Cyclopropenimine Superbases: Competitive Initiation Processes in Lactide Polymerization

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• 作者：Tyler S. Stukenbroeker ; Jeffrey S. Bandar ; Xiangyi Zhang ; Tristan H. Lambert ; Robert M. Waymouth
• 刊名：ACS Macro Letters
• 出版年：2015
• 出版时间：August 18, 2015
• 年：2015
• 卷：4
• 期：8
• 页码：853-856
• 全文大小：304K
• ISSN：2161-1653

文摘

Cyclopropenimine superbases were employed to catalyze the ring-opening polymerization of lactide. Polymerization occurred readily in the presence and absence of alcohol initiators. Polymerizations in the absence of alcohol initiators revealed a competitive initiation mechanism involving deprotonation of lactide by the cyclopropenimine to generate an enolate. NMR and MALDI-TOF analysis of the poly(lactides) generated from cyclopropenimines in the absence of alcohol initiators showed acylated lactide and hydroxyl end groups. Model studies and comparative experiments with guanidine and phosphazene catalysts revealed the subtle influence of the nature of the superbase on competitive initiation processes.