Thiourea-Based Bifunctional Organocatalysis: Supramolecular Recognition for Living Polymerization
Citations Over TimeTop 10% of 2005 papers
Abstract
A versatile, metal-free, organocatalytic approach to the living ring-opening polymerization of lactide using a bifunctional thiourea-tertiary amine catalyst is described. Mild and highly selective polymerization conditions produced poly(lactides) with predictable molecular weights and extremely narrow polydispersities ( approximately 1.05), characteristic of a living polymerization. The extraordinary selectivity of this catalyst system for polymerization relative to transesterification is remarkably unusual. The low polydispersities and exceptional control observed are a consequence of selective transesterification of lactide relative to the open chain esters. Presumably, the ring strain of lactide provides both a driving force for the polymerization and a kinetic preference for polymerization relative to transesterification with catalyst. We postulate that the initiating/propagating alcohol is activated by acid-base interaction with the tertiary amine moiety and the carbonyl of the lactide monomer is simultaneously activated by hydrogen bonding to the thiourea moiety of the catalyst.
Related Papers
- → Controlled/Living Ring-Opening Polymerization of δ-Valerolactone Using Triflylimide as an Efficient Cationic Organocatalyst(2010)87 cited
- → Biodiesel from Triglycerides via Transesterification(2007)9 cited
- → Transesterification of dimethyl terephthalate with ethylene glycol(1984)5 cited
- Influence of Transesterification Inhibitor on Transesterification of PC/PAR Blends(2008)
- Advances in Transesterification Reactions of Biodegradable Polymer Blends(2014)