Naumann Stefan, Epple Stefan, Bonten Christian, Buchmeiser Michael R
Institute of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.
Institut für Kunststofftechnik, University of Stuttgart, Böblingerstr. 70, D-70199 Stuttgart, Germany.
ACS Macro Lett. 2013 Jul 16;2(7):609-612. doi: 10.1021/mz400199y. Epub 2013 Jun 24.
The cyclic amide ε-caprolactam (ε-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 ε-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 -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 °C, the best activity displayed by 1,3-dicyclohexyltetrahydropyrimidinium-2-carboxylate (). In situ rheology during polymerization showed the characteristics typical for the anionic polymerization of ε-CLA.
环状酰胺ε-己内酰胺（ε-CLA）可通过热潜伏的C-2保护的N-杂环卡宾（NHC）高效聚合，得到相应的聚酰胺（PA 6）。二氧化碳和金属盐保护的NHC用作预催化剂，其中游离卡宾通过热产生。通过这种方式，可以将相应的引发剂与ε-CLA预混合，得到可储存且可直接聚合的混合物。对各种不同结构的卡宾进行筛选表明，活性物种的碱性很重要，从而揭示出含烷基的四氢嘧啶基卡宾是最具活性的。在180℃本体聚合中可以快速高产率地生产PA 6，1,3-二环己基四氢嘧啶-2-羧酸盐（ ）表现出最佳活性。聚合过程中的原位流变学显示出ε-CLA阴离子聚合的典型特征。
