Media effects on the optical properties of proton donor group containing azobenzene derivatives

A series of hydroxy and carboxy group containing azobenzene compounds were synthesized and investigated by UV-vis and fluorescence spectroscopy. It could be shown that the ambient medium exerted a strong influence on the absorption behavior and the trans-cis isomerization behavior of the azo compounds. Especially in the case of hydroxy group functionalized azobenzenes, deprotonation with NaOH or a polymeric base changed the spectral behavior of the compounds remarkably. A strong bathochromic shift of the dyes' longest wavelength absorption band was observed. Furthermore, the influence of different solvents and different polymeric matrices on the trans-cis isomerization behavior of the azobenzenes was investigated. The results are discussed in terms of utilization of the azo dyes as probe molecules for interactions in polymer blends.