This study dealt with the use of various quantities of modified red mud as a nanofiller in a poly(hydroxy ether) of bisphenol A (Phe) based matrix. Phe-based polymer nanocomposites reinforced with acidically and organically modified layered red mud were prepared by a conventional solvent-casting technique. The best dispersion occurred in the polymer nanocomposites where the interactions between the functional groups of the polymer matrix and those of the organic substitution of the red mud appeared to be the highest. The particle size of the modified red mud was determined by field emission scanning electron microscopy. The as-synthesized composite films were typically characterized by Fourier transform infrared spectroscopy and X-ray diffraction. The dispersion of the modified fillers within the matrix was studied by transmission electron microscopy. The thermal properties measured by thermogravimetric analysis showed enhanced thermal stability of a series of composite materials. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 515-522, 2011