Effect of azobenzene derivatives on the photochemical stability of poly(methyl methacrylate) films

The effect of three azobenzene modifiers and UV-irradiation on physico-chemical properties of poly(methyl methacrylate) (PMMA) has been studied. The PMMA matrix doped with 5% (wt) of diazobenzene (DAB), diazoaminobenzene (DAAB) or p-aminodiazobenzene (ADAB) was exposed to polychromatic radiation. Moreover, pure PMMA and modifiers were irradiated alone in the same conditions. For all samples the photochemical changes were monitored by FTIR and UV-Vis spectroscopy. The surface properties of modified and irradiated PMMA were determined by contact angle measurements. Degradation process in the polymer was proved by viscometric measurements. It was found that azobenzene additives hampered photooxidative degradation of PMMA. These additives absorb incident light and undergo both reversible isomerization and direct photolysis. UV-irradiation of PMMA and its compositions, containing azobenzene derivatives, caused an increase in surface polarity. The least effective degradation and the smallest changes in surface free energy were found for PMMA with ADAB.