Polymerization of 蔚-Caprolactam by Latent Precatalysts Based on Protected N-Heterocyclic Carbenes

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• 作者：Stefan Naumann ; Stefan Epple ; Christian Bonten ; Michael R. Buchmeiser
• 刊名：ACS Macro Letters
• 出版年：2013
• 出版时间：July 16, 2013
• 年：2013
• 卷：2
• 期：7
• 页码：609-612
• 全文大小：249K
• 年卷期：v.2,no.7(July 16, 2013)
• ISSN：2161-1653

文摘

The cyclic amide 蔚-caprolactam (蔚-CLA) is efficiently polymerized by thermally latent C-2-protected N-heterocyclic carbenes (NHCs) to give the corresponding polyamide (PA 6). Carbon dioxide- and metal salt-protected NHCs were used as precatalysts, out of which the free carbenes were generated thermally. This way, a premixing of the corresponding initiator with 蔚-CLA was possible to yield a storable and directly polymerizable mixture. The screening of a variety of differently constituted carbenes showed the importance of basicity of the active species, thereby revealing N-alkyl-bearing tetrahydropyrimidinium-based carbenes as the most active ones. Rapid production of PA 6 in high yields was possible in bulk polymerization at 180 掳C, the best activity displayed by 1,3-dicyclohexyltetrahydropyrimidinium-2-carboxylate (6-Cy-CO₂). In situ rheology during polymerization showed the characteristics typical for the anionic polymerization of 蔚-CLA.