Termination reaction of living poly(3-hexylthiophene) using thiophene Grignard reagents: Substituent effect on the functionalization
Termination reaction of living poly(3-hexylthiophene) using thiophene Grignard reagents: Substituent effect on the functionalization
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DOI：
10.1016/j.polymer.2017.04.041
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发表时间：
2017-05
期刊：
影响因子：
4.6
通讯作者：
Koji Takagi;J. Kawai;Ryo Kouchi
中科院分区：
文献类型：
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作者：
Koji Takagi;J. Kawai;Ryo Kouchi
采用2个3位和4位甲氧基的2-氯镁噻吩进行活性聚3-己基噻吩（P3HT）的终止反应。所得P3HT的数均分子量与理论值基本一致，证实了聚合物具有较高的区域规整性。P3HT的1h NMR谱与模型化合物的1h NMR谱比较以及MALDI-TOF质谱分析表明P3HT中含有甲氧基噻吩单元。用2-氯镁-3-甲氧基噻吩（GT1）和2-氯镁-4-甲氧基噻吩（GT2）进行终止反应，得到末端结构不均匀的P3HT和两端分别有终止单元的P3HT。这些事实可归因于催化循环中基本过程（金属转化、还原消除、反链行走和氧化加成）的效率。另一方面，2-氯镁-3-恶唑基噻吩（GT3）由于明显的位阻而表现出较差的金属转化活性。结果表明，在P3HT中加入LiCl加速了金属转化过程，同时苯乙烯的存在捕获了零价镍配合物，使得P3HT在扩展端带有恶唑基噻吩单元。
Two 2-chloromagnesiothiophenes having the methoxy group at the 3- and 4-position were applied for the termination reaction of living poly(3-hexylthiophene) (P3HT). The number-averaged molecular weights of obtained P3HT approximately agreed with the theoretical value, and the high regioregularity of polymers were confirmed. The comparison of the1H NMR spectra of P3HT with those of model compounds in addition to the analysis of the MALDI-TOF mass spectra suggested the incorporation of the methoxythiophene unit. The termination reaction using 2-chloromagnesio-3-methoxythiophene (GT1) and 2-chloromagnesio-4-methoxythiophene (GT2) resulted in P3HT with the non-uniform terminal structure and that having the terminating unit at both chain ends, respectively. These facts can be ascribed to the efficiency of the elementary process (transmetallation, reductive elimination, reverse chain walking, and oxidative addition) in the catalytic cycle. On the other hand, 2-chloromagnesio-3-oxazolylthiophene (GT3) exhibited the poor transmetallation activity due to the pronounced steric hindrance. It was found that the addition of LiCl for accelerating the transmetallation step and the coexistence of styrene for trapping the zero-valent nickel complex give P3HT bearing the oxazolylthiophene unit at the propagating end.