength has also been determined.