| pubmed-article:19334780 | rdf:type | pubmed:Citation | lld:pubmed |
| pubmed-article:19334780 | lifeskim:mentions | umls-concept:C0220781 | lld:lifeskim |
| pubmed-article:19334780 | lifeskim:mentions | umls-concept:C0314672 | lld:lifeskim |
| pubmed-article:19334780 | lifeskim:mentions | umls-concept:C0679199 | lld:lifeskim |
| pubmed-article:19334780 | lifeskim:mentions | umls-concept:C1883254 | lld:lifeskim |
| pubmed-article:19334780 | lifeskim:mentions | umls-concept:C2587213 | lld:lifeskim |
| pubmed-article:19334780 | lifeskim:mentions | umls-concept:C0439596 | lld:lifeskim |
| pubmed-article:19334780 | lifeskim:mentions | umls-concept:C0071444 | lld:lifeskim |
| pubmed-article:19334780 | pubmed:issue | 13 | lld:pubmed |
| pubmed-article:19334780 | pubmed:dateCreated | 2009-4-1 | lld:pubmed |
| pubmed-article:19334780 | pubmed:abstractText | The zwitterionic ring-opening polymerization of lactide initiated by N-heterocyclic carbenes generates cyclic polylactides with well-defined molecular weights between M(n) = 5000 and 30,000 g/mol with narrow polydispersities (M(w)/M(n) < or = 1.31). These zwitterionic polymerizations are extremely rapid (k(p) = 48.7 M(-1) s(-1)), but also exhibit exceptional control of molecular weight and molecular weight distribution. The unusual kinetic features of these zwitterionic polymerizations are illuminated with kinetic and mechanistic investigations, which implicate a mechanism that involves a slow initiation step (second order in [M]), a propagation step (first order in [M]) that is much faster than initiation (k(i) = 0.274 M(-2) s(-1)), cyclization (k(c) = 0.0575 s(-1)), and depropagation (k(d) = 0.208 s(-1)). Numerical and stochastic simulations of the kinetic data provide a kinetic rationale for the evolution of molecular weight with monomer conversion: the molecular weights increase with increasing monomer conversion, exhibit a nonzero intercept near 0% monomer conversion, and are relatively insensitive to the initial monomer-to-initiator ratio. The observed narrow molecular weight distributions are due to a high rate of propagation relative to cyclization and chain transfer. Kinetic simulations define the kinetic criteria under which the active zwitterions remain in solution; these simulations were substantiated by chain-extension experiments, which provide experimental evidence for chain extension of the zwitterions and reinitiation by the N-heterocyclic carbenes liberated upon macrocyclization. The kinetic model rationalizes some of the unique features of zwitterionic ring-opening polymerization and provides a useful mechanistic framework to optimize these polymerizations as a strategy to generate well-defined cyclic polyesters. | lld:pubmed |
| pubmed-article:19334780 | pubmed:language | eng | lld:pubmed |
| pubmed-article:19334780 | pubmed:journal | http://linkedlifedata.com/r... | lld:pubmed |
| pubmed-article:19334780 | pubmed:citationSubset | IM | lld:pubmed |
| pubmed-article:19334780 | pubmed:chemical | http://linkedlifedata.com/r... | lld:pubmed |
| pubmed-article:19334780 | pubmed:chemical | http://linkedlifedata.com/r... | lld:pubmed |
| pubmed-article:19334780 | pubmed:chemical | http://linkedlifedata.com/r... | lld:pubmed |
| pubmed-article:19334780 | pubmed:status | MEDLINE | lld:pubmed |
| pubmed-article:19334780 | pubmed:month | Apr | lld:pubmed |
| pubmed-article:19334780 | pubmed:issn | 1520-5126 | lld:pubmed |
| pubmed-article:19334780 | pubmed:author | pubmed-author:WaymouthRober... | lld:pubmed |
| pubmed-article:19334780 | pubmed:author | pubmed-author:HedrickJames... | lld:pubmed |
| pubmed-article:19334780 | pubmed:author | pubmed-author:CulkinDarcy... | lld:pubmed |
| pubmed-article:19334780 | pubmed:author | pubmed-author:JeongWonheeW | lld:pubmed |
| pubmed-article:19334780 | pubmed:author | pubmed-author:ShinEun JiEJ | lld:pubmed |
| pubmed-article:19334780 | pubmed:issnType | Electronic | lld:pubmed |
| pubmed-article:19334780 | pubmed:day | 8 | lld:pubmed |
| pubmed-article:19334780 | pubmed:volume | 131 | lld:pubmed |
| pubmed-article:19334780 | pubmed:owner | NLM | lld:pubmed |
| pubmed-article:19334780 | pubmed:authorsComplete | Y | lld:pubmed |
| pubmed-article:19334780 | pubmed:pagination | 4884-91 | lld:pubmed |
| pubmed-article:19334780 | pubmed:meshHeading | pubmed-meshheading:19334780... | lld:pubmed |
| pubmed-article:19334780 | pubmed:meshHeading | pubmed-meshheading:19334780... | lld:pubmed |
| pubmed-article:19334780 | pubmed:meshHeading | pubmed-meshheading:19334780... | lld:pubmed |
| pubmed-article:19334780 | pubmed:meshHeading | pubmed-meshheading:19334780... | lld:pubmed |
| pubmed-article:19334780 | pubmed:meshHeading | pubmed-meshheading:19334780... | lld:pubmed |
| pubmed-article:19334780 | pubmed:year | 2009 | lld:pubmed |
| pubmed-article:19334780 | pubmed:articleTitle | Zwitterionic polymerization: a kinetic strategy for the controlled synthesis of cyclic polylactide. | lld:pubmed |
| pubmed-article:19334780 | pubmed:affiliation | Department of Chemistry, Stanford University, Stanford, California 94305, USA. | lld:pubmed |
| pubmed-article:19334780 | pubmed:publicationType | Journal Article | lld:pubmed |
| pubmed-article:19334780 | pubmed:publicationType | Research Support, U.S. Gov't, Non-P.H.S. | lld:pubmed |
| pubmed-article:19334780 | pubmed:publicationType | Research Support, Non-U.S. Gov't | lld:pubmed |
