Abstract
A hyperbranched aromatic polyamide has been prepared by direct polycondensation of 5-(4-aminobenzoylamino)isophthalic acid (ABZAIA), using the modified Higashi's method. The resultant polymer is soluble in aprotic polar solvents such as DMF, DMAc, NMP, and DMSO. Intrinsic viscosities of poly(ABZAIA) samples, measured in sulfuric acid at 25°C, are in the range between 0.2 and 0.3 dL·g–1. Glass transition temperature (Tg) is placed around 150°C and onset temperature of thermal decomposition at about 275°C. Full molecular weight distribution, evaluated by a SEC apparatus equipped with three different detectors, gives Mw values in the range between 55 000 and 300 000 g·mol–1, with a polydispersity index, Mw/Mn, relatively large and generally around 3–4. Poly(ABZAIA), synthesized in suitable experimental conditions, shows rather low values of Mark-Houwink a constant. Together with [η] data, these a values are consistent with a hyperbranched, close-to-globular shape of our polymer. Highly concentrated polymer solutions (> 40 wt.-%) in NMP show shear birefringence under polarized light. The specific surface area of the powdered material, calculated by nitrogen adsorption/desorption isotherm, is ca. 40 m2·g–1.
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