Monte carlo simulation studies on the effect of entropic attraction on the electric conductivity in polymer nano-composites

The effect of non-conductive nano-particles on the electrical percolating network formation and the electrical conductivity of conductive nano-particles in polymer matrices is investigated using Monte Carlo simulations and a percolation theory. Both conductive and non-conductive nano-particles are modeled as spheres but with different diameters. Non-conductive nano-particles are up to four times bigger than conductive nano-particles. Equilibrated configurations for mixtures of nano-particles are obtained via Monte Carlo simulations and are used to estimate the probability (P ) of forming an electrical percolating network and the percolation threshold conductive nano-particle volume fraction (φ_c). As the volume fraction (φ_nc) of non-conductive nano-particles increases, φ_c decreases significantly, thus increasing the electrical conductivity. When non-conductive nano-particles mix with conductive nano-particles, they make the effective interaction energy W(r) between conductive nano-particles attractive, which should facilitate the formation of the electrical percolating network. For a given φ_nc, φ_c increases slightly with an increase in the non-conductive nano-particle diameter (σ_nc). We also carry out simulations with non-conductive nano-particles of different structures and find that φ_c is relatively insensitive to the non-conductive nano-particle structure.