In situ determination of thickness and electrical properties of multilayers from weak polyelectrolytes.

An electro-optical study of the role that the outermost layer plays in the behavior of a multilayer film of the weak polyelectrolytes poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) was carried out. The film surface was enriched with the chains of the last adsorbed polyelectrolyte when a fully ionized polymer was combined with nearly fully charged chains of the other polyelectrolyte. A distinct influence of the chain length on the critical frequency of relaxation of the electro-optical effect was demonstrated, indicating that polarization of condensed counterions of the last adsorbed polymer governs the behavior of the whole film.