New Functions of Rotaxane-based Supramolecular Mechanophores via Structural Modification

Organic polymer materials are utilized in a wide range of applications, making the extension of their lifespan crucial for resource conservation and cost reduction. Understanding molecular-level force transduction within bulk polymers is key to preventing material degradation. Mechanochromic mechanophores, molecular structures that exhibit changes in absorption and/or fluorescence in response to mechanical stimuli, have gained significant attention as reliable tools for probing small forces at the molecular scale. We have developed supramolecular mechanophores that alter their fluorescence properties through the disruption of intra- or intermolecular interactions upon mechanical stimulation. Unlike traditional mechanophores, these supramolecular mechanophores do not require covalent bond cleavage for activation, allowing pN-scale forces to be visualized instantly and reversibly. Among our motifs, “rotaxane-based supramolecular mechanophores” stand out for their versatile molecular architectures, enabling new photofunctions and distinctive mechanoresponsiveness. In this review, we show how replacing luminophores or varying stopper sizes alters the photophysical properties and activation behavior of rotaxane-based supramolecular mechanophores.