Direct Observation of a Cyclic Vinyl Polymer Prepared by Anionic Polymerization using N-Heterocyclic Carbene and Subsequent Ring-Closure without Highly Diluted Conditions

Keiji Naruse, Akinori Takasu, Masahiro Higuchi

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

A 1:1 adduct of methyl sorbate (MS) and 1,3-di-tert-butylimidazol-2-ylidene (NHCtBu) initiates anionic polymerization of a nonconjugated polar alkene, allyl methacrylate (AMA) in toluene at −20 °C. After the monomer is consumed quantitatively using a bulky aluminum Lewis acid, methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD), as an additive, successive ring-closure occurs without highly dilute conditions to give a cyclic poly(AMA) containing α-terminal MS unit, and an Mn of 8.8 × 103−58.5 × 103 with a narrow molecular dispersity index (Mw/Mn = 1.14–1.37). The lack of a need for dilution is due to the fact that an α-terminal NHCtBu group is acting as the counter cation for the propagating center in the polymerization. From 1H NMR and matrix assisted laser desorption/ionization (MALDI-TOF) mass spectra, combined with transmittance electron microscope (TEM) observation of a synthesized poly(AMA) with longer alkyl side chains prepared via a thiol-ene click reaction, it is concluded that once the monomer is consumed, nucleophilic attack at the neighboring methine of the α-terminal NHCtBu residue by the propagating anionic center causes ring-closing to cyclic poly(AMA).

Original languageEnglish
Article number2000004
JournalMacromolecular Chemistry and Physics
Volume221
Issue number10
DOIs
Publication statusPublished - May 1 2020
Externally publishedYes

Keywords

  • cyclic polymers
  • cyclizations
  • ring-closures

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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