Fast switchable nematic emulsions with twisted director

Switchable nematic emulsions, obtained by a fast cooling of isotropic mixtures of nematic liquid crystal and monomers, show very low saturation fields but rather long relaxation times because of the bipolar configuration adopted by nematic directors. Such inconvenience has prevented up to now use of switchable nematic emulsions as electro-optical devices. In order to obtain a good compromise between low saturation fields and fast relaxation times, we have experimentally studied the effect of the addition of a chiral dopant on the electro-optical properties of switchable nematic emulsions. The addition of chiral molecules results in a significant decrease of decay times, while the saturation fields are slightly affected. Results are in a rather good agreement with a phenomenological model, which takes into account the increase of elastic energy due to the induced twist deformation. (C) 2001 American Institute of Physics.