Colloidal particle interactions at the oil-water interfaceColloidal dispersions at fluid interfaces share many of the characteristics of bulk suspensions, including the ability to control the colloidal interactions to tailor their stability, structure and rheology. As a result, interparticle interactions between particles at the interface of immiscible fluids have been intensely studied. At interfaces in which one of the fluids has a low dielectric permittivity, repulsive interactions arise from the asymmetric charge dissociation across the interface, which creates a dipole-dipole repulsion that is significantly stronger and longer-ranged than screened Coulomb interactions in an aqueous medium. Under pristine conditions, these interactions lead to remarkable two-dimensional crystals that are stable for weeks. Upon the addition of salt or surfactants, particles aggregate to form clusters and ramified microstructures. Here, we show by direct particle pair measurements that the attraction between spherical particles is consistent with capillary forces caused by local deformation of the interface. A combination of dipole-dipole repulsion and capillary attraction is sufficient to describe all of the pairwise interactions measured between colloids at an oil-water interface [1].[1] Park, B. J.; Furst, E. M. Soft Matter 2011, 7, 7676�7682.

Colloidal particle interactions at the oil-water interface

243rd National Meeting (2012)

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