Interfacial Assembly Behavior of Alkylamine Modulated Graphene Oxide with Different Oxidation Degree.

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 by using two GOs varied in oxidation degree (GO_L and GO_H). Study on the oil-water interfacial behaviors show 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 interaction of π-π stacking, so the bGO_L displays a broader capability to modulate interfacial tensions than that of bGO_H. The bGO based Pickering emulsion was prepared and their interfacial behavior at liquid-solid interface was investigated. Study on the interfacial anti-rust performances demonstrate that grafted alkyl chains in bGOs can form more compact and ordered protective films on the metal surface and enhance the hydrophobicity due to the similar structure to oil in emulsion system, which makes Pickering emulsions show better anti-rust abilities than water dispersions. Meanwhile, bGO_H emulsion show a better anti-rust property than that of bGO_L emulsion. Study on the interfacial tribological behaviors show that the lubricity of bGO_L is better than that of bGO_H. XPS analysis shows that high content of C-O-C/C-OH in lubricating films contribute to the improvement of lubricity. The modulated interfacial assembly properties of GO at both liquid-liquid and solid-liquid interfaces, suggesting their potential applications in surface protection, lubrication, controllable drug deliveries, absorption and separation, nanocomposites and catalysts fields.