Unpillared montmorillonite PGV and five organoclays (Nanocor's Nanomer 1.44P, 1.24TL and 1.34TCN and Southern Clay Product's C25A and C30B) were high shear melt-blended (2.5 wt%) into poly(propylene carbonate) (PPC). Solubility parameters of the clay pillaring agents versus that of PPC were used to predict clay/PPC miscibilities and these were compared to XRD and TEM nanoclay dispersion measurements. Clays 1.34TCN and C30B, with the highest predicted pillaring agent/PPC miscibilites, had partially exfoliated morphologies. Clays 1.24TL, C25A and 1.44P, with pillaring agents predicted to be less PPC miscible, were less highly nanodispersed. Quaternary ammonium pillars with two 2-hydroxyethyl groups promoted the best narrodispersion in PPC. 12-Aminoclodecanoic acid (in 1.24TL) promoted the intercalation. Dimethyl dialkyl quaternary ammoniums (in 1.44P and C25A) were less effective. Organoclay dispersion improved the thermal stability. The PPC/1.24TL nanocomposite, with the most stable 12-aminododecanoic acid pillar, was the most thermally stable (PPC/1.34TCN and PPC/C30B were the second and third). The nanocomposites exhibited narrower linear viscoelastic zones than PPC and solid-like behaviors in these linear zones. (C) 2008 Elsevier Ltd. All rights reserved.