Synthesis and properties of novel fluorinated poly(amide-imide)s from the 4,4′-bis(4-trimellitimido-2-trifluoromethylphenoxy)biphenyl and aromatic diamines

A novel fluorinated diimide dicarboxylic acid, 4,4-bis(4-trimellitimido-2-trifluoromethylphenoxy)biphenyl (111), was synthesized from the condensation of 4,4 '-bis(4-amino-2-trifluoromethylphenoxy)biphenyl (1) and trimellititc anhydride. A series of soluble poly(amide-imide)s (PAI) Va-h having inherent viscosities of 0.56-0.97 dL/g were prepared from reacting III with an equivalent amount of diamines by direct polycondensation using triphenyl phosphite and pyridine as condensing agents. The polymer V series afforded tough, transparent, and flexible films. They had tensile strengths ranging from 88 to 112 MPa, elongations at break from 8 to 31 %, and initial moduli from 1.9 to 2.7 GPa. The glass-transition temperature (T-g) of the polymers was recorded at 235-300 degrees C. They had 10% weight loss at a temperature above 502 degrees C and left more than 54% residue even at 800 degrees C in nitrogen. In comparison with the nonfluorinated PAI VI series, the fluorinated V exhibited better solubility.