Stability of Liquid Crystalline Macroemulsions

Abstract

The thermodynamic stability of emulsions of liquid crystal in water (glycerol) matrices is demonstrated for a wide range of materials and concentrations. Coalescence is prevented by an energy barrier for a topological ring defect formation in a neck between the two merging droplets. There is a characteristic size of emulsion droplets, typically tens of microns or more, controlled by the balance of elastic and anchoring energies of the liquid crystal. On removal of liquid crystallinity (by raising the temperature above $T_{ni}$ in thermotropic nematic materials, for example) the energy barriers for coalescence disappear and emulsion droplets can merge quickly, controlled only by the traditional kinetic effects. Practical applications of this effect, as well as some wider theoretical implications are discussed in the end.