Intrinsic emission and tunable phosphorescence of perfluorosulfonate ionomers with evolved ionic clusters

Intrinsic emission from unorthodox luminogens without traditional conjugated building blocks is drawing increasing attention. However, the emission mechanism is still controversial. Herein, we demonstrate the intriguing emission from perfluorosulfonate ionomers (PFSIs), which can be explained by the clustering triggered emission (CTE) mechanism. Despite being free of any conventional chromophores, PFSIs exhibit bright emission and multi-color phosphorescence (77 K) in concentrated solutions, powders and membranes with obvious aggregation-induced emission (AIE) characteristics. Clustered sulfonic acids are responsible for the light emission, and their connection and evolution are deeply explored via X-ray diffraction (XRD) and small angel X-ray scattering (SAXS), in which the electron overlap determined by the clustered status results in the extended conjugation and simultaneously rigidified conformations. These results demonstrate that it is feasible to use fluorescence analysis to explore the ionic cluster structure and evolution of PFSI, and it can be applied in the pure organic luminescent field as well.