Ordered polyelectrolyte multilayers. 3. Complexing clay platelets with polycations of varying structure

Different poly(ammonium) salts with various chemical structures were self-assembled by the layer-by-layer method with a synthetic hectorite, Laponite. Using X-ray reflectometry, we show that internal order is present in all multilayers. The structure of the polycation slightly modulates the spatial extent of order in the film as well as the value of the repeat period which increases with the volume per charge of macromolecule. By combining XRR, XPS, and TGA results, we demonstrate that the internal order in multilayers is due to the regular intercalation of organic polymer between individual platelets of Laponite and not due to the presence of nonexfoliated particules. This conclusion is corroborated by a structural analysis of the bulk complex between Laponite and a poly(diallylammonium) salt.