Supramolecular mechanofluorophores based on charge-transfer interactions between fluorescent electron-rich pyrene and electron-deficient naphthalene diimide(s) are newly developed and show turn-on fluorescence upon application of mechanical forces.

One promising application of self-healing polymeric materials is biomedical use. Although chargetransfer (CT) interactions have been employed to construct self-healing polymers as well as other reversible bonds and interactions, their potential for biomedical applications have never been investigated. In this study, we fabricated self-healable and cell-compatible polyurethane elastomers cross-linked by CT complexes between electron-rich pyrene (Py) and electron-deficient naphthalene diimide (NDI) by simple blending of two linear polymers with Py or NDI as a repeating unit. The elastomers at different blend ratios self-healed damage during 1 day in mild conditions including in air and water at 30-100 °C. The mechanical properties of damaged elastomers were almost restored after healing in air at 100 °C, and even in air at 30 °C and in water at 70 °C, healing was also possible to a certain extent. The good cell-compatibility of the polyurethane elastomers was demonstrated by culturing two kinds of cells on the thin film substrates.