Synthesis and Properties of Hyperbranched Aromatic Polyamide

Previous experiments from our group [Macromolecules 1998, 31, 5964] have established that thermal polymerization of 3,5-bis(4-aminophenoxy)benzoic acid (monomer 1) gave a hyperbranched aromatic polyamide (polymer 1). Here we show that thermal polymerization of methyl 3,5-bis(4-aminophenoxy)benzoate (monomer 2), having the same reaction behavior as that of monomer 1, gives a hyperbranched aromatic polyamide (polymer 2). In addition, the direct polycondensation of monomer 1 was conducted in the presence of triphenyl phosphite and pyridine as condensing agents in NMP to give a hyperbranched aromatic polyamide (polymer 3). The structures of the resulting polymers were confirmed to be identical by IR, 1H NMR, and 13C NMR. All three polymers were soluble in DMF, DMAc, NMP, DMSO, and 2-methoxyethanol. The inherent viscosity of the polymers in DMF ranged from 0.17 to 0.19 dL/g. Absolute molecular weights (Mw) determined by laser light scattering for polymers 1, 2, and 3 were 74 600, 47 800 and 36 800, respectively, and the corresponding polydispersities were 2.6, 3.2, and 1.8. The glass transition temperatures (Tg) of polymers 1, 2, and 3 were 200, 180, and 200 °C, respectively. End-capping reactions of the terminal amino groups in polymer 3 was easily accomplished with several kinds of acid chlorides. Thermal properties and solubility of the polymers changed after end-capping reactions.