Synthesis and Properties of Novel Aromatic Poly(ester amide)s Bearing Naphthalene-2,7-diyl Units

Abstract

Two new naphthalene ring-containing diamino-diesters, 2,7-bis(4-aminobenzoyloxy)naphthalene (p-2) and 2,7-bis(3-aminobenzoyloxy)naphthalene (m-2), were synthesized from the condensation of 2,7-dihydroxynaphthalene with 4-nitrobenzoyl chloride and 3-nitrobenzoyl chloride, respectively, followed by catalytic hydrogenation. Two series of naphthalene-containing poly(ester amide)s with inherent viscosities of 0.49–0.97 and 0.36–0.73 dL g-1 were prepared by the phosphorylation polyamidation of p-2 and m-2, respectively, with various aromatic dicarboxylic acids. Most of the poly(ester amide)s had excellent solubilities in polar aprotic solvents such as N-methyl-2-pyrrolidone and N,N-dimethylacetamide, especially for the m-series polymers. Some of the poly(ester amide)s could be cast into transparent, flexible, and tough films from DMAc solutions. The poly(ester amide)s derived from rigid dicarboxylic acids such as terephthalic acid, 4,4’-biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid and 4,4’-sulfonyldibenzoic acid were semicrystalline and showed less solubility. Except for three examples, most of the poly(ester amide)s displayed discernible glass transitions between 187 and 237 °C in the DSC traces. These poly(ester amide)s showed insignificant decomposition below 400 °C in nitrogen or air. The investigation of the thermal decomposition of the poly(ester amide)s using infrared spectroscopy and pyrolysis-gas chromatography/mass spectrometry (pyrolysis-GC/MS) indicated that the primary breakage of the ester linkages started at around 400 °C, which initiated the polymer chain scission.