Fluorescence characteristics of europium ions stabilized in solid polymer electrolytes containing polyether structure

Polyethylene oxide (PEO) oligomers can dissolve lanthanide salts. The terminal hydroxyl groups of PEO affect the solubility of the lanthanide salts in the PEO considerably. However, no intensive fluorescence was observed from Eu³⁺ dispersed in PEO or other ion-conductive polymers containing terminal hydroxyl groups, because of the quenching effect of the terminal hydroxyl groups. Copolymer of ω-methoxy oligo(oxyethylene) methacrylate and methyl methacrylate (P(MEOM-co-MMA)) could dissolve small amount of Eu(NO₃)₃, but the copolymer film containing Eu³⁺ shows intensive fluorescence (Ex = 269.0 nm, Em = 570.0 nm). This was prepared as a soft film, and there was a clear dependence of the Eu³⁺ concentration on the fluorescence intensity. A linear relation between the film thickness and the fluorescence intensity was also observed. Little fluorescence was found for Eu³⁺ in the blend of the corresponding two homopolymers, i.e. poly-(ω-methoxy oligo (oxyethylene) methacrylate) (PMEOM) and poly(α-methyl methacrylate) (PMMA). This strongly suggests that intensive fluorescence requires a mixed state of MEOM and MMA units at molecular level.