AbstractA new series of modified polyisophthalamides bearingN‐benzylidene pendant groups was prepared by reacting various aromatic diamines with 5‐(N‐benzylidene) isophthalic acid. The latter was synthesized from the reaction of 5‐aminoisophthalic acid with benzaldehyde and characterized by IR and1H‐NMR spectroscopy. Triphenyl phosphite and pyridine was used as condensing agents for preparing polyamides. In addition, the corresponding unsubstituted polyisophthalamides were prepared under identical experimental conditions for comparative purposes. Characterization of modified polyamides was accomplished by IR as well as inherent viscosity measurements. They showed a slightly lower solubility in various media than the corresponding unsubstituted polyamides. The cured modified polyamides displayed significantly higher thermal stability than the cured unsubstituted polyamides. They were stable up to 355–308°C in N2or air and afforded anaerobic char yield of 66–61% at 800°C. © 1992 John