¹²⁹Xe NMR Investigation of the Anisotropic Environment of a Thermotropic Nematic Liquid Crystal 4-Cyano-4′-Pentylbiphenyl

Abstract

The anisotropic environment of the thermotropic nematic liquid crystal (LC),, is probed by using 129 Xe NMR spectroscopy. The temperature versus 129 Xe nuclear shielding of the xenon gas dissolved in 5CB LC has clearly shown the nematic-isotropic phase transition. The observed linear and non-linear behavior of 129 Xe chemical shifts in the isotropic and nematic phases, respectively, are explained by using the pair-wise additive model. Furthermore, the parameters such as 129 Xe shielding constant (σ 0 ), the anisotropy of the shielding tensor (σ 0 ), the temperature dependence of the isotropic shielding (ε), and the shielding anisotropy (χ ), are derived.

Recent Advances in Theoretical and Physical Aspects of NMR Chemical Shifts

“…This dependence of 129 Xe shielding on cage volume and charge is also evident in 129 Xe NMR spectra of Xe in clathrate hydrate lattices doped with NH4F (Shin et al, 2014). 129 Xe NMR spectroscopy has proven to be useful as well in characterizing the anisotropic environment of the thermotropic nematic liquid crystal 4cyano-4'-pentylbiphenyl (Vemulapalli et al, 2015). On the other hand, 131 Xe, a quadrupolar nucleus, via its EFG tensor, has been shown to report on the symmetry of phases in thermotropic nematic liquid crystals (Jokisaari and Zhu, 2014).…”