Abstract
Summary: A CF~3~‐containing diamine, 4,4′‐bis(4‐amino‐2‐trifluoromethylphenoxy)biphenyl (I), was synthesized from 4,4′‐biphenol and 2‐chloro‐5‐nitrobenzotrifluoride. The imide‐containing diacids (V~a‐b~ and VI~a‐l~) were prepared by condensation reaction of amino acids, aromatic diamines and trimellitic anhydride. Then, a series of soluble aromatic polyamides (VII~a‐f~) and poly(amide‐imide)s (VIII~a‐b~ and IX~a‐l~) were synthesized from diamine I with various aromatic diacids (II~a‐f~) and the imide‐containing diacids (V~a‐b~ and VI~a‐l~) via direct polycondensation with triphenyl phosphate and pyridine. Aromatic polyamides and poly(amide‐imide)s had inherent viscosities of 0.60–0.85 dL/g and 0.52–1.44 dL/g, respectively. All synthesized polymers showed excellent solubility in amide‐type solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide (DMAc) and N‐dimethylforamide and afford transparent and tough films by DMAc solvent casting. These polymer films had tensile strengths of 87–135 MPa, elongations to break of 8–22%, and initial moduli of 2.0–3.0 GPa. Glass transition temperature of these polymers were in the range of 259–317 °C, and the poly(amide‐imide)s had better thermal stability than aromatic polyamides. In comparison with the isomeric X series, the IX series exhibited less coloring and showed a lower b* (yellowness index) values than the corresponding IX series.
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