Predicting the Mechanical and Electrical Properties of Nanocomposites Formed from Polymer Blends and Nanorods

Abstract

By integrating different simulation techniques, we investigate the self-assembly and macroscopic properties of nanocomposites composed of nanoscale rods and a binary polymer blend. In particular, we combine a Cahn–Hilliard (CH) theory for binary mixtures and a Brownian dynamics (BD) for nanorods to create a hybrid model that allows us to determine the structural evolution of the nanocomposite. The incorporation of the nanorods into the minority phase of the phase-separating blend yields a bicontinuous morphology, where the nanorods form a percolating network within the continuous minority phase. This morphology serves as the input to a lattice spring model (LSM), which is used to determine the mechanical properties, and a finite difference model (FDM), which is used to calculate the electrical conductance of the material. We find that in this doubly percolating system, the reinforcement efficiency of the nanorods and the electrical conductivity of the material are significantly increased relative to the behavior in composites where the nanorods are randomly dispersed in a homogeneous matrix. The integration of these various techniques allow us to predict the complex nanorod/polymer morphologies as a function of the constituents' characteristics, determine the mechanical and electrical, behavior of the resultant material and consequently relate the nanoscopic structure of the mixture to the macroscopic properties of the composite.