Induced smectic mesomorphism in some binary mixtures: A new type of electrohydrodynamic pattern in the nematic phase of the mixtures

Abstract

We have studied the phase diagrams of the following binary mixtures: (a) 4,4'- (a) 4,4'- (7CB) and (b) (2-hydroxyl-p-ethoxybenzylidene-pl-butylaniline (OH-EBBA) with 7CB. Though none of the pure compounds exhibits the smectic A phase, the two mixtures exhibit an 'induced' smectic A phase over certain ranges of composition. The nematic phase occurring just above the induced smectic A phase has positive dielectric anisotropy and negative conductivity anisotropy. We have observed electrohydrodynamic instabilities in these nematics. The instability patterns, seen in homeotropically aligned samples, develops with a circular symmetry at various points in the field of view and for low frequencies of the applied field goes over to the dynamic scattering state at high enough voltages.