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Volumn 114, Issue 2, 2001, Pages 1032-1050

Model for the aggregation state of living anionic polymers

Author keywords

[No Author keywords available]

Indexed keywords

AGGLOMERATION; ANIONIC POLYMERIZATION; BINDING ENERGY; MATHEMATICAL MODELS; MICELLES; NEGATIVE IONS; QUANTUM THEORY;

EID: 0035121066     PISSN: 00219606     EISSN: None     Source Type: Journal    
DOI: 10.1063/1.1328068     Document Type: Article
Times cited : (17)

References (68)
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    • note
    • The ceiling temperature of polystyrene with styryllithium headgroups is about 250°C, so that in living PS solutions at usual experimental temperatures all the monomers are incorporated and depolymerization is highly unlikely. A similar state of play exists for isoprenyllithium headgroups. Furthermore, isoprenyllithium headgroups are stable over a long life time. GPC measurements of terminated polymers showed no difference between samples drawn from freshly made living isoprenyllithium polymer solutions and those drawn from living polymer allowed to sit for three to four weeks before being terminated. Similar features have been observed for butadienyllithium headgroups. L. J. Fetters (private communication).
  • 9
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    • note
    • In the literature, the term "living polymer" is also used to describe cylindrical micelles of short-chain or polymeric surfactants, which in equilibrium can change length. We will indeed discuss cylindrical micelles here, but will refer to them as such. Also, some living polymers, such as (poly)α-methylstyrene, can be observed at temperatures where the polymerization and depolymerization reactions are in equilibrium, so that the molecular weight distribution becomes broad (see Ref. 5 and references therein). That is not the case in the experiments of Ref. 4 (see previous note).
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    • note
    • Calculations of the point charges on the atoms of the aggregates depended on the method used; for small aggregates of methyllithium (tetramers, hexamers, and octomers), the semiempirical PM3 method found charges of approximately +0.25e on the lithium atoms and -0.3e to -0.45e on the carbons, with small charges on the hydrogens. More precise ab initio calculations with a 3-21G basis set found charges of +0.6e on the lithium atoms and - 1.0e on the carbons, with about +0.15e on the hydrogen atoms.
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