Nanoparticle induced director distortion and disorder in liquid crystal-nanoparticle dispersions

Colloidal dispersions of nanoparticles in liquid crystals have been investigated experimentally using a model system consisting of the thermotropic liquid crystalline compound 4-n-octyloxy-4'-cyanobiphenyl (8OCB) doped with BaTiO(3) nanoparticles. We show that the physical properties of these dispersions can vary considerably depending on the method of preparation of the dispersions. We also find that aging the sample can improve dispersal of the nanoparticles in the host liquid crystal. Decreases in the isotropic to nematic transition temperature, parallel component of the dielectric constant and orientational order parameter are observed for the dispersions compared to the behaviour of pure 8OCB. These decreases have been explained in terms of orientational disorder and defects induced by the nanoparticles.