In this work, organically modified layered double hydroxides (OLDHs) were prepared and used to make exfoliated polystyrene (PS) nanocomposites by solvent blending method. First, Mg-Al, Co-Al, Ni-Al, Cu-Al, Cu-Fe, and Cu-Cr LDHs were synthesized by coprecipitation method at constant pH using their nitrate salts. The organically modified LDHs (OLDHs) were synthesized using sodium dodecyl sulfate (SDS). Then, PS nanocomposites containing 5 wt % of the above modified LDHs were developed by solvent blending method. The structural and thermal properties of LDHs and their corresponding nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), FTIR spectroscopy, and thermogravimetric analysis (TGA). The formation of exfoliated PS/OLDH nanocomposites is demonstrated by XRD and TEM analysis. TEM analysis also confirms the nanoscale dispersion of the LDH layers in the PS matrix. The presence of sulfate groups in the modified LDHs is confirmed by FTIR spectroscopy. The entire PS/OLDH nanocomposites exhibit enhanced thermal stability relative to pure PS. When 50% weight loss is selected as point of comparison, the decomposition temperature of the nanocomposites is about 5-13 degrees C higher than that of pure PS. Water uptake of the PS nanocomposites is found to be less when compared to pure PS. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2485-2495, 2011