The ferroelectricity effect of nanoparticles on thermodynamics and electro-optics of novel cyanobiphenyl eutectic binary mixture liquid crystals

摘要

The phase transition of pentylcyanobiphenyl (5CB) 55% and heptylcyanobipheny (7CB) 45% (E-5CN7) doped with TiO2 and Fe3O4 was investigated using differential scanning calorimetry (DSC) and polarized optical microscopy (POM) techniques. Based on the obtained results, noticeable differences were indicated in nematic-isotropic phase transition temperature and thermodynamic properties including enthalpy and entropy changes between the pure and doped compounds. The mentioned phenomena were attributed to the spherical structure of nanoparticles while the LC texture showed completely different results which were attributed to the formation of Schlieren textures by TiO2. Furthermore, electronic properties of LCs doped with TiO2 and Fe3O4 were monitored using impedance spectroscopy. The impedance results showed that Fe3O4 NP effect on LC semiconducting properties is stronger compared to TiO2. Doping of LCs with NPs forms the colloidal LCs with negative anisotropic properties and nanoparticles change the local ordering of liquid crystals. The diffusion coefficient calculations showed that the insertion of NPs reduces the diffusion of LCs toward the electrode surface. The dielectric constant of mentioned systems was studied as well. (C) 2015 Elsevier B.V. All rights reserved.