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Stress-responsive polymers containing cyclobutane core mechanophores: reactivity and mechanistic insights.

Publication ,  Journal Article
Kean, ZS; Niu, Z; Hewage, GB; Rheingold, AL; Craig, SL
Published in: Journal of the American Chemical Society
September 2013

A primary goal of covalent mechanochemistry is to develop polymer bound mechanophores that undergo constructive transformations in response to otherwise destructive forces. The [2 + 2] cycloreversion of cyclobutane mechanophores has emerged as a versatile framework to develop a wide range of stress-activated functionality. Herein, we report the development of a class of cyclobutane bearing bicyclo[4.2.0]octane mechanophores. Using carbodiimide polyesterification, these stress-responsive units were incorporated into high molecular weight polymers containing up to 700 mechanophores per polymer chain. Under exposure to the otherwise destructive elongational forces of pulsed ultrasound, these mechanophores unravel by ∼7 Å per monomer unit to form α,β-unsaturated esters that react constructively via thiol-ene conjugate addition to form sulfide functionalized copolymers and cross-linked polymer networks. To probe the dynamics of the mechanochemical ring opening, a series of bicyclo[4.2.0]octane derivatives that varied in stereochemistry, substitution, and symmetry were synthesized and activated. Reactivity and product stereochemistry was analyzed by (1)H NMR, which allowed us to interrogate the mechanism of the mechanochemical [2 + 2] cycloreversion. These results support that the ring opening is not concerted but proceeds via a 1,4 diradical intermediate. The bicyclo[4.2.0]octanes hold promise as active functional groups in new classes of stress-responsive polymeric materials.

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Published In

Journal of the American Chemical Society

DOI

EISSN

1520-5126

ISSN

0002-7863

Publication Date

September 2013

Volume

135

Issue

36

Start / End Page

13598 / 13604

Related Subject Headings

  • Polymers
  • Molecular Structure
  • General Chemistry
  • Cyclobutanes
  • Cyclization
  • 40 Engineering
  • 34 Chemical sciences
  • 03 Chemical Sciences
 

Citation

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Kean, Z. S., Niu, Z., Hewage, G. B., Rheingold, A. L., & Craig, S. L. (2013). Stress-responsive polymers containing cyclobutane core mechanophores: reactivity and mechanistic insights. Journal of the American Chemical Society, 135(36), 13598–13604. https://doi.org/10.1021/ja4075997
Kean, Zachary S., Zhenbin Niu, Gihan B. Hewage, Arnold L. Rheingold, and Stephen L. Craig. “Stress-responsive polymers containing cyclobutane core mechanophores: reactivity and mechanistic insights.Journal of the American Chemical Society 135, no. 36 (September 2013): 13598–604. https://doi.org/10.1021/ja4075997.
Kean ZS, Niu Z, Hewage GB, Rheingold AL, Craig SL. Stress-responsive polymers containing cyclobutane core mechanophores: reactivity and mechanistic insights. Journal of the American Chemical Society. 2013 Sep;135(36):13598–604.
Kean, Zachary S., et al. “Stress-responsive polymers containing cyclobutane core mechanophores: reactivity and mechanistic insights.Journal of the American Chemical Society, vol. 135, no. 36, Sept. 2013, pp. 13598–604. Epmc, doi:10.1021/ja4075997.
Kean ZS, Niu Z, Hewage GB, Rheingold AL, Craig SL. Stress-responsive polymers containing cyclobutane core mechanophores: reactivity and mechanistic insights. Journal of the American Chemical Society. 2013 Sep;135(36):13598–13604.
Journal cover image

Published In

Journal of the American Chemical Society

DOI

EISSN

1520-5126

ISSN

0002-7863

Publication Date

September 2013

Volume

135

Issue

36

Start / End Page

13598 / 13604

Related Subject Headings

  • Polymers
  • Molecular Structure
  • General Chemistry
  • Cyclobutanes
  • Cyclization
  • 40 Engineering
  • 34 Chemical sciences
  • 03 Chemical Sciences