J. Phys. France 41, 869-878 (1980)
DOI: 10.1051/jphys:01980004108086900

Ordering and intramolecular mobility in the nematic phase of PAA investigated by means of NMR lineshape analysis and computer simulations of the lineshape

St. Limmer, H. Schmiedel, B. Hillner, A. Lösche et S. Grande

Sektion Physik der Karl-Marx-Universität Leipzig, DDR-701 Leipzig, Linnéstrasse 5, R.D.A.

Abstract
We have recorded the 1H- and 2H-NMR spectra of PAA, PAA-d6, and PAA-d8. The order parameter S = Szz = 1/2. < 3 cos2 θ - 1 > has been determined from the different types of NMR experiments and shown to be quite sufficient for the interpretation of both proton and deuterium NMR data since the values of the tentatively calculated second order parameter Sxx- Syy (from 2H- resonance of PAA-d8) are very small. From a comparison of the proton NMR spectra of PAA-d6 and PAA and theoretical spectra computed using an approximative procedure for different kinds of intramolecular motions some conclusions are drawn concerning intramolecular mobility of the PAA molecules.

Résumé
Nos études expérimentales par RMN de 1H et 2H dans la phase nématique de PAA, PAA-d6 et PAA-d8 suggèrent que le paramètre d'ordre orientationnel S = Szz = 1/2. < 3 cos2 θ - 1 > est suffisant pour expliquer les spectres obtenus. On présente une méthode approximative de calcul des spectres des protons. L'ordre orientationnel des protons dans la molécule PAA est seulement caractérisé par les paramètres Sj qui permettent une description d'ordre intramoléculaire.

PACS
6130G - Orientational order of liquid crystals; electric and magnetic field effects on order.
7660 - Nuclear magnetic resonance and relaxation.

Key words
nematic liquid crystals -- nuclear magnetic resonance -- organic compounds