Preparation Of Benzoic Acid Derivative-functionalized Polystyrene And Research On Photoluminescence Properties Of Its Complex With Eu(Ⅲ) Ion

Bond-type polymer-rare earth complexes is a high performance luminescencematerials. The complex possesses the excellent photoluminescence andelectroluminescence properties, and easy processing characteristics of polymers.Polymer-rare earth complexes is a investigative hotspot in luminescence materials.Aromatic carboxylic acid gets a lot attention in preparing bond-type polymer-rare earthcomplexes because it has dual-function of coordination and sensibilization. In this paper,via bond small molecule ligands on side chains of polystyrene, four species ofpolymer-metal complexes were prepared by choosing four benzoic acid derivative, andtheir fluorescence properties and structure-function relationship were mainlyinvestigated. This provides an important reference in the area of developing newpolymer-rare earth complexes materials.First, the nucleophilic substitution reaction between the chloromethyl group ofchloromethylated polystyrene (CMPS) and phenolic hydroxyl group of3-nitro-4-hydroxy benzoic acid (NHBA) was conducted with chloromethylated CMPSas starting substance and NHBA as nucleophilic reagent, resulting in the functionalpolymer PS-NBA. By using the same method, we also prepared other three benzoic acidderivative-functionalized polystyrene, PS-FBA, PS-MOBA and PS-HBA. The chemicalstructure of the products were characterized by infrerad spectroscopy(FTIR) and1H-NMR spectroscopy. By taking PS-NBA as an example, the effects of main factors onnucleophilic substitution reaction were investigated emphatically. The experimentalresults show that reaction temperature and the polarity of the solvents affect the nucleophilic substitution reaction greatly. The stronger polarity solvents and higherreaction temperature are favorable for the substitution reaction. The optimal reactionconditions are as follows: reaction temperature at70℃and solvent DMF. Under theoptimal reaction condition, we obtain functional polymer PS-NBA whose bondingamount is2.63mmol/g.Moreover, two benzoic acid derivative-functionalized polystyrenes, PS-NBA andPS-FBA, were prepared by the two ligands with electron-withdrawing substituent groups.The two macromolecular ligands were allowed to be coordinated with Eu(Ⅲ) ion, andthe binary complexes PS-(NBA)3-Eu(Ⅲ) and PS-(FBA)3-Eu(Ⅲ) were prepared. At thesame time, ternary complexes were prepared with small molecular phenanthroline (Phen)as the second ligand. The photo physical behaviors of these complexes were examined,and the effects of the two electron-withdrawing substituent groups, nitro group andformyl group, on the luminescence property of these complexes were mainlyinvestigated. The experimental results indicate that the two electron-withdrawingsubstituent groups affect the luminescence property of the complexes of benzoicacid-functionalized polystyrene and Eu(Ⅲ) ion greatly. They make the excitation energyof ligands to be dissipated through an intraligand charge transfer (ILCT), which leads thetriplet state energy of ligands to be declined. As a result, the matching degree betweenthe lowest triplet level of ligands and resonance energy level of Eu(Ⅲ) ion is enhancedmarkedly, and ligands produce a stronger sensitization for the florescence emission ofEu(Ⅲ) ion, resulting in the strong florescence emission of the complexes. However, onthe other hand, the fluorescence quenching action of nitro group for the fluorescence ofthe complexes still occurs, resulting in the decreasing of the luminescence property ofthe complexes with increasing complex concentration.Finally, two benzoic acid derivative-functionalized polystyrenes, PS-MOBA andPS-HBA, were prepared by the other two ligands with electron-donating substituent groups. The two macromolecular ligands were allowed to be coordinated with Eu(Ⅲ)ion, and the binary complexes PS-(MOBA)3-Eu(Ⅲ) and PS-(HBA)3-Eu(Ⅲ) wereprepared. At the same time, ternary complexes were prepared with small moleculephenanthroline (Phen) as the second ligand. The photo physical behaviors of thesecomplexes were examined, and the effects of the two electron-donating substituentgroups, Methoxy group and hydroxy group, on the luminescence property of thesecomplexes were mainly investigated. The experimental results indicate that the twoelectron-donating substituent groups affect the luminescence property of the complexesof benzoic acid-functionalized polystyrene and Eu(Ⅲ) ion greatly. They can decrease theexcitation energy of ligand BA through p-π conjugation effect, which leads the tripletstate energy of ligand BA to be declined. As a result, the matching degree between thelowest triplet level of ligand BA and resonance energy level of Eu(Ⅲ) ion is enhancedmarkedly, and ligand BA produces a stronger sensitization for the florescence emissionof Eu(Ⅲ) ion, resulting in that the florescence emission of the binary complexes ofPS-(MOBA)3-Eu(Ⅲ) and PS-(HBA)3-Eu(Ⅲ) are much higher than that of the binarycomplex of PS-(BA)3-Eu(Ⅲ). The florescence emissions of the ternary complexes andsolid films of the complexes also exhibit a similar trend.