Deposition of core latex particles encapsulated in polyelectrolyte shells at modified mica surfaces.

We used an oblique impinging jet (OIJ) cell to determine the initial deposition rates of model microcapsules at bare and modified by multilayer polyelectrolyte (PE) film mica surfaces. The transport conditions in the cell were quantitatively established by studying the kinetics of deposition of negatively charged latex at mica surfaces converted to positively charged by adsorption of (3-aminoprolyl)triethoxysilane. The dependence of reduced particle flux on the Reynolds number of the flow in the OIJ cell was determined by a direct counting of particles deposited on the mica surface. The results are described in terms of convective-diffusion theory taking into account hydrodynamic, dispersive, and electrostatic interactions, between the charged particles/capsules and the mica plate. In this way, transport conditions in the cell were characterized and they were used to interpret the results concerning the deposition of microcapsules with PE shells of various thickness obtained by layer-by-layer polyelectrolyte adsorption on colloidal cores. We demonstrated that the initial deposition rate of capsules is governed by the charge of the solid/liquid interface and the outermost layer of the capsule shell, and is largely independent of the thickness of the capsule shell or the number of PE layers at the mica surface. The deposition rates were in good agreement with theoretical predictions derived from the convective-diffusion theory.