Dielectric Relaxation of Unoriented and Field-Oriented
Liquid-Crystalline 1,4-(4-Cyano-4-azobiphenyloxy)heptyl
Oligoacrylate¹

N. A. Nikonorova*, T. I. Borisova*, A. I. Stakhanov**, S. G. Kostromin**,
and V. P. Shibaev**

* Institute of Macromolecular Compounds, Russian Academy of Sciences,
Bol’shoi pr. 31, St. Petersburg, 199004 Russia

** Department of Chemistry, Moscow State University,
Vorob’evy gory, Moscow, 119899 Russia

Received June 11, 1998;
Revised Manuscript Received July 7, 1998

Abstract—Dielectric relaxation spectroscopy was applied to study a thermotropic comblike 1,4-(4-cyano-4-
azobiphenyloxy)heptyl oligoacrylate. Two regions of local relaxation of the dipole polarization were found to
exist below the glass transition temperature. These regions are associated with the mobility of spacers (the
₁relaxation process) and the reorientation of mesogenic groups with respect to their long axes (the -relax-
ation process). In the rubberlike state, the cooperative - and -relaxation transitions were observed, which are
due to reorientation of the mesogenic groups with respect to their long and short axes, respectively. When ori-
ented under the action of mechanical or oscillating electric fields, the mesogenic groups acquire a homeotropic
orientation. Application of a constant electric field results in the planar orientation of the mesogenic groups.
The order parameter is shown to depend on the strength and frequency of the orienting electric field. Orientation
does not affect the relaxation times of the cooperative modes of mobility.

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