NMR-STUDY OF THE EFFECTS OF ELECTRIC-DIPOLE INTERACTIONS ON THE ORDERING OF CHAIN SOLUTES IN THE NEMATIC PHASE

The existence of residual electric dipole interactions in nematic liquid crystals is demonstrated by comparatively analyzing deuterium NMR spectra of alpha,omega-dibromoalkanes and n-alkanes dissolved in nematic solvents. It is shown that these interactions generate an additional orientational bias that has sizable and readily measurable effects on the order parameter profiles of the dibromoalkane solute. The residual electric dipole interaction modifies both the local and global ordering of the electric dipole carrying chain solutes. The study of the dependence of these changes in solute ordering on the dipole moment constitution of the solvent offers new insights into the interplay of the different types of intermolecular interactions operative in the liquid crystal's average intermolecular potential.