Open AccessCyclopropenimine Superbases: Competitive Initiation Processes in Lactide Polymerization
Author(s) -
Tyler S. Stukenbroeker,
Jeffrey S. Bandar,
Xiangyi Zhang,
Tristan H. Lambert,
Robert M. Waymouth
Publication year - 2015
Publication title -
acs macro letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.966
H-Index - 92
ISSN - 2161-1653
DOI - 10.1021/acsmacrolett.5b00421
Subject(s) - superbase , lactide , phosphazene , polymerization , deprotonation , ring opening polymerization , polymer chemistry , guanidine , chemistry , monomer , catalysis , organic chemistry , polymer , ion
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.