Enhancing the adhesion of graphene to polymer substrates by controlled defect formation

Abstract

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.

Wettability of graphene by molten polymers

“…1, the values of surface tension of PMMA as reported by Wu [23] have been adopted for all the investigated temperatures. It is interesting noting that the values of work of adhesion for the system PMMA/CVD graphene estimated here on the bases of the proposed approach are in strict agreement with those estimated via AFM measurements for a similar system [24]. It is important to underline here that the thermodynamic work of adhesion would correlate with the strength of the adhesion; however, first of all, eq.2 is applicable to systems with secondary force interactions (no chemical bonds across the interface) and with no mechanical interlocking.…”

Enhanced Adhesion Energy at Oxide/Ag Interfaces for Low-Emissivity Glasses: Theoretical Insight into Doping and Vacancy Effects

“…However, our previous theoretical calculations indicate that the defect-free ZrO 2 (111)/Ag­(111) interface exhibits a very poor adhesion . The mechanical properties of heterogeneous materials depend mostly on the strength of adhesion between their components . Therefore, one challenge in this field is to promote a strong adhesion at the metal oxide/metal interface.…”

Stress-transfer from polymer substrates to monolayer and few-layer graphenes

“…MPa for graphene-polymer systems by converting the Raman data to strain maps and by considering the balance of shear-to-axial forces at the interface 17,20,[22][23] . These values are relatively low and methods for increase them have been proposed by previous work of the group, such as the creation of a wrinkled interface which significantly enhances the stress transfer efficiency from the polymer to graphene 16 or the introduction of artificial 'defects' to the filler that enhances the anchoring of graphene to the host polymer 24 . Moreover, the chemical modification of the interface polymer-graphene has proven to be effective in increasing the ISS 25 .…”