Ultrafast and Reversible Multiblock Formation by the SET-Nitroxide Radical Coupling Reaction
Ultrafast and Reversible Multiblock Formation by the SET-Nitroxide Radical Coupling Reaction
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DOI：
10.1071/ch10092
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发表时间：
2010-08
影响因子：
1.1
通讯作者：
J. Kulis;C. Bell;A. Micallef;M. Monteiro
中科院分区：
文献类型：
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作者：
J. Kulis;C. Bell;A. Micallef;M. Monteiro
利用单电子转移-氮氧自由基偶联（SET-NRC）反应，在50°C下，通过双官能度遥爪聚苯乙烯（Br-PSTY-Br）与二氮氧自由基的偶联，在3 min内制备了高分子量的多嵌段聚合物。众所周知的二甲基亚砜作为溶剂和Me 6 TREN作为配体的组合促进了CuIBr的高活性新生Cu 0物种的原位还原。该SET反应允许聚合物自由基从其相应的卤化物端基快速形成。捕获这些碳为中心的自由基在接近扩散控制率的二氮氧化物导致高分子量的多嵌段聚合物。我们的研究结果表明，CuI的纯化是获得这些超快反应的关键，并确认活化主要是通过Cu 0。我们利用NRC反应在高温下的可逆性，通过用单官能氮氧自由基封端链端，将多嵌段解耦回到原始PSTY结构单元。这些烷氧基胺端基进一步与炔单官能氮氧自由基（克里思-1）交换，并通过与N3-PSTY-N3的CuI催化的叠氮化物/炔环加成（CuAAC）反应“点击”以改革多嵌段。这最后的“点击”反应，即使在连续的解耦和氮氧交换反应，仍然有效地产生高分子量的多嵌段。这些SET-NRC反应将在可重复使用的塑料中具有理想的应用，并可能作为自修复材料。
The single electron transfer-nitroxide radical coupling (SET-NRC) reaction has been used to produce multiblock polymers with high molecular weights in under 3 min at 50°C by coupling a difunctional telechelic polystyrene (Br-PSTY-Br) with a dinitroxide. The well known combination of dimethyl sulfoxide as solvent and Me6TREN as ligand facilitated the in situ disproportionation of CuIBr to the highly active nascent Cu0 species. This SET reaction allowed polymeric radicals to be rapidly formed from their corresponding halide end-groups. Trapping of these carbon-centred radicals at close to diffusion controlled rates by dinitroxides resulted in high-molecular-weight multiblock polymers. Our results showed that the disproportionation of CuI was critical in obtaining these ultrafast reactions, and confirmed that activation was primarily through Cu0. We took advantage of the reversibility of the NRC reaction at elevated temperatures to decouple the multiblock back to the original PSTY building block through capping the chain-ends with mono-functional nitroxides. These alkoxyamine end-groups were further exchanged with an alkyne mono-functional nitroxide (TEMPO–≡) and ‘clicked’ by a CuI-catalyzed azide/alkyne cycloaddition (CuAAC) reaction with N3–PSTY–N3 to reform the multiblocks. This final ‘click’ reaction, even after the consecutive decoupling and nitroxide-exchange reactions, still produced high-molecular-weight multiblocks efficiently. These SET-NRC reactions would have ideal applications in re-usable plastics and possibly as self-healing materials.