Novel Oligomers of 9,9-Dialkylated Fluorenes for Thermally Stable Hole-Transport Materials in OLEDs
作者:Makoto Kimura、Toshihiko Kurata、Yasuhiko Sawaki、Yasumasa Toba、Toshio Enokida、Katsuhiko Takagi
DOI:10.1246/bcsj.80.418
日期:2007.1.15
Using 9,9-dialkyl-functionalized fluorenes as monomers, novel fluorene-based oligomers were prepared in order to improve the thermal stability of a typical hole-transport material (HTM), N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), in organic light emitting diodes (OLEDs). 2,7-Bis(diphenylamino)fluorene was utilized as a TPD unit throughout the present synthetic work. 9,9-Bis(2-methylallyl)fluorene and its TPD congener underwent a new cyclopolymerization reaction affording six-membered oligomers under acid catalysis with p-toluenesulfonic acid. Intermolecular Suzuki coupling of a 9,9-bis(p-bromobenzyl)fluorene analogue with the corresponding bis-boronate afforded a new oligomer containing the TPD substructure. These oligomers (3 and 6) for use as HTMs have high glass-transition temperatures (Tg’s) (147 and 167 °C, respectively); the values are much higher than the Tg for TPD (63 °C). These materials are soluble in organic solvents to allow easy processing for preparing layered devices, though their electroluminescent performances were lower than that of the single molecule TPD.
为了提高有机发光二极管(OLED)中典型的空穴传输材料(HTM)--N,N′-双(3-甲基苯基)-N,N′-二苯基联苯胺(TPD)的热稳定性,本研究以 9,9-二烷基官能化芴为单体,制备了新型芴基低聚物。在整个合成过程中,2,7-双(二苯基氨基)芴被用作 TPD 单元。在对甲苯磺酸的酸催化下,9,9-双(2-甲基烯丙基)芴及其 TPD 同系物发生了新的环聚合反应,生成了六元低聚物。9,9-双(对溴苄基)芴类似物与相应的双硼酸酯发生分子间铃木偶联反应,产生了含有 TPD 子结构的新低聚物。这些用作 HTM 的低聚物(3 和 6)具有很高的玻璃转化温度(Tg)(分别为 147 和 167 °C);其数值远高于 TPD 的 Tg(63 °C)。虽然这些材料的电致发光性能低于单分子 TPD,但它们可溶于有机溶剂,便于加工制备分层器件。