Effects of carbon nanotubes on the physical properties of a nematic liquid crystal N-(4′-methoxybenzylidene)-4-butylaniline

Abstract

In this work, the nematic liquid crystal (LC) N-(4′-methoxybenzylidene)-4-n-butylaniline (MBBA) was prepared and doped with different concentrations (0.025, 0.05, 0.06, 0.07, 0.08, and 0.1wt.%) of multi-walled carbon nanotubes (CNTs) at room temperature to study the electric properties of (LC–CNTs) cell. The experimental results showed that capacitance of (LC–CNTs) cell became higher than that of pure LC cell. The dielectric permittivity is determined as a function of applied frequency (100Hz to 100kHz) at voltage (5V); it is found that increasing concentration of CNTs (0.1wt.%) led to increase in the real part dielectric constant and decrease in imaginary part for (LC–CNTs) cell compared with the pure liquid crystal. Also conductivity of (LC–CNTs) cell was increased with increasing concentration of CNTs more than 0.05wt.%. Theoretical study was carried out by using PM3 method for stable geometries of a nematic liquid crystal molecule of MBBA assembled parallel on a molecule of single-walled carbon nanotube (CNT). The result showed that the interaction caused by π,π-stacking between MBBA molecule and the wall of CNT and that may lead to formation of the local short range orientation order by LC molecules on the surface of the CNT. The binding energy of the LC molecule on the CNT wall was within the typical van der Waals interaction.