Defects structure and effective pair interactions in nematic colloids

Tasinkevych, M.¹

¹ Max Planck Institute for Metals Research, Stuttgart, Germany

We use the Landau-de Gennes free energy formalism to study nematic-mediated effective interactions between spherical particles, assuming strong homeotripic anchoring at the surface of the particles. A single particle of large enough radius generates a dipolar director configuration with a small companion disclination ring. While small particles generate quadrupolar configurations with an equatorial disclination ring.   In the dipolar configuration the disclination ring has a nontrivial orientation which locally breaks the polar symmetry of the far field director. Both configurations have a wide range of metastability (as a function of particle radius and temperature) which is responsible for a very complex effective pair-wise interaction. At short distances the corresponding force-distance curves exhibit jumps and hysteresis upon approach/separation due to the rearrangements of the corresponding disclination rings. At large distances the interaction potential behaves like dipole-dipole, dipole-quadrupole, or quadrupole-quadrupole depending on the nematic distortions around particles.