Critical Role of Free Amine Groups in the Imine Bonds Exchange in Dynamic Covalent Networks,Macromolecules

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Critical Role of Free Amine Groups in the Imine Bonds Exchange in Dynamic Covalent Networks
Macromolecules ( IF 5.1 ) Pub Date : 2024-08-23 , DOI: 10.1021/acs.macromol.4c01221
Gregory P. Carden ₁ , Murillo L. Martins ₁ , Gaukhar Toleutay ₁ , Sirui Ge ₁ , Bingrui Li ₁ , Sheng Zhao ₁ , Alexei P. Sokolov _{1,

2}

Affiliation

Introducing dynamic covalent bonds in polymers is a promising solution to improve their recyclability and self-healing abilities minimally compromising the mechanical properties. Imine bonds are exciting candidates as dynamic functionalities because of their rapid exchange and easy chemical synthesis. Although the exchange mechanisms of imines in small molecules are well-established, some misconceptions still exist regarding their behavior in polymers. Hence, we investigate the dynamic and viscoelastic properties of imine-bearing model systems and highlight that imine bond exchange only happens when mediated by unreacted amine groups. Therefore, imine metathesis is unlikely at temperatures below polymeric decomposition, and transimination is the major mechanism of bond exchange. Surprisingly, the energy barrier for this mechanism depends on the concentration of functional groups forming imine bonds. We hypothesize that the hydrogen bonds between amine and aldehyde groups might affect this process, but further work is needed to solve this puzzle.

中文翻译：

游离胺基团在动态共价网络中亚胺键交换中的关键作用

在聚合物中引入动态共价键是一种有前途的解决方案，可以提高其可回收性和自修复能力，同时最大限度地减少机械性能的影响。亚胺键由于其快速交换和易于化学合成而成为令人兴奋的动态功能候选者。尽管小分子中亚胺的交换机制已经很成熟，但对其在聚合物中的行为仍然存在一些误解。因此，我们研究了含亚胺模型系统的动态和粘弹性特性，并强调亚胺键交换仅在未反应的胺基介导时发生。因此，亚胺复分解在低于聚合物分解的温度下不太可能，转亚胺化是键交换的主要机制。令人惊讶的是，该机制的能垒取决于形成亚胺键的官能团的浓度。我们假设胺和醛基之间的氢键可能会影响这一过程，但需要进一步的工作来解决这个难题。

更新日期：2024-08-23

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