A polyfluorinated aromatic diamine, 3,3 ', 5,5 '-tetrafluoro-4,4 '-diaminodiphenylmethane (TFDAM), was synthesized and characterized. A series of polyimides, PI-1-PI-4, were prepared by reacting the diamine with four aromatic dianhydrides via a one-step high-temperature polycondensation procedure. The obtained polyimide resin had moderate inherent viscosity (0.56-0.68 dL/g) and excellent solubility in common organic solvents. The polyimide films exhibited good thermal stability, with an initial thermal decomposition temperature of 555 degrees C-621 degrees C, a 10% weight loss temperature of 560 degrees C-636 degrees C, and a glass-transition temperature of 280 degrees C-326 degrees C. Flexible and tough polyimide films showed good tensile properties, with tensile strength of 121-138 MPa, elongation at break of 9%-12%, and tensile modulus of 2.2-2.9 GPa. The polyimide films were good dielectric materials, and surface and volume resistance were on the order of a magnitude of 10(14) and 10(15) Omega cm, respectively. The dielectric constant of the films was below 3.0 at 1 MHz. The polyfluorinated films showed good transparency in the visible-light region, with a cutoff wavelength as low as 302 nm and transmittance higher than 70% at 450 nm. (c) 2006 Wiley Periodicals, Inc.