Synthesis and Properties of Novel Aromatic Poly(esterimide)s Bearing Naphthalene-2,7-Diyl Units

Abstract

Two series of 2,7-naphthalenediyl units-containing homoand copoly(ester imide)s were prepared from 2,7-bis(4-aminobenzoyloxy)naphthalene and 2,7-bis(3-aminobenzoyloxy)naphthalene, respectively, with six commercially available aromatic tetracarboxylic dianhydrides and their mixtures via a conventional two-stage synthesis that included ring-opening polyaddition to give poly(amic acid)s followed by chemical imidization to polyimides. The intermediate poly(amic acid)s obtained in the first stage had inherent viscosities of 0.59∼1.15 and 0.51∼1.20 dL g-1, respectively. Some of the poly(ester imide)s derived from less rigid dianhydrides had excellent solubility in polar aprotic solvents such as N-methyl-2-pyrrolidone and N,N-dimethylacetamide and could be solution-cast into transparent, flexible, and tough films. The poly(ester imide)s derived from rigid dianhydrides such as pyromellitic dianhydride (PMDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) were semicrystalline and showed less solubility. Except for some examples, most of the poly(ester imide)s displayed discernible glass-transition temperatures ( Tgs) between 233 and 295°C in the differential scanning calorimetry traces. These poly(ester imide)s showed insignificant decomposition below 450°C in nitrogen or air. The investigation of the thermal decomposition of the poly(ester imide)s using pyrolysis-gas chromatography/mass spectrometry (pyrolysis-GC/MS) indicated that a dramatic breakage of the ester linkages occurred at around 450°C, which initiated the polymer chain scission.