Impact of Co-doped TiO ₂ nanoparticles on the physical properties of a nematic liquid crystal

Abstract

We have studied the electro-optical properties of the 4-pentyl-4-biphenylcarbonitrile nematic liquid crystal also known as 5CB doped by 0.5%wt of pure and cobalt-incorporated TiO2 nanoparticles. The obtained results show that the effect of the NPs on the electrooptical properties is mainly due to the modification of the dielectric and the viscoelastic properties of the nematic in the presence of the NPs. Furthermore, the nematic isotropic transition temperature of all doped samples remained almost unchanged. This indicates that the order parameter was almost unchanged too. A significant decrease in the dielectric anisotropy and the splay elastic constant was observed. The rotational viscosity has been deduced from response time data; it was found that rotational viscosity shows a significant increase for cobalt-incorporated TiO2. However, the rotational viscosity was decreased for pure TiO2 nanoparticles compared to pure 5CB.