Cyclopropenimine Superbases: Competitive Initiation Processes in Lactide Polymerization Article Swipe

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Superbase Lactide Phosphazene Polymerization Deprotonation Ring-opening polymerization Polymer chemistry Guanidine Monomer Chemistry Materials science Catalysis Organic chemistry Polymer Ion

Tyler S. Stukenbroeker , Jeffrey S. Bandar , Xiangyi Zhang , Tristan H. Lambert , Robert M. Waymouth ·

YOU? · · 2015 · Open Access · · DOI: https://doi.org/10.1021/acsmacrolett.5b00421 · OA: W2275000160

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 endgroups. Model studies and comparative experiments with guanidine and phosphazene catalysts revealed the subtle influence of the nature of the superbase on competitive initiation processes.