Materials that receive force (mechanical stimulus) and show changes in appearance color or emission (fluorescence) characteristics are expected to be used in various ways because the damage and force received by the material can be easily visualized and evaluated. ..Especially recently, mainly in the field of polymer chemistry, research on molecular skeletons called "mechanophores" that show color changes under mechanical stimulation has been actively conducted.However, since the existing mechanophore needs to break the covalent bond, there are problems such as poor reversibility.

　The research group needs to focus on rotaxane, one of the interlocking molecules (a molecule in which several parts are mechanically combined), which has been studied for many years in the field of supramolecular chemistry, and to break covalent bonds. We have been developing a supramolecular mechanophore.This time, we have developed a rotaxane-type supramolecular mechanophore that uses blue, green, and orange fluorescent groups (the part that emits fluorescence), and by introducing it into polyurethane, each fluorescent color changes instantly and reversibly in response to expansion and contraction. We have developed a rubber material that can be turned ON / OFF repeatedly as many times as necessary.This demonstrated that the same mechanism can be used to obtain responsiveness to similar mechanical stimuli even if the fluorophore is changed.

　There have been many reports of organic materials that emit white light, but this is the first material that switches white fluorescence ON / OFF by mechanical stimulation.Since such materials can detect mechanical stimuli reversibly and sensitively, they are expected to be applied to sensors in various materials and to visualization and quantitative evaluation of damage received by materials.

Paper information:[ACS Central Science] Rotaxane-based Mechanophores Enable Polymers with Mechanically Switchable White Photoluminescence