水介质中Cu(II)-PAMAM催化剂催化作用下2,6-二甲基苯酚氧化偶合沉淀聚合

材料科学论文编号:CL077  论文字数:15079,页数:35

目  录
中文摘要............................................................Ⅰ
英文摘要............................................................Ⅲ
目录................................................................Ⅵ
1. 绪论...............................................................1
    1.1 DMP的氧化机理................................................2
1.1.1 DMP的氧化............................................2 1.1.2 DMP的偶合..............................................3
    1.2 催化剂........................................................4
        1.2.1 铜-胺类络合物...........................................4
        1.2.2 铜-含氮杂环络合物.......................................6
        1.2.3 铜-大环配体络合物.......................................7
        1.2.4 金属离子-树形分子络合物催化剂...........................8
    1.3 PPO的合成方法................................................12
        1.3.1 有机溶剂中DMP的氧化聚合................................12
        1.3.2 油/水两相介质中DMP的氧化聚合..........................14
        1.3.3 水介质中DMP的氧化聚合..................................15
2. 实验部分..........................................................16
    2.1 试剂和仪器...................................................16
        2.1.1 试剂和原料.............................................16
        2.1.2 仪器...................................................17
    2.2 Cu(II) –PAMAM树形分子络合物催化剂作用下PPO的制备............17
3. 结果与讨论........................................................18
    3.1 PPO的表征....................................................18
    3.2 PPO的得率与PAMAM代数的关系................................18
    3.3 改变铜和G3的配比............................................20
4. 总结与展望........................................................21
致谢................................................................23
参考文献............................................................24

 摘 要：2,6-二甲基苯酚（DMP）的溶液聚合被广泛应用于PPO的工业生产，但是溶液聚合需要溶液的回收和防爆反应器。水介质在DMP氧化聚合中的使用使其成为一种环境友好的反应， PPO也由于其不溶于水可以很容易的分离出来。因此，在DMP的氧化聚合中使用水作为反应介质是一个很重要的进展。
 在这篇论文中，我们报道了Cu(II)-PAMAM络合物催化剂首次用于水介质中DMP的氧化聚合，并有很高的催化效率（单体与催化剂的摩尔比率为2000）。这个结果是很重要的，原因如下：第一，这是Cu(II)-PAMAM络合物催化剂用作催化剂的第一个例子；第二，Cu(II)-PAMAM络合物催化剂在水介质中，在温和的条件下的DMP氧化聚合对PPO有很高选择性；第三，Cu(II)-PAMAM络合物催化剂比之前文献所报道的催化剂的催化效率有显著提高。
 PAMAM树形分子的代数会强烈的影响Cu(II) –PAMAM树形分子络合物催化剂的催化效率。在铜浓度从200 μmol/L下降到16.67μmol/L这个过程中，Cu(II)-G1和 Cu(II)-G2催化剂催化作用下的DMP聚合反应的PPO得率有很大幅度的下降，同时Cu(II)-G3催化剂所催化的DMP聚合反应的PPO得率几乎不变。
 另一个影响催化效率的重要因素就是Cu(II)与配体的比率。每一个聚合反应都是在固定铜浓度的条件下进行的，随着 Cu(II)与 PAMAMG3摩尔比的提高，PPO的得率逐渐升高。当Cu(II)与 PAMAMG3摩尔比较低时，PPO的得率也较低，原因可能是Cu(II)-树形分子络合物比较分散，不会产生浓度效应；也可能是大量的未配位的氨基阻碍了聚合反应的进行。事实上，多余的配体会与苯氧阴离子竞争与铜离子的配位，从而抑制聚合反应的进行。因此，这些结果十分清楚地说明了铜离子络合物的浓度对催化效率的高低至关重要。
 关键词：2,6-二甲基苯酚(DMP)；氧化聚合；水介质；PAMAM树形分子；催化效率

Abstract: The solution polymerization of 2,6-dimethylphenol (DMP) is widely used in industrial production of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), an important engineering plastics. However, both a solvent recovery process and an explosion- proof reactor are required. The use of water as the reaction medium is environmentally friendly and PPO can be separated easily due to its insolubility in water. Therefore, the oxidative polymerization of DMP to form PPO using water as the reaction medium would be of significance.
 In this paper we report the first catalytic Cu(II)-PAMAM dendrimer complexes that catalyze aerobic oxidative polymerization of DMP in water with significantly high catalytic efficiency ([monomer]/[catalyst]=2000). The results are significant for three reasons as follows. First, it is the first example that Cu(II)-PAMAM dendrimer complexes are used as catalysts. Second, Cu(II)-PAMAM complex catalyzed aerobic oxidative polymerization of DMP under mild condition in water with a good selectivity to PPO. Third, the catalytic efficiency greatly enhanced compared with the catalyst reported in the literature.
 The generation of PAMAM strongly influences the catalytic efficiency of Cu(II)-PAMAM dendrimer catalyst. Remarkably, the PPO yield remained still high (81.45%) at a copper concentration of 25μmol/L, which was even comparable with the results obtained through Cu(II)-G1, Cu(II)-G2, Cu(II)-EDTA at a much higher copper concentration (200 μmol/L). This clearly illustrates a distinct advantage of Cu(II)-G3 catalyst over other catalysts since almost the same high PPO yield was obtained at a extremely low catalyst concentration (25μmol/L).
 Another important factor on catalytic efficiency is the ratio of copper ion to ligand. The low PPO yield at lower [Cu(II)]/[PAMAMG3] ratio could be ascribed to the dispersed state of copper complexes which do not have concentration effect, and might also be duo to inhibition of polymerization by uncoordinated nitrogen sites.
 Keywords: 2,6-dimethyl; oxidative polymerization; water; PAMAM dendrimer; catalytic efficiency