A polymer film that has been sandwiched between two Teflon sheets curls when hit with ultraviolet (UV) light, a result of the film's highly ordered three-dimensional (3D) molecular structure. Such 3D ordering over macroscopic length scales could aid in the design of advanced materials and devices.
Takuzo Aida and Takanori Fukushima at the RIKEN Advanced Science Institute in Saitama, Japan, and their colleagues designed a brush-shaped polymer bearing multiple photoresponsive azobenzene groups. They then hot pressed the polymer film between two Teflon sheets that were stretched along one axis. Spectroscopic measurements revealed that, during hot pressing, the Teflon sheets imposed a certain molecular order on the film, such that the concerted motion of the photoresponsive units caused the film to curl in response to UV only when the drawing directions of the Teflon sheets had been parallel to each other.