Study on the Liquid-Liquid and Liquid-Solid Interfacial Behavior of Functionalized Graphene Oxide

Area of Science:

• Materials Science
• Surface Chemistry
• Tribology

Background:

• Carbon neutrality drives interest in carbon-based materials like graphene oxide (GO).
• GO possesses reactive groups on its basal plane and edges, influencing its interfacial properties.
• Modifying GO's functional groups is key to tailoring its behavior in emulsions and for lubrication.

Purpose of the Study:

• To functionalize graphene oxide (GO) with dodecylamine to create basal plane-functionalized GO (bGO) and edge-functionalized GO (eGO).
• To investigate the impact of GO functionalization on oil/water interfacial activity and emulsion properties.
• To evaluate the friction-reducing performance of functionalized GO in poly-α-olefin/water emulsions.

Main Methods:

• Synthesis of bGO and eGO via dodecylamine functionalization of GO.
• Interfacial tension measurements at various oil/water interfaces.
• Interfacial dilatational rheology studies of eGO and fatty alcohol polyoxyethylene ether-4 (MOA4).
• Friction coefficient (COF) measurements of eGO/MOA4 complex emulsions under shear.
• Rheological analysis of the prepared emulsions.

Main Results:

• Functionalized GOs (fGOs) significantly reduced interfacial tension, particularly at the poly-α-olefin/water interface.
• Edge-functionalized GO (eGO) demonstrated greater interfacial tension reduction compared to bGO.
• eGO/MOA4 emulsions exhibited excellent friction-reducing performance, with COF reduced by up to 37.42%.
• eGO addition enhanced emulsion elasticity, and the emulsions displayed shear-thinning and friction-thickening behavior.
• MOA4 gradually replaced eGO at the interface with increasing MOA4 concentration.

Conclusions:

• Edge functionalization of GO profoundly alters interfacial properties, outperforming basal plane functionalization for specific applications.
• eGO-based emulsions offer significant friction reduction and improved lubrication film formation on metal surfaces.
• These findings highlight the potential of tailored GO functionalization for advanced applications in lubrication, active material encapsulation, surface protection, and pollutant adsorption/separation.