Macroscopic order in a nematic liquid crystal: Perturbation by spontaneous director fluctuations

Abstract

The dynamic alignment of the nematic director by near-orthogonal electric and magnetic fields has been investigated. The intermediate states during the relaxation process were found, with the aid of time-resolved deuterium NMR spectroscopy, to be markedly nonuniform. The macroscopic order was perturbed, although the initial and final states of the director appear to be essentially uniform. However, the initial state does have a profound influence on the uniformity of the director in the intermediate states. We have developed a fundamental model based on the effect of spontaneous director fluctuations to explain these unusual NMR observations.

Peculiarities in the Director Reorientation and the NMR Spectra Evolution in a Nematic Liquid Crystals under the Effect of Crossed Electric and Magnetic Fields

“…The theoretical analysis is based on the hydrodynamic theory including both the director motion and fluid flow, with appropriate boundary and initial conditions, whereas the experimental progress in understanding both the structural and dynamic properties of LC materials is based on the nuclear magnetic resonance (NMR) spectroscopy [1][2][3][4]. Recently, the time-resolved deuterium NMR spectroscopic measurements of field-induced director reorientations have been performed [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Taking into account that the quadrupolar splitting is related to the angle α made by the director n with the magnetic field B (see Figure 1a), deuterium NMR spectroscopy is found to be a powerful method to investigate the dynamic director reorientation in nematic films.…”