Defect Repair of Polyelectrolyte Bilayers Using SDS: The Action of Micelles Versus Monomers

Defects within single, double, and triple polyelectrolyte bilayers derived from poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethyammonium chloride) (PDDA) have been repaired using aqueous solutions of sodium dodecyl sulfate (SDS), as evidenced by a reduction in their permeability and an increase in their permeation selectivity. In contrast to the use of monomer solutions of SDS, which were moderately effective in repairing only double and triple bilayers, micellar solutions proved highly effective for all three assemblies. Evidence for intact micelles or micellar fragments being deposited on the surface of single bilayers of PSS/PDDA has been obtained from a combination of atomic force microscopy, X-ray photoelectron spectroscopy, ellipsometry, and contact angle measurements. Observed CO₂ permeances of ca. 200 GPU and CO₂/N₂ selectivities of ca. 30 for SDS-repaired, single bilayers of PSS/PDDA suggest that further development of such assemblies could have the practical potential for the separation of CO₂ from N₂ in the flue gas.