Specific Anion Effects on the Growth of a Polyelectrolyte Multilayer in Single and Mixed Electrolyte Solutions Investigated with Quartz Crystal Microbalance

The specific anion effects on the deposition of a multilayer formed by poly(sodium 4-styrene sulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDDA) have been investigated by use of quartz crystal microbalance with dissipation (QCM-D) in single and mixed electrolyte solutions. In the case of single electrolyte solutions, the frequency change (−Δf) demonstrates that the multilayer in NaBr, NaClO3, and NaCl solutions grows in a nonlinear mode, which is dominated by the penetration of PSS. In NaF, CH3COONa, NaH2PO4, and Na2SO4 solutions, the multilayer growth mainly determined by the conformation of PDDA chains exhibits a linear mode. The growth shows a mode in between in NaHCO3 solution. The dissipation change (ΔD) has slight dependence on anion species except in the cases of Br−, HCO3−, and SO42−. ΔD remarkably increases with layer number in NaHCO3 solution, indicating the formation of a relatively loose multilayer. In a mixed electrolyte solution containing chaotropic and kosmotropic anions, the multilayer growth is dominated by the chaotropic anions due to the anion competition effects. The effects of anions on the deposition of multilayer are nonadditive.