Mechanochromism of polyurethane based on folding–unfolding of cyano-substituted oligo(p-phenylene) vinylene dimer

Abstract

The incorporation of mechanophores, motifs that transform mechanical stimulus into chemical reaction or optical variation, allows creating materials with stress-responsive properties. The most widely used mechanophore generally features a weak bond, but its cleavage is typical an irreversible process. Here, we showed that this problem can be solved by folding–unfolding of a molecular tweezer. We systematically studied the mechanochromic properties of polyurethanes with cyano-substituted oligo(p-phenylene) vinylene (COP) tweezer (DPU). As a control experiment, a class of polyurethanes containing only a single COP moiety (MPU) was also prepared. The DPU showed prominent mechanochromic properties, due to the intramolecular folding–unfolding of COP tweezer under mechanical stimulus. The process was efficient, reversible and optical detectable. However, due to the disability to form either intramolecular folding or intermolecular aggregation, the MPU sample was mechanical inert.

Graphical abstract

Keywords

mechanochromism / molecular tweezer / folding–unfolding / cyano-substituted oligo(p-phenylene) vinylene / polyurethane

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Disclosure of potential conflicts of interest

The authors declare that they have no conflict of interest.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 52103141 and 51803090) and the Natural Science Foundation of Jiangsu Province (Grant Nos. BK20181025 and BK20191022) for financial support.

Electronic supplementary information

Supplementary materials can be found in the online version at https://doi.org/10.1007/s11706-023-0640-1, which include Scheme S1, Figs. S1‒S46, and Videos S1 and S2.

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