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, H-1 NMR, and C-13 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 (M-w) 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 (T-g) of polymers 1, 2, and 3 were 200, 180, and 200 degrees 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.