| Abstract
| - We show, in this paper that multivalent ferrocyanide anions can penetrate into exponentially growing(PGA/PAH)n multilayer films whatever the nature of the last deposited layer. These ions are not able todiffuse out of the film when it is brought in contact with a pure buffer solution. However, the contact ofthis film with a poly(allylamine) (PAH) or a poly(l-glutamic acid) (PGA) solution leads to the release offerrocyanide ions from the multilayer. It is shown that the release of ferrocyanide anions, when the filmis in contact with a PGA solution, is due to the diffusion of the PGA chains into the film so that an exchangebetween ferrocyanide ions and PGA chains takes place inside the film. On the other hand, PAH chainsdo not diffuse into PGA/PAH multilayers. When the film is then brought in contact with a PAH solution,the PAH chains from the solution are expected to strongly interact with the ferrocyanide ions and thusinduce a diffusion mechanism of the multivalent anions out of the film, the film/solution interface playingthe role of a sink for these ions. This work thus shows that interactions between multivalent ions andexponentially growing films are much more complex than expected at first sight and that polyelectrolytemultilayers must be seen as dynamic entities in which diffusion and exchange processes can take place.
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