A Deuterium Nuclear Magnetic Resonance Investigation of Field-induced Director Dynamics in a Nematic Slab Subject to Magnetic and Pulsed Electric Fields

Abstract

Deuterium nuclear magnetic resonance (NMR) spectroscopy has been used to investigate the field-induced director dynamics in a nematic liquid crystal, 4-pentyl-d_2-4'-cyanobiphenyl (5CB-d_2) deuteriated in the α-position of the pentyl chain, confined between two glass plates. The NMR spectra have been measured as a function of time after turning an electric field on and off. It is demonstrated that the field-induced director dynamics in the nematic liquid crystal cells can be successfully time-resolved. In addition, it is found that the doublet NMR spectra are changed into powder-like spectra during the turn-on and turn-off processes. It is shown that values for the rotational viscosity and the diamagnetic anisotropy of 5CB-d_2 can be determined from the time-resolved NMR spectra by assuming uniform alignment of the director.