Graphene oxide (GO) nanosheets as oil-in-water emulsion stabilizers: Influence of oil phase polarity

Hypothesis: Two-dimensional nanoparticles such as graphene oxide (GO) can serve as emulsion stabilizers due their ability to adsorb at oil-water (o/w) interfaces with high atom efficiency. The ability for GO to act as a surfactant is hypothesized to be highly dependent on the nature (i.e. polarity) of the oil phase, which has not considered previously. Modelling and experiments: The stabilization energy associated with adsorption of GO sheets at an o/w interface was modelled as a function of the polarity of the oil phase using surface tension contributions terms and Hansen solubility parameters (HSPs). Oil-in-water (o/w) miniemulsions were prepared via ultrasonication in the presence of GO for a variety of different oil phases, and were studied using dynamic light scattering (DLS). Findings: The stabilization energy associated with GO adsorption was greater for non-polar oil phases compared to more polar oils. This behaviour is driven by the significant reduction in the oil-water interfacial tension as the polarity of the oil increases, to the point where GO adsorption is no longer thermodynamically favourable. This was verified by DLS measurements experiments, as GO-stabilized emulsion were successfully prepared for hydrophobic and aromatic oil phases (e.g. styrene), but not for polar oil phases such as methyl methacrylate. (C) 2014 Elsevier Inc. All rights reserved.