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Orientational order of near D-3h solutes in nematic liquid crystals

TitleOrientational order of near D-3h solutes in nematic liquid crystals
Publication TypeJournal Article
Year of Publication2009
AuthorsDanilovic, Z, Burnell, EE
JournalJournal of Chemical Physics
Volume130
Pagination11
Date PublishedApr
Type of ArticleArticle
ISBN Number0021-9606
KeywordsAB-INITIO, ELECTRIC-FIELD GRADIENT, electrostatic, interactions, liquid crystals, LIQUID MIXTURES, liquid structure, MEAN TORQUE, molecular orientation, MOLECULAR-HYDROGEN, MONTE-CARLO SIMULATIONS, nematic, NMR, polarisability, POTENTIALS, SHAPE, SOLVENTS
Abstract

Solutes that are similar in size, have a shape that is close to D-3h symmetry but contain dissimilar substituent groups (methyl versus chloro, contributing different electrostatic interactions to the anisotropic intermolecular potential), are used to delineate the short- and long-range anisotropic intermolecular interactions that lead to solute orientational order in nematic liquid crystals. The short-range interactions should be similar for all solutes and for D-3h symmetry should yield a single independent order parameter, whereas the long-range interactions are expected to differ with solute. Short-range size and shape mechanisms account for solute orientational order measured in magic mixtures (e.g., 55 wt % ZLI-1132/N-p-ethoxybenzylidene-p(’)-n-butylaniline), whereas additional mechanisms are required in other nematic liquid-crystal solvents. The results obtained for long-range interactions cannot be rationalized in detail using simple mean-field models that incorporate solute dipoles, quadrupoles, or polarizabilities. The results suggest that details of the solute electrostatics may need to be incorporated into the description of the anisotropic intermolecular potential.

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