Abstract
Scale-up manufacturing of engineered graphene-like nanomaterials to deliver the industry needs for development of high-performance polymer nanocomposites still remains a challenge. Herein, we introduce a quick and cost-effective approach to scalable production of functionalized graphite nanoplatelets using “kitchen blender” approach and Diels-Alder chemistry. We have shown that, in a solvent-free process and through a cycloaddition mechanism, maleic anhydride can be grafted onto the edge-localized electron rich active sites of graphite nanoplatelets (GNP) resulting from high collision force, called “graphite collision-induced activation”. The mechanical impact was modelled by applying the point charge method using density functional theory (DFT). The functionalization of GNP with maleic anhydride (m-GNP) was characterized using various spectroscopy techniques. In the next step, we used a recyclable process to convert m-GNP to the highly-reactive GNP (f-GNP) which exhibits a strong affinity towards the epoxy polymer matrix. It was found that at a low content of f-GNP e.g., 0.5 wt%, significant enhancements of ~54% and ~65% in tensile and flexural strengths of epoxy nanocomposite can be achieved, respectively. It is believed that this new protocol for functionalization of graphene nanomaterials will pave the way for relatively simple industrial scale fabrication of high performance graphene based nanocomposites.
Highlights
Scale-up manufacturing of engineered graphene-like nanomaterials to deliver the industry needs for development of high-performance polymer nanocomposites still remains a challenge
maleic anhydride (MA) stabilizes these active sites through its LUMO orbitals by forming sigma bonds with highly-activated HOMO orbitals of graphite nanoplatelets (GNP) edges
“graphite collision-induced activation” term refers exposing the graphite nanoplatelets to the high collision force generated by a simple kitchen blender, which results in creating electron-active sites
Summary
Scale-up manufacturing of engineered graphene-like nanomaterials to deliver the industry needs for development of high-performance polymer nanocomposites still remains a challenge. The covalent chemistry assuring good bonding between the graphene and modifying agents can be obtained via four different approaches: nucleophilic substitution, electrophilic addition, condensation, and addition[26,27,28] Among these methods, wet chemical functionalization of graphene such as hydrogenation, cycloaddition reactions (e.g. Aryne cycloaddition, Diels-Alder and Bingel reactions), addition of diazonium species, nitrene addition, and acylation reactions have been used to tailor the surface chemistry of graphene oxide, reduced graphene oxide, and GNPs within epoxy polymers in order to modify their dispersion levels and improved interfacial interactions[29,30,31,32,33]. A fairly costly and time-consuming ball milling process of graphite led to edge-selected functionalization of graphene in the presence of maleic anhydride and maleimid using Diels-Alder cycloaddition mechanism[37]
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