SHAPE-DOMINATED ORDERING IN NEMATIC SOLVENTS - A DEUTERIUM NMR-STUDY OF CYCLOALKANE SOLUTES

We examine a series of closely related, relatively inert, cyclic aliph atic solutes-cyclohexane, methylcyclohexane, 1,1-dimethylcyclohexane, 1,4-trans-dimethylcyclohexane, 1,4-cis-dimethylcyclohexane, trans-deca lin, and cis-decalin-in a nematic solvent and demonstrate that their o rientational ordering can be accurately described in terms of purely h ard-body interactions with the solvent molecules. These interactions a re treated explicitly in the context of a statistical mechanical appro ximation wherein the orientational correlations among the solvent mole cules are not taken into account directly. We test the theory by predi cting the observed order parameters of the aliphatic solutes as determ ined with deuterium nuclear magnetic resonance. The utility and limita tions of a description of solute ordering derived exclusively from har d-body interactions is discussed.