We demonstrate that the electro-optics of nanostructured nematic liquid crystal (LC) doped with a small amount of photoactive LC molecules can be efficiently controlled by light. In particular, the inclusion of 3 wt.% azobenzene LC 4-(4'-ethoxyphenylazo)phenyl hexanoate (EPH) into a gel nanocomposite material produced from nematic LC heptylcyanobiphenyl (7CB) and 3 wt.% hydrophilic silica nanoparticles of size ca. 7 nm (Aerosil 300) allows both the static (the transmittance versus the voltage) and the dynamic (amplitude-frequency electrooptic modulation) characteristics of thin films (25 μm) of such a complex LC system in an alternating-current electric field to be enhanced by UV light at a wavelength of 375 nm. This photo-effect that is reversed with white light is based on the photo-isomerization of the doped azobenzene molecules. The efficient photo control makes the considered EPH-doped Aerosil/7CB photo-responsive nematic nanocomposites attractive for specific electro-optic applications.
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