Transparent polysilsesquioxane films obtained from bridged ureasil precursors: tunable photoluminescence emission in the visible region and filtering of UV-radiation

MARÍA L. GÓMEZ; DIANA P. FASCE; ROBERTO J. J. WILLIAMS; CARLOS M. PREVITALI; HERNÁN A. MONTEJANO

MACROMOLECULAR MATERIALS AND ENGINEERING (PRINT)

WILEY-V C H VERLAG GMBH

Lugar: Weinheim; Año: 2010 vol. 295 p. 1042 - 1048

1438-7492

Bridged ureasil precursors were synthesized by the reaction of either ethylenediamine (EDA, 1 mol) or m-xylylenediamine (XDA, 1 mol) with isocyanatepropyltriethoxysilane (IPTES, 2 moles). Transparent polysilsesquioxane films were obtained by the hydrolytic condensation of the pure precursors or the co-condensation of both precursors in a 50:50 molar ratio. While films based on pure ureasil precursors showed a blue photoluminescent emission band assigned to the photoinduced proton-transfer among H-bonded urea groups and the subsequent radiative recombination of ionized groups, films synthesized by the co-condensation of both precursors exhibited a significant red-shift of their absorption, excitation and emission spectra. The observed behavior was associated to de-localization of H-bonds produced by variations in the conformation of the organic bridges of the two different precursors when assembled at random between siliceous domains. An interesting property of films synthesized from the blend of precursors was the high absorption of UV-radiation and the high transparency in the visible region. Coatings based on these materials might find applications based on their intrinsic photoluminescence and the UV-filtering capacity.