Photoisomerization of azobenzene derivatives in polymeric thin films

The photoisomerization of disperse red 1 (DR1) in polymethylmethacrylate thin films is demonstrated by monitoring the refractive index variations by the attenuated total reflection method. Absorption spectrum measurements give a confirmation of this phenomenon. The kinetics of photoisomerization and of thermal relaxation are nonexponential. Some other molecules are studied. As in solution, azobenzene derivatives (N—N) produce reversible isomerization while dimethylaminonitrostilbene, a stilbene derivative (C—C), exhibits no thermal cis→trans relaxation.