Dielectric relaxation in the smectic E phase of a liquid crystal

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Abstract
In this paper, we present a study of the dielectric relaxation of p-phenyl-benzylidene p'-butylaniline. When the electric field is perpendicular to the optical axis, an absorption domain due, in particular, to the rotation of the molecules round their longitudinal axis is observed. At the transition SB → SE, the critical frequency of this domain sharply decreases. This frequency is about five times lower in the SE than in the S B phase. Moreover, the activation energy of this mechanism of rotation, which is 0.26 eV in the SB phase, moves to 0.62 eV in the S E phase. These results clearly show that the rotation at motion of the molecules is strongly hindered in the SE phase. To our knowledge, the study of this notion in the SE phase using dielectric relaxation with these conditions is the first one performed