Síntese e caracterização de materiais híbridos siloxano-PMMA dopados com íons Eu(III)

Abstract

In this work siloxane-polymethyl methacrylate (PMMA) hybrid materials were synthesized and doped with Eu (III) from solid europium chloride, solid europium (III) nitrate, europium chloride (III) in alcoholic solution and 3-aminopyrazine-2-carboxylate of lanthanum and europium complex. The hybrid was prepared from methyl methacrylate (MMA) and 3-methacryloxy-propyl-trimethoxysilane (MPTS), using benzoyl peroxide (BPO) as polymerization initiator. The use of the sol-gel method by acid catalysis allowed to obtain pure solid materials and doped with europium different sources with amorphous characteristics, as evidenced by the X-ray diffraction powderdata. The insertion of the europium complex in the polycrystalline matrix did not changethe structural characteristics of the samples. It was observed that the materials doped with europium in solution, showed greater adsorbed amounts of solvents and structural features that changethe spectroscopic properties. The samples containing solid salts showed similar structural features. It was observed that the average life time of the radioactive emissions increase with the heat treatment, indicating that the temperature reduces the number of suppressor luminescence groups in the coordinationenvironment oflanthanides ion and the character non monoexponentialof the decay is indicative of the presence different coordination environments. In the 29Si NMR measurementsfor samples containing alcoholic solution of europium chloride are observed monomer (RSi(OSi)(OH)2), diimeric(R-Si(OSi)2(OH)) and fully condensed (RSi(OSi)3)species,having a polycondensationdegree up to 78% . The materialsdoped with europium complex show strong luminescence, except tosamples treated at 200 ° C, which is indicative of thermal degradation of the coordination complex. It was observed that presence of solvent changedthermal stability, different heat treatments and europium sources exerted strong influence on the coordination environment of the Eu (III) ions in the organic -inorganic hybrid materials.