The unexpected photomechanical effect in glassy “T-type” azopolyimides

Abstract

We demonstrate an intriguing photomechanical response of a series of glassy azobenzene polyimides containing the chromophores covalently attached to the polymer backbone – “T-type” polymers. To our knowledge, it is the first report on photodriven bending of cantilevers for this class of azomaterials. The studies were performed for high molar mass functionalized azo(polyamide imide)s capable of forming free-standing films of good optical quality. It was found that the bending angles may reach extraordinarily large values of 90° upon ca. 60 second exposure to 445 nm polarized light of moderate intensity. The underlying mechanism of the observed photomechanical response was proved to be reorientational, as a bidirectional cantilever deflection either towards or away from a linearly polarized laser source was observed. No relaxation of cantilevers bent by a maximum angle to their original shape was observed for several days after irradiation.