Synthesis and photochromism of organosiloxane-based organic/inorganic hybrid containing an inorganic component derived from tungstic acid

The organosilxane-based organic/inorganic hybrid was synthesized by adding 3-glycidoxypropyltrimethoxysilane (GPTMS) to an aqueous solution of tungstic acid and gelling it at 70-150 degrees C. The FT-Raman and C-13 NMR studies revealed that the alkoxy and epoxy groups of GPTMS were subject to hydrolysis and ring-opening reaction, respectively. The 29 Si NMR study revealed that the inorganic component derived from tungstic acid appeared to have Si-O-W bonds with the GPTMS-derived siloxane network. The GPTMS-derived organic/inorganic hybrid containing the inorganic component derived from tungstic acid was transparent and colorless. In addition, it showed the photochromism that resulted from the incorporation of the inorganic component derived from tungstic acid into the GPTMS-derived organic/inorganic hybrid. A broad peak around 880 mn with a shoulder peak around 650 nm was observed in the spectra after the UV-irradiation, meaning two kinds of d-d bond intervalence transition states exist in the organic/ inorganic hybrid. Assuming that the photochromism was the first-order reaction, the reaction rate constant was estimated to be 1.9 x 10(-1) min(-1).