Thermodynamic and Mechanical Properties of Non-Spherical Nematic Colloids: A Computational Study

We investigate the effects of particle size and shape on the thermodynamic and mechanical properties of non-spherical particles in a nematic liquid crystalline solvent. The particles' inclusion distorts the nematic, which form defect structures around the particles that give rise to anisotropic, strong interparticle interactions (up to several thousands of kT for micron-sized spherical particles). These interactions can be used to bind the particles together into ordered structures [1-4], which have potential applications in colloidal crystals, photonics, optical sensors and nanoscale electronics.

We report numerical calculations for the defect structures and the nematic-mediated potentials of mean force, interparticle interactions and torques for systems containing a few particles in a nematic. Using a mesoscale theory in terms of the tensor order parameter Q of the nematic, we analyze several systems of particles with different shapes (e.g., spherocylindrical, cubic, triangular prisms), and we compare with similar results for spherical particles of comparable sizes. Our results [5] indicate that the nematic forms defect structures consisting of distorted Saturn rings around the non-spherical particles. When the particles are close to each other, the Saturn ring defects can become entangled depending on the size and shape of the particles. Our calculations suggest that the nematic-mediated interparticle interactions are highly directional and strong, up to 5700 kT for the case of nm-sized spherocylinders with their long axis parallel to each other. These interactions can bind the particles together at specific locations, and thus could be used to assemble the particles into ordered structures with different morphologies.

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