A novel aromatic unsymmetrical fluorinated diamine monomer, (4’-(4’’-amino-2’’-trifluoro-
methylphenoxy)-3’,5’-dimethylphenyl)(4-aminophenyl)methanone (3), was successfully synthesized in three steps using 2,6-dimethylphenol and 4-nitrobenzoyl chloride as starting material, which was then employed to prepare a fluorinated poly(ether imide) with commercial aromatic dianhydride, 4,4’-oxydiphthalic anhydride. The inherent viscosity of the resulting polyimide was 0.68 dL/g, and it exhibited an excellent solubility and optical property. It was readily soluble not only in some strong polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide, but also had a good solubility in some low-boiling-point solvents such as chloroform, tetrahydrofuran, and dichloromethane. The polyimide film showed high optical transparency and colorless, with a UV-vis absorption edge at 352 nm. Furthermore, the polyimide also showed good thermal and mechanical properties. Onset decomposition temperature (Td) of the polyimide was at 508 ℃ under nitrogen atmosphere, and its glass-transition temperature (Tg) was at 288 ℃. The polyimide film had strengths at break at 91 MPa, elongations to break of 10%～15%, and initial moduli at 1.7 GPa.

Key words: polyimide, solubility, transparency, trifluoromethyl, unsymmetrical