High Performance Soluble Polyimides from Ladder-Type Fluorinated Dianhydride with Polymorphism

摘要

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 1 S ,2 R ,4 S ,5 R -cyclohexanetetracarboxylic dianhydride (HPMDA), the resulting polyimide (PI) films based on 8FDA exhibited an obviously higher glass transition temperature ( T g , 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.