SPECTROSCOPIC INVESTIGATION OF THE THERMAL CIS-TRANS ISOMERIZATION OFDISPERSE-RED-1 IN HYBRID POLYMERS

The thermal cis-trans isomerization of disperse red 1 in hybrid polyme rs has been investigated. We employed transient absorption spectroscop y in order to measure the reaction kinetics of doped and functionalize d systems of three matrices. The matrices show different rigidity. In most of the cases the thermal decay of the cis-isomers can be fitted b y a sum of two first-order reactions, a slow and a fast one, which are interpreted on the basis of rotational and translational relaxation p rocesses of chain segments. We found that the rate constants of the tw o 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 do ped systems than in the functionalized ones due to a more rigid organi c network. Chromophores which are freely distributed in a polymer can be more easily enclosed in the synthesis, thus being less disturbing i n the buildup process of the organic polymer. The polymer around the c hromophore is more regular, and a cooperative translational motion of adjacent chain segments is more likely.