Copolymerization behavior of direct polycondensation of AB2 and AB monomers that forms hyperbranched aromatic polyamide copolymers

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Abstract
The copolymerization behavior of the one‐step direct polycondensation of 3,5‐bis‐(4‐aminophenoxy)benzoic acid (AB2 monomer) and 3‐(4‐aminophenoxy)benzoic acid (AB monomer) was investigated by IR and 13C NMR measurements. IR measurements revealed that the content of the AB2 units in the polymer was higher in the early stages of polymerization. 13C NMR spectra of the polymers indicated that the number of dendritic units increased slowly with increasing reaction time. The stepwise copolymerization of the AB2 and AB monomers was also carried out, and the structure was analyzed by 13C NMR measurements. Copolymer synthesized stepwise by adding AB2 monomer first (polymer II) had more dendritic units and less terminal units as compared with the one‐step copolymer (polymer I). Copolymer synthesized stepwise by adding AB monomer first gave a resulting copolymer (polymer III) composed of long AB chains. The solubility of the stepwise copolymers was low, and the inherent viscosity was high in comparison with the one‐step copolymer as a result of the difference in architecture of the copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3304–3310, 2001

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