PHOTOCHROMISM OF SPIROPYRANS IN ALUMINOSILICATE GELS

Aluminosilicate sol-gels containing photochromic spiropyran molecules (6-nitro-1′,3′,3′-trimethylspiro[2H-1-benzopyran-2,2′- indoline] and its derivatives) were prepared. The photochromism was studied by transient absorption spectroscopy and luminescence spectroscopy. Stable, solid photochromic gels were prepared whose photochromic properties remained constant after an initial aging period. Four stages of the gelation process were observed and proved by the rates and spectra of the encapsulated photochromic molecules. The rate of return of the excited photochromic molecule to the initial state was measured during the various stages of the gelation process. © 1990 American Chemical Society.