13C solid-state NMR study of polyelectrolyte multilayers

Polyelectrolyte multilayers have been prepared by consecutively adsorbing poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) from aqueous solution onto colloidal silica (70-100 nm in diameter), with a total of five bilayers being prepared. The multilayer growth was followed by electrophoretic mobility as well as solid-state NMR spectroscopy. The electophoretic mobility measurements show the expected reversal in the zeta-potential with the alternate adsorption of the polycation and polyanion. The alternation in the relative intensities observed in the C-13 solid-state NMR spectra was used to qualitatively follow the layer-by-layer growth. Relaxation measurements show that the mobility of the polyanion is found to remain constant throughout the layer-by-layer assembly, while the mobility of polycation decreases with increasing numbers of layers.