화학공학소재연구정보센터
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol.363, 85-95, 2001
Homogeneous and inhomogeneous director dynamics of a fluorinated liquid crystal
The director reorientation of a thermotropic nematic liquid crystal in electric and magnetic fields has been investigated by means of H-1 and F-19 nuclear magnetic resonance, A new method which uses electric fields to set the desired initial angle of the nematic director with respect to the magnetic field is described. Using this method it was possible to perform reorientation experiments in the magnetic field starting in a large number of initial angles and to investigate the transition from homogeneous to inhomogeneous reorientation processes in detail. It is shown that reorientation processes in the presence of both electric and magnetic fields remain homogeneous for initial angles close to 90 degrees. An analysis of the H-1 and F-19 NMR spectra shows inhomogeneous processes in the magnetic field beginning at considerably smaller angles. An intermediate region of about 6 degrees where homogeneous and inhomogeneous processes take place at the same time has been found.