The oligomeric poly(styrene-acrylamidevinylbenzylchloride) (P(St-AM-VBC)) quaternary ammonium salts have been prepared from the reactions of trimethylamine with the corresponding P(St-AM-VBC)s, which were synthesized by free-radical polymerization of a mixture of styrene, acrylamide, and vinylbenzylchloride; Then the swelling tunable oligomeric poly(styrene-coacrylamide) modified clays have been prepared through cation exchange of the sodium ions in the clay with the corresponding P(St-AM-VBC) quaternary ammonium salts. The P(St-AM-VBC) and its modified clays have been characterized by infrared spectra (IR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), proton nuclear magnetic resonance (H-1 NMR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The solvent-swelling capacity of poly(styrene-co-acrylamide) modified clays have also been tested, and the experimental results have indicated that these clays are novel swelling tunable organic clays. XRD and TEM studies have shown that these novel swelling tunable clays are well-intercalated or exfoliated. Furthermore, TGA analysis shows that these polymerically modified clays have high thermal stability for nanocomposites by melt blending. (c) 2008 Wiley Periodicals, Inc.