title: Surfactant-Mediated Transfer of Colloidal Silica Particles from Water into an Immiscible Weakly Polar Solvent.
abstract: Spontaneous transfer of discrete colloidal silica particles from water into 2,6-dimethyl-4-heptanone (DH) is obtained upon preliminary adsorption of dodecylbenzyldimethylammonium bromide (DBDAB) from the aqueous phase onto the solid. Partitioning of the surfactant between the silica surface and both liquid phases is evaluated through the determination of the isotherm in the aqueous phase, taking into account their mutual solubility. The organosol particles are found to be covered by a statistical monolayer of surfactant molecules presumably hydrated to the extent of 20% on a mole ratio basis. Monodispersion of this stable suspension is ascertained by dynamic light scattering. Evidence of DBDAB association in the monolayer emerges from the conductimetric behavior of the amphiphile in DH and from the reversal of the silica native charge in the organosol, as shown by electrophoretic mobility determinations. Disorganization of the water layer contacting silica upon adsorption of DBDAB is argumented to originate from the presence of sparsely distributed dodecyl chains. Copyright 1998 Academic Press.
authors.affiliation: Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques, Université des Sciences et Techniques du Languedoc, Place E. Bataillon, Montpellier Cedex 05, 34095, France
authors.initials: A
authors.lastname: Kasseh
authors.initials: E
authors.lastname: Keh