A NOVEL CLASS OF LUMINESCENT POLYMERS OBTAINED BY THE SOL-GEL APPROACH

A series of amorphous Eu3+-doped hybrid organic/inorganic materials pr epared by the sol-gel process is presented. The host matrix of the so- called ureasils is a silica network to which oligopolyoxyethylene chai ns are grafted by means of urea bonds. Trivalent europium is present a s a triflate salt, Eu(CF3SO3)(3). Four different compositions of salt have been considered: n=184, 92, 55 and 37, where n represents the num ber 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 tem perature (about 250 degrees C) occurs with composition n=92. This comp osition also exhibits the highest conductivity at room temperature (ap proximately 10(-5) Ohm(-1) cm(-1)). The photoluminescence spectra of t hese 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 l uminescent devices. (C) 1998 Elsevier Science S.A.