The Aqueous Lyotropic Analogues of Thermotropic Nematics and Cholesterics

Abstract

The motional non-equivalence in a deuteriated -CD₂-segment of a hydrocarbon chain near a chiral carbon atom has been investigated in a series of nematic and cholesteric phases. The deuterium nuclear magnetic resonance signals show the number of non-equivalent motions as equal to the number of different quadrupole doublet splittings. It is shown that a necessary but not sufficient condition for motional non-equivalence is the presence of a chiral carbon. The chiral carbon is not sufficient because in some cases the two quadrupole doublets may accidentally overlap. The composition of a number of nematic and cholesteric meso-phases has been located and recorded.The non-equivalence is affected to a large extent by the protonation of the chiral head group, showing that head group anchoring is changed in this chemical modification.