Photoinduced bending of polymer films

Photoinduced bending and unbending behavior of cross-linked polymer films, prepared by in-situ polymerization of liquid-crystalline (LC) monomers with azobenzene moieties, is discussed. Various modes of bending have been achieved with various alignments of the photoactive mesogens in the elastomers. Exposure of a monodomain film to UV light to cause trans-cis isomerization of the azobenzene moieties leads to the bending of the film toward irradiation direction of the actinic light. Irradiation of a polydomain film with linearly polarized light results in the bending along the polarization direction of the light, which enables bending of the film along any direction. The LC alignment in the films significantly affected the photoinduced bending behavior.