Synthesis and characterization of novel aromatic polyamides via Yamazaki–Higashi phosphorylation method

Abstract We synthesized four aromatic diacids: 1,3‐bis(3‐carboxyphenoxy)benzene, 1,4‐bis(4‐carboxyphenoxy)benzene, 1,4‐bis(3‐carboxyphenoxy) benzene, and 1,3‐bis(4‐carboxyphenoxy)benzene, following a procedure of a previously reported synthesis (Ueda and Komatsu, J Polym Sci Part A: Polym Chem 1989, 27, 1017). These diacids were condensed directly with aromatic diamines 4,4′‐oxydianiline (ODA), via the Yamazaki–Higashi phosphorylation method in the presence of triphenylphosphite (TPP), pyridine (Py) and halide salts to give high molecular aromatic polyamides (PAs). The synthesized PAs were obtained in quantitative yields with inherent viscosities between 0.5 and 1.0 dL g −1 . The structures and properties of the obtained PAs were characterized by Fourier transform infrared (FTIR) spectra, nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), polarizing optical microscope (POM). Four PAs all showed good solubility in polar solvents, such as dimethylsulfoxide (DMSO), N , N ‐dimethylacetamide (DMAc), N ‐dimethylformamide (DMF), 1‐methylpyrrolidone (NMP), and so on. The obtained polymers showed high thermal stability with decomposition temperature around 400°C. The polyamide membranes manifest excellent mechanical properties, with Young's modulus of 2.5–5.5 GPa. Interestingly, the film of PA‐1, PA‐2, and PA‐3 is completely transparent in the visible range, while PA‐4 film is opaque. Crystallization was observed in PA‐4 film, although the molecular structure of PA‐4 is not as symmetrical as PA‐2. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012