Molecular Alignment in Nematic Liquid Crystals

Abstract

Abstract The relative effectiveness of electric and magnetic fields on the molecular alignment in the nematic phase, of p-methoxy and p-ethoxy p'-n-butyl azo benzenes exhibiting positive dielectric and positive conductivity anisotropies, using rf dielectric constant measurements at 1 MHz and different moderately thick samples are carried out. It is found that, in low frequencies conductivity anisotropy plays a dominant role and in high frequencies relative effectiveness of electric and magnetic fields on the molecular alignment is independent of thickness of the sample in 100–500 μm range. The optical observations are correlated to the changes in molecular alignment and dielectric constant measurements. The behaviour of the distortion of twist in a twisted nematic liquid crystal in the presence of electric fields is also investigated using rf dielectric constant measurements.