Brownian Dynamics of Colloidal Particles in Lyotropic Chromonic Liquid Crystals

We employ video microscopy to study Brownian dynamics of colloidal particles suspended in the nematic phase of the lyotropic chromonic liquid crystal , Disodium Chromoglycate, (DSCG). DSCG is water soluble, and its nematic phase is characterized by an unusually small twist elastic constant, which leads to formation of chiral director configurations. The mean-square displacement for polystyrene microspheres moving parallel to the far-field director is sub-diffusive for lag times up to several seconds and then diffusive at longer times. Dynamics perpendicular, by contrast, is slower and never quite becomes diffusive, even after hundreds of seconds of lag time. We also compared the diffusion of spheres inducing energetically distinct director field configurations and found them to be different depending on chirality. We compare our observations to previous diffusion experiments in nematic LCs [1-4], and seek to understand our results using conventional diffusion theory.
[1] G. J. Krüger, Physics Reports 82, 229 (1982).
[2] J. C. Loudet, et al., Science 306, 1525 (2004)
[3] T. Turiv, et al., Science 342, 1351 (2013).
[4] M. Gomez-Gonzales, et al., Soft Matter 12, 5758 (2016)