N.M.R. of methanes in liquid crystal mixtures

Dipolar and quadrupolar couplings are reported for methane and its deuterated analogues dissolved in the liquid crystals Merck ZLI 1132, N-(ρ-ethoxybenzylidene)- ρ'-n-butylaniline, and a mixture of these liquid crystals. Previous studies indicate that D₂ dissolved in the same mixture has almost zero orientational order. This was interpreted as a reduction in the average electric field gradient on mixing. It is shown that methane in the same mixture and in its constituents experiences the same average field gradients as D₂. Moreover, provided one does not neglect the variation of the relevant molecular tensors with bond stretching, the dipolar couplings of methane dissolved in liquid crystals can be described with a bond-additivity model.