Supramolecular Hyperbranched Poly(amino ester)s with Homogeneous Electron Delocalization for Multi-Stimuli-Responsive Fluorescence

Nonconventional luminogens without conjugated chromophores have attracted much interest for their intriguing fluorescence and potential wide applications. Their emission mechanism, however, remains an open question. Herein, hyperbranched poly(amino ester) (HPAE) with novel structure is synthesized through a simple one-pot polycondensation reaction. The HPAE exhibits strong fluorescence and aggregation-induced emission (AIE) characteristic. Transmission electron microscopy and theoretical calculation results demonstrate that the fluorescence is attributed from electron delocalization in the supramolecular self-assemblies of HPAE. Meanwhile, supramolecular self-assemblies, induced by the synergy effect of inter/intramolecular hydrogen bond and amphipathicity of HPAE, rigidify the molecule conformation, leading to enhanced fluorescence. Furthermore, the HPAE exhibits single-color emission due to its generation of homogeneous electron delocalization. Interestingly, such HPAE shows multi-stimuli-responsive fluorescence to solvent, temperature, pH, and Fe³⁺. Therefore, this work not only provides an important step forward in exploring the emission mechanism of nonconventional luminogens, but also develops a multi-functional unconjugated AIE probe.