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Cross-polarisation applied to the study of liquid crsytalline ordering

Ramanathan, Krishna V and Sinha, Neeraj (2002) Cross-polarisation applied to the study of liquid crsytalline ordering. In: Monatshefte für Chemie / Chemical Monthly, 133 (12). pp. 1535-1548.

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Abstract

Cross polarisation is extensively used in solid state NMR for enhancing signals of nuclei with low gyromagnetic ratio. However, the use of the method for providing quantitative structural and dynamics information is limited. This arises due to the fact that the mechanism which is responsible for cross polarisation namely, the dipolar interaction, has a long range and is also anisotropic. In nematic liquid crystals these limitations are easily overcome since molecules orient in a magnetic field. The uniaxial ordering of the molecules essentially removes problems associated with the angular dependence of the interactions encountered in powdered solids. The molecular motion averages out intermolecular dipolar interaction, while retaining partially averaged intramolecular interaction. In this article the use of cross polarisation for obtaining heteronuclear dipolar couplings and hence the order parameters of liquid crystals is presented. Several modifications to the basic experiment were considered and their utility illustrated. A method for obtaining proton-proton dipolar couplings, by utilizing cross polarisation from the dipolar reservoir, is also presented.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Springer.
Keywords: Cross-polarisation;Liquid crystals;Dipolar couplings; Ordering;Order parameter
Department/Centre: Division of Chemical Sciences > Sophisticated Instruments Facility
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 21 Jul 2011 09:17
Last Modified: 21 Jul 2011 09:17
URI: http://eprints.iisc.ernet.in/id/eprint/39124

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