Synthesis and characterization of fluorinated polyimides derived from novel unsymmetrical diamines

Two kinds of aromatic, unsymmetrical diamines with ether–ketone group, 3-amino-4′-(4-amino-2-trifluoromethylphenoxy)-benzophenone and 4-amino-4′-(4-amino-2-trifluoromethylphenoxy)-benzophenone, were successfully synthesized with two different synthetic routes. Then, they were polymerized with 4,4′-oxydiphthalic anhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, and 2,2′-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride to form a series of fluorinated polyimides via a conventional two-step thermal or chemical imidization method. The resulting polyimides were characterized by measuring their solubility, viscosity, mechanical properties, IR-FT, and thermal analysis. The results showed that the polyimides had inherent viscosities of 0.48–0.68 dl/g and were easily dissolved in bipolarity solvents and common, low-boiling point solvents. Meanwhile, the resulting strong and flexible polyimide films exhibited excellent thermal stability, e.g., decomposition temperatures (at 10% weight loss) are above 575 °C and glass-transition temperatures in the range of 218–242 °C. The polymer films also showed outstanding mechanical properties, such as tensile strengths of 86.5–132.8 MPa, elongations at break of 8–14%, and initial moduli of 1.32–1.97 GPa. These outstanding combined features ensure that the polymers are desirable candidate materials for advanced applications.

Two kinds of novel diamines were designed and synthesized. The unsymmetrical structure, CF3 and ether–ketone group were introduced to polymer chains to improve its solubility. The CF3 group could result in the polyimides with lower moisture absorption. The ketone group could crosslink with amine group, that can make the polyimides exhibit better thermal properties and mechanical properties.Figure optionsDownload as PowerPoint slide