A novel kind of water‐soluble fluorescent hyperbranched poly(amino ester) (PAE) is prepared through a one‐pot polycondensation reaction of citric acid (CA) and N‐methyldiethanolamine (NMDEA). The PAE exhibits enhanced and red‐shift fluorescence with increasing solution concentration, showing distinct aggregation‐induced emission character. Interestingly, the resulting PAE exhibits tunable photoluminescence from blue, cyan, and green to red irradiated by altering the excitation wavelengths. Such unique emission of non‐conjugated PAE is attributed to the clustering of ester and tertiary amine groups derived from PAE self‐assembly aggregates. Moreover, the fluorescence of PAE is very sensitive to Fe3+ ions. The facile preparation and unique optical features make PAE potentially useful in numerous applications such as multicolor cellular imaging, Fe3+ ions probe, and light‐emitting diodes.

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Fluorescent polymers without π‐aromatic structure have been a hot spot in recent years. Polycarbonate has been applied in industry for many years; however, the fluorescent behavior of the polycarbonate has not been reported yet. Therefore, a kind of hyperbranched polycarbonate (HBPC) has been synthesized under solvent and catalyst‐free condition. Unexpectedly, the novel HBPC containing no conventional chromophores exhibits unimagined bright blue fluorescence under the irradiation of 334 nm UV light. The intensity of the HBPC fluorescence is rising in step with its concentration going up, showing an aggregation‐induced enhanced emission (AIEE). It is more interestingly that the fluorescence of HBPC could be affected by pH and metal ions. Specifically, the fluorescence of HBPC is extraordinarily sensitive to the Fe3+. TEM micrographs show that the HBPC self‐assemble to clustering in water. Rudimentary investigation illustrates that the formation of cluster accounts for the unexpected fluorescence in the HBPC. This phenomenon is typical of Clustering‐Triggered emission (CTE). This study exhibits a novel route for the design of CTE fluorescent polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3690–3696

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.

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