Impact of graphene oxide arrangement on the mechanical and viscoelastic properties of polymer nanocomposites

Graphene oxide (GO) is a promising reinforcing nanofiller for polymer nanocomposites due to its exceptional strength and strong adhesion to polymers. Despite extensive research, the effects of GO sheet arrangement and oxidation profiles on the mechanical and viscoelastic properties of these nanocomposites remain underexplored, and the underlying deformation mechanisms have not been explicitly unveiled. In this study, we employ coarse-grained molecular dynamics simulations to investigate how distinct GO arrangements (separated vs. stacked sheets), varying interfacial interactions, and a range of oxidation profiles impact the mechanical and viscoelastic properties of GO-polymethyl methacrylate (PMMA) nanocomposites. Our findings reveal that GO sheet arrangement plays a crucial role in determining the mechanical properties of nanocomposites, with separated GO sheets typically resulting in higher elastic and shear moduli due to increased interfacial area and stronger nanoconfinement effects. Additionally, stronger interfacial interactions enhance these moduli, with oxidation degree playing a complex role by simultaneously weakening GO's intrinsic stiffness. Under shear deformation, stacked GO cases exhibit inter-sheet sliding, driven by weaker GO inter-sheet interactions and stronger GO-PMMA adhesion. The inter-sheet sliding enhances the loss modulus and loss tangent of the GO-PMMA nanocomposites, with the sliding magnitude directly correlating with the dynamic moduli. Our results indicate that polymers reinforced with stacked GO sheets can achieve superior damping capability through the activation of GO inter-sheet sliding. This makes them particularly suitable for applications requiring enhanced energy dissipation. This study highlights the pivotal role of GO arrangement in shaping the mechanical and viscoelastic behavior of polymer nanocomposites, providing valuable insights for tailored nanocomposite design.