Spectroscopic investigation of the thermal cis trans isomerization of disperse red 1 in hybrid polymers

The thermal cis-trans isomerization of disperse red 1 in hybrid polymers has been investigated. We employed transient absorption spectroscopy in order to measure the reaction kinetics of doped and functionalized systems of three matrices. The matrices show different rigidity. In most of the cases the thermal decay of the cis-isomers can be fitted by a sum of two first-order reactions, a slow and a fast one, which are interpreted on the basis of rotational and translational relaxation processes of chain segments. We found that the rate constants of the two reactions increase and the fraction of the fast reacting cis-isomers (x(b)) decreases with increasing rigidity of the matrix. The apparent influence of the matrix rigidity on x(b)-which is associated with the cooperative translational movement of chain segments-is greater in doped systems than in the functionalized ones due to a more rigid organic network. Chromophores which are freely distributed in a polymer can be more easily enclosed in the synthesis, thus being less disturbing in the buildup process of the organic polymer. The polymer around the chromophore is more regular, and a cooperative translational motion of adjacent chain segments is more likely.