Figure 1.

Schematic illustration of the thermally stable supercooled liquid and shear-triggered lighting-up crystallization of DPP8. (A) Chemical structure of DPP8 and its derivatives. A subtle force balance between two different intermolecular interactions acting in opposite directions makes DPP8 exhibit small ΔG between supercooled liquid and crystalline solid phases, resulting in intriguing thermally stable supercooled liquid. Fluorescence images are from crystalline solids of the derivatives. (B) Reversible phase transformation with large optical property change between the two forms by means of independent stimuli. (C) Nucleation is restricted in DPP8 supercooled liquid due to an unattainable yet required large critical radius (r*), which results from small ΔG between two phases, at 25 and 120 °C. However, when molten DPP8 was cooled to −50 °C, subsequent heating developed crystallization. (D) Shear-triggered lighting-up crystallization of DPP8. Photographs (A, B, and D) were taken under 365 nm UV light.