A novel class of luminescent polymers obtained by the sol-gel approach

A series of amorphous Eu3+-doped hybrid organic/inorganic materials prepared by the sol-gel process is presented. The host matrix of the so-called ureasils is a silica network to which oligopolyoxyethylene chains are grafted by means of urea bonds. Trivalent europium is present as a triflate salt, Eu(CF3SO3)(3). Four different compositions of salt have been considered: n=184, 92, 55 and 37, where n represents the number of (OCH2CH2) polymer repeat units per ion group of Eu(CF3SO3)(3). Infrared spectroscopic studies suggest that the doped ureasils contain both free and coordinated triflate ions. The lowest decomposition temperature (about 250 degrees C) occurs with composition n=92. This composition also exhibits the highest conductivity at room temperature (approximately 10(-5) Ohm(-1) cm(-1)). The photoluminescence spectra of these materials present a series of narrow lines assigned to D-5(0) --> F-7(0,1,2,3,4) transitions. The high emission intensity observed is a promising property for application of the ureasils in technological luminescent devices. (C) 1998 Elsevier Science S.A.