Polystyrene-organoclay nanocomposites, wide angle x-ray scattering, clay, cation exchange 12 capacity (CEC) 13A series of polystyrene-clay nanocomposites, based on two natural clay types (Na-14Montmorillonite and Hectorite), and two synthetic clays (Laponite and Li-Fluorohectorite), were 15 prepared via in situ intercalative polymerization after surface modification with an organic 16 2 ammonium cation (CTAB). The structural characteristics of the organically modified clays as 17 well as the nanocomposites were investigated by means of wide angle x-ray scattering (WAXS), 18 and the thermal properties were studied with TGA. In organically modified clays, the silicate 19 interlayer spacing increases and the magnitude seems to be directly correlated with the amount of 20 clay surface charge. In nanocomposites, polymer intercalation is also observed but partial 21 exfoliation is present, modifying significantly the morphology of the material. The degree of 22 dispersion of the clay platelets, as well as the resulting properties of the nanocomposites, were 23 found again to be systematically, and almost linearly correlated with the intrinsic surface charge 24 of the clays, which varied between 44 and 120 meq/100g. Increased dispersion was seen in the 25 nanocomposites made from clays with low surface charge, here Hectorite and Laponite, 26 suggesting that these can be suitable alternatives to the more employed Montmorillonite for 27 enhancement of thermal properties. The thermal stability was found to be better for the 28 nanocomposites than for the pure polystyrene. 29