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- Title
Xenon NMR of phase biaxiality in liquid crystals.
- Authors
Jokisaari, Jukka; Zhu, Jianfeng
- Abstract
Biaxial thermotropic nematic liquid crystals would be of great importance in liquid crystal display technology. Less than a decade ago, such liquid crystals were suggested. The biaxiality of the phases was confirmed using 2H NMR spectroscopy of deuterated probe molecules. The spectra were collected from a sample rotating around an axis perpendicular to the external magnetic field, resulting in a two-dimensional powder pattern. We have proposed an alternate technique that is based on the second order quadrupole shift detectable in 131Xe NMR spectra of dissolved xenon. The method has many advantages, such as the NMR spectra are taken from a static sample and the 131Xe quadrupole coupling tensor is extremely sensitive to the symmetry of the phase. In the present study, we report results obtained on a 600-MHz NMR spectrometer. Together with the data of our earlier study, they confirm that the asymmetry parameter of the 131Xe quadrupole coupling tensor in the nematic phase of a ferroelectric liquid crystal is 0.85 and in the smectic A phase ca 0.62, indicating significant phase biaxiality. Copyright © 2014 John Wiley & Sons, Ltd.
- Subjects
XENON isotopes; NUCLEAR magnetic resonance spectroscopy; FERROELECTRIC liquid crystals; LIQUID crystals; MAGNETIC fields
- Publication
Magnetic Resonance in Chemistry, 2014, Vol 52, Issue 10, p556
- ISSN
0749-1581
- Publication type
Article
- DOI
10.1002/mrc.4077