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Azobenzene as a photoswitchable mechanophore

Nature Chemistry volume 16, pages 446–455 (2024)Cite this article

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Abstract

Azobenzene has been widely explored as a photoresponsive element in materials science. Although some studies have investigated the force-induced isomerization of azobenzene, the effect of force on the rupture of azobenzene has not been explored. Here we show that the light-induced structural change of azobenzene can also alter its rupture forces, making it an ideal light-responsive mechanophore. Using single-molecule force spectroscopy and ultrasonication, we found that cis and trans para-azobenzene isomers possess contrasting mechanical properties. Dynamic force spectroscopy experiments and quantum-chemical calculations in which azobenzene regioisomers were pulled from different directions revealed that the distinct rupture forces of the two isomers are due to the pulling direction rather than the energetic difference between the two isomers. These mechanical features of azobenzene can be used to rationally control the macroscopic fracture behaviours of polymer networks by photoillumination. The use of light-induced conformational changes to alter the mechanical response of mechanophores provides an attractive way to engineer polymer networks of light-regulatable mechanical properties.

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Fig. 1: SMFS measurement of azobenzene derivatives.
Fig. 2: SMFS and dynamic force spectroscopy results for 4-AZB in water.
Fig. 3: SMFS and dynamic force spectroscopy results for 3-AZB and 2-AZB in water.
Fig. 4: UV–vis and GPC characterization of the rupture of 4-AZB isomers in water.
Fig. 5: Quantum-chemical calculation of the force-induced rupture of AZB isomers.
Fig. 6: Mechanical performance of 4-AZB-embedded mechanically active gel networks.

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Acknowledgements

We thank Y. Li and X. Wang for helpful discussions. This work was supported mainly by the National Natural Science Foundation of China (nos. T2225016, 12002149, T2322010 and 11934008) to Y. Cao, Y.L., B.X. and W.W., the National Key R&D Program of China (grant no. 2020YFA0908100) to Y. Cao, the Fundamental Research Funds for the Central Universities (grant no. 020514380274) to Y. Cao and the Natural Science Foundation of Jiangsu Province (no. BK20220120) to B.X. This work was partially supported by JSPS KAKENHI (grant no. JP22H04968) to J.P.G. and T.N., by JST, PRESTO, Japan (grant no. JPMJPR2098) to T.N. and by a scholarship of MEXT Japan to Z.J.W.

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Authors and Affiliations

  1. Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid-State Microstructure, Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, Department of Physics, Nanjing University, Nanjing, China

    Yiran Li, Bin Xue, Jiahui Yang, Jing Liu, Yanyan Zhou, Junsheng Zhang, Zhenshu Zhu, Wei Wang & Yi Cao

  2. Medical School, Nanjing University, Nanjing, China

    Yiran Li

  3. Hokkaido University, Sapporo, Japan

    Julong Jiang & Satoshi Maeda

  4. College of Chemistry, Jilin University, Changchun, China

    Mengjiao Wu & Yulan Chen

  5. Tianjin Key Laboratory of Molecular Optoelectronic Science, Department of Chemistry, Tianjin University, Tianjin, China

    Yuan Yuan

  6. Graduate School of Life Science, Hokkaido University, Sapporo, Japan

    Zhi Jian Wang

  7. Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo, Japan

    Zhi Jian Wang, Yu Harabuchi, Tasuku Nakajima, Satoshi Maeda & Jian Ping Gong

  8. Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan

    Tasuku Nakajima & Jian Ping Gong

  9. Institute for Brain Sciences, Nanjing University, Nanjing, China

    Yi Cao

  10. Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, China

    Yi Cao

  11. Chemistry and Biomedicine Innovation Center, Nanjing University, Nanjing, China

    Yi Cao

  12. MOE Key Laboratory of High Performance Polymer Materials and Technology, Nanjing University, Nanjing, China

    Yi Cao

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  1. Yiran Li
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Y. Cao, J.P.G., T.N., S.M. and W.W. conceived the idea and designed the study. Y.L. performed the experiments and analysed the results. J.L., J.Z. and Z.Z. performed some of the SMFS experiments. J.Y., B.X. and Z.J.W. prepared the hydrogel samples and tensile tests. Y.Z., M.W. and Y. Chen performed some of the ultrasonication tests. Y.Y., J.J., Y.H., and S.M. performed the quantum calculations. Y. Cao, W.W., S.M. and J.P.G. wrote and refined the paper. Y. Cao and W.W. supervised the project. All authors discussed the results.

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Correspondence to Wei Wang, Satoshi Maeda, Jian Ping Gong or Yi Cao.

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Nature Chemistry thanks Constantino Creton, Anne-Sophie Duwez and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Tables 1–6, Figs. 1–21, text, references and the Cartesian coordinates of the optimized structures.

Supplementary Data 1

Source data for Supplementary Figures.

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Source Data Fig. 2

Force curves and statistical source data.

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Statistical source data.

Source Data Fig. 4

GPC and UV–vis curves presented in Fig. 4.

Source Data Fig. 5

Distance–force curves presented in Fig. 5.

Source Data Fig. 6

Stress–strain curves and statistical source data presented in Fig. 6.

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Li, Y., Xue, B., Yang, J. et al. Azobenzene as a photoswitchable mechanophore. Nat. Chem. 16, 446–455 (2024). https://doi.org/10.1038/s41557-023-01389-6

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