Issue 10, 2023

Red-light photoswitching of indigos in polymer thin films

Abstract

Through simple synthetic derivatisation, the parent indigo dye becomes a red-light E–Z photoswitch exhibiting negative photochromism and tuneable thermal isomerisation kinetics. These attributes make indigo derivatives extremely attractive for applications related to materials and living systems. However, there is a lack of knowledge in translating indigo photoswitching dynamics from solution to solid state – the environment crucial for most applications. Herein, we study the photoswitching performance of six structurally distinct indigo derivatives in five polymers of varying rigidity. Three key strategies are identified to enable efficient photoswitching under red (660 nm) light: (i) choosing a soft polymer matrix to minimise its resistance toward the isomerisation, (ii) creating free volume around the indigo molecules through synthetic modifications, and (iii) applying low dye loading (<1% w/w) to inhibit aggregation. These strategies are shown to improve both photostationary state distributions and the thermal stability of the Z isomer. When all three strategies are implemented, the isomerisation performance (>80% Z form in the photostationary state) is nearly identical to that in solution. These findings thus pave the way for designing new red-light photochromic materials based on indigos.

Graphical abstract: Red-light photoswitching of indigos in polymer thin films

Supplementary files

Article information

Article type
Edge Article
Submitted
09 Dec 2022
Accepted
29 Jan 2023
First published
22 Feb 2023
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., 2023,14, 2482-2488

Red-light photoswitching of indigos in polymer thin films

K. Kuntze, J. Viljakka, M. Virkki, C. (. Huang, S. Hecht and A. Priimagi, Chem. Sci., 2023, 14, 2482 DOI: 10.1039/D2SC06790K

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