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. (C) 2002 Elsevier Science B.V. All rights reserved.