Orientational Order of Long-Chain Molecules in the Nematic Phase

Abstract

It is shown here that the quadrupole splittings arising from the different deuterium sites of long-chain molecules constituting nematic liquid crystal phases can be well understood with a single order parameter tensor S defined for the whole molecule by its long molecular axis, as has been suggested elsewhere. This is demonstrated explicitly for p-cyanobenzylidene-p'-d ₁₇-octyloxyaniline and p-butyloxybenzylidene-p'-d ₁₇-octyl-2,6-d ₂-aniline. The role of molecular conformations in relation to the observed splittings has been made evident by recovering the average quadrupole coupling constants and orientations of different C—D bonds for both molecules. These values are in reasonable agreement.