水介質(zhì)中Cu(II)-PAMAM催化劑催化作用下2,6-二甲基苯酚氧化偶合沉淀聚合

材料科學(xué)論文編號:CL077  論文字?jǐn)?shù):15079,頁數(shù):35

目  錄
中文摘要............................................................Ⅰ
英文摘要............................................................Ⅲ
目錄................................................................Ⅵ
1. 緒論...............................................................1
    1.1 DMP的氧化機(jī)理................................................2
1.1.1 DMP的氧化............................................2 1.1.2 DMP的偶合..............................................3
    1.2 催化劑........................................................4
        1.2.1 銅-胺類絡(luò)合物...........................................4
        1.2.2 銅-含氮雜環(huán)絡(luò)合物.......................................6
        1.2.3 銅-大環(huán)配體絡(luò)合物.......................................7
        1.2.4 金屬離子-樹形分子絡(luò)合物催化劑...........................8
    1.3 PPO的合成方法................................................12
        1.3.1 有機(jī)溶劑中DMP的氧化聚合................................12
        1.3.2 油/水兩相介質(zhì)中DMP的氧化聚合..........................14
        1.3.3 水介質(zhì)中DMP的氧化聚合..................................15
2. 實(shí)驗(yàn)部分..........................................................16
    2.1 試劑和儀器...................................................16
        2.1.1 試劑和原料.............................................16
        2.1.2 儀器...................................................17
    2.2 Cu(II) –PAMAM樹形分子絡(luò)合物催化劑作用下PPO的制備............17
3. 結(jié)果與討論........................................................18
    3.1 PPO的表征....................................................18
    3.2 PPO的得率與PAMAM代數(shù)的關(guān)系................................18
    3.3 改變銅和G3的配比............................................20
4. 總結(jié)與展望........................................................21
致謝................................................................23
參考文獻(xiàn)............................................................24

 摘 要：2,6-二甲基苯酚（DMP）的溶液聚合被廣泛應(yīng)用于PPO的工業(yè)生產(chǎn)，但是溶液聚合需要溶液的回收和防爆反應(yīng)器。水介質(zhì)在DMP氧化聚合中的使用使其成為一種環(huán)境友好的反應(yīng)， PPO也由于其不溶于水可以很容易的分離出來。因此，在DMP的氧化聚合中使用水作為反應(yīng)介質(zhì)是一個(gè)很重要的進(jìn)展。
 在這篇論文中，我們報(bào)道了Cu(II)-PAMAM絡(luò)合物催化劑首次用于水介質(zhì)中DMP的氧化聚合，并有很高的催化效率（單體與催化劑的摩爾比率為2000）。這個(gè)結(jié)果是很重要的，原因如下：第一，這是Cu(II)-PAMAM絡(luò)合物催化劑用作催化劑的第一個(gè)例子；第二，Cu(II)-PAMAM絡(luò)合物催化劑在水介質(zhì)中，在溫和的條件下的DMP氧化聚合對PPO有很高選擇性；第三，Cu(II)-PAMAM絡(luò)合物催化劑比之前文獻(xiàn)所報(bào)道的催化劑的催化效率有顯著提高。
 PAMAM樹形分子的代數(shù)會強(qiáng)烈的影響Cu(II) –PAMAM樹形分子絡(luò)合物催化劑的催化效率。在銅濃度從200 μmol/L下降到16.67μmol/L這個(gè)過程中，Cu(II)-G1和 Cu(II)-G2催化劑催化作用下的DMP聚合反應(yīng)的PPO得率有很大幅度的下降，同時(shí)Cu(II)-G3催化劑所催化的DMP聚合反應(yīng)的PPO得率幾乎不變。
 另一個(gè)影響催化效率的重要因素就是Cu(II)與配體的比率。每一個(gè)聚合反應(yīng)都是在固定銅濃度的條件下進(jìn)行的，隨著 Cu(II)與 PAMAMG3摩爾比的提高，PPO的得率逐漸升高。當(dāng)Cu(II)與 PAMAMG3摩爾比較低時(shí)，PPO的得率也較低，原因可能是Cu(II)-樹形分子絡(luò)合物比較分散，不會產(chǎn)生濃度效應(yīng)；也可能是大量的未配位的氨基阻礙了聚合反應(yīng)的進(jìn)行。事實(shí)上，多余的配體會與苯氧陰離子競爭與銅離子的配位，從而抑制聚合反應(yīng)的進(jìn)行。因此，這些結(jié)果十分清楚地說明了銅離子絡(luò)合物的濃度對催化效率的高低至關(guān)重要。
 關(guān)鍵詞：2,6-二甲基苯酚(DMP)；氧化聚合；水介質(zhì)；PAMAM樹形分子；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