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Comparison of the reactivity of isomeric 2H- and 3H-naphthopyran mechanophores

Osler, Skylar K. and McFadden, Molly E. and Robb, Maxwell J. (2021) Comparison of the reactivity of isomeric 2H- and 3H-naphthopyran mechanophores. Journal of Polymer Science, 59 (21). pp. 2537-2544. ISSN 2642-4150. doi:10.1002/pol.20210417.

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Naphthopyrans are molecular switches that produce highly colored merocyanine dyes upon photochemical or mechanochemical activation in polymers. The mechanochromic behavior of these molecular force probes enables the straightforward visualization of stress and/or strain in materials. To date, research on the mechanochemistry of naphthopyran has largely focused on the 3H-naphtho[2,1-b]pyran (3H) scaffold, whereas isomeric 2H-naphtho[1,2-b]pyrans (2H) exhibit complementary properties as suggested from their photochemical reactivity. Here we directly compare the reactivity of two isomeric 2H- and 3H-naphthopyran mechanophores in solution-phase ultrasonication experiments and in crosslinked polydimethylsiloxane elastomers subjected to uniaxial tensile deformation. The prototypical 3H-naphthopyran mechanophore produces a yellow merocyanine dye that reverts quickly, while the 2H-naphthopyran mechanophore generates a red merocyanine dye that reverts significantly slower. The trends in absorption and reversion measured in solution are also reflected in solid polymeric materials activated in tension. Building on recent research into substituent effects, this study identifies naphthopyran isomerism as a simple lever for modulating the mechanochromic properties of the naphthopyran mechanophore used in the development of force-responsive polymers.

Item Type:Article
Related URLs:
URLURL TypeDescription
Osler, Skylar K.0000-0003-1021-7011
McFadden, Molly E.0000-0003-3174-6385
Robb, Maxwell J.0000-0002-0528-9857
Additional Information:© 2021 Wiley Periodicals LLC. Issue Online: 01 November 2021; Version of Record online: 26 June 2021; Manuscript accepted: 17 June 2021; Manuscript revised: 17 June 2021; Manuscript received: 02 June 2021. Funding information: California Institute of Technology.
Funding AgencyGrant Number
Subject Keywords:mechanophore; naphthopyran; Polymer mechanochemistry
Issue or Number:21
Record Number:CaltechAUTHORS:20210701-173741992
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Official Citation:Comparison of the reactivity of isomeric 2H- and 3H-naphthopyran mechanophores. Osler, S. K., McFadden, M. E., Robb, M. J., J Polym Sci 2021, 59(21), 2537.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109705
Deposited By: Tony Diaz
Deposited On:02 Jul 2021 20:28
Last Modified:12 Nov 2021 19:14

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