Electric field-induced alignment of the directors in the smectic A phase of 4-octyl-4'-cyanobiphenyl. A deuterium NMR study

Luckhurst, G. R., Miyamoto, T., Sugimura, A. and Timimi, B. A. (2000) Electric field-induced alignment of the directors in the smectic A phase of 4-octyl-4'-cyanobiphenyl. A deuterium NMR study. Molecular Crystals and Liquid Crystals, 347, 391-400.

Abstract

Deuterium nuclear magnetic resonance (NMR) spectroscopy has been used to investigate the electric field-induced alignment of the director of the smectic A phase of the liquid crystal, 4-?,?-d(2)-octyl-4'-cyanobiphenyl (8CB-d(2)), at 303.3K. The electric field is arranged to be orthogonal to the magnetic field. The alignment process has been investigated at different electric field strengths and the rate of director alignment was monitored by recording the deuterium NMR spectra as a function of time after the electric field was switched on. The results reveal a complex pattern of electric field-induced director alignment. At high electric field strengths a rapid process is observed in which the director switches from an orientation parallel to the magnetic field to one in which it is parallel to the electric field. An induction period is also observed in which no apparent change in director orientation occurs. This induction period becomes longer (hours in magnitude) as the electric field strength is lowered. Other, intermediate, director orientations are observed as the electric field strength is lowered further. The role of defects is invoked in trying to interpret some of the observed processes underlying the mechanism of the director alignment in the smectic A phase.

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