Reverse-mode operation switchable nematic emulsions

Switchable nematic emulsions are dispersions of micron-sized liquid crystal droplets in a monomer matrix, which can be switched from an opaque OFF state to a transparent ON state by application of very low electric fields. In this paper, we present our preliminary results concerning the behavior of switchable nematic emulsions operating in a reverse mode, that is, droplets characterized by a transparent OFF state that can be electrically turned into an opaque ON state. Radial droplets of liquid crystal with a negative dielectric anisotropy have been prepared with a well-defined transparent state by choosing a monomer mixture that matched the average refractive index of the liquid crystal droplets. The application of an electric field determines the reorientation of liquid crystal directors through an elastic distortion and the achievement of a more scattering state. The effect of temperature on the electro-optical response is also reported.