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. 2021 Jul 9;12:4243. doi: 10.1038/s41467-021-24501-1

Fig. 1. Principle of a mechanochromic torsional spring.

Fig. 1

a A donor-acceptor (DA) unit with a large torsional angle φ is covalently incorporated into a polymer chain. b Stretching of the polymer backbone causes a decrease of φ. c Schematic reversible shift of the UV-vis-absorption band as a response to elongational stress. d Structure of the DA-system reported here based on diphenyldiketopyrrolopyrrole (PhDPP).