POLYELECTROLYTE ADSORPTION ON OXIDES .2. REVERSIBILITY AND EXCHANGE

We studied the reversibility of the adsorption of polyelectrolytes on oxides by deliberately creating nonequilibrium situations either by ch anging the experimental conditions or by performing exchange experimen ts. Subsequently, we monitored the return to the equilibrium situation . Our measurements indicate that polyelectrolyte adsorption on oxides is only partially reversible, due to the strong (electrostatic) intera ction with the surface, which slows down reconformation processes. Thi s interaction is weakened, and thereby the reversibility enhanced, by the addition of salt. A model for the structure of adsorbed layers, al lowing little reconformation, predicts that heterogeneous layers are f ormed. (C) 1996 Academic Press, Inc.