Dual catalysis with an N‐heterocyclic carbene and a Lewis acid: Thermally latent precatalyst for the polymerization of ε‐caprolactam,Journal of Polymer Science

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Dual catalysis with an N‐heterocyclic carbene and a Lewis acid: Thermally latent precatalyst for the polymerization of ε‐caprolactam
Journal of Polymer Science ( IF 3.9 ) Pub Date : 2020-10-03 , DOI: 10.1002/pol.20200502
Hagen J. Altmann ₁ , Mark Steinmann ₂ , Iris Elser ₁ , Mathis J. Benedikter ₁ , Stefan Naumann ₁ , Michael R. Buchmeiser _{1,

2}

Affiliation

So far, the earlier reported strong correlation between basicity of an N‐heterocyclic carbene (NHC) and its reactivity in poly(ε‐caprolactam) (PA6) synthesis resulted in a substantial limitation of applicable carbenes. Here, to overcome this issue, 1,3‐dimethylimidazolium‐2‐carboxylate, an easily accessible, air and moisture‐stable NHC, was applied as thermally latent initiator. In order to compensate for its low basicity, reactivity was enhanced by the addition of both a Lewis acid and an activator to ease the initial polymerization step. The resulting mixtures of ε‐caprolactam, the CO₂‐protected NHC, a Lewis acid and N‐acylazepan‐2‐one constitute homogeneous, thermally fully latent “single‐component” blends for the anionic polymerization‐based synthesis of PA6. They can be stored both in the liquid and solid state for days and months, respectively, without any loss in activity. The role of the Lewis acid as well as technical implications of the prolonged pot‐times are discussed.

中文翻译：

N-杂环卡宾和路易斯酸的双重催化：ε-己内酰胺聚合的热潜前催化剂

迄今为止，较早前报道的N杂环卡宾（NHC）的碱度与其在聚（ε-己内酰胺）（PA6）合成中的反应性之间存在很强的相关性，导致可应用的碳烯受到很大限制。在这里，为了克服这个问题，将1,3-二甲基咪唑-2-羧酸盐（一种易于获取，对空气和湿气稳定的NHC）用作热潜在引发剂。为了弥补其低碱性，通过加入路易斯酸和活化剂来增强反应性以简化初始聚合步骤。ε-己内酰胺，CO ₂保护的NHC，路易斯酸和N的混合物acylazepan-2-one构成均相的，具有热潜能的“单组分”共混物，用于基于阴离子聚合的PA6合成。它们可以分别以液态和固态两种方式储存数天和数月，而没有任何活性损失。讨论了路易斯酸的作用以及延长补锅时间的技术含义。

更新日期：2020-11-17

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