Orientational ordering studies of fluorinated thermotropic liquid crystals by NMR spectroscopy

Fluorinated calamitic thermotropic liquid crystals represent an important class of materials for high‐tech applications, especially in the field of liquid crystal displays. The investigation of orientational ordering in these systems is fundamental owing to the dependence of their applications on th...

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Bibliographic Details
Published in:Magnetic resonance in chemistry 2014-10, Vol.52 (10), p.625-639
Main Authors: Calucci, Lucia, Geppi, Marco, Urban, Stanislaw
Format: Article
Language:English
Subjects:
13C
13C-19F dipolar and scalar coupling
19F
Anisotropy
chemical shift anisotropy
Coupling (molecular)
dielectric spectroscopy
Dielectrics
Fluorination
Liquid crystals
Nuclear magnetic resonance
optical spectroscopy
Order disorder
Order parameters
SLF
VAS
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Summary:Fluorinated calamitic thermotropic liquid crystals represent an important class of materials for high‐tech applications, especially in the field of liquid crystal displays. The investigation of orientational ordering in these systems is fundamental owing to the dependence of their applications on the anisotropic nature of macroscopic optical, dielectric, and visco‐elastic properties. NMR spectroscopy is the most powerful technique for studying orientational order in liquid crystalline systems at a molecular level thanks to the possibility of exploiting different anisotropic observables (chemical shift, dipolar couplings, and quadrupolar coupling) and nuclei (2H, 13C, and 19F). In this paper, the basic theory and NMR experiments useful for the investigation of orientational order on fluorinated calamitic liquid crystals are reported, and a review of the literature published on this subject is given. Finally, orientational order parameters determined by NMR data are discussed in comparison to those obtained by optical and dielectric anisotropy measurements. Copyright © 2014 John Wiley & Sons, Ltd. The basic theory and NMR experiments useful for the investigation of orientational order on thermotropic fluorinated liquid crystals, an important class of materials for high‐tech applications, are summarized. A review of the 2H, 13C, and 19F NMR studies reported in the literature is given. Orientational order parameters determined by NMR are discussed in comparison to those obtained by optical and dielectric spectroscopies.
ISSN:0749-1581
1097-458X
DOI:10.1002/mrc.4106