Mommer Stefan, Sokołowski Kamil, Olesińska Magdalena, Huang Zehuan, Scherman Oren A
Melville Laboratory for Polymer Synthesis, Yusuf Hamied Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
Chem Sci. 2022 Jun 7;13(30):8791-8796. doi: 10.1039/d2sc02072f. eCollection 2022 Aug 4.
Extended polymeric structures based on redox-active species are of great interest in emerging technologies related to energy conversion and storage. However, redox-active monomers tend to inhibit radical polymerisation processes and hence, increase polydispersity and reduce the average molecular weight of the resultant polymers. Here, we demonstrate that styrenic viologens, which do not undergo radical polymerisation effectively on their own, can be readily copolymerised in the presence of cucurbit[]uril (CB[]) macrocycles. The presented strategy relies on pre-encapsulation of the viologen monomers within the molecular cavities of the CB[] macrocycle. Upon polymerisation, the molecular weight of the resultant polymer was found to be an order of magnitude higher and the polydispersity reduced 5-fold. The mechanism responsible for this enhancement was unveiled through comprehensive spectroscopic and electrochemical studies. A combination of solubilisation/stabilisation of reduced viologen species as well as protection of the parent viologens against reduction gives rise to the higher molar masses and reduced polydispersities. The presented study highlights the potential of CB[]-based host-guest chemistry to control both the redox behavior of monomers as well as the kinetics of their radical polymerisation, which will open up new opportunities across myriad fields.
基于氧化还原活性物种的扩展聚合物结构在与能量转换和存储相关的新兴技术中备受关注。然而，氧化还原活性单体往往会抑制自由基聚合过程，从而增加多分散性并降低所得聚合物的平均分子量。在此，我们证明了苯乙烯基紫精自身不能有效地进行自由基聚合，但在葫芦脲（CB[]）大环存在下可以很容易地进行共聚。所提出的策略依赖于将紫精单体预包封在CB[]大环的分子腔内。聚合后，发现所得聚合物的分子量高出一个数量级，多分散性降低了5倍。通过全面的光谱和电化学研究揭示了这种增强作用的机制。还原态紫精物种的增溶/稳定以及母体紫精免受还原的保护共同导致了更高的摩尔质量和更低的多分散性。本研究突出了基于CB[]的主客体化学在控制单体的氧化还原行为及其自由基聚合动力学方面的潜力，这将在众多领域开辟新的机遇。
