Effects of alkoxysilanes and reaction time of sol on the thermal decay of photochromic thin gel films containing spirobenzopyran and Malachite Green Leucocyanide were examined. The colored form of spirobenzopyran in thin gel film prepared by the sol-gel method is dependent on the gel matrix influenced by reaction time of sol, and more than two colored forms were appeared in thin gel film prepared from tetraalkoxysilane derivatives, with longer reaction time of sol.
On the other hand, in thin gel films prepared from methyltrialkoxysilane derivatives which was expected to form larger pores in gel films, ordinary thermal decay was observed which was independent of reaction time of sol.
It was found that the thermal decay reaction of the colored form of Malachite Green Leucocyanide in thin gel films prepared from various alkoxysilanes stopped at 70-80% of the initial absor-bance, and the green-colored form was held in gel thin films.
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