This paper deals with the preparation of organoclays by intercalating poly(ethylene glycol) molecules (PEG) between Na montmorillonite (Na-MMT) layers in a clay-water suspension system. X-ray diffraction (XRD) results of organoclays revealed that galleries of MMT were expanded after their intercalation with three different low molecular weight PEGs, including PEG600, PEG1000 and PEG1500. Thus, the distance of the interlayer spacing of MMT, d = 1.38 nm, was increased to d = 1.72, 1.75 and 1.69 nm, respectively, in the organoclay samples. The results of Fourier transform infrared spectroscopic (FTIR), thermogravimetric (IG) and scanning electron microscopic (SEM) analyses supported the findings of XRD and implied that the clay mineral mainly lost its hydrophilic character and gained organophilic features. The organoclay samples also presented improved thermal stabilities. In addition, polyurethane rigid nanocomposite foams composed of 2% organoclays were synthesized, and the effects of the organoclays on the thermal and mechanical performance of the nanocomposite foams were investigated. (C) 2010 Elsevier B.V. All rights reserved.