Polymorph Selectivity of AIE Luminogen under Nano-Confinement to Visualize Polymer Microstructure
Despite the huge progress of luminescent molecular assemblies over the past decade, it is still challenging to understand their confined behavior in semi-crystalline polymers for constrained space recognition. Here, we report a polymorphic luminogen with aggregation-induced emission (AIE), capable of selective growth in polymer amorphous and crystalline phases with distinct color. The polymorphic behaviors of the AIE luminogen embedded within polymer network is dependent on the size of nano-confinement: a thermodynamically stable polymorph of the AIE luminogen 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 luminogen as a fluorescent marker for visualization of polymer microstructures in terms of amorphous and crystalline phases distribution, quantitative polymer crystallinity measurement, and spatial morphological arrangement. Our findings demonstrate that confinement of AIE luminogen in polymer network can achieve the free space recognition, also provide a correlation between microscopic morphologies and macroscopic optical signals. We envision our strategy will inspire the development of other materials with spatial confinement to incorporate AIE luminogen for various applications.