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Abstract
A new aromatic diamine, 4-(4-trifluoromethyl)phenyl-2,6-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]pyridine, was synthesized by a modified Chichibabin reaction of 4-(4-nitro-2-trifluoromethylphenoxy)acetophenone with 4-triflouromethylbenzaldehyde, followed by catalytic reduction. A series of fluorinated pyridine-containing aromatic poly(ether imide)s (PEIs) were prepared from the diamine monomer with various aromatic dianhydrides via conventional two-step thermal imidization method. The resulting PEIs had inherent viscosities values of 0.68–0.90 dL/g, and could be cast and thermally converted into transparent, flexible, and tough polymer films. These PEIs were predominantly amorphous, had good solubility in common solvents such as NMP, DMAc and m-cresol at room temperature, and displayed excellent thermal stability with the glass transition temperatures of 258–315 °C, the temperatures at 5% weight loss of 550–585 °C, and the residue of higher than 55% at 750 °C in nitrogen. Moreover, the PEIs films showed outstanding mechanical properties with tensile strengths of 74.8–103.5 MPa, tensile moduli of 1.08–1.45 GPa, and elongations at break of 10.6–24.4%. These PEIs also exhibited low dielectric constants of 2.81–2.98 (1 MHz) and water uptake 0.39–0.68%, as well as high optical transparency with the UV cutoff wavelength in the 350–378 nm range and the wavelength of 80% transparency in the range of 412–510 nm.
Graphical Abstract
A series of fluorinated pyridine-containing poly(ether imide)s derived from a new diamine 4-(4-trifluoromethyl)phenyl-2,6-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]pyridine with various dianhydrides were investigated. The resulting polymers exhibited improved solubility, high optical transparency and low dielectric constants, combined with good thermal and mechanical properties.