Magic cyclodextrins turn blue on rubbing: mechanochromism

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Prof. Aoki wrote this short summary for our blog on their unique achievement:

In this study, we have used cyclodextrins (CDs) as mechanical-force transducers. Mechanochromic functionality, i.e., a color change in response to mechanical stimuli, can be used to visualize stress and damage in materials [1]. The introduction of mechanophores, which are building blocks that change their chemical structure in response to mechanical stimuli, into polymer matrices, especially into the polymer mid-chain, is an effective method to endow materials with such mechanochromism.
               Although mechanophore-containing polymers have the advantage of easy fabrication, it should also be noted here that polymers are considered to have relatively ill-defined structures due to the often inevitable molecular-weight distribution. To investigate the relationship between structure and mechanoresponsiveness using an easy-to-fabricate system, we focus herein on CDs as structurally well-defined molecules. 

               Consequently, mechanophores with CDs can easily produce a high level of activated states per volume of a specific material due to their high mechanoresponsiveness and low molecular weight, which is particularly important for the molecular design of mechanophore materials that exhibit color change, release small molecules, or engage in other useful reactions.

[1] Sugita, Y., Aoki, D., Otsuka, H. (2022) Mechanochromic cyclodextrins. Chem. Commun. DOI: 10.1039/d2cc00363e

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