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Improvement of photofatigue resistance of spirooxazine entrapped in organic-inorganic composite synthesized via the sol-gel process

A photochromic dye, spirooxazine (SO), was incorporated in organic-inorganic composite (OIC) materials by the advantages of sol-gel processing. It has been found that the photochromic response is high enough and the fading rate is similar to the dye-in-ethanol solution while the photofatigue resistance is strongly dependent on the matrix composition and the starting compounds. In the present work, we present results on the effect of matrix composition and starting compounds as well as additives on the photofatigue resistance of SO- OIC photochromic coatings. Sol-gel coatings synthesized from methyltrimethoxysilane (MTMS) and glycidyloxypropyltrimethoxysilane (GPTMS) as starting compounds, and using 1H,1H,2H,2H-perfluoroalkyltrimethoxysilane (FAS) and 1-methylimidazole (MI) as additives provide the SO dye with a favorable matrix environment in terms of photofatigue, so that the overall photochromic performance of the dye can be optimized. The photofatigue resistance reaches the same level as, while both the photochromic response and fading rate are much better than the SO-PMMA coatings.