A Smart Single‐Fluorophore Polymer: Self‐Assembly Shapechromic Multicolor Fluorescence and Erasable Ink

Abstract A novel smart fluorescent polymer polyethyleneimine‐grafted pyrene (PGP) is developed by incorporating four stimuli‐triggers at molecular level. The triggers are amphiphilicity, supramolecular host–guest sites, pyrene fluorescence indicator, and reversible chelation sites. PGP exhibits smart deformation and shape‐dependent fluorescence in response to external stimuli. It can deform into three typical shapes with a characteristic fluorescence color, namely, spherical core–shell micelles of cyan‐green fluorescence, standard rectangular nanosheets of yellow fluorescence, and irregular branches of deep‐blue fluorescence. A quasi‐reversible deformation between the first two shapes can be dynamically manipulated. Moreover, driven by reversible coordination and the resulting intramolecular photoinduced electron transfer, PGP can be used as an aqueous fluorescence ink with erasable and recoverable properties. The fluorescent patterns printed by PGP ink on paper can be rapidly erased and recovered by simple spraying a sequence of Cu²⁺ and ethylene diamine tetraacetic acid aqueous solutions. This erase/recover transformation can be repeated multiple times on the same paper. The multiple stimulus responsiveness of PGP makes it have potential applications in nanorobots, sensing, information encryption, and anticounterfeiting.