Effect of compatibility between europium complexes and styrene monomer on preparation of europium-encapsulated microspheres by dispersion polymerization

Two europium organic complexes of Eu(DBM)3Phen (DBM = dibenzoylmethane, Phen = 1,10-phenanthroline) and Eu(TTA)3·2H2O (TTA = 2-thenoyltrifluoroacetone) with different structures are successfully encapsulated into polystyrene (PSt) microspheres by in situ dispersion polymerization. These fluorescent microspheres are monodisperse and spherical in shape with the homogeneous distribution of europium complexes in the polymer matrix, as investigated by field emission scanning electron microscopy and confocal laser scanning microscopy. The europium content in the microspheres is measured by inductively coupled plasma atomic emission spectrometer. It is shown that the compatibility of the europium complex with the styrene monomer has a great impact upon the europium content in the PSt microspheres by dispersion polymerization. As the complex amount increases, the europium content in the microspheres containing Eu(DBM)3Phen increases, while that in the microspheres containing Eu(TTA)3·2H2O first increases and then reaches a saturated value at a high addition amount. Fluorescence properties indicate that the PSt polymer is a valuable matrix for improving the emission intensity of Eu(DBM)3Phen yet not an ideal matrix for Eu(TTA)3·2H2O, which is demonstrated by the measurement of fluorescence lifetime.