INTERACTION AND ORIENTATION OF A CHIRAL SOLUTE IN CHOLESTERIC LYOTROPIC MESOPHASES

Cholesteric lyotropic mesophases are prepared by addition of 2,3:4,6-di-O-isopropylidene-alpha-L-sorbofuranose or diacetone-sorbose, DAS, to nematic matrices based on several amphiphiles. The orientation of the DAS solute is investigated by deuterium NMR of the labelled DAS-d(6) derivative. This compound was obtained by exchanging one acetone ligand for perdeuteriated acetone. The resulting deuteriated methyl groups are observed as coincident or distinguishable doublets. Quadrupolar splitting values are used for the calculation of parameters of the solute's Saupe ordering matrix, defined in a molecule fixed coordinate system. Decylsulphate lyomesophases containing both caesium and sodium counter-ions are also investigated. For these mesophases, caesium-133 NMR spectra of the counter-ion and deuterium NMR of the residual HDO are also obtained. The present work points out that the DAS ordering in lyomesophases is dependent on the charge and nature of the amphiphile headgroup. The exchange of Na+ for Cs+ counter ions in decylsulphate mesophases affects the anisotropic properties of the liquid crystalline medium, changing the ordering of the DAS solute.