Computer simulation study of the materials properties of intercalated and exfoliated poly(ethylene)glycol clay nanocomposites

Abstract

Very large-scale molecular dynamics simulations are performed to investigate the effects of montmorillonite clay filler on poly(ethylene) glycol in the formation of clay-polymer nanocomposites. We present the results of MD simulations of intercalated and exfoliated nanocomposites at sizes which approach those of a realistic clay platelet. The simulations allow us to determine the difference between polymer adsorbed on the surface of the clay and that more remote from it. All polymers arrange themselves in layers parallel to the surface, each layer being approximately 4 Å thick. We find the polymer conformation of the inner-most layer is distinct, due to complexation with the counterions found near the charged clay surface. The diffusion of polymer within this layer is much lower than that of others layers, which effectively increases the size of the nanofiller and makes gas permeation more tortuous. We perform non-equilibrium molecular dynamics simulations by imposing a strain on the model and analysing the stress response. By partitioning the stress response into clay and different polymer layers, we find that the inner-most polymer layer has a much higher Young's modulus than the remaining layers in the direction of the polymer chains.