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 bond) produce reversible isomerization while dimethylaminonitrostilbene, a stilbene derivative (C = C bond), exhibits no thermal cis --> trans relaxation.