Manipulating the Interfacial Mechanical Properties of Polymer-Grafted Graphene Reinforced Polymer Nanocomposites via Coarse-Grained Molecular Dynamics Simulation.

Abstract

Understanding the interfacial mechanical behavior of graphene-polymer nanocomposites is of great significance to achieve a balance between high strength and high toughness. Grafting polymer chains onto the surface of graphene can effectively improve the dispersibility of graphene in the polymer matrix and alter the interfacial mechanical properties between graphene and the polymer matrix. In this work, we conduct coarse-grained molecular dynamics simulations to systematically study the interfacial mechanical properties between the polymer-grafted graphene and the polymer matrix. By performing normal and shear separation tests, the influences of separation velocity, graft chain length, grafting density, and matrix cross-linking density on the interfacial mechanical properties are comprehensively investigated. Results indicate that compared with pristine graphene, grafting polymer chains onto the surface of graphene can significantly enhance the fracture toughness of the graphene-polymer interface system at the expense of weakening strength. The use of medium-length graft chains and low grafting density helps to find a balance between high strength and high toughness, achieving optimal design of high-performance nanocomposites. In addition, during high-velocity separation, an increase in matrix cross-linking density is beneficial to improve the interfacial cohesive and shear strength but has no significant effect on interfacial fracture toughness. This study sheds new light on the interface design of graphene-polymer nanocomposites with desired performance.