Perspective on metal-mediated polar monomer/alkene copolymerization

Ayusman Sen, Sachin Borkar

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

A major unsolved problem in polymer synthesis is the design of efficient metal-mediated systems for the copolymerization of alkenes with polar vinyl monomers, such as acrylates and methacrylates. There are several reasons for the absence of efficient transition metal-based insertion copolymerization catalysts. First, following insertion, the ester group of the acrylate coordinates to the metal thereby hindering subsequent monomer coordination. A second reason stems from the preferred 2,1-insertion of acrylates into metal-carbon bonds resulting in the placement of the ester group on the α-carbon. This makes the metal-alkyl species particularly prone to homolysis because of the enhanced stability of the resultant alkyl radical, one that is essentially the same as the propagating species in radical-initiated acrylate polymerization. In this perspective we focus on this issue of facile metal-carbon bond homolysis, especially following acrylate insertion, using examples from our own work. We suggest ways to circumvent these issues, for example forcing 1,2-insertion by imposing steric crowding at the metal. Finally, we discuss the danger of relying on radical traps as probes for polymerization mechanism. Radical traps can react with metal-hydrides and attenuate metal-centered nonradical reactions. However, even when radical traps fail to stop an observed polymerization, it may be wrong to conclude that a nonradical mechanism is at work since the traps can be destroyed under certain reaction conditions.

Original languageEnglish (US)
Pages (from-to)3291-3299
Number of pages9
JournalJournal of Organometallic Chemistry
Volume692
Issue number15
DOIs
StatePublished - Jul 1 2007

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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