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Designing naphthopyran mechanophores with tunable mechanochromic behavior

Versaw, Brooke A. and McFadden, Molly E. and Husic, Corey C. and Robb, Maxwell J. (2020) Designing naphthopyran mechanophores with tunable mechanochromic behavior. Chemical Science, 11 (17). pp. 4525-4530. ISSN 2041-6520. PMCID PMC8159456. doi:10.1039/d0sc01359e.

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Mechanochromic molecular force probes conveniently report on stress and strain in polymeric materials through straightforward visual cues. We capitalize on the versatility of the naphthopyran framework to design a series of mechanochromic mechanophores that exhibit highly tunable color and fading kinetics after mechanochemical activation. Structurally diverse naphthopyran crosslinkers are synthesized and covalently incorporated into silicone elastomers, where the mechanochemical ring–opening reactions are achieved under tension to generate the merocyanine dyes. Strategic structural modifications to the naphthopyran mechanophore scaffold produce dramatic differences in the color and thermal electrocyclization behavior of the corresponding merocyanine dyes. The color of the merocyanines varies from orange-yellow to purple upon the introduction of an electron donating pyrrolidine substituent, while the rate of thermal electrocyclization is controlled through electronic and steric factors, enabling access to derivatives that display both fast-fading and persistent coloration after mechanical activation and subsequent stress relaxation. In addition to identifying key structure–property relationships for tuning the behavior of the naphthopyran mechanophore, the modularity of the naphthopyran platform is demonstrated by leveraging blends of structurally distinct mechanophores to create materials with desirable multicolor mechanochromic and complex stimuli-responsive behavior, expanding the scope and accessibility of force-responsive materials for applications such as multimodal sensing.

Item Type:Article
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URLURL TypeDescription Information CentralArticle
Versaw, Brooke A.0000-0002-6200-7203
McFadden, Molly E.0000-0003-3174-6385
Husic, Corey C.0000-0003-0248-7484
Robb, Maxwell J.0000-0002-0528-9857
Additional Information:© 2020 The Royal Society of Chemistry. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. Submitted 06 Mar 2020; Accepted 16 Apr 2020; First published 17 Apr 2020. Financial support from Caltech and the Dow Next Generation Educator Fund is gratefully acknowledged. B. A. V. and M. E. M. were supported by NSF Graduate Research Fellowships (DGE-1745301). We thank the Center for Catalysis and Chemical Synthesis of the Beckman Institute at Caltech for access to equipment and Dr Mona Shahgholi and the CCE Multiuser Mass Spectrometry Laboratory for assistance with mass spectrometry. There are no conflicts to declare.
Funding AgencyGrant Number
Dow Next Generation Educator FundUNSPECIFIED
NSF Graduate Research FellowshipDGE-1745301
Issue or Number:17
PubMed Central ID:PMC8159456
Record Number:CaltechAUTHORS:20200423-135418974
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102756
Deposited By: Tony Diaz
Deposited On:23 Apr 2020 21:01
Last Modified:16 Nov 2021 18:15

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