Investigation of reversible photo-mechanical properties of azobenzene-based polymer films by nanoindentation

Photo-induced mechanical properties of two copolymer thin films with 3.5 and 6 mol% azobenzene chromophores in the side chain, were investigated by nanoindentation. After ultraviolet irradiation the stiffness of the films was found to increase by about 10–28% compared to their original ‘virgin’ state. The altered mechanical properties were attributed to conformational changes in the polymer chains via a trans–cis isomerisation of the chromophores.