Multiscale Morphological Visualization of a Semi-crystalline Polymer by a Polymorphic AIE Marker

Direct spatial mapping of polymer morphologies remains challenging owing to poor imaging contrast across different microstructures. Now this conundrum is addressed by a polymorphic molecule with aggregation-induced emission (AIE), capable of selectively lighting up amorphous and crystalline phases with distinct color. The polymorphic behaviors of the AIE molecule embedded within polymer network is dependent on the size of nano-confinement: a thermodynamically stable polymorph of the AIE molecule with green emission is stabilized in amorphous phase, while a metastable polymorph with yellow emission is confined in crystalline phase. The information on polymer crystalline and amorphous phases is transformed into distinct fluorescence colors, allowing a single AIE molecule as a fluorescent marker for multiscale visualization of polymer morphologies in terms of amorphous and crystalline phases distribution, quantitative polymer crystallinity measurement, and spatial morphological arrangement. The proposed strategy provides a correlation between microscopic morphologies and macroscopic optical signals, opens an avenue of fluorescence imaging in materials science.