Web Release Date: October 18,
Exploration, Optimization, and Application of Supramolecular Thiourea-Amine Catalysts for the Synthesis of Lactide (Co)polymers
and
IBM Almaden Research Center, 650 Harry Road, San Jose, California 95032, Kenyon College, Gambier, Ohio 43022, and Department of Chemistry, Stanford University, Stanford, California 94305
Received July 17, 2006
Revised Manuscript Received August 14, 2006
Abstract:
The structural flexibility and efficacy of thiourea-amine catalysts for the supramolecular activation and ring-opening polymerization (ROP) of lactide are described. The nature of the hydrogen bonding group and its strength as well as the steric congestion have been altered, leading to shorter polymerization times, better control, and pathways to influence the stereochemistry of the resulting polymer. The tolerance to functionality and the mild conditions of the ROP mechanism allow for block copolymer synthesis by combination of nitroxide-mediated polymerization as well as reversible addition fragmentation and chain transfer polymerization using dual-headed initiators. Tandem hydrogen bond activation to organocatalyze ROP of lactide is an effective, versatile means to generate polymers with predictable molecular weights, narrow polydispersities, control of microstructure and a variety of complex architectures and block copolymers.
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