Correlation of the Swelling and Permeability of Polyelectrolyte Multilayer Films

Alternating adsorption of polycations and polyanions on porous supports yields a variety of size-selective membranes whose swelling and transport properties depend on constituent polyelectrolytes, capping layer choice (polycation or polyanion), and deposition conditions. This report shows that in aqueous experiments, ellipsometrically determined swelling percentages correlate well with nanofiltration (NF) rejections and diffusion dialysis fluxes. For example, hyaluronic acid (HA)/chitosan films swell 4 times more than poly(styrene sulfonate) (PSS)/poly(allylamine hydrochloride) coatings, and in NF experiments, the HA/chitosan membranes permit a 250-fold greater fractional passage of sucrose. In general, films prepared from polyelectrolytes with a high charge density show low swelling and slow solute transport, presumably because of a high degree of ionic cross-linking. In the case of PSS/poly(diallyldimethylammonium chloride) (PDADMAC), PDADMAC-capped films can swell 4-fold more than their PSS-terminated ...