title: Cyclopropenimine Superbases: Competitive Initiation Processes in Lactide Polymerization.
abstract: 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.
authors.affiliation: Department of Chemistry, Stanford University, Stanford CA 94305.
authors.forename: Tyler S
authors.initials: TS
authors.lastname: Stukenbroeker
authors.affiliation: Department of Chemistry, Columbia University, 3000 Broadway, New York, NY 10027.
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Bandar
authors.affiliation: Department of Chemistry, Stanford University, Stanford CA 94305.
authors.forename: Xiangyi
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Columbia University, 3000 Broadway, New York, NY 10027.
authors.forename: Tristan H
authors.initials: TH
authors.lastname: Lambert
authors.affiliation: Department of Chemistry, Stanford University, Stanford CA 94305.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Waymouth