Polyelectrolyte multilayer capsule permeability control

The permeability properties of hollow polyelectrolyte multilayer capsules for different substances were investigated as a function of pH and salt concentration. Capsules were prepared by layer-by-layer (LBL) adsorption of oppositely charged polyelectrolytes onto the surface of melamine formaldehyde and CdCO3 particles followed by core removal. It was shown that the capsules are closed at a pH value of 8 and higher, but at a pH lower than 6 the macromolecules permeate into the capsule interior. For low molecular weight molecules capsules, templated on CdCO3 cores were found to be less permeable than MF-derived capsules. The open and closed states of the capsule wall are reversible. It provides thus an opportunity to encapsulate different materials into polyelectrolyte capsules.