Assembly of alternated multivalent ion/polyelectrolyte layers on colloidalparticles. Stability of the multilayers and encapsulation of macromolecules into polyelectrolyte capsules

Alternating adsorption of multivalent ions and oppositely charged polyelect rolytes on colloid particles has been investigated. Multilayer films compos ed of Tb3+/polysterene sulfonate (PSS) and 4-pyrene sulfate/polyallylamine (PAH) were successfully assembled on polysterene sulfonate (PS) and melamin e formaldehyde (MF) latex particles. The amount of assembled material was e stimated by fluorescence and the linear growth of the film versus the numbe r of layers was demonstrated. These multilayers are not stable and can be d ecomposed by salt and temperature, Dissolution of MF particles leads to for mation of hollow capsules consisting of multivalent ion/polyelectrolyte mul tilayers. Comparative analysis of the capsules was done by confocal and sca nning force microscopy. Complex hollow spheres consisting of Tb3+/PSS or 4- PS/PAH as an inner shell and stable PSS/PAH as an outer shell were produced . Due to selective permeability of the outer shell after degradation of the inner shell the multivalent ions are released out of the capsule while the polyelectrolytes fill the capsule interior. This is indicative of swelling of the capsule by osmotic pressure. The filled capsules were studied by co nfocal and scanning electron microscopy. Possibilities of encapsulating mac romolecules in defined amounts per capsule are discussed. (C) 2000 Academic Press.