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Solute-Solvent Interactions in the Nematic and Smectic A Phases of 4 4-di-n-Heptylazoxybenzene Studied by Deuteron NMR

1987; Taylor & Francis; Volume: 2; Issue: 3 Linguagem: Inglês

10.1080/02678298708086681

1366-5855

Donata Catalano, Claudia Forte, Carlo Alberto Veracini, J.W. Emsley, G. N. Shilstone,

Surfactants and Colloidal Systems

Abstract The orientational order parameters have been measured by deuteron N.M.R. of both solute (at low dilution) and solvent in various binary mixtures involving the liquid crystal 4,4′-di-n-heptylazoxybenzene (HAB). The solutes studied were azoxybenzene-d10 and n-heptylbenzene-d7 which are fragments of HAB, azobenzene-d 10 because of its similarity to azoxybenzene, and anthracene-d10 because of its known structure and symmetric shape. The major and biaxial order parameters of the solutes are analysed in terms of a molecular field model for the potential of mean torque for biaxial particles. The behaviour of the solute order parameters on approaching and entering the smectic A phase is interpreted in terms of a temperature and phase dependent partitioning of the solute between aromatic and aliphatic regions of the solvent.