Dynamics and stability of dispersions of polyelectrolyte-filled multilayer microcapsules

We report dynamic and coagulation properties of a dispersion of polyelectrolyte multilayer microcapsules filled with solutions of a strong polyelectrolyte. The capsule self-diffusion coefficient in the vicinity of the wall is measured using a particle tracking procedure from confocal images of the dispersion. Our results suggest that the microcapsules take a charge of encapsulated polyions, which indicates a semi-permeability of the shell and a leakage of counter-ions. The diffusion of capsules in the force field is qualitatively similar to that of charged solid particles: The effective interaction potential contains a weak local attractive minimum and an electrostatic barrier. We also found that the aggregation of suspended capsules occurs faster than their sedimentation and adhesion onto a glass surface.