NMR Studies of PAH/PSS Polyelectrolyte Multilayers Adsorbed onto Silica

Solid-state NMR spectroscopy is used to monitor the layer-by-layer (L-B-L) growth of polyelectrolyte multilayers on colloidal silica. The dynamics and conformation of polyelectrolyte multilayers comprised of the weak polycation, poly(allylamine) hydrochloride, and the strong polyanion, poly(sodium-4-styrene sulfonate), assembled at pH 7 and pH 10 were studied by a combination of 1 H and 13 C NMR measurements. NOESY spectra detect the association of water to the polyanion, while relaxation measurements show that the outermost layer and the water content influence the mobility of the polyelectrolytes and the adsorbed water. Differences in mobility for films assembled at high and neutral pH are explained by the conformation of the polycation during the assembly process. Finally, the strong−weak polyelectrolyte multilayers are compared to a previous NMR study of strong−strong polyelectrolyte multilayers.