Frequency dependence of dielectric permittivity and conductivity of functionalized carbon nanotube-nematic liquid crystal nanocomposite

Abstract

The addition of carbon nanotubes (CNTs) to nematic liquid crystal (NLC) medium is known to enhance the orientational order along with the enhancement in electro-optical and dielectric properties of the liquid crystal (LC). The studies on the dielectric behavior of LC-nanocomposites at wide range frequencies are essential for optimizing the LC based device performances. The nanocomposites of octadecylamine functionalized single-walled carbon nanotubes (ODA-SWCNTs) with NLC are studied with the aid of dielectric spectroscopy. The important parameters of LCs relevant to display related applications such as dielectric permittivity, relaxation frequency, threshold voltage, and conductivity are investigated over a wide range of frequency and temperatures in planar as well as homeotropic configurations. The doping of ODA-SWCNTs into the NLC increases the local orientational order in the nematic matrix due to the strong interaction between LC and CNT molecules. The optimum doping decreases threshold voltage due to enhancement of dielectric anisotropy and decrease in splay elastic constant. The experimental data obtained from impedance spectroscopy measurements are fitted with a suitable equivalent electric circuit model, and the estimated electrical components are studied as a function of temperature. Investigation on interfacial and bulk properties of pure and ODA-SWCNT nanocomposites of 7CB NLC are also discussed.