Abstract Ring-opening polymerization (ROP) of propylene oxide (PO) is achieved at 25 °C either in bulk or in solution, using N-heterocyclic carbenes (NHCs) and triisobutylaluminum (i-Bu3Al) as a bicomponent catalytic system. Transfer to monomer was not observed and poly(propylene oxide)s with predictable molar masses up to 60 000 g·mol−1 and low dispersities were obtained. In presence/absence of an alcohol as the initiator, the polymerization of PO follows anionic or zwitterionic ROP mechanisms, respectively. The addition of the Lewis acid strongly improves the efficiency of NHCs for the polymerization of substituted epoxides. It is established that i-Bu3Al is involved both in the formation of an initiating/propagating complex of moderate basicity/nucleophilicity and in the coordination of PO, enabling the activation of the monomer towards the complexed nucleophilic active species. Block copolyethers are also prepared by PPO chain extension experiments. All (co)polyethers were thoroughly characterized by 1H NMR spectroscopy, SEC and MALDI-TOF mass spectrometry as means to prove the control and benefit of this NHC approach for epoxides ROP.

中文翻译：

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N-杂环卡宾/路易斯酸介导的环氧丙烷开环聚合。第 1 部分：作为有效控制剂的三异丁基铝

摘要 环氧丙烷 (PO) 的开环聚合 (ROP) 在 25 °C 下以本体或溶液形式实现，使用 N-杂环卡宾 (NHC) 和三异丁基铝 (i-Bu3Al) 作为双组分催化体系。没有观察到向单体的转移，并且获得了可预测摩尔质量高达 60 000 g·mol-1 和低分散性的聚（环氧丙烷）。在醇作为引发剂的存在/不存在下，PO 的聚合分别遵循阴离子或两性离子 ROP 机制。路易斯酸的加入极大地提高了 NHC 聚合取代环氧化物的效率。已确定 i-Bu3Al 参与中等碱度/亲核性的引发/传播复合物的形成以及 PO 的配位，使单体朝着复合的亲核活性物质活化。嵌段共聚醚也可通过 PPO 扩链实验制备。所有（共）聚醚均通过 1 H NMR 光谱、SEC 和 MALDI-TOF 质谱进行彻底表征，以此证明这种 NHC 方法对环氧化物 ROP 的控制和益处。