DETERMINATION OF ORIENTATIONAL ORDER PARAMETERS IN LIQUID-CRYSTALS FROM TEMPERATURE-DEPENDENT C-13 NMR EXPERIMENTS

We have shown that natural abundance C-13 NMR of solutes in liquid crystals may be used to obtain order parameters from a series of temperature-dependent measurements even with limited information on the carbon shift tensors. A procedure for simultaneously analysing data at the various temperatures is proposed. We have obtained the ordering matrix as a function of temperature for various biaxial (D2h) solutes: pyrene, perylene, naphthalene, anthracene and for one effectively uniaxial probe (triphenylene), in the nematic mixture ZLI-1167. We compare these results with deuterium data where possible and we also provide estimates of the chemical shift tensors for perylene and anthracene, where solid-state data are, as yet, unavailable.