Sodium montmorillonite (Na-MMT) was swollen with protonated p-phenylenediamine, and the latter was converted to maleamic acid. Intercalation of the swelling agents was confirmed by FTIR, XRD, and TGA data. Exfoliation of the organoclay took place easily in the melt of the Bismaleimide-modified allylated novolac resin. It is remarkable that, as a result of layer delamination, introduction of 2 phr organoclay MAA-MMT brought in a rise in steady shear viscosity for over two orders of magnitude at low shear rates. Major improvement in thermal stability, flexural strength, and modulus was achieved by incorporation of the exfoliated clay layers, in contrast to the composite using pristine Na-MMT as reinforcement. (C) 2005 Wiley Periodicals, Inc.