Yamago Shigeru, Yamada Takeshi, Togai Manabu, Ukai Yuu, Kayahara Eiichi, Pan Na
Institute for Chemical Research, Kyoto University, Uji, Kyoto, Japan.
Chemistry. 2009;15(4):1018-29. doi: 10.1002/chem.200801754.
Several organostibine chain-transfer agents possessing polar functional groups have been prepared by the reactions of azo initiators and tetramethyldistibine (1). Carbon-centered radicals thermally generated from the azo initiators were trapped by 1 to yield the corresponding organostibine chain-transfer agents. The high yields observed in the synthesis of the chain-transfer agents strongly suggest that distibines have excellent radicophilic reactivity. As the reactions proceeded under neutral conditions, functional groups that are incompatible with ionic conditions were incorporated into the chain-transfer agents. The chain-transfer agents were used in living radical polymerization to synthesize the corresponding alpha-functionalized polymers. As the functional groups in the chain-transfer agents did not interfere with the polymerization reaction, well-controlled polymers possessing number-average molecular weights (M(n)s) predetermined by the monomer/transfer agent ratios were synthesized with low polydispersity indices (PDIs). The organostibanyl omega-polymer ends were transformed into a number of different functional groups by radical-coupling, radical-addition, and oxidation reactions. Therefore, it was possible to synthesize well-controlled telechelic polymers with the same and also with different functional groups at their alpha- and omega-polymer ends. Distibine 1 was also found to increase PDI control in the living radical polymerization of styrene and methyl methacrylate (MMA) using a purified organostibine chain-transfer agent. Well-controlled poly(methyl methacrylate)s with M(n) values ranging from 10 000 to 120 000 with low PDIs (1.05-1.15) were synthesized by the addition of a catalytic amount of 1. The results have been attributed to the high reactivity of distibine 1 towards polymer-end radicals, which are spontaneously deactivated to yield organostibine dormant species.
通过偶氮引发剂与四甲基二锑（1）的反应，制备了几种具有极性官能团的有机锑链转移剂。偶氮引发剂热产生的碳中心自由基被1捕获，生成相应的有机锑链转移剂。在链转移剂合成中观察到的高产率强烈表明二锑具有优异的亲自由基反应活性。由于反应在中性条件下进行，与离子条件不相容的官能团被引入到链转移剂中。链转移剂用于活性自由基聚合，以合成相应的α-官能化聚合物。由于链转移剂中的官能团不干扰聚合反应，因此合成了具有由单体/转移剂比例预先确定的数均分子量（M(n)）且多分散指数（PDI）较低的可控聚合物。通过自由基偶联、自由基加成和氧化反应，将有机锑ω-聚合物端基转化为许多不同的官能团。因此，有可能合成在其α-和ω-聚合物端具有相同和不同官能团的可控遥爪聚合物。还发现二锑1在使用纯化的有机锑链转移剂进行苯乙烯和甲基丙烯酸甲酯（MMA）的活性自由基聚合时可提高PDI控制。通过添加催化量的1，合成了M(n)值范围为10000至120000且PDI较低（1.05 - 1.15）的可控聚甲基丙烯酸甲酯。这些结果归因于二锑1对聚合物端基自由基的高反应活性，聚合物端基自由基会自发失活生成有机锑休眠物种。
