Nanocornposites of polystyrene (PS) were prepared using a melt compounding or co-solvent method. Two commercial PS were used, and two organoclays-one prepared in this laboratory (COPS), and the other commercial Cloisite (R) 10A (C10A). The COPS is a product of clay intercalation with a copolymer of styrene and vinyl benzyl tri-methyl ammonium chloride. According to the XRD diffraction data, the clay platelets in COPS and its PNC with PS were relatively well dispersed, i.e. with the interlayer spacings of d(001) = 7-8 nm. By contrast, d(001) in PNC prepared with C10A was only 4 nm. However, the number of clay platelets per stack in PS/COPS was found to be significantly larger than that in PS/C10A, viz. m = 3-12, compared to m = 2-6. The scanning and transmission electron microscopy indicated that in the PS matrix COPS existed in form of large, immiscible domains. (c) 2005 Elsevier Ltd. All rights reserved.