A Latent Mechanoacid for Time-Stamped Mechanochromism and Chemical Signaling in Polymeric Materials.


Journal Article

Mechanically coupled proton transduction offers potential for stress-responsive polymeric materials whose properties can be switched via acid-triggered coloration, polymerization/cross-linking, or degradation. The utility of currently available mechanoacids, however, is limited by modest force-free stability or a scissile response that caps mechanoacid generation at one proton per strained polymer chain. Here, we report a new mechanoacid based on 2-methoxy-substituted gem-dichlorocyclopropane (MeO-gDCC). Pulsed ultrasonication leads to the mechanochemical ring opening of the MeO-gDCC and the subsequent elimination of either HCl or MeCl, with ∼0.58 equiv of HCl released per mechanophore activation and ∼67 protons per chain scission event. Single-molecule force spectroscopy reveals that the methoxy substituent lowers the force required for rapid (kopen ∼102 s-1) ring opening to ca. 900 pN, vs 1300 pN required for the parent gDCC. The utility of the mechanoacid is demonstrated in silicone elastomers, where its mechanical activation leads to a strain-triggered color change prior to fracture of the elastomer. The postactivation kinetics of coloration are used to demonstrate a new concept in mechanochromism, namely, a spectroscopic indicator of not only whether and where a mechanical event has occurred but when it occurred.

Full Text

Duke Authors

Cited Authors

  • Lin, Y; Kouznetsova, TB; Craig, SL

Published Date

  • January 2020

Published In

Volume / Issue

  • 142 / 1

Start / End Page

  • 99 - 103

PubMed ID

  • 31875388

Pubmed Central ID

  • 31875388

Electronic International Standard Serial Number (EISSN)

  • 1520-5126

International Standard Serial Number (ISSN)

  • 0002-7863

Digital Object Identifier (DOI)

  • 10.1021/jacs.9b12861


  • eng