Article (Scientific journals)
Anionic polymerization of acrylic monomers. 14. Carbon-13 and lithium-7 NMR characterization of the complexation of methyl α-lithioisobutyrate with various lithium cation-binding ligands in tetrahydrofuran
Wang, Jin-Shan; Jérôme, Robert; Warin, R. et al.
1994In Macromolecules, 27 (12), p. 3376-3382
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Keywords :
anionic polymerization; (meth)acrylate
Abstract :
[en] The aggregation equilibrium and electronic structure of methyl alpha-lithioisobutyrate (MIBLi), a monomeric model structurally corresponding to a living poly(methyl methacrylate) chain end associated with a lithium countercation, has been examined by Li-7 and/or C-13 NMR spectroscopy in tetrahydrofuran (THF) in the presence of various lithium cation-binding ligands. The addition of dimethoxyethane (DME), triglyme (glyme-3),12-crown-4 (12-CE-4), and hexamethylphosphoric triamide (HMPA) to coexisting tetrameric and dimeric MIBLi in THF induces an increase in dimeric population in the order DME < glyme-3 < 12-CE-4 <HMPA. That order corresponds to an increasing strength of complexation between MIBLi (lithium cation) and the (solvating) ligands For either tetrameric or dimeric species, moreover, the negative charge distribution around MIBLi does not seem to be significantly modified due to the presence of these complexing agents. In striking contrast, complexation of MIBLi by cryptand 211 (K211) does shift the equilibrium between tetramer and dimer toward the formation of a single monomeric K211-complexed species, which gives rise to ca. 13 and 5 ppm upfield shifts at C(alpha) in the C-13 NMR spectra, compared to tetrameric and dimeric species, respectively. The effect of 12-CE-4/K211 on the original aggretation equilbrium for MIBLi in THF nicely explains the significantly different MWD of PMMA anionically prepared in the presence of each of these ligands.
Research center :
Center for Education and Research on Macromolecules (CERM)
Disciplines :
Chemistry
Materials science & engineering
Author, co-author :
Wang, Jin-Shan;  Université de Liège - ULiège > Department of Chemistry > Center for Education and Research on Macromolecules (CERM)
Jérôme, Robert ;  Université de Liège - ULiège > Department of Chemistry > Center for Education and Research on Macromolecules (CERM)
Warin, R.;  Université de Liège - ULiège > Department of Chemistry > Center for Education and Research on Macromolecules (CERM)
Zhang, H.;  Université de Liège - ULiège > Department of Chemistry > Center for Education and Research on Macromolecules (CERM)
Teyssié, Philippe ;  Université de Liège - ULiège > Department of Chemistry > Center for Education and Research on Macromolecules (CERM)
Language :
English
Title :
Anionic polymerization of acrylic monomers. 14. Carbon-13 and lithium-7 NMR characterization of the complexation of methyl α-lithioisobutyrate with various lithium cation-binding ligands in tetrahydrofuran
Publication date :
06 June 1994
Journal title :
Macromolecules
ISSN :
0024-9297
eISSN :
1520-5835
Publisher :
American Chemical Society, Washington, United States - District of Columbia
Volume :
27
Issue :
12
Pages :
3376-3382
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
Elf Atochem [FR]
BELSPO - SPP Politique scientifique - Service Public Fédéral de Programmation Politique scientifique
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