Lithium amides as initiators of anionic polymerisation of methyl methacrylate

S A Couper, Robert Mulvey, D C Sherrington

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Reaction of (BuLi)-Li-n with isopropylcyclohexylamine and 2,6-dimethylpiperidine allows isolation of the corresponding lithium amides. Both of these are effective initiators of polymerisation of methyl methacrylate (MMA). A more convenient procedure however is to generate the lithium amides in situ and six secondary amines have been used in this way. Polymerisations in THF at -78 degrees C, both with and without added TMEDA Lewis base, yield polymer quantitatively with a high degree of syndiotacticity. (M) over bar(n) values, however, are somewhat larger than expected for clean living systems and likewise molecular weight distributions are rather broad. Similar reactions at 25 degrees C give much lower yields of polymer, somewhat reduced syndiotacticity and similar molecular weight effects. Using diisopropylaminolithium as the initiator in toluene solution at -78 degrees C yields highly isotactic polymer essentially quantitatively. Again the (M) over bar(n) and molecular weight distributions are higher than ideal. Adding trace levels of TMEDA to this polymerisation switches the microstructure of the polymer to high levels of syndiotacticity, but the initiator efficiency is reduced at the same time resulting in a very high (M) over bar(n), and a broad molecular weight distribution. Addition of varying levels of LiOBut to the polymerisation in toluene retains the isotactic selectivity of the propagation and improves the initiator efficiency significantly. The results are discussed in the light of current understanding of anionic vinyl polymerisations. (C) 1998 Elsevier Science Ltd. All rights reserved.

LanguageEnglish
Pages1877-1887
Number of pages11
JournalEuropean Polymer Journal
Volume34
Issue number12
DOIs
Publication statusPublished - Dec 1998

Fingerprint

Anionic polymerization
Methacrylates
initiators
Lithium
Amides
amides
polymerization
lithium
Polymerization
molecular weight
Polymers
Molecular weight distribution
polymers
Toluene
toluene
Lewis Bases
Lewis base
Amines
isolation
amines

Keywords

  • diisopropylamide LDA
  • crystal structures
  • polymerization
  • complexes
  • monomers

Cite this

Couper, S A ; Mulvey, Robert ; Sherrington, D C . / Lithium amides as initiators of anionic polymerisation of methyl methacrylate. In: European Polymer Journal. 1998 ; Vol. 34, No. 12. pp. 1877-1887.
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Lithium amides as initiators of anionic polymerisation of methyl methacrylate. / Couper, S A ; Mulvey, Robert; Sherrington, D C .

In: European Polymer Journal, Vol. 34, No. 12, 12.1998, p. 1877-1887.

Research output: Contribution to journalArticle

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AB - Reaction of (BuLi)-Li-n with isopropylcyclohexylamine and 2,6-dimethylpiperidine allows isolation of the corresponding lithium amides. Both of these are effective initiators of polymerisation of methyl methacrylate (MMA). A more convenient procedure however is to generate the lithium amides in situ and six secondary amines have been used in this way. Polymerisations in THF at -78 degrees C, both with and without added TMEDA Lewis base, yield polymer quantitatively with a high degree of syndiotacticity. (M) over bar(n) values, however, are somewhat larger than expected for clean living systems and likewise molecular weight distributions are rather broad. Similar reactions at 25 degrees C give much lower yields of polymer, somewhat reduced syndiotacticity and similar molecular weight effects. Using diisopropylaminolithium as the initiator in toluene solution at -78 degrees C yields highly isotactic polymer essentially quantitatively. Again the (M) over bar(n) and molecular weight distributions are higher than ideal. Adding trace levels of TMEDA to this polymerisation switches the microstructure of the polymer to high levels of syndiotacticity, but the initiator efficiency is reduced at the same time resulting in a very high (M) over bar(n), and a broad molecular weight distribution. Addition of varying levels of LiOBut to the polymerisation in toluene retains the isotactic selectivity of the propagation and improves the initiator efficiency significantly. The results are discussed in the light of current understanding of anionic vinyl polymerisations. (C) 1998 Elsevier Science Ltd. All rights reserved.

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