Synthesis and characterization of rare earth metal‐containing polymers. I. Fluorescent properties of ionomers containing Dy3+, Er3+, Eu3+, and Sm3+

Rare earth metal (Dy3+, Er3+, Eu3+, and Sm3+) salts of copolymers of methyl methacrylate–methacrylic acid, styrene–acrylic acid, 1‐vinylnaphthalene–acrylic acid and 1‐vinylanthracene–styrene–acrylic acid were prepared. The fluorescence of these polymer salts under ultraviolet excitation was investigated. The fluorescent intensity of polymer–Eu3+ films varied with film thickness because of incomplete absorption of exciting light, hence most of the measurements were made on pressed fine powders. The fluorescent intensity of mixed samples of Eu(III) acetate in a polymer matrix increased linearly with Eu content. However, the Eu3+–polymer complex system displayed typical concentration‐quenching behavior, reaching a maximum at 4–5 wt % Eu and decreasing with further increases in Eu content. This suggests that the ionomer contains ionic aggregates, in agreement with a recently proposed model. Such aggregates would create locally high Eu ion concentrations, whose interactions lead to concentration quenching at low nominal concentrations. The fluorescent intensity of the acrylic copolymers decrassed in the order methacrylate > styrene > naphthalene > anthracene. This sequence is explained by incrasing competition for the exciting light by the aromatic groups with negligible energy transfer from the aromatic groups to the Eu3+ ions. This is also consistent with the hypothesis that the ionic regions of the polymer are segregated.