A short review of the photomechanical effect in azo-containing amorphous (glassy) polymers

The photomechanical effect has been studied so far mainly in elastomers, but recently more and more publications, in which this effect is studied for other materials too, so-called glassy or amorphous polymers (in particular polyimides), have appeared. This mini-review describes the photomechanical effect in polyimides containing light-sensitive derivatives of azobenzene and, in some cases, for comparison, in polyamides and polystyrenes. The work aims to present the influence of chemical structure factors on the bending angle of free-standing polymer films and their long-term stability. We focused on aspects of polymer structure such as the content of azo-moieties, the flexibility of the backbone, kind of azobenzene attachment (covalent/non-covalent), degree of crystallinity, influence the intermolecular H-bonds. The paper should help in designing new amorphous azopolymers with properties tailored to specific applications.