Using absorbance spectroscopy, optical second harmonic generation, and atomic force microscopy, we have determined the orientation distribution of the azobenzene group, the molecular surface density, and the topography of the monolayer. These results help to understand the monolayer's high sensitivity to polarized actinic radiation, which reversibly controls anisotropy in the orientation distribution. We have used dichroism spectroscopy to monitor the evolution of the in-plane surface order parameter under low-level actinic illumination. The actinic light is sufficient to rapidly rotate the surface director of a nematic liquid crystal adjacent to the monolayer.

The photoresponsive monolayer also develops an irreversible anisotropy under simultaneous exposure to high-intensity actinic light and oxygen. These properties have made it possible to construct a nematic liquid crystal light valve using the same material for the alignment layers on each of two control surfaces: one which behaves reversibly and the other which is permanently anisotropic. This is accomplished without contacting either surface.