Aromatic polyimides, which had trifluoromethyl group at 2,2′-position of the diphenyl ether, were synthesized from bis(4-amino-2-trifluoromethylphenyl)ether (1) and previously prepared tetracarboxylic dianhydrides, 3,3′′′,4,4 ′′′-p-quaterphenyltetracarboxylic dianhydride (2d), 3,3′′′ ′,4,4′′′ ′-p-quinquephenyltetracarboxylic dianhydride (2e) and 3,3′ ′ ′ ′ ′ ,4,4 ′ ′ ′ ′ ′ -p-sexiphenyltetracarboxylic dianhydride (2f), and the properties were compared than those of corresponding polyimides from commercially available tetracarboxylic dianhydrides. The polyimides were synthesized by the conventional two-step procedure of ring-opening polyaddition in N-methyl-2-pyrrolidinone (NMP) and subsequent thermal cyclic dehydration. The polyimides were characterized by differential scanning calorimetry (DSC), thermogravimetry, and dynamic mechanical analysis (DMA). The polyimides showed excellent thermal stability, and had glass transition temperature (T
g) at 234—300 °C. The properties of polyimides were compared with those of previously prepared polyimides, which had phenyl group at 2,2′-position of the diphenyl ether, and the effect of the trifluoromethyl groups at the 2, 2′- positions of the diphenyl ether were observed in the thermal properties, solubility and optical properties of polyimides.
