Free-radical copolymerisation of acrylamides, acrylates, and α-olefins

Rebecca K. Carlson, Rachel A. Lee, Jed H. Assam, Rollin A. King, Megan L. Nagel

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Abstract

We report the results of a joint theoretical and experimental investigation into the copolymerisation of acrylamides and acrylates with α-olefins in free-radical processes. The transition-state structures of models for free-radical homo- and copolymerisation involving acrylamide, methylacrylamide, methacrylate, methyl methacrylate, and ethylene have been determined using density functional theory. The reaction energies and barrier heights comport with the experimentally observed properties, including the prevalence of monomer alternation, the realised stereospecificity, and the reaction yield. Continuum solvation models have been applied to determine the sensitivity of the relative energies to the bulk solvent properties. Experimentally, a Lewis acid catalyst is demonstrated to increase the incorporation of nonpolar 1-alkenes in copolymerisations with polar acrylamides and acrylates. In the presence of the Lewis acid, scandium (III) trifluoromethanesulfonate, the copolymerisation of 1-hexene and acrylamide results in an 8.5 mol % incorporation, up from 3.9 mol % in the absence of the Lewis acid. Computations incorporating Mg2+ as a model Lewis acid elucidate the mechanism of this catalysis. In the addition of methacrylate to a methyl methacrylate radical terminated polymer, the Lewis acid binds to the carbonyls on both promoting isotactic addition, while for the addition of an alkene to the same polymer, the Lewis acid binds to the polymer, reducing the barrier for alkenyl addition inductively by withdrawing electron density. We have demonstrated the ability of computational studies to aid experimentalists in the synthesis of new copolymers with desired properties.

Original languageEnglish (US)
Pages (from-to)1809-1822
Number of pages14
JournalMolecular Physics
Volume113
Issue number13-14
DOIs
StatePublished - Jul 18 2015

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Acrylamides
Acrylates
Lewis Acids
Alkenes
copolymerization
acrylates
free radicals
Copolymerization
alkenes
Free Radicals
Methacrylates
acids
Polymers
Acrylamide
polymers
hexenes
scandium
Solvation
alternations
Homopolymerization

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Molecular Biology
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

Cite this

Carlson, Rebecca K. ; Lee, Rachel A. ; Assam, Jed H. ; King, Rollin A. ; Nagel, Megan L. / Free-radical copolymerisation of acrylamides, acrylates, and α-olefins. In: Molecular Physics. 2015 ; Vol. 113, No. 13-14. pp. 1809-1822.
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Free-radical copolymerisation of acrylamides, acrylates, and α-olefins. / Carlson, Rebecca K.; Lee, Rachel A.; Assam, Jed H.; King, Rollin A.; Nagel, Megan L.

In: Molecular Physics, Vol. 113, No. 13-14, 18.07.2015, p. 1809-1822.

Research output: Contribution to journalArticle

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T1 - Free-radical copolymerisation of acrylamides, acrylates, and α-olefins

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AU - Lee, Rachel A.

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AB - We report the results of a joint theoretical and experimental investigation into the copolymerisation of acrylamides and acrylates with α-olefins in free-radical processes. The transition-state structures of models for free-radical homo- and copolymerisation involving acrylamide, methylacrylamide, methacrylate, methyl methacrylate, and ethylene have been determined using density functional theory. The reaction energies and barrier heights comport with the experimentally observed properties, including the prevalence of monomer alternation, the realised stereospecificity, and the reaction yield. Continuum solvation models have been applied to determine the sensitivity of the relative energies to the bulk solvent properties. Experimentally, a Lewis acid catalyst is demonstrated to increase the incorporation of nonpolar 1-alkenes in copolymerisations with polar acrylamides and acrylates. In the presence of the Lewis acid, scandium (III) trifluoromethanesulfonate, the copolymerisation of 1-hexene and acrylamide results in an 8.5 mol % incorporation, up from 3.9 mol % in the absence of the Lewis acid. Computations incorporating Mg2+ as a model Lewis acid elucidate the mechanism of this catalysis. In the addition of methacrylate to a methyl methacrylate radical terminated polymer, the Lewis acid binds to the carbonyls on both promoting isotactic addition, while for the addition of an alkene to the same polymer, the Lewis acid binds to the polymer, reducing the barrier for alkenyl addition inductively by withdrawing electron density. We have demonstrated the ability of computational studies to aid experimentalists in the synthesis of new copolymers with desired properties.

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