【作者】 徐存进；

【导师】 李伯耿；

【作者基本信息】 浙江大学 ， 化学工程， 2011， 博士

【摘要】 稀土聚合物由于兼具稀土离子发光强度高、色纯度高和高分子材料优良的加工性能等优点而倍受瞩目。以化学键结合的形式将稀土配合物与聚合物连结在一起,生成的键合型的稀土聚合物,可以使稀土配合物均匀地分布在聚合物基体中,在稀土含量较高时仍具有优良的荧光性能,而且其荧光强度随稀土离子含量的增加而增强,呈现出线性递增的现象。目前,多数研究利用丙烯酸与稀土的键合作用将C=C双键引入到稀土配合物中,再与甲基丙烯酸甲酯、苯乙烯等烯类单体共聚,制得键合型的稀土高分子复合材料。但应当指出,这些键合型的复合材料中,丙烯酸类配体对稀土离子的荧光发射贡献不明显,但是却占用了稀土离子的一部分配位数,明显影响了材料的荧光性能。本文旨在通过多功能配体的设计来合成具有高荧光强度的稀土聚合物,发展高性能稀土聚合物发光材料的合成与制备方法。论文的主要内容如下：1)针对邻菲罗啉和8-羟基喹啉配体具有刚性大、吸光系数大、配位能力强等特点,设计合成了基于这两种物质的多功能配体——5-丙烯酰胺基-1,10-邻菲罗啉(Aphen)和5-丙烯酰氧乙氧基甲基-8-羟基喹啉(Hamq),并对合成工艺进行了优化。分别实验考察了两种配体的荧光发射光谱及低温磷光光谱,发现两者都具有具有较强的向稀土离子能量转移的趋势,它们的最低三重态能级分别为20000和22370 cm-1,与Eu3+离子的共振发射能级(5D0,17200 cm-1)具有良好匹配,其中,配体Aphen的匹配程度优于Hamq。2)研究了系列配合物Eu(β-diketone)3(Aphen)、Eu(TTA)2(amq)、Eu(TTA)3(H2O)2、Eu(TTA)2(AA)的光物理性能(光色纯度、荧光强度、荧光寿命、量子效率等),发现在Eu(β-diketone)3 (Aphen)系列配合物中,Eu(TTA)3(Aphen)的荧光性能最强(荧光寿命、量子产率分别为590μs、40.1%),其5D0→7F2跃迁的荧光发射强度分别为配合物Eu(TTA)3(H2O)2、Eu(TTA)2(AA)和Eu(TTA)2(amq)的4.5、11.3和3.9倍。指出丙烯酸配体AA对Eu3+离子的发光基本不起作用,而配位水分子则对Eu3+离子的发光起到荧光猝灭作用,揭示了配体Aphen、Hamq敏化Eu3+离子发光的Antenna效应、协同效应。3)通过强荧光稀土配合物单体Eu(TTA)3(Aphen)、Eu(TTA)2(amq)分别与MMA的共聚合反应成功地合成了基于邻菲罗啉和8-羟基喹啉衍生物的键合型强荧光稀土聚合物复合发光材料。实验考察了稀土聚合物的红外光谱、紫外光谱、核磁共振氢谱、分子量及其分布、热稳定性、荧光寿命、荧光激发及发射光谱,发现：①稀土配合物单体具有良好的共聚合性能,其结构单元在聚合及提纯过程中不容易解离；②稀土配合物结构单元的引入有助于提高共聚物的热稳定性及玻璃化转变温度；③共聚物中甲基丙烯酸甲酯单元虽参与配位,但是起能量传递作用的主要物质依然是TTA；④共聚物的荧光同样表现为稀土离子的特征发射,均观测到5D0→7FJ(J=0-4)的跃迁,其中5D0→7F2跃迁的强度最大,在所研究的Eu含量范围内,共聚物荧光强度随Eu含量增加而增大,没有出现明显的荧光猝灭现象。指出共聚物荧光性能的提高与配合物结构单元在聚合物基质中所处的微环境有关：一方面由于甲基丙烯酸甲酯单元参与配位,使得稀土配位趋于饱和,从而荧光性能大为增强；另一方面由于配合物单体与MMA共聚后,每一个配合物单元都被PMMA柔韧链围绕,而且还可能被高分子链扭曲,稀土离子就象被圈在聚合物的笼子中一样,产生所谓的“笼蔽效应”,在这种特殊的构象下,稀土小分子配合物单元之间的相互作用变得非常微弱,稀土离子的聚集体不容易生成,同时由于高分子链的介入,更进一步降低了Eu3+的对称性,增加了5D0→7F2跃迁的可能性。4)在Eu(TTA)2(amq)/PMMA的共混体系中,当Eu的含量较低时,共混物的荧光强度随Eu含量的增加而增强,基本呈现了良好的线性关系,当Eu%=3.30wt%时,荧光强度值达到最大,在此以后,随Eu%的增加荧光强度逐渐降低,出现荧光猝灭现象。更多还原

