Synthesis And Luminescence Properties Of Rare Earth Polymer Materials

Luminescent rare earth complexes have attracted considerable attention to organic electroluminescent (EL) devices as well as for optical microcavity emitters owing to their inherent extremely sharp emission bands and potentially high internal quantum efficiency. However, there are many problems for the rare earth complexes that have small molecular weight such as the instability in organic solution and poor compatibility with other materials. Thus, to extend the application of rare earth-containing polymers has attracted attention in the past decade. In comparison with small molecular weight rare earth complexes, besides the advantage of the desired mechanical flexibility, polymer-based rare earth luminescent materials can be soluble or fused processable, which is attractive for optical and electronic applications.There are two techniques which are usually used to synthesize rare earth-containing polymers materials. One is the copolymerization of rare earth-containing monomers and polymeric monomers.The other is the direct reaction of the polymer ligands with rare earth ions.In this paper, the rare earth complexes serving as chromophores were attached successfully on polymers through two different methods mentioned above. The synthesized complexes and rare earth-containing polymers were characterized by the methods of nuclear magnetic resonance (NMR), mass spectrography (MS), infrared spectra (IR), ultra-violet-visible spectra (UV), element analysis (EA), differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and fluorescence spectra, respectively.(1) The ternary complex Eu/Thenoyltrifluoroaceton/N-methyl-2-pyrrolidone [Eu (TTA)₃·2 NMP] was doped into three types of polymer including Polyvinylpyrrolidone (PVP), Polyvinyl alcohol (PVA) and Polymethyl methacrylate (PMMA). The luminescence properties of the blends was studied in this paper. According to the results, it showed that the fluorescence intensity of the polymer doping with ternary complex was stronger than that of ternary complex itself, no matter what the ternary complex was both in solution and film state. The fluorescence intensity of polymer film was 2⁵ times higher than that of solution. And the FT-IR spectra showed that there was interaction existing between the rare earth complex and film material. The polymer material had higher fluorescence intensity than that of small molecular weight rare earth complexes and was more stable.The luminescence properties of the doping materials of Tb/Norfloxacin [Tb(NFLX)₃·8H₂O] with five types of water soluble polymers including polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyacrylamide (PAM),β-Cyclodextrin and Starth was studied. According to the results, it exhibitted that the fluorescence intensity of the doped-polymer except B-PAM was stronger than the binary complex. It also indicated that Starch, PVA,β-Cyclodextrin and PVP could enhance the fluorescence intensity of Tb³⁺.(2) An europium-containing polymer Poly(MMA-co-Eu(TTA)₂AA) was successfully prepared via copolymerization of MMA with the organic complex containing Eu(TTA)₂AA, which was synthesized via the reaction among EuCl₃, TTA, AA and MMA. Compared with the doped-polymer Eu(TTA)₂AA/PMMA, the fluorescence intensity of the copolymer Poly(MMA-co-Eu(TTA)₂AA) increased with the concentration of Eu increasing and there was no concentration quenching effect while the fluorescence intensity of Eu(TTA)₂AA/PMMA decreased upon increasing the concentration of Eu once the concentration of Eu was higher than 3.67% in the Eu(TTA)₂AA/PMMA. The decrease of fluorescence intensity of Eu(TTA)₂AA/PMMA was due to the aggregation of complex, excitonic transfer and concentration quenching. From the analysis of XRD, we found that Eu(TTA)₂AA could regularly be dispersed uniformly in the polymer complex and emit strong fluorescence.An europium-containing polymer Poly(NVK-co-Eu(TTA)₂AA) was successfully prepared via copolymerization of NVK with the organic complex containing Eu(TTA)₂AA, which was synthesized via the reaction among EuCl₃ ,TTA, AA and NVK. Compared with the doped-polymer Eu(TTA)₂AA/PVK, the fluorescence intensity of copolymer Poly(NVK-co-Eu(TTA)₂AA) increased with the concentration of Eu and there was no concentration quenching effect. From the analysis of XRD, we found that Eu(TTA)₂AA could regularly disperse in the polymer complex and emit strong fluorescence. (3) In this paper, 5-acrylamido-1, 10-phenanthroline (AP) was synthesized, then the luminescence material containing Eu-polymer complexes was obtained by two methods. Compared with the rare earth-containing polymer synthesied by the reaction of rare earth with the polymer ligand (Poly(MMA-co-AP)), the one prepared by copolymerization of polymeric monomer with small molecular complex (Poly(MMA-co-Eu(AP)₃) had high and stable fluorescence intensity with the Eu contents was incresed to 0.31%. By comparing the two materials prepared via different methods, we have set down the useful basement for the study of the luminescence material containing Eu-polymer complexes.In particularly, the typical features of rare earth-containing polymers prepared in this dissertation would make them very suitable to be used as polymer electroluminescence materials.