Determination of orientational order parameters in liquid crystals from temperature-dependent 13C NMR experiments

Abstract

We have shown that natural abundance ¹³C 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 (D_2h) 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.