A supramolecular chiroptical switch using an amorphous azobenzene polymer

Supramolecular chirality has been optically induced in an achiral epoxy-based polymer containing photoresponsive azobenzene groups. The origin of this effect is the long-range helical arrangement of the azobenzenes, which extends through the entire thickness of the film. The helicity induced by the handedness of the laser can be reversibly switched by alternately exposing the film to a 488 nm laser with right- and left-handed elliptical polarization. The chiral properties of these films have been characterized by circular dichroism spectroscopy and optical rotation. After five switching cycles, the fatigue resistance is seen to depend on the absorption wavelength of the film, probably due to differences in the photoresponsive speed of the azobenzenes and the polymeric segments.