MECHANISM OF THERMAL DECOLORIZATION OF BENZOSPIRANS IN SOME AMORPHOUS POLYMETRIC MATRICES

The photochromic effect has been investigated for three compounds of the benzospiran group dissolved in amorphous polymers: poly(methyl methacrylate), poly(n-butyl methacrylate), poly(vinyl acetate), and poly(vinyl n-butyrate). The kinetics of the thermal bleaching reaction above T//g of the matrix follow a first-order equation. A more complex mechanism of decolorization below T//g has been considered from the point of view of unequal, discrete distribution of environments in which the photochromic molecules exist in the glassy matrix. It seems that, in addition to steric restrictions for trans-cis isomerization in the decolorization process, one must consider the interactions of photochromic molecules with the matrix as well as their chemical nature.