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Synfacts 2007(6): 0600-0600
DOI: 10.1055/s-2007-968584
DOI: 10.1055/s-2007-968584
Synthesis of Materials and Unnatural Products
© Georg Thieme Verlag Stuttgart · New York
Synthesis of Cyclic Poly(Lactide) via Zwitterionic Polymerization
D. A. Culkin, W. Jeong, S. Csihony, E. D. Gomez, N. P. Balsara, J. L. Hedrick, R. M. Waymouth*
Stanford University, University of California, Berkeley and IBM Almaden Research Center, San Jose, USA
Further Information
Publication History
Publication Date:
22 May 2007 (online)
![](https://www.thieme-connect.de/media/synfacts/200706/lookinside/thumbnails/10.1055-s-2007-968584-1.jpg)
Significance
Zwitterionic ring-opening polymerization of lactide 1 catalyzed by N-heterocyclic carbenes (NHCs, 2) provided cyclic polyesters (3) of defined molecular weight and narrow molecular weight distribution. The cyclic structure of the polymers was determined by 1H NMR spectroscopy, mass spectrometry and comparisons of the solution properties of the cyclic polymers with their linear congeners. Polymerization of optically pure l-lactide generated crystalline cyclic poly(l-lactide), indicating that the polymerization proceeds with retention of stereochemistry. These NHC-mediated zwitterionic polymerizations also display a remarkable degree of control and exhibit some features of living polymerizations.