Preparation and properties of melt‐processable polyimides based on fluorinated aromatic diamines and aromatic dianhydrides

Two series of melt‐processable polyimides were prepared from 4,4′‐bis(3‐amino‐5‐trifluoromethylphenoxy)biphenyl (m‐6FBAB) and 4,4′‐bis(4‐amino‐5‐trifluoromethylphenoxy) biphenyl (p‐6FBAB) with various aromatic dianhydrides. The effects of the chemical structures of the polyimides on their properties, especially the melt processability and organic solubility, were investigated. The experimental results demonstrate that some of the fluorinated aromatic polyimides showed good melt processability at elevated temperatures (250–360°C) with relatively low melt viscosities and could be melt‐molded to produce strong and tough polyimide sheets. Meanwhile, the polyimides showed excellent organic solubility in both polar aprotic solvents and common solvents to give stable polyimide solutions with high polymer concentrations and relatively low viscosities. Thus, we prepared high‐quality polyimide films by casting the polyimide solutions on glass plates followed by baking at relatively low temperatures. The polyimides derived from m‐6FBAB showed better melt processability and solubility than the p‐6FBAB based polymers. The melt‐processable polyimides showed a good combination of thermal stability and mechanical properties, with decomposition temperatures of 547–597°C, glass‐transition temperatures in the range 205–264°C, tensile strengths of 81.3–104.9 MPa, and elongations at break as high as 19.6%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008