Oligomeric poly(styrene-co-acrylonitrile) quaternary ammonium salts were prepared through reactions of trimethylamine with corresponding poly(styrene-acrylonitrile-vinyl benzyl chloride)s, which were synthesized by the free-radical polymerization of a mixture of styrene, acrylonitrile, and vinyl benzyl chloride. Then, oligomeric poly(styrene-co-acrylonitrile)-modified clays were prepared through the cation exchange of the sodium ions in the clay with the corresponding poly(styrene-co-acrylonitrile) quaternary ammonium salts. The poly(styrene-acrylonitrile-vinyl benzyl chloride)s, poly(styrene-co-acrylonitrile) quaternary ammonium salts, and their clay complexes were characterized with infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis, proton nuclear magnetic resonance, X-ray diffraction, and transmission electron microscopy. X-ray diffraction and transmission electron microscopy studies showed that these novel clay complexes were well intercalated. Furthermore, thermogravimetric analysis data indicated that this series of polymerically modified clays had high enough thermal stability for nanocomposites by melt blending. The thermal treatment of one of these novel clays at 250 degrees C under nitrogen was also conducted. Solubility and infrared studies of this thermally treated clay complex revealed that a novel polyimine/enamine structure clay complex had been formed in the gallery of the clay. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 3355-3361, 2009