Physics of colloidal dispersions in nematic liquid crystals

This article reviews the physics of colloidal dispersions in nematic liquid crystals as a novel challenging type of soft matter. We first investigate the nematic environment of one particle with a radial anchoring of the director at its surface. Three possible structures are identified and discussed in detail; the dipole, the Saturn-ring and the surface-ring configuration. Secondly, we address dipolar and quadrupolar two-particle interactions with the help of a phenomenological theory. Thirdly, we calculate the anisotropic Stokes drag of a particle in a nematic environment which determines the Brownian motion of particles via the Stokes–Einstein relation. We then turn our interest towards colloidal dispersions in complex geometries where we identify the dipolar configuration and study its formation. Finally, we demonstrate that surface-induced nematic order above the nematic-isotropic phase transition results in a strongly attractive but short-range two-particle interaction. Its strength can be controlled by temperature and thereby induce flocculation in an otherwise stabilized dispersion.