Photoelectrochromic switchable nematic emulsions

Abstract

Switchable nematic emulsions are composite systems formed by liquid-crystal droplets dispersed in a fluid, homogeneous, monomer matrix. These systems can be switched from an opaque to a transparent state by application of a suitable alternating electric field. An electrochromic device provides a reversible and visible change in its transmittance as a result of either oxidizing or reducing electrochemical processes. A photochromic device provides a reversible and visible change in its transmittance as the result of a single chemical transformation of the species induced by suitable electromagnetic radiation. These devices have been proven to be useful for a variety of electro-optical applications as switchable windows, electromagnetic shutters, and displays. Our article reports preliminary results on trifunctional devices based on nematic emulsions that host electrochromic and photochromic guest molecules. These trifunctional films are able to modulate the light transmission (with an external alternating electric field) and to change their color (with static field or UV light) by means of suitable electric fields or electromagnetic radiation.