Even though asphaltenes do not have the well-defined amphiphilic structure characteristic of surfactants, it has been shown that they can stabilise water-in-oil emulsions. We propose that this stabilisation occurs because asphaltene aggregation results in the formation of a network within the thin oil film separating approaching emulsified water droplets. This network changes the rheology of the film to non-Newtonian, which prevents drainage of the film at thicknesses less than about 50–100 nm. The presence of the network also imparts steric stabilisation to the emulsion. The proposed stabilisation mechanism does not invoke any surfactant-like behaviour of asphaltenes. Instead, it relies solely on their propensity to aggregate.
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