Dielectric Study of Dipole−Dipole Interactions in Anisotropic Solutions

Abstract

This paper describes an experimental investigation of dipole−dipole interactions between molecules in an orientationally ordered environment. Measurements are reported of the dielectric properties of a series of anisotropic solutions of two structurally similar dipolar solutes (1-cyano-2-fluoro-4-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]benzene (CP1) and 1,2-difluoro-4-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]benzene (CP3)) dissolved in a nonpolar nematic liquid crystal solvent (1-[trans-4-ethylcyclohexyl]-2-[4-ethyl-2-fluorobiphenyl]ethane (I22)). The solvent provides an orienting medium for the solute molecules, and by varying the temperature the degree of orientational order of the solutions is changed. The measurements have been made on aligned thin films of the liquid crystalline solutions for different concentrations and over a range of frequencies from 1 kHz to 10 MHz. All solutions exhibited a low-frequency relaxation associated with end-over-end reorientation of the polar solutes in the...