Macroscopic Deformation of Photoactuator Triggered by Isomerization of Azobenzene at Cryogenic Temperature

Abstract

We prepared 4 types of crosslinked liquid-crystalline polymer films containing azobenzene moieties with different alkyl chains. We evaluated photoisomerization behavior of azobenzene in the films and photoinduced deformation triggered by the shape change of azobenzene moieties in liquid nitrogen (77 K). We irradiated the films with UV light at room temperature and observed bending of all the films toward an actinic light source. Then we put the bent films in liquid nitrogen and irradiated with visible light. The films containing azobenzene moieties with a short spacer remained unchanged, while the films containing azobenzene with a long spacer reverted to the initial flat shape with concomitant cis-trans isomerization of azobenzene in the films.