Effects of defects on the interfacial shear characteristics between graphene and poly (methyl methacrylate)

Pullout simulations were conducted to investigate the interfacial shear properties between defective graphene (DGr) and polymethyl methacrylate (PMMA) through molecular dynamics simulations with ReaxFF reactive force fields. The effects of number of defects (Stone-Wales [SW] and double-vacancy [DV] defects) were investigated. Our results showed that these two types of defects can obviously enhance the interfacial shear strengths of DGr /PMMA nanocomposites. And the DV defects have a greater contribution to the interfacial shear strength enhancement compared to the SW defects. Analysis of the morphology of DGr indicated that surface roughness, which was induced by defects, plays an important role in enhancing the interfacial shear strength at the interface between the DGr and PMMA. Moreover, the effects of chemical functionalization at the defect sites were also investigated. We observed that the C-O bonds of functional groups (hydroxyls) at defect sites inclined from the datum plane (z = 0 plane) of the graphene sheet. The inclination of C-O bonds, which weakened the mechanical interlocking between functional graphene and PMMA matrix, differently influenced by the DV defect and SW defect.