Article (Scientific journals)
Anionic polymerization of acrylic monomers. 11 NMR investigation of the mixed complexation of methyl α-lithioisobutyrate and lithium chloride
Wang, Jin-Shan; Warin, R.; Jérôme, Robert et al.
1993In Macromolecules, 26, p. 6776-6781
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Keywords :
anionic polymerization; (meth)acrylate
Abstract :
[en] Solutions of methyl α-lithioisobutyrate (MIBLi) in THF added with various amounts of lithium chloride (LiCl) have been analyzed by Li-7 NMR spectroscopy in a wide range of temperatures. Although below ca. 205 K tetramers of MIBLi have been reported to be in equilibrium with dimers, 1/1 and 2/1 LiCl/MIBLi mixed complexes instantaneously form upon the addition of 1 and 2 mol equiv of LiCl, respectively. Further addition of LiCl more likely promotes the formation of a less stable 3/1 complex. Both 1/1 and 2/1 adducts are stable between -80-degrees-C and at least +12-degrees-C. From C-13 NMR spectroscopy, it appears that the addition of an equimolar amount of LiCl to the MIBLi solution in THF is at the origin of a ca. 7.0 ppm upfield shift of the metalated α-carbon compared to the tetrameric MIBLi species and a ca. 1.0 ppm downfield shift with respect to the dimeric MIBLi. However, the charge distribution over the carbanion does not change anymore when the amount of LiCl exceeds 1 mol equiv. In contrast to nonligated MEBLi, the OR group has a considerable rotational freedom in LiCl-modified MIBLi. A comparison of the structure and dynamics of the LiCl-modified MIBLi species in THF at 197 K with the characteristic features of the anionic polymerization of MMA under the same conditions suggests that the formation of one type of LiCl-complexed species has a decisive effect on the control of the living polymerization of MMA. This conclusion is in agreement with a kinetic study carried out by Muller for the same system.
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)
Warin, R.;  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)
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. 11 NMR investigation of the mixed complexation of methyl α-lithioisobutyrate and lithium chloride
Publication date :
06 December 1993
Journal title :
Macromolecules
ISSN :
0024-9297
eISSN :
1520-5835
Publisher :
American Chemical Society, Washington, United States - District of Columbia
Volume :
26
Pages :
6776-6781
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
BELSPO - SPP Politique scientifique - Service Public Fédéral de Programmation Politique scientifique
Elf Atochem [FR]
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