New sol-gel photochromic thin films made by super-fine particles of organic photochromic compounds

Abstract

New photochromic thin gel films have been prepared by the dipping method from a sol-gel coating solution containing Malachite Green Leucocyanide soluble in sol and super-fine dispersed solution of spiropyran or spironaphthooxazine, which was effective to increase the concentration of photochromic compounds in gel film. Photochromism of these gel films is compared with that in sol under the conditions of acid catalysis. Though in sols using spiropyran and Malachite Green Leucocyanide normal photochromism was not observed, photochromism in thin gel films prepared from the same sol was confirmed. Normal photochromism of spironaphthooxazine in thin gel films was similar to that in solution. The reaction rate from the colored form to the spiro form of spiropyran and spironaphthooxazine in thin gel film is dependent on the gel matrix, which is influenced by the reaction time of the sol.