129Xe and 2H nuclear magnetic resonance (NMR) of xenon and deuterated-chloroform solutes in a thermotropic biaxial nematic liquid crystal

Abstract

Properties of a thermotropic nematic liquid crystal (LC) TM35 (organosiloxane tetrapode) were investigated by means of nuclear magnetic resonance (NMR) spectroscopy of probe atoms and molecules. 129Xe isotope enriched xenon gas and 2H isotope enriched chloroform were used as probes. Both 129Xe and 2H NMR measurements were carried out over a wide temperature range, covering isotropic, nematic, and glass phases. A clear change in the behavior of the LC is observed within the nematic phase at 289 K by changing the temperature from low to high and inspecting the spectral line width. The derivative curve of the 129Xe chemical shift also reveals a change at 289 K. These changes may be an indication of hindered molecular rotation around the long axis, and the appearance of a biaxial nematic phase.