Mobility changes of side chains ascribed to density modulations along columnar structures detected by 2D NMR

M. Werth; J. Leisen; C. Boeffel; R. Y. Dong; H. W. Spiess

doi:doi:10.1051/jp2:1993111

Numéro		J. Phys. II France Volume 3, Numéro 1, January 1993


Page(s)		53 - 67
DOI		https://doi.org/10.1051/jp2:1993111

DOI: 10.1051/jp2:1993111
J. Phys. II France 3 (1993) 53-67

Mobility changes of side chains ascribed to density modulations along columnar structures detected by 2D NMR

M. Werth¹, J. Leisen¹, C. Boeffel¹, R. Y. Dong² and H. W. Spiess¹

¹ Max-Planck-Institut für Polymerforschung, Postfach 3148, D-6500 Mainz, Germany
² Dept. of Physics and Astronomy, Brandon University, Brandon, Manitoba, Canada

(Received 19 June 1992, revised 27 August 1992, accepted 20 October 1992)

Abstract
The molecular dynamics and phase transitions of a columnar liquid crystal bades on hexaether-substituted rufigallol mesogens were studied by a combination of X-ray scattering as well as 1D and 2D solid-state NMR spectroscopy. A correlation of the anisotropic molecular motion, with the molecular symmetry and the phase symmetry was established. 2D-exchange NMR spectra revealed a slow dynamic process involving the side chains, which is attributed to changes in the packing density of the molecules along the column. In this way the packing problem of columnar liquid crystals resulting from the incommensurability of the aromatic core moieties and the aliphatic side chains is solved as proposed by de Gennes.