THE INFLUENCE OF SOLVENTS AND POLYMER MATRICES ON THE PHOTOINDUCED ISOMERIZATION OF AN AZOBENZENE CHROMOPHORE

The thermal cis to trans (Z to E) isomerization process following the photoisomerization of N,N-dimethylaminoazobenzene (methyl yellow) in a number of different solvent matrices; solutions, polymers and a liqui d crystal are compared. In the solvents, dichloromethane, methanol, an d polyacrylonitrile, a photoinduced stable cis isomer population could only be observed at -90 degrees C. In other solvents such as toluene and polycarbonate, at room temperature, the half-life of the cis form was about thirty minutes. The trans to cis conversion of the methyl ye llow was exploited in a low molar mass liquid crystal matrix. Photoind uced shifts of up to 17 degrees C were observed in the nematic to isot ropic phase transition temperature.