NMR of deuterium in liquid crystal mixtures

Phenotypic Plasticity of Capitulum Morphogenesis in Microseris pygmaea (Asteraceae: Lactuceae)

“…It isassumed that the interaction of an external efg Fzz with the molecular quadrupole moment of the hydrogen molecule is solely responsible for the orientation of the solute. The range of sample values for the efg Fzz includes the available estimates of the external efg present in various nematic liquid crystal solvents from NMR experiments employing molecular deuterium as a probe molecule [1][2][3][4][5]28]. A number of observations that have been made before in these studies--using a gas-phase molecule model with additional simplifying assumptions about the internal and rotational motions--are confirmed by the much more advanced calculations presented here.…”

“…It has been established from experimental studies of molecular deuterium dissolved in various liquid crystal solvents that the interaction between the molecular quadrupole moment and a mean efg accounts for most (but not all) of the orientational ordering [4]. If this particular interaction is assumed to be solely responsible for the orientation of molecular hydrogen and its deuterated analogues, then [3] A(r) = 1…”

“…Such studies have brought to light that in nematic liquid crystals the presence of a non-zero average electric field gradient (efg) is important [1][2][3][4][5]. The interaction between these efg's and the solute molecular quadrupole moments provides the predominant contribution to the degree of orientation of hydrogens and its isotopomers and is far from negligible in the case of other solutes.…”

Monte Carlo simulations of zero electric field gradient liquid crystal mixtures

“…Experiments on larger methyl-and chloro-substituted benzenes indicate that these larger solutes experience an F ZZ of the same sign but reduced magnitude compared to that observed for D 2 [4±6]. It is possible to prepare mixtures of liquid crystals for which the average F ZZ experienced by small solutes is zero [7].…”

The orientational behaviour of dichlorobenzenes in nematic liquid crystal solvents

“…Burnell and co-workers (19)(20)(21)(22)(23) have proposed that the interaction between the solute molecular quadmpole moment and the solvent electric field gradient makes an important contribution to the ordering potential, particularly for small molecules. In recent studies of the orientation behaviour of monochlorobenzene (17), dissolved in two nematic liquid crystal solvents of different properties, EBBA and 1132, it was shown that the ring moiety played an important role in determining the difference in the solute orientational order in these two solvents.…”