Molecular Dynamics study of the effect on the interfacial activity of Alkylamine-Modified graphene oxide

Several experimental studies have shown that chemical modification of graphene oxide with n-alkylamines allow to control its interfacial activity in oil-water systems, altering its dispersibility and favoring the formation of emulsions. However, due to the complexity of its chemical structure and exper-imental limitations, the emulsification mechanism and interfacial properties have not been fully under-stood. In order to understand the behavior at the oil-water interface of alkylamine functionalized Graphene Oxide (GO) based materials, in this research we evaluated the interfacial activity of GO func-tionalized with different alkylamines (aGO) with different aliphatic chain lengths of 1, 3, 5, 7, 9 and 12 carbon atoms by Molecular Dynamics simulations. The dispersibility of the GO-based materials was ana-lyzed and it was found that the Hydrophilic-Lipophilic Balance (HLB) of the GO can be controlled with the alkylamine chain length, making the GO more hydrophobic as the aliphatic chain length of the alkylami-nes becomes longer. Alkylamine chains bonded on the GO structure were capable to modifying the ori-entation relative to the Toluene/Water interface, going from parallel for the GO case to orthogonal for the aGO nanosheets, adopting a head-tail configuration due to the hydrophobic effect between the alipha-tic chains and the Water molecules. Simulations also revealed that synergistic effect of aGO can decrease the interfacial tension of the Toluene-Water system as the aliphatic chain length and number of sheets increase obeying the Traubes rule, indicating a behavior like molecular surfactant, where the IFT of the system decreases as the amount of surfactant increases. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Experimental studies have shown that chemical modification of graphene oxide with n-alkylamines can control its interfacial activity in oil-water systems and favor the formation of emulsions. In this research, Molecular Dynamics simulations were used to evaluate the interfacial activity of graphene oxide functionalized with different alkylamines of varying chain lengths. The results indicate that the alkylamine chain length can control the hydrophilicity and hydrophobicity of the graphene oxide, and the functionalized materials exhibit decreased interfacial tension in the oil-water system.