Synthesis and properties of fluorinated polyimides from a new unsymmetrical diamine:: 1,4-(2′-trifluoromethyl-4′,4"-diaminodiphenoxy)benzene

A new aromatic, unsymmetrical ether diamine with a trifluoromethyl pendent group, 1,4-(2'-trifluoromethyl-4',4"-diaminodiphenoxy)benzene, was successfully synthesized in three steps with hydroquinone as a starting material and polymerized with various aromatic tetracarboxylic acid dianhydrides, including 4,4'-oxydiphthalic anhydride, 3,3,4,4'-benzophenone tetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride, and pyromellitic dianhydride, via a conventional two-step thermal or chemical imidization method to produce a series of fluorinated polyimides. The polyimides were characterized with solubility tests, viscosity measurements, IR, H-1 NMR, and C-13 NMR spectroscopy, X-ray diffraction studies, and thermogravimetric analysis. The polyimides had inherent viscosities of 0.56-0.77 dL/g and were easily dissolved in both polar, a protic solvents and common, low-boiling-point solvents. The resulting strong and flexible polyimide films exhibited excellent thermal stability, with decomposition temperatures (at 5% weight loss) above 522 degrees C and glass-transition temperatures in the range of 232-272 degrees C. Moreover, the polymer films showed outstanding mechanical properties, with tensile strengths of 74.5-121.7 MPa, elongations at break of 6-13%, and initial moduli of 1.46-1.95 GPa, and good dielectric properties, with low dielectric constants of 1.82-2.53 at 10 MHz. Wide-angle X-ray diffraction measurements revealed that these polyimides were predominantly amorphous. These outstanding combined features ensure that the polymers are desirable candidate materials for advanced microelectronic applications. (c) 2006 Wiley Periodicals, Inc.