Issue 5, 2021

Fast reversible isomerization of merocyanine as a tool to quantify stress history in elastomers

Abstract

A mechanochemistry based approach is proposed to detect and map stress history during dynamic processes. Spiropyran (SP), a force sensitive molecular probe, was incorporated as a crosslinker into multiple network elastomers (MNE). When these mechanochromic MNEs are loaded, SP undergoes a well-known force-activated reaction to merocyanine (MC) changing its absorption in the visible range (visible blue color). This SP to MC transition is not reversible within the time frame of the experiment and the color change reports the concentration of activated molecules. During subsequent loading–unloading cycles the MC undergoes a fast and reversible isomerization resulting in a slight shift of absorption spectrum and results in a second color change (blue to purple color corresponding to the loading–unloading cycles). Quantification of the color changes by using chromaticity shows that the exact color observed upon unloading is characteristic not only of the current stress (reported by the shift in color due to MC isomerization), but of the maximum stress that the material has seen during the loading cycle (reported by the shift in color due to the change in MC concentration). We show that these two color changes can be separated unambiguously and we use them to map the stress history in the loading and unloading process occurring as a crack opens up and propagates, breaking the material. Color maps on fractured samples are compared with finite element simulations and the agreement is excellent.

Graphical abstract: Fast reversible isomerization of merocyanine as a tool to quantify stress history in elastomers

Supplementary files

Article information

Article type
Edge Article
Submitted
08 Nov. 2020
Accepted
08 Dec. 2020
First published
17 Dec. 2020
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2021,12, 1693-1701

Fast reversible isomerization of merocyanine as a tool to quantify stress history in elastomers

Y. Chen, C. J. Yeh, Q. Guo, Y. Qi, R. Long and C. Creton, Chem. Sci., 2021, 12, 1693 DOI: 10.1039/D0SC06157C

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