Unprecedented strong blue photoluminescence from hyperbranched polycarbonate: From its fluorescence mechanism to applications

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.