Photochromism of spirooxazine-doped gels

Spirooxazine photochromic dyes were trapped in gel thin films. Organically modified doped gels showed normal photochromism. The kinetics of the photochromism in these gels was quantified using both Gaussian and simple biexponential models in order to take into account the inhomogeneous distribution of free volume in the gel matrix and to compare the photodynamics with that in organic polymers. In organic-inorganic hybrid matrices, a competition was observed between normal and reverse photochromisms because of the presence of two chemical environments for the dye molecules. The kinetics of photodegradation for dye-doped gels was deduced from the recording of the excitation/emission spectra during UV light irradiation.