Adsorption of Microstructured Particles at Liquid−Liquid Interfaces

Abstract

The solid particles are adsorbed at interfaces and form self-assembled structures when the particles have\nsuitable wettability to both liquids. Here, we show theoretically how the microstructure on the particle surface\naffects their adsorption properties. The physical properties of the interface adsorbing a particle will be described\nby taking into account the surface roughness due to the microstructure. The microstructure on the surface\nchanges drastically the wettability and the equilibrium position of the adsorbed particle. Therefore, the contact\nangle of the particle at the three-phase contact line shifts with the particle surface area, because the surface\nroughness enhances the interfacial properties of the particle surface. Moreover, the range of the interfacial\ntensions at which the particle is adsorbed becomes narrower with the increase of the surface roughness. The\neffect of the particle shape on the adsorption properties is also studied. In the case of disk-shaped particles,\nthe energy changes discontinuously when the plane surface of the particle contacts the liquid−liquid interface.\nThe adsorbing position does not change with the surface roughness. The orientation of a parallelepiped particle\nat the liquid−liquid interface is governed by the aspect ratio and the surface area of the particle. On the other\nhand, the particle which is partially covered with the microstructured surface is adsorbed firmly at the interface\nin an oriented state. We should consider not only the interfacial tensions but also the surface structure and the\nparticle shape to control the adsorption behavior of the particle.