MD Simulations Of The Structure And Young’s Modulus Of Polymer-clay Nanocomposites

Clay-based polymer nanocomposites are well known for their many advantageous properties,e.g., electrical, thermal and optical properties, especially the greatly reinforced mechanicalproperties. No matter how fast improvement of these materials was made during the lastdecades, there are still some problems needing to be solved to accelerate their development.One is the absence of cost-effective method to effectively control the dispersion of nanofillersin the polymer matrix. Another is the lack of structure-property relationships.There are three structures exhibited when montmorillonite (MMT) is dispersed inside nylon6matrix to generate nylon6/MMT nanocomposites. One is traditional composites; the other isintercalated and exfoliated nanocomposites, respectively. Among them, exfoliatednanocomposites behave the best of mechanical properties. In this research, we study thestructure and mechanical properties of exfoliated nylon6/MMT nanocomposites. It is widelyrecognized that interface has a crucial influence on the properties of nanocomposites.Experimentalists have used many advanced instrumentations and techniques to characterizethe structure of the nanocomposites and quantitatively determine their interfacecharacteristics. However, the nano-scale nature of the system and the ambiguity between theinterface and the matrix, have made quantifying the thickness of the interface extremelychallenging. Thus, interface’s effects on the overall mechanical performance of thenanocomposites are yet to be clarified. We investigate the interfacial interactions betweendifferent components (e.g. MMT, polymer, and surfactant) and interface structure anddetermine its thickness of both fully and partially exfoliated nanocomposites by moleculardynamics (MD) simulations. Then effective clay clusters (fully exfoliated single-layereffective clay cluster and partially exfoliated two-layer and three-layer effective clay clusters)are built and treated as building blocks in the nanocomposites. Young’s moduli of thesebuilding blocks are calculated and analysed by MD simulations, Young’s modulus of polymerclay nanocomposites are calculated based on MD simulations and rule-of-mixtures.