Syntheses and properties of fluorinated polyamides and poly(amide imide)s based on 9,9-bis[4-(4-amino-2-trifluromethylphenoxy)phenyl]fluroene, aromatic dicarboxylic acids, and various monotrimellitimides and bistrimellitimides

A diamine, 9,9-bis[4-(4-amino-2-trifluromethylphenoxy)phenyl]fluroene (I) containing the CF₃ group, was prepared from 9,9-bis(4-hydroxyphenyl)fluorene and 2-chloro-5-nitrobenzotrifluoride. The imide-containing diacids (V _a-j and VI _a,b) were prepared by condensation reaction of amino acids, aromatic diamines, and trimellitic anhydride. Then, a series of soluble fluorinated polyamides (VII _a-e) and poly(amide imide)s (VIII _a-j and X _a,b) were synthesized from diamine (I) with various aromatic diacids II _a-h and the imide-containing diacids (V _a-j and VI _a,b) via direct polycondensation with triphenyl phosphate and pyridine. All polymers showed excellent solubility in amide-type solvents such as N-dimethylforamide and can also be dissolved in pyridine, m-cresol, and tetrahydrofuran. Polymers afford transparent and tough films by solvent casting. The glass transition temperature of these polymers were in the range of 278–366°C, and the poly(amide imide)s had better thermal stability than polyamides. In comparison with the isomeric IX _a-d, VIII _a-d showed a lighter color with lower b* (yellowness index) values than the corresponding IX series.