Synthesis and properties of fluorinated poly(ether ketone imide)s based on a new unsymmetrical and concoplanar diamine: 3,5-Dimethyl-4-(4-amino-2-trifluoromethylphenoxy)-4′-aminobenzophenone

A new unsymmetrical and concoplanar aromatic diamine monomer containing trifluoromethyl and dimethyl groups, 3,5-dimethyl-4-(4-amino-2-trifluoromethylphenoxy)-4′-aminobenzophenone (3), was synthesized in a three-step reaction using 2,6-dimethylphenol and 4-nitrobenzoyl chloride as starting materials. A series of fluorinated poly(ether ketone imide)s (PEKIs) (5a–d) were prepared from diamine 3 with four aromatic dianhydrides via a one-step high-temperature polycondensation procedure. The obtained PEKIs were readily soluble in some organic solvents and could be solution cast into flexible and tough films. These PEKI films exhibited high optical transparency with a cutoff wavelength of 354–375 nm and low dielectric constants (2.26–2.45 at 1 MHz). They also showed good thermal stability with glass-transition temperatures (Tgs) above 289 °C, 10% weight loss temperatures in the range of 518–531 °C, and the weight residue more than 52% at 800 °C in nitrogen. Moreover, the PEKI films possessed tensile strengths and initial modulus ranged from 91 to −128 MPa and 1.7 to 2.4 GPa, respectively. Due to their properties, these fluorinated PEKIs could be considered as photoelectric and microelectronic materials.