Thermal cis-to-trans isomerisation of triazene dyes in doped polymer films

The kinetics of the thermal conversion of the cis to the trans isomeric forms of 1,3-diphenyltriazene and 1-phenyltriazenes derived from cyclic amines were determined in both poly(methyl methacrylate) and polystyrene doped films in the glassy state, using UV–visible absorption spectroscopy. The kinetics of 1,3-diphenyltriazene are well explained by a two-exponential function, whilst those of 1-phenyltriazene derivates fit a first-order rate law. In all cases, the rate of thermal cis-to-trans isomerisation is higher in poly(methyl methacrylate) than in polystyrene. Rate dependence on dye structure and polymer matrix polarity is consistent with isomerisation taking place via a rotation mechanism.