title: Structure and dynamics of particle monolayers at a liquid-liquid interface subjected to shear flow.
abstract: The effect of shear flow on the structure and dynamics of monodisperse spherical polystyrene particles suspended at the interface between decane and water was observed. While undisturbed, the particles arrange themselves on a hexagonal lattice due to strong dipole-dipole repulsion resulting from ionizable sulfate groups on their surfaces. As the interface is subjected to shear flow, however, the lattice adopts a new semi-ordered, anisotropic state for which two distinct regimes are observed. At low particle concentrations or high shear rates, nearest neighbors in the lattice align in the flow direction and create strings of particles that slip past each other fairly readily. This results in a stretching of the overall structure and achievement of a steady state orientation in the system. In contrast, at high concentrations or low shear rates, the interparticle forces gain importance and tend to keep the particles more strongly in their lattice positions. As a result, domains within the lattice are forced to rotate, thus giving rise to movement of particles perpendicular to the flow direction. Thus a rotation, in addition to stretching, of the structure is apparent in this case.
authors.affiliation: Department of Chemical Engineering, Stanford University, Stanford CA 94305-5025, USA.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Stancik
authors.forename: Grant T
authors.initials: GT
authors.lastname: Gavranovic
authors.forename: Martin J O
authors.initials: MJ
authors.lastname: Widenbrant
authors.forename: Alex T
authors.initials: AT
authors.lastname: Laschitsch
authors.forename: Jan
authors.initials: J
authors.lastname: Vermant
authors.forename: Gerald G
authors.initials: GG
authors.lastname: Fuller
mesh_terms: D000336:Aerosols; D000465:Algorithms; D003102:Colloids; D016503:Drug Delivery Systems; D008567:Membranes, Artificial; D011137:Polystyrenes; D012212:Rheology; D013535:Suspensions
chemical_list: D000336:Aerosols; D003102:Colloids; D008567:Membranes, Artificial; D011137:Polystyrenes; D013535:Suspensions