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Force-induced activation of covalent bonds in mechanoresponsive polymeric materials

Nature volume 459, pages 6872 (07 May 2009) | Download Citation



Mechanochemical transduction enables an extraordinary range of physiological processes such as the sense of touch, hearing, balance, muscle contraction, and the growth and remodelling of tissue and bone1,2,3,4,5,6. Although biology is replete with materials systems that actively and functionally respond to mechanical stimuli, the default mechanochemical reaction of bulk polymers to large external stress is the unselective scission of covalent bonds, resulting in damage or failure7. An alternative to this degradation process is the rational molecular design of synthetic materials such that mechanical stress favourably alters material properties. A few mechanosensitive polymers with this property have been developed8,9,10,11,12,13,14; but their active response is mediated through non-covalent processes, which may limit the extent to which properties can be modified and the long-term stability in structural materials. Previously, we have shown with dissolved polymer strands incorporating mechanically sensitive chemical groups—so-called mechanophores—that the directional nature of mechanical forces can selectively break and re-form covalent bonds15,16. We now demonstrate that such force-induced covalent-bond activation can also be realized with mechanophore-linked elastomeric and glassy polymers, by using a mechanophore that changes colour as it undergoes a reversible electrocyclic ring-opening reaction under tensile stress and thus allows us to directly and locally visualize the mechanochemical reaction. We find that pronounced changes in colour and fluorescence emerge with the accumulation of plastic deformation, indicating that in these polymeric materials the transduction of mechanical force into the ring-opening reaction is an activated process. We anticipate that force activation of covalent bonds can serve as a general strategy for the development of new mechanophore building blocks that impart polymeric materials with desirable functionalities ranging from damage sensing to fully regenerative self-healing.

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We acknowledge the support of the ARO MURI programme (grant number W911NF-07-1-0409) for this research.

Author information

Author notes

    • Jinglei Yang
    •  & Todd J. Martínez

    Present addresses: School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore (J.Y.); Department of Chemistry, Stanford University, Stanford, California, USA (T.J.M.).


  1. Department of Chemistry,

    • Douglas A. Davis
    • , Lee D. Cremar
    • , Stephanie L. Potisek
    • , Mitchell T. Ong
    • , Paul V. Braun
    • , Todd J. Martínez
    •  & Jeffrey S. Moore
  2. Department of Mechanical Science and Engineering,

    • Andrew Hamilton
  3. The Beckman Institute,

    • Jinglei Yang
    • , Paul V. Braun
    • , Todd J. Martínez
    • , Scott R. White
    • , Jeffrey S. Moore
    •  & Nancy R. Sottos
  4. Department of Materials Science and Engineering,

    • Dara Van Gough
    • , Paul V. Braun
    • , Jeffrey S. Moore
    •  & Nancy R. Sottos
  5. Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Illinois 61801, USA

    • Scott R. White


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Corresponding author

Correspondence to Nancy R. Sottos.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    This file contains Supplementary Methods, Supplementary Figures S1-S5 with Legends and Supplementary Tables S1-S2; a Supplementary Discussion, Supplementary Figures S6-S21 with Legends and Supplementary References.


  1. 1.

    Supplementary Video S1

    Video S1 shows mechanophore-linked PMA-1-PMA dog bone specimen loaded in uniaxial tension to failure.

  2. 2.

    Supplementary Video S2

    Video S2 shows SMD simulations of 1t showing C-O spiro bond rupture at a force of 2.0 nN.

  3. 3.

    Supplementary Video S3

    Video S3 shows SMD simulations of 3t showing no bond rupture at a force of 2.0 nN.

  4. 4.

    Supplementary Video S4

    Video S4 shows SMD simulations of 1e showing spiro C-O bond rupture at a force of 3.0 nN.

  5. 5.

    Supplementary Video S5

    Video S5 shows SMD simulations of 1e showing C-O ester bond rupture at a force of 3.0 nN.

  6. 6.

    Supplementary Video S6

    Video S6 shows SMD simulations of 3e showing C-C ester bond rupture at a force of 3.0 nN.

  7. 7.

    Supplementary Video S7

    Video S7 shows active PMMA-4 beads under compressive loading.

  8. 8.

    Supplementary Video S8

    Video S8 shows control PMMA-5 beads under compressive loading.

Zip files

  1. 1.

    Supplementary Data

    This zipped data file shows XYZ coordinate data for all molecules used in molecular modelling.

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