Synthesis of an acrylic copolymer bearing fluorescent dye pendants and characterization as a luminescence conversion material in fabrication of a luminescence conversion light-emitting diode

A polymerizable arcyl group was incorporated into modified 4-N,N-diphenyl-9-(4-tert-butylphenyl)-1,8-naphthalimide (DBN), and the resulting compound (P-DBN) was copolymerized with methyl methacrylate (MMA) to obtain the corresponding copolymer (PMMA-co-DBN). A DBN/PMMA blend film underwent phase separation upon heating, while PMMA-co-DBN did not exhibit the phase separation problem under the same conditions. However, the fluorescence quantum yield (Фrel) of P-DBN was much lower (65%) than that of free DBN, and the Фrel of PMMA-co-DBN (36%) was lower still. The luminescent output power of a luminescence conversion light-emitting diode (LUCO LED), fabricated using PMMA-co-DBN, was not detectably changed during 288 h of operation at 20 mA, due to adequate stability of the copolymer under the experimental conditions.