Preparation And Fluorescence Properties Of Novel Rare Earth-Coordinated Polyaryletherketone Complexes

Rare earth coordination polymers possess both unique luminescence properties of rare earth ions and excellent processability of polymer materials, which endow them potential applications in many fields such as light-emitting display, optics communications, solar-energy conversion systems, and so on. Therefore, the study on synthesis and properties of new rare earth coordination polymers is of theoretical and practical significance. In this work, using polyaryletherketones as macromolecular ligands, a series of novel rare earth complexes with excellent fluorescence properties were designed and synthesized. The relationship between the structures and properties of these materials were discussed systematically in order to obtain new rare earth functional polymeric materials with promising applications.Three carboxyl-containing polyaryletherketones with different alkyl substitutents (PEKs=PEK-1, PEK-2, PEK-3) were prepared via solution nucleophilic polycondensation reaction. The number-average molecular weights (Mn) of PEK-1, PEK-2 and PEK-3 were 66.4,46.1 and 45.6 kg/mol, respectively. PEKs all displayed the amorphous structures, and could easily dissolve in solvents such as DMSO, DMF, THF at the room tempreture. The glass transition temperatures (Tg) and 5% thermal decomposition temperatures (T5) were over 210 and 402℃, respectively.Using PEK-1, PEK-2 and PEK-3 as macromolecular ligand, respectively, and 1,10-phenanthroline (Phen) as synergistic ligand, a series of novel rare earth coordination polymers (PEK-RE3+-Phens, PEK=PEK-1, PEK-2, PEK-3, RE3+=Eu3+, Tb3+, Dy3+, Sm3+) with visible fluorescence emission were prepared. The rare earth ions could disperse homogeneously in the polymer matrix due to the formation of coordination bonds between rare earth ions and the carboxyl groups on the polymer backbone. PEK-RE3+-Phens showed good solubility and could dissolve in DMF, DMAc, NMP, and the uniform and smooth thin films could be obtained easily by spin-coating or solution-casting method. PEK-RE3+-Phens exhibited the characteristic fluorescence of the corresponding rare earth ions under UV excitation. Furthermore, PEK-RE3+-Phens showed the much higher intensities than the corresponding PEK-RE3+s and RE3+-Phens complexes, attributed to the synergistic effects of macromolecular ligand and small molecular ligand. Compared with PEK-2 and PEK-3, PEK-1 owned the most alkyl substituents, which was responsible for the higher fluorescence intensities of PEK-1-RE3+-Phens than those of PEK-2-RE3+-Phens and PEK-3-RE3+-Phens. PEK-RE3+-Phens showed the longer fluorescence lifetimes than RE3+-Phens. The fluorescence lifetimes of PEK-1-Eu3+-Phen and PEK-1-Tb3+-Phen were as long as 1130 and 960μs, respectively. The powder, DMF solution and film samples of PEK-1-Eu3+-Phen and PEK-1-Tb3+-Phen could emit bright red and green light under the UV lamp of 365 nm, respectively.By the chloroformylation and amidation reactions, Phen with conjugate and rigid structure was attached onto the PEK-1 backbone to yield 1,10-phenanthroline-functionalized polyaryletherketone (PPEK), which showed good solubility and owned the higher thermal stability than PEK-1. Subsequently, using PPEK as macromolecular ligand and Phen as synergistic ligand, a series of novel rare earth coordination polymers (PPEK-RE3+-Phens, RE3+= Eu3+, Tb3+, Sm3+, Dy3+) with visible fluorescence emission were prepared. PPEK participated in the cooridnation reaction with rare earth ions by the nitrogen atoms of Phen groups attached on PEK-1 chain. PPEK-RE3+-Phens exhibited good solubility and film-formation. PPEK-Eu3+-Phen, PPEK-Tb3+-Phen, PPEK-Dy3+-Phen and PPEK-Sm3+-Phen could emit the characteristic fluorescence of the corresponding rare earth ions under UV excitation.In order to enhance the fluorescece intensities of the rare earth coordination polymers, La3+and Ce3+were introduced into the PEK-1-Eu3+-Phen and PEK-1-Tb3+-Phen systems, respectively, and PEK-1-Eu3+0.5La3+x-Phens and PEK-1-Tb3+0.5Ce3+x-Phens were prepared. The fluorescence analysis confirmed that the introduction of La3+and Ce3+could obviously improve the emission intensities of PEK-1-Eu3+-Phen and PEK-1-Tb3+-Phen, respectively. In addition, PEK-1-Eu3+xTb3+1-x-Phens were prepared and the fluorescence properties were investigated by their fluorescence spectra, as well as the CIE1931xy chromaticity diagram. The results showed that, the rare earth coordination polymers emitting various combinations of red and green color, including yellow color, could be obtained through adjusting the contents of Eu3+and Tb3+in the PEK-1-Eu3+xTb3+1-x-Phen systems.Using Er3+, Nd3+or Yb3+as the central ions, PEK-1 as macromolecular ligand and 8-hydroxyquinoline (HQ) as synergistic ligand, a series of novel rare earth coordination polymers (PEK-1-RE3+-HQs, RE3+= Er3+, Nd3+, Yb3+) with near-infrared fluorescence emission were prepared, in which rare earth ions were coordinated simultaneously with PEK-1 and HQ. The two steps of thermal decomposition of PEK-1-Er3+-HQ were attributed to the cleavage of quinoline ring of HQ and macromolecular chains of PEK-I, respectively. PEK-1-RE3+-HQs could dissolve in the common solvents, such as DMF, DMAc and DMSO, and showed good film-forming capability. PEK-1-Er3+-HQ, PEK-1-Nd3+-HQ and PEK-1-Yb3+-HQ could emit intense fluorescence in the near-infrared region, and the strongest emission peaks located at 1527,1060 and 978 nm, respectively. The synergistic effects of PEK-1 and HQ could enhance obviously the emission intensities of these coordination polymers.