Sulfonated ethylenediamine–acetone–formaldehyde condensate: preparation, unconventional photoluminescence and aggregation enhanced emission†
The unconventional photoluminescence of sulfonated acetone–formaldehyde (SAF) and acetone–formaldehyde (AF) condensates are uncovered and studied in this work. Their fluorescence had been ignored although they were developed and commercialized as water reducing agents in the concrete industry decades ago. More importantly, based on the traditional mechanism of the Mannich reaction, sulfonated ethylenediamine–acetone–formaldehyde (SEAF) was successfully synthesized by introducing imino groups to SAF. It shows highly enhanced fluorescence both in solution and the solid state. The emission mechanism of these polymers is proposed to be via the cluster of carbonyl groups within the long linear nonconjugated chain. Hydroxy, sulfonic and amino groups in SEAF can produce strong ionic and hydrogen bonds, which contribute to its fluorescent enhancement. Furthermore, it is more interesting that SAF and SEAF possess an aggregation-enhanced emission (AEE) effect, while AF shows aggregation-caused quenching (ACQ). This result confirms the previous report that hydrogen bonds can induce AEE effects. Our study provides a novel perspective for the design of water-soluble luminescent materials with green photoluminescence and AEE property.