Interfacial mechanics and viscoelastic properties of patchy graphene oxide reinforced nanocomposites

Graphene oxide (GO) is a promising building block for nanocomposites due to its excellent mechanical properties and tunable interfacial interactions with polymers. While experiments have shown that GO sheets consist of graphitic regions clustering into patches and oxidized regions constituting the remaining areas, the role that these heterogeneous patches play on interfacial and mechanical properties of GO reinforced nanocomposites have not yet been investigated. To address this issue at spatiotemporal scales beyond atomistic simulations, we employ recently developed coarse-grained models of GO sheet and polybutadiene to model patchy GO sheets and a representative GO/polybutadiene nanocomposite with GO sheets serving as fillers. We quantify how interfacial adhesion energy and polymer conformations depend on the size of patches and corroborate these findings with the viscoelastic behaviors of the nanocomposite determined via oscillatory shear simulations conducted at multiple temperatures. We find that heterogeneous patchy structures on GO sheets are responsible for variations in interfacial and viscoelastic properties. Specifically, larger patches result in stronger filler-matrix adhesion or enhanced material stiffness with strong or weak oxidized region-polymer interactions, respectively. Our study provides fundamental insights into the interfacial mechanisms of GO-polymer nanocomposites and the influence of heterogeneous functionalized surfaces of the fillers on the mechanical properties of polymer nanocomposites.