Imide-DOPO derivative endows epoxy resin with excellent flame retardancy and fluorescence without losing glass transition temperature

The aggregation and plasticizing of most 9,10-dihydro-9-oxa-10-phosphaphenanthrene −10-oxide (DOPO) derived additives often result in deteriorating the glass transition temperature and mechanical properties of epoxy resins (EP). To address this issue, an imide-DOPO derivative (BMP) with bulky aromatic structure was successfully synthesized. Benefitting from the space hindering and intermolecular interaction (π-π stacking) of BMP, it does not lead to the loss of glass transition temperature, and only a minor damage of tensile and impact strengths is caused. Additionally, with only 0.78 wt% loading of phosphorus (10 wt% BMP), the EP/BMP_10% achieves UL-94 V-0 and high LOI value of 35%. Simultaneously, both the heat release rate and total smoke production are markedly reduced. More excitingly, BMP exhibits aggregation-induced emission enhancement of fluorescence in the N, N-dimethylformamide/water mixed solution as well as epoxy resin. This work provides a new insight in simultaneously imparting flame retardancy and fluorescence to epoxy resins without losing glass transition temperature.