Synthesis, characterization and properties of a hyperbranched aromatic polyamide: poly(ABZAIA)

A hyperbranched aromatic polyamide has been prepared by direct polycondensa tion of 5-(4-aminobenzoylamino)isophthalic acid (ABZAIA), using the modifie d Higashi's method. The resultant polymer is soluble in aprotic polar solve nts such as DMF, DMAc, NMP, and DMSO. Intrinsic viscosities of poly(ABZAIA) samples, measured in sulfuric acid ata 25 degreesC, are in the range betwe en 0.2 and 0.3 dL.g(-1). Glass transition temperature (T-g) is placed aroun d 150 degreesC and onset temperature of thermal decomposition at about 275 degreesC. Full molecular weight distribution, evaluated by a SEC apparatus equipped with three different detectors, gives (M) over bar (w) values in t he range between 55 000 and 300 000 g.mol(-1), with a polydispersity index, (M) over bar (w)/(M) over bar (n), relatively large and generally around 3 -4. Poly(ABZAIA), synthesized in suitable experimental conditions, shows ra ther low values of Mark-Houwink a constant. Together with [eta] data, these a values are consistent with a hyperbranched, close-to-globular shape of o ur polymer. Highly concentrated polymer solutions (>40 wt.-%) in NMP show s hear birefringence under polarized light. The specific surface area of the powdered material, calculated by nitrogen adsorption/desorption isotherm, i s ca. 40 m(2).g(-1).