Organo-soluble fluorinated polyimides derived from 4,4′-bis (3-amino-5-trifluoromethylphenoxy)-3,3′,5,5′-tetramethyl biphenyl (TFMDA) and aromatic dianhydrides

A series of organo-soluble polyimides based on a new fluorinated diamine, 4,4'-bis(3-amino-5-trifluoromethylphenoxy)-3,3',5,5'-tetramethyl biphenyl (3,5-TFMDA) and various aromatic dianhydrides, were synthesized and characterized. The structures of the obtained polyimides were affirmed by Fourier transform infrared measurement and the properties were evaluated by wide-angle X-ray diffraction measurement, ultraviolet-visible analysis, thermogravimetry (TG), differential scanning calorimetry (DSC), tensile and electrical tests, and solubility tests. It was shown that the polyimides have good solubility not only in polar aprotic solvents, but in many common solvents, such as cyclopentanone, chloroform, and even in toluene for PI-4, derived from TFMDA and 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA). The polyimide solutions could be cast into flexible and tough films, which exhibited good thermal stability up to 500 degrees C and showed glass transition temperatures in the range of 250-280 degrees C. The Films also showed acceptable tensile properties and good electrical insulating properties. Furthermore, the polyimide films exhibited good transparency in the visible light region with transmittance higher than 80% at 450 nm and a cut-off wavelength lower than 360 nm.