Selection of droplet size and the stability of nematic emulsions

Abstract

The topological stability of emulsions of thermotropic nematic liquid crystal dispersed in water is examined for a wide range of materials and concentrations. There is a characteristic size of emulsion droplets, R* = K/W, determined by the ratio of Frank elastic, K, and surface anchoring, W, energies of the liquid crystal. Nematic droplets below this size are not topologically charged and coalesce freely. Droplets with R>R* possess a topological charge +1 and present a high elastic energy barrier for coalescence. We studied the evolution of droplet size distribution with time, illustrating their accumulation in the narrow region around R*, and the dependence of the droplet size distribution on temperature and type of surfactant that controls the director anchoring on droplet inner surfaces.