  The mechanical integrity of composite materials depends primarily on the
interface strength and the defect density of the reinforcement which is the
provider of enhanced strength and stiffness. In the case of graphene/ polymer
nanocomposites which are characterized by an extremely large interface region,
any defects in the inclusion (such as folds, cracks, holes etc.) will have a
detrimental effect to the internal strain distribution and the resulting
mechanical performance. This conventional wisdom, however, can be challenged if
the defect size is reduced beyond the critical size for crack formation to the
level of atomic vacancies. In that case, there should be no practical effect on
crack propagation and depending on the nature of the vacancies the interface
strength may be in fact increase. In this work we employed argon ion (Ar+)
bombardment and subsequent exposure to hydrogen (H2) to induce (as revealed by
X-ray & Ultraviolet photoelectron spectroscopy (XPS/UPS) and Raman
spectroscopy) passivated atomic single vacancies to CVD graphene. The modified
graphene was subsequently transferred to PMMA bars and the morphology,
wettability and the interface adhesion of the CVD graphene/PMMA system were
investigated with Atomic Force Microscopy technique and Raman analysis. The
results obtained showed clearly an overall improved mechanical behavior of
graphene/polymer interface, since an increase as well a more uniform shift
distribution with strain is observed. This paves the way for interface
engineering in graphene/polymer systems which, in pristine condition, suffer
from premature graphene slippage and subsequent failure.
