1H Multiple-Pulse Solid-State NMR Investigations of Electrically Oriented Liquid Crystals

✍ Scribed by Peter Holstein; Ana C. D. Lopes; Jürgen Rauchfuss; Dieter Geschke

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 202 KB
• Volume: 35
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199706)35:6<420::aid-omr105>3.0.co;2-w

✦ Synopsis

For the discussion of orientional states in liquid crystals, quadrupolar (2H NMR) and dipolar (1H NMR) interactions have mainly been exploited. There have also been attempts to describe the individual (regarding di †erent positions in a molecule) orientation and order by means of chemical shift information (13C NMR). Owing to the large chemical shift range of carbons, 13C NMR spectroscopy is suitable for providing resolved spectra of highly ordered systems such as low molecular mass liquid crystals. In the case of 1H NMR, the chemical shift range is much smaller than the dominating dipolar interactions. An attempt to use multiple-pulse techniques to extract chemical shift information for static samples is presented. The tensor character of the chemical shift is reÑected in the orientational dependence of the line position. The orientation of the liquid crystals can be manipulated by the in situ application of electric Ðelds.