The mechanisms responsible for the enhancement of physical properties of polymer clay nanocomposites (PCN) over pristine polymers are not well understood. This knowledge is important for obtaining a better control over the physical properties of PCN and designing PCN with tailored properties. The interactions among the different constituents of PCN may be a key factor for controlling physical properties of PCN. The interaction energy is an important measure of the interactions among different constituents of composites. Molecular dynamics (MD) is a useful tool for studying the nature and quantitative analysis of interaction energies of a molecular system. In this work, the interaction energies among different components of intercalated organically modified montmorillonite (OMMT) and PCN have been investigated. Here, the interaction of polymer or organic modifier with clay and polymer and modifier is studied. Also, the nature and quantitative contributions arising from functional groups or backbone chain have been assessed. This investigation provides important insight into the mechanism of intercalation, and specific information about the interactions of different constituents in the nanocomposites system. In this current work using MD, for the first time, we have provided a detailed quantitative picture of interactions among the different components of OMMT and PCN. (c) 2006 Elsevier Ltd. All rights reserved.