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Photochromic sol-gel derived hybrid polymer coatings: the influence of matrix properties on kinetics and photodegradation

Klukowska A., Posset U., Schottner G., Jankowska-Frydel A., Malatesta V.

Materials Science Poland

2004

Vol. 22, No. 3

187--199

Photochromic dyes undergo a reversible change in their absorption characteristics upon UV light irradiation. By incorporating such photochromophores into sol-gel derived inorganic-organic hybrid polymers, versatile coatings with a fast photochromic response and high photochromic activity can be obtained. In the present study, the isomerization kinetics of spirooxazine dyes entrapped in hybrid polymer coatings were investigated in situ. The chemical properties of the matrices used were characterised in terms of their inorganic network connectivity (NMR measurements) and paramagnetic properties (EPR spectroscopy). Their photodegradation behaviour was studied by means of artificial weathering.

Photochromic hybrid sol-gel coatings: preparation, properties, and applications

Klukowska A., Posset U., Schottner G., Wis M. L., Salemi-Delvaux C., Malatesta V.

Materials Science

2002

Vol. 20, No. 1

95-104

Inorganic-organic hybrid polymer (ORMOCER?) coatings with a fast photochromic response and high photochromic activity were prepared by incorporation of the photochromophore Variacrol ?Blue D into hydrolysates of organofunctional alkoxysilanes, with subsequent thermal curing. Besides the traditional way of doping the sol-gel materials by physically dissolving the dye, a graftable derivative was prepared and covalently attached to two matrices of different rigidity. The resulting thin films showed good photochromic activity, no blooming, mechanical properties at least comparable to the pure host material, and can be applied to different glass and plastic substrates. Photochemical degradation was studied by means of artificial weathering and factors infl uencing the fatigue behaviour of the coatings assessed. The graftable dye showed improved photochemical fatigue resistance. The more rigid matrix was preferable, too, in terms of photodegradation.