Light-induced transformation of defect structures in photochromic liquid-crystal emulsions

We investigated photoresponsive behavior of azobenzene-containing liquid crystals dispersed with glycerol or water droplets. At an initial state, Saturn ring and hedgehog defects were formed around the glycerol and water droplets, respectively, indicating that homeotropic anchoring was induced by adsorption of the azobenzene molecules onto the droplets. For the glycerol droplets, we observed structural transformation between Saturn ring and boojums on irradiation with ultra-violet and visible light. For the water droplets, an inter-droplet distance varied by changes of the defect size on the irradiation. These phenomena would result from modulation of anchoring conditions by the photoisomerization of the adsorbed dyes.