Synthesis and characterization of novel fluorinated aromatic polyimides derived from 1,1‐bis(4‐amino‐3,5‐dimethylphenyl)‐1‐(3,5‐ditrifluoromethylphenyl)‐2,2,2‐trifluoroethane and various aromatic dianhydrides

A novel fluorinated aromatic diamine, 1,1-bis(4-amino-3,5-dimethylphenyl)-1-(3,5-ditrifluoromethylphenyl)-2,2,2-trifluoroethane (9FMA), was synthesized by the coupling reaction of 3′,5′-ditrifluoromethyl-2,2,2-trifluoroacetophenone with 2,6-dimethylaniline under the catalysis of 2,6-dimethylaniline hydrochloride. A series of fluorinated aromatic polyimides were synthesized from 9FMA and various aromatic dianhydrides, including pyromellitic dianhydride, 3,3′4,4′-biphenyl tetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), and 4,4′-hexafluoroisopropylidene diphthalic anhydride, via a high-temperature, one-stage imidization process. The inherent viscosities of the polyimides ranged from 0.37 to 0.74 dL/g. All the polyimides were quickly soluble in many low-boiling-point organic solvents such as tetrahydrofuran, chloroform, and acetone as well as some polar organic solvents such as N-methyl-2-pyrrolidinone, N,N′-dimethylacetamide, and N,N′-dimethylformamide. Freestanding fluorinated polyimide films could be prepared and exhibited good thermal stability with glass-transition temperatures of 298–334 °C and outstanding mechanical properties with tensile strengths of 69–102 MPa and elongations at break of 3.3–9.9%. Moreover, the polyimide films possessed low dielectric constants of 2.70–3.09 and low moisture absorption (<0.58%). The films also exhibited good optical transparency with a cutoff wavelength of 303–351 nm. One polyimide (9FMA/BTDA) also exhibited an intrinsic negative photosensitivity, and a fine pattern could be obtained with a resolution of 5 μm after exposure at the i-line (365-nm) wavelength. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2665–2674, 2006