Dielectrical, electro-optical and textural studies of 5CB nematic liquid crystal doped with TiO₂ and Cu-TiO₂ nanoparticle

Abstract

We investigated dielectric and viscoelastic properties of the 4-pentyl-4-biphenylcarbonitrile nematic liquid crystal also known as 5CB doped by 0.5%wt of pure and copper-incorporated TiO2 nanoparticles. Optical microscopy observations showed uniform copper-incorporated TiO2 nanoparticles dispersion into the nematic 5CB while we have seen nanoparticles aggregations for pure TiO2. Further, except the pure TiO2 nanoparticles, the nematic isotropic transition temperature of all doped samples slightly increased by about 1.4–2.4°C as compared to the pure 5CB. This indicates that the order parameter was increased. Significant decrease in the dielectric anisotropy, response time, splay elastic constant and threshold voltage was observed for all samples. The rotational viscosity has been deduced from response time data, it was found that rotational viscosity shows a slight increase with respect to pure 5CB for copper-incorporated TiO2 and a clear decreasing for pure TiO2 nanoparticles.