Comparative study of low frequency dielectric properties of Hexyloxybenzylidine hexylaniline and Heptyloxybenzylidine hexylaniline

This article presents a comparative study of low frequency dielectric properties of two Alkyloxybenzylidine alkylaniline compounds—Hexyloxybenzylidine hexylaniline (6O.6) and Heptyloxybenzylidine hexylaniline (7O.6). Dielectric study is made by using cells with ITO coated surface pretreated with polyvinyl alcohol as the aligning layer. We have found that the switching of dielectric anisotropy from negative to positive value is related to the change in orientation of alkyloxy dipole. It indicates 6O.6 (and lower members) to be negative dielectric anisotropic material while 7O.6 (and higher members) to be positive dielectric anisotropic materials. Further comparative study on the interfacial polarization between the two types of interfaces (PVA-6O.6 and PVA-7O.6) with different relaxation times support the differences of the two liquid crystal samples. The dc electric field characteristics of the two samples are drastically different in behaviour and can be explained satisfactorily on the interplay between the dipole orientation and the ionic motion. (author)