Role of the transition metal in Grignard metathesis polymerization (GRIM) of 3-hexylthiophene
Role of the transition metal in Grignard metathesis polymerization (GRIM) of 3-hexylthiophene
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过渡金属在 3-己基噻吩 格氏复分解聚合 (GRIM) 中的作用
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
M. Stefan
中科院分区：
文献类型：
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作者：
M. Bhatt;H. D. Magurudeniya;P. Sista;E. Sheina;M. Jeffries‐EL;Benjamin G. Janesko;R. D. Mccullough;M. Stefan
区域规整聚(3-烷基噻吩基)S在太阳能电池、场效应管等有机电子领域有着广泛的应用。考察了镍、钯和铂的二苯基膦乙烷配合物对2，5-二溴-3-己基噻吩格氏歧化(GRIM)聚合和2-溴-5-碘-3-己基噻吩格氏歧化(GRIM)聚合的催化性能。镍引发的聚合产生了区域规则、低多分散性的聚(3-己基噻吩基)，其分子量定义明确，符合“活的”链增长机制。相比之下，钯引发的聚合反应采用逐级生长机制，得到的聚合物的头尾偶联率低于80%。铂催化聚合得到了极低相对分子质量的产物。动力学和计算结果表明，镍催化剂起到了引发剂的作用，并与不断增长的聚合物链保持联系，而钯则从不断增长的链中解离出来。为离解Pd(0)催化剂的各种副反应提供了理论和实验依据，这些副反应可以产生阶梯生长机制和较低的区域不规则性。
Regioregular poly(3-alkylthiophene)s are widely used in organic electronics applications such as solar cells and field effect transistors. Nickel, palladium, and platinum diphenylphosphinoethane complexes were tested as catalysts for the Grignard metathesis (GRIM) polymerization of 2,5-dibromo-3-hexylthiophene and 2-bromo-5-iodo-3-hexylthiophene. Nickel-mediated polymerization generated regioregular, low-polydispersity poly(3-hexylthiophene) with well-defined molecular weight consistent with a “living” chain-growth mechanism. By contrast, palladium-mediated polymerization proceeded by a step-growth mechanism and generated polymers with less than 80% head-to-tail couplings. Platinum-mediated polymerization gave very low molecular weight products. Kinetic and computational results suggested that the nickel catalyst acts as an initiator and remains associated with the growing polymer chain, while palladium dissociates from the growing chain. Computational and experimental evidence was provided for various side reactions of dissociated Pd(0) catalyst, which could yield a step growth mechanism and lower regioirregularity.