In this work we have evaluated molecular interactions in organically modified clay and polymer clay nanocomposite using a combination of experimental (photoacoustic FFIR, XRD) and computational (molecular dynamics (MD)) techniques. The FTIR data reveals hydrogen bond and ionic bond interaction between functional end groups of organic modifier and surface oxygen of interlayer clay sheet lying in the organically modified clay: and, the hydrogen bond formation between intercalated polymer and organic modifier and surface oxygen of clay sheet lying in the interlayer clay gallery in the polymer clay nanocomposite. In this work we report the nature of interactions between clay and polymer, clay and organic modifier in polymer-clay nanocomposites through experiments and molecular dynamics simulations. (c) 2005 Elsevier Ltd. All rights reserved.