Natural abundance H-2 NMR for liquid crystal studies. Application to 4'-(hexyloxy)-4-cyanobiphenyl

Quadrupolar splitting In deuterium NMR (H-2 NMR) is a powerful means to evaluate microscopic orientational orders of liquid crystals. So far, because of the low sensitivity of H-2 NMR at natural abundance, application of H-2 NMR to liquid crystals has been considered possible only for samples with deuterium enrichment. However, in the present work, we show that by taking advantage of the high sensitivity of a recent high-field NMR spectrometer, detection of H-2 NMR signals al the natural abundance of the H-2 isotope is possible under proton decoupling, Assignments of the H-2 NMR signals to specific chemical groups in the molecule may be made by comparing H-2 chemical shift in the liquid crystalline phase with those of H-1 chemical shift in the isotropic phase, Subsequent evaluation of quadrupolar splittings gives microscopic orientational orders of the molecule, With this technique, temperature dependence of microscopic orders of 4'-(hexyloxy)-4-cyanobiphenyl is demonstrated.