Optically driven diffusion and mechanical softening in azobenzene polymer layers

Mechau, N.; Neher, D.; Börger, V.; Menzel, H.; Urayama, K.
December 2002
Applied Physics Letters;12/16/2002, Vol. 81 Issue 25, p4715
Academic Journal
A study of the thermally induced and photoinduced changes in the mechanical properties of thin azobenzene polymer layers utilizing electromechanical spectroscopy is presented. Upon illumination at room temperature, weak photoinduced plasticization is observed. This is well below the degree of softening induced by heating the layer above the glass transition temperature. At the same time, the polymer layer roughens, indicating light-induced diffusion of the macromolecules over micrometer distances. We propose an active photoinduced diffusion mechanism, in which free volume generated during the photoisomerization of one chromophore is reoccupied in the course of the photoinduced isomerization of an adjacent azobenzene molecule.


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