Interfacial Assembly Behavior of Alkylamine-Modulated Graphene Oxide with Different Oxidation Degrees

Multitudinous studies have been carried out on the controllable functionalization and performance evaluation of graphene oxide (GO). In this study, the correlation between the amount of grafted alkylamine on GO and its interfacial assembly behavior at liquid-liquid and liquid-solid interfaces was studied. GO was modified with n-octylamine through basal functionalization (bGO). The grafting amount of alkylamines was regulated using two GOs varied in oxidation degree (GO_L and GO_H). A study on the oil-water interfacial behaviors shows that bGO_L has better ability to modulate the interfacial tension than that of bGO_H. Grafting alkylamine on GO will not only increase the interaction strength with oil while weaken that with water but also do damage to the graphene lattice and weaken the interaction of π-π stacking; therefore, bGO_L displays a broader capability to modulate interfacial tensions than that of bGO_H. The bGO-based Pickering emulsion was prepared, and the interfacial behavior at the liquid-solid interface was investigated. A study on the interfacial anti-rust performances demonstrates that grafted alkyl chains in bGOs can form more compact and ordered protective films on the metal surface and enhance the hydrophobicity as a result of the similar structure to oil in the emulsion system, which makes Pickering emulsions show better anti-rust abilities than water dispersions. Meanwhile, the bGO_H emulsion shows a better anti-rust property than that of the bGO_L emulsion. A study on the interfacial tribological behaviors shows that the lubricity of bGO_L is better than that of bGO_H. X-ray photoelectron spectroscopy analysis shows that a high content of C-O-C/C-OH in lubricating films contributes to the improvement of lubricity. The modulated interfacial assembly properties of GO at both liquid-liquid and solid-liquid interfaces suggest their potential applications in surface protection, lubrication, controllable drug deliveries, absorption and separation, nanocomposites, and catalyst fields.