PEG基氮氧自由基嵌段共聚物的制备及催化性能

发布时间：2018-04-30 17:22

本文选题：聚乙二醇 + 氮氧自由基　；参考：《河北科技大学》2017年硕士论文

【摘要】：在醇的选择性催化氧化反应中,2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)作为高效催化剂尤为引人注目。但是TEMPO价格昂贵,分子量小不易回收,难以循环再利用,实现TEMPO的固载化可以有效解决以上问题。本课题将含氮氧自由基结构单元的聚(甲基丙烯酸-2,2,6,6-四甲基哌啶-1-氮氧自由基酯)(PTMA)负载在具有良好溶解性和相转移特性的聚乙二醇(PEG)上,得到了两亲性的含氮氧自由基嵌段共聚物。考察了该嵌段共聚物选择性催化氧化醇的催化性能,并研究了其链结构对催化性能的影响。含氮氧自由基嵌段共聚物通过电子转移活化再生催化剂原子转移自由基聚合(ARGET ATRP)制得。首先利用2-溴异丁酰溴与PEG发生酯化反应,得到大分子引发剂;单体甲基丙烯酸2,2,6,6-四甲基哌啶醇酯(TMPM)由大分子引发剂引发ARGET ATRP反应得到嵌段共聚物PEG-PTMPM;最后,3-氯过氧苯甲酸(m-CPBA)将PTMPM中的氨基氧化为氮氧自由基,制得含氮氧自由基嵌段共聚物。采用红外光谱、紫外可见光谱、凝胶渗透色谱、透射电镜等对含氮氧自由基嵌段共聚物进行了表征。制备的嵌段共聚物(PEG-PTMA)具有结构可控、分子量分布范围窄的优点。其中,甲基封端的聚乙二醇负载的两嵌段共聚物(MPEG-PTMA)的分子量范围从8700到17000,聚乙二醇负载的三嵌段共聚物(PTMA-PEG-PTMA)的分子量从11200到39000。分散指数在1.5左右。将制备的含氮氧自由基嵌段共聚物PEG-PTMA应用到醇的选择性催化氧化中,分别以次氯酸钠(NaClO)和分子氧(O2)为氧化剂,研究了PEG-PTMA结构对苯甲醇催化性能的影响。PEG-PTMA表现出良好的催化选择性,未出现过度氧化现象。NaClO作氧化剂时,MPEG2000和PEG2000负载的嵌段共聚物表现出极为突出的催化性能,二者的催化效果甚至超过了未负载的TEMPO。此外,嵌段共聚物PEG-PTMA对其它伯醇也有较好的催化氧化效果。分子氧作氧化剂时,分别以N,N-二甲基甲酰胺(DMF)和乙腈/水为溶剂,研究了催化剂的催化性能。以DMF为溶剂时,MPEG5000-PTMA的催化效果较好,其它嵌段共聚物PEG-PTMA的催化效果并不理想。在乙腈/水两相溶剂条件下,MPEG2000负载的嵌段共聚物的催化效果要优于TEMPO。通过简单的沉淀和过滤步骤即可实现嵌段共聚物的回收,其循环使用性能良好。
[Abstract]:In the selective catalytic oxidation of alcohols, the catalytic activity of Tetramethylpiperidine-6-tetramethylpiperidine-1-oxygen free radical (TEMPO) is particularly attractive. However, TEMPO is expensive, low molecular weight is not easy to be recovered, and it is difficult to recycle. So, the above problems can be effectively solved by immobilization of TEMPO. In this paper, the poly (tetramethylpiperidine-1-nitroxyl ester) (PTMAA) with nitrogen-containing oxygen free radical structure unit was loaded on polyethylene glycol (PEG) with good solubility and phase transfer property. Amphiphilic block copolymers containing nitrogen and oxygen free radicals were obtained. The catalytic properties of the block copolymers for selective catalytic oxidation of alcohols were investigated and the effect of chain structure on the catalytic performance was studied. The nitrogen-containing oxygen radical block copolymers were prepared by atom transfer radical polymerization (ARGET ATRP). Firstly, 2-bromoisobutylol bromide was esterified with PEG to obtain macromolecular initiator. The block copolymers PEG-PTMPM were prepared by the ARGET ATRP reaction initiated by macromolecular initiators, and the N-oxygen radical block copolymers were prepared by oxidation of amino groups in PTMPM into nitroxyl radicals. The nitrogen-containing oxygen radical block copolymers were characterized by IR, UV-Vis, gel permeation chromatography and transmission electron microscope. The block copolymer PEG-PTMA has the advantages of controllable structure and narrow molecular weight distribution. The molecular weight of MPEG-PTMAs is from 8700 to 17000, and the molecular weight of PEG-PTMA-PEG-PTMAs is 11200 to 39000. The dispersion index was about 1.5. The nitrogen-containing oxygen radical block copolymer (PEG-PTMA) was applied to the selective catalytic oxidation of alcohols with sodium hypochlorite (NaClO) and molecular oxygen (O _ 2) as oxidants, respectively. The effect of PEG-PTMA structure on the catalytic performance of benzyl alcohol was studied. PEG-PTMA showed good catalytic selectivity, and the block copolymers supported on PEG2000 and MPEG2000 showed excellent catalytic performance when there was no excessive oxidation. The catalytic effect of the two was even higher than that of unsupported TEMPO. In addition, block copolymer PEG-PTMA also has good catalytic oxidation effect on other primary alcohols. The catalytic performance of the catalyst was studied using N- (N-dimethylformamide) and acetonitrile / water as solvents respectively when molecular oxygen was used as oxidant. When DMF was used as solvent, the catalytic effect of MPEG5000-PTMA was better than that of other block copolymers PEG-PTMA. The catalytic effect of block copolymers supported on MPEG2000 was better than that of TEMPO in acetonitrile / water two-phase solvent. The block copolymers can be recovered by simple precipitation and filtration, and the recycling performance of the block copolymers is good.
【学位授予单位】：河北科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O631.5;O643.36

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