Electro-optical and dielectric performance analysis: the influence of azo dye on polymer/LC composite structures

In the present work, electro-optical and dielectric properties of polymer/LC doped with azo dye methyl red (MR) were investigated. Norland optical adhesive (NOA65) and nematic liquid-crystal (E63-coded nematic liquid crystal) materials were used to compose of polymer/LC composite structure. A doping agent ratio of MR was chosen 1% wt/wt in polymer/LC composite structure. Dielectric measurements of the obtained samples were held between 10 Hz and 10 MHz at room temperature using dielectric/impedance analyzer. Physical parameters such as dielectric permittivity, dielectric anisotropy, electric modulus, loss tangent, relaxation frequency, relaxation time, threshold voltage, and splay elastic constant were obtained from experimental data. Optical bandgap values of polymer/LC and polymer/LC/MR composite structures were estimated using UV spectroscopy technique. Polymer/LC composite structures' electro-optical properties were affected the MR dispersal which was reduced the anchoring force between polymer and LC molecules; therefore, threshold voltage and splay elastic constant decreased. In addition, dispersal of MR caused a decrease in optical bandgap values of polymer/LC composite structures. Due to the increase in charge density caused by MR, the value of the current passing through the polymer/LC composite structures increased as well as its dependence on voltage. Results show that MR dispersal enhanced electro-optical and dielectric properties of polymer/LC composite structures and makes it suitable to design new based on optoelectronic device applications.