Swelling and Smoothing of Polyelectrolyte Multilayers by Salt

By use of in situ atomic force microscopy, polyelectrolyte multilayers were shown to swell on exposure to solutions containing salt. The quasilinear swelling response, used to estimate swelling coefficients and equilibria, exhibits orders of magnitude of difference, depending on the pair of polyelectrolytes constituting the multilayer. The surface roughness of as-made multilayers was observed to decrease significantly upon annealing in salt solutions.