【Abstract】 The rare earth polymer materials have attracted considerable interests for their good luminescent characteristics, high color purity of rare earths and the excellent processability of polymers. The bonding-type rare earth polymers in which the lanthanide complexes are covalently bound in the main chain would cause the lanthanide complexes to distribute evenly in the polymer marixes, and could still maintain the luminescence intensity when the rare earth metal content is high. Furthermore, the luminescence intensities of the polymers increase linearly with an increase in the rare earth content. Up to now most of the approaches to bind a lanthanide complex to a polymer backbone take advantage of a polymerizable ligand such as acrylic acid. But it should be noted that the acrylic acid ligand makes little contribution to the luminescence of the complexes, and occupies the coordination number of rare earth ions, which would significantly affect the luminescence properties of the polymers. This thesis aims to synthesize highly luminescent rare earth polymers through the design of multifunctional ligands, and to develop the synthesis and preparation methods for the rare earth polymer luminescent materials with high performance. The following results have been achieved:1) Two multi-functional ligands,5-acrylamido-1,10-phenanthroline (Aphen) and 5-acryloxyethoxymethyl-8-hydroxyquinoline (Hamq), were designed and synthesized, and their synthesis processes were optimized. Our design is based upon the fact that the ligands phenanthroline and 8-hydroxyquinoline have characteristics of big rigid planar, large absorption coefficient, and strong coordination. The luminescence emission spectra and the low temperature phosphorescence spectra of the two ligands were studied, and the experimental results showed that they have a strong tendency of energy transfer to the rare earth ion, and that the triplet state energies of Aphen and Hamq were 20000 and 22370 cm-1, respectively, which are much higher in energy than the resonance levels of Eu3+(5D0, 17200 cm-1), indicating that the triplet state energies of the two ligand are suitable for the sensitization of the luminescence of Eu3+, especially Aphen.2) The photophysical properties (color purity, luminescence intensity, lifetime, and quantum yield) of a series Eu(β-diketone)3(Aphen) complexes, complex Eu(TTA)2(amq), Eu(TTA)3(H2O)2 and Eu(TTA)2(AA) were investigated. The results showed that the complex Eu(TTA)3(Aphen) has the strongest luminescence emission among the series Eu(β-diketone)3(Aphen) complexes, and its luminescence intensity of 5D0→7F2 transition is 4.5, 11.3, and 3.9 times as high as that of Eu(TTA)3(H2O)2、Eu(TTA)2(AA) and Eu(TTA)2(amq), respectively, indicating that the acrylic acid ligand plays little or no role in the luminescence of Eu(TTA)2(AA) and the coordinated water molecules can effectively quench the luminescence intensity of Eu(TTA)3(H2O)2, and that the ligands Aphen and Hamq can sensitize the luminescence of Eu(Ⅲ) ion efficiently.3) Highly luminescent bonding-type Eu-containing copolymers were synthesized through the copolymerization of Eu(TTA)3(Aphen) or Eu(TTA)2(amq) with MMA, and characterized by FT-IR, UV-Vis,1H NMR, GPC, TGA, DSC, lifetime, and luminescence excitation and emission spectra. The results indicated that the Eu-complex moieties are directly bonded to the polymer backbone as an integrated unit, and the dissociation of the complex unit is negligible during the copolymerization and purification processes, that the thermal stabilities and the glass transition temperatures of the copolymers are enhanced upon the introduction of the Eu-complex moiety into the polymer chain, that the energy transfer is still mainly from the coordinated TTA although the MMA unit has taken part in the coordination, and that the copolymers all display the characteristic emissions of Eu(III) ions and five narrow emission peaks centered at 579,591, 612,651 and 698 nm, assigned to the 5D0→7F0,5D0→7F1,5D0→7F2,5D0→7F3,5D0→7F4 transitions, respectively, are well resolved, and the hypersensitive 5Do→7F2 transition is very intense. The luminescence intensities of the copolymers increased with an increase in the Eu content, and no significant concentration quenching phenomenon was observed at the Eu content within the studied range. The improvement of the luminescence properties for the copolymers may be attributed to the special microenvironment. On the one hand, the coordination stability of the Eu-complex unit in the copolymer is improved because the coordination degree of the unsaturated Eu-complex unit is satisfied through the intra- and intermolecular coordination, which results in the decrease of nonradiative decay rate of the excited levels of Eu(III) ion and the increase of the luminescence lifetime. On the other hand, the Eu-complex units can be twisted or distorted by the surrounding polymer chain, as the rare earth ions are kept in cages in the same polymer, resulting in so-called "cage effect". This may further lower the symmetry of the Eu(III) ion and consequently enhance the 5D0→7F2 transition of Eu-copolymers.4) In the Eu(TTA)2(amq)/PMMA blend system, the luminescence intensity increases with the increase in the Eu content and reaches a maximum at 3.30 wt% and then exhibits typical emission concentration quenching on further increase in the Eu content.更多还原