Abstract
A novel rigid semi-alicyclic dianhydride 9,10-difluoro-9,10-bis(trifluoromethyl)-9,10-dihydroanthracene-2,3,6,7-tetracarboxylic acid dianhydride (8FDA) was reported, and its single crystal X-ray diffraction result revealed the existence of the polymorphic structure in this compound. The detail geometric configuration transition during the synthesized process was investigated, exhibiting a transition of from trans- to cis- when the hydroxyl groups were substituted by fluoride with diethylaminosulfur trifluoride (DAST). Compared with the dianhydride 4,4′-(Hexaflouroisopropylidene) diphthalic anhydride (6FDA) and 1S,2R,4S,5R-cyclohexanetetracarboxylic dianhydride (HPMDA), the resulting polyimide (PI) films based on 8FDA exhibited an obviously higher glass transition temperature (Tg, 401 °C) and a much lower coefficient of thermal expansion (CTE, 14 ppm K−1). This indicates that 8FDA is an ideal building block in high-performance soluble PIs with low CTE.
Highlights
The demand of high-performance transparent polymer substrates increases dramatically with the rapid development of flexible electronics, especially for the flexible OLED displays [1,2,3].Because of the severe conditions during the TFT fabrication for OLED displays, the ideal flexible transparent substrates require a high Tg over 370 ◦ C, a small coefficient of thermal expansion (CTE) value lower than 20 ppm K−1, high transparency, and so on [4]
Because of the severe conditions during the TFT fabrication for OLED displays, the ideal flexible transparent substrates require a high Tg over 370 ◦ C, a small CTE value lower than 20 ppm K−1, high transparency, and so on [4]
Due to their outstanding chemical and irradiation resistance, high thermal stability, and excellent optical and mechanical properties, transparent PI films became the best choice for transparent substrates in flexible OLED displays [5,6,7,8,9]
Summary
The demand of high-performance transparent polymer substrates increases dramatically with the rapid development of flexible electronics, especially for the flexible OLED displays [1,2,3]. Because of the severe conditions during the TFT fabrication for OLED displays, the ideal flexible transparent substrates require a high Tg over 370 ◦ C, a small CTE value lower than 20 ppm K−1 , high transparency, and so on [4]. Due to their outstanding chemical and irradiation resistance, high thermal stability, and excellent optical and mechanical properties, transparent PI films became the best choice for transparent substrates in flexible OLED displays [5,6,7,8,9]. A rigid semi-alicyclic dianhydride 8FDA was developed to prepare high-performance, transparent PIs. The rigid structure of 8FDA was expected to increase the Tg and decrease the CTE at the same time. The single crystal X-ray diffraction test proved that 8FDA is a novel polymorphic crystal [35]
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