Photoluminescence Properties of Copolyimides Containing Naphthalene Core and Analysis of Excitation Energy Transfer between the Dianhydride Moieties

Long‐Lived Luminescence Emitted from Imide Compounds Dispersed in Polymer Matrices after Continuous Ultraviolet Irradiation and its Relation to Oxygen Quenching

“…In air, unlike fluorescent ICs (NT‐IC, s BP‐IC, and OD‐IC), 2Br‐IC exhibited weak FL at 415 nm and a strong and broad RTP at 528 nm, whereas BT‐IC exhibited only a broad RTP with vibronic structures at 520 nm. The ISC and PH processes in 2Br‐IC are promoted by heavy bromines, which is called the heavy atom effect [14–17] . In contrast, the T 1 state is generated with a high quantum yield in BT‐IC owing to its benzophenone moiety [59] .…”

“…However, heavy metals adversely affect the environment and human health. To avoid such effects and reduce costs, RTP has been realized by introducing heavy halogens, such as Cl, Br, and I, into luminescent polymer materials [14–17] . We recently reported polyimides (PIs) that exhibit RTP by substituting heavy halogens in the aromatic main chain [14,15,17,18] .…”

“…In this study, we synthesized three fluorescent imide compounds (ICs), N,N′ ‐dicyclohexylnaphthalene‐2,3,6,7‐tetracarboxylic diimide (NT‐IC), [17] N,N′ ‐dicyclohexylbiphenyl‐3,3′,4,4′‐tetracarboxylic diimide ( s BP‐IC), and N,N′ ‐dicyclohexyl‐4,4′‐oxydiphthalic imide (OD‐IC), and two phosphorescent ICs, 1,5‐dibromo‐ N,N′ ‐dicyclohexylnaphthalene‐2,3,6,7‐tetracarboxylic diimide (2Br‐IC) and N,N′ ‐dicyclohexylbenzophenone‐3,3′,4,4′‐tetracarboxylic diimide (BT‐IC) (Figure 1). It was determined that these ICs dispersed in poly(methyl methacrylate) (PMMA) exhibited an intriguing delayed luminescence phenomenon at room temperature in air, known as prolonged irradiation‐induced delayed luminescence (PIDL).…”

“…To avoid such effects and reduce costs, RTP has been realized by introducing heavy halogens, such as Cl, Br, and I, into luminescent polymer materials. [14][15][16][17] We recently reported polyimides (PIs) that exhibit RTP by substituting heavy halogens in the aromatic main chain. [14,15,17,18] The PIs exhibit reddish to bright green RTP with very large Stokes shifts of 10,000-12,200 cm À 1 due to the inclusion of bromine or iodine.…”

“…[14][15][16][17] We recently reported polyimides (PIs) that exhibit RTP by substituting heavy halogens in the aromatic main chain. [14,15,17,18] The PIs exhibit reddish to bright green RTP with very large Stokes shifts of 10,000-12,200 cm À 1 due to the inclusion of bromine or iodine. They are completely colorless and transparent films because the biphenyl-based dianhydride moiety has intramolecular rotational freedom and the steric hindrance by the rotation prevents aggregation.…”