The photoluminescence (PL) properties of four types of blue fluorescent semi-aliphatic polyimides (PIs) derived from aromatic dianhydrides (ODPA, BPDA, HQDEA, and BPADA) and an alicyclic diamine (DCHM) were investigated at temperatures ranging from room temperature (RT, 298 K) to 30 K to analyse the origins of their non-radiative relaxation (NR) processes. These PIs exhibited significant increases in fluorescence (FL) intensity and lifetimes when lowering the temperature, stabilising below 100 K. The PIs containing ether (–O–) linkages showed a shoulder peak at around 500 nm below 150 K, which is attributable to phosphorescence (PH). These results show that the NR deactivation at RT includes three processes: intersystem crossing (ISC) from the excited singlet (S₁) to the triplet (T₁) state, temperature-dependent NR from the S₁ state, which becomes suppressed below around 100 K, and temperature-independent NR. Based on the analyses of the temperature dependences, polymer structures, and quantum chemical analysis of molecular orbitals, we contemplate that the temperature-dependent NR is attributable to the excitation quenching by defect states mediated by excitation migration, and the temperature-independent NR may be caused by the deactivation of the excited state induced by molecular vibrations.

中文翻译：

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低温下半脂肪族聚酰亚胺双荧光和磷光发射的光物理分析


研究了由芳香族二酐（ODPA、BPDA、HQDEA 和 BPADA）和脂环族二胺 (DCHM) 衍生的四种蓝色荧光半脂肪族聚酰亚胺 (PI) 在室温 (RT) 范围内的光致发光 (PL) 特性。 ，298 K）到 30 K 来分析其非辐射弛豫（NR）过程的起源。当降低温度并稳定在 100 K 以下时，这些 PI 的荧光 (FL) 强度和寿命显着增加。含有醚 (-O-) 键的 PI 在 150 K 以下约 500 nm 处显示出肩峰，这归因于磷光（PH）。这些结果表明，室温下的 NR 失活包括三个过程：从激发单线态 (S ₁ ) 到三线态 (T ₁ ) 的系间窜越 (ISC)、温度依赖性来自 S ₁ 态的 NR，在低于 100 K 左右时被抑制，以及与温度无关的 NR。基于对温度依赖性、聚合物结构和分子轨道的量子化学分析的分析，我们认为温度相关的NR可归因于激发迁移介导的缺陷态的激发猝灭，而与温度无关的NR可能是由分子振动引起的激发态失活引起。