DISPERSIVE 1ST-ORDER REACTIONS .2. PHOTOCHROMIC MODEL SYSTEM

The photochromic reactions spiropyran-merocyanine in polymeric matrice s have been analysed with respect to their distributions of rates in o rder to understand the matrix effects on the kinetics in the transitio n range from a static to fluid environment. Employing the technique of part I we find a static matrix situation only below the Vogel-Fulcher temperature T(VF) of the polymer where different species are identifi ed in terms of distinct but distributed decolouration rates. Above the glass transition T(G) the ensemble averaged reaction approaches an ex ponential decay pattern, due to the fluctuations of site specific barr iers and exchange mechanisms among the set of merocyanine isomers.