Monitoring the salt stability and solvent swelling behavior of PAH‐based polyelectrolyte multilayers by quartz crystal microbalance with dissipation

Abstract

This contribution is aimed to examine the layer stability and solvent swelling behavior of polyelectrolyte multilayers (PEMs) obtained from poly(allylamine hydrochloride) (PAH), poly(styrene sulfonic acid sodium salt) (PSS), and poly(acrylic acid) against different salt solutions using Quartz Crystal Microbalance with Dissipation in terms of the solution concentration, charge type of the top layer, and PEM structure. In general, all multilayers remain stable against MgCl2 and NaCl, phosphate buffer saline, ionic liquid, and solvents, namely methanol and heptane, while 4.5‐bilayered PAH‐PSS film displays partial layer decomposition against 1 M NaOCl. Additionally, it is found that the stability of Layer‐by‐Layer (LbL) films remains unaffected by the surface charge type, although variations in the adsorbed and desorbed amounts, as well as the viscoelastic properties, occur during the salt passage and rinsing steps. Along the salt exposure, changes in dissipation (ΔD) significantly increase because of the fast diffusion of ions through the multilayers but return to their initial value after washing. Especially high and reversible ΔD values of the PEMs against methanol are evaluated as swelling in methanol without chemical disintegration. This behavior can be attractive for solvent‐induced release behavior for the LbL‐assembled films or microcapsules.Highlights Multilayer stability and solvent swelling of PEMs are discussed using QCM‐D. PAH‐PSS films have the highest stability against salt solutions. PAH‐PAA films exhibited significant changes in dissipation values. PEMs did not show multilayer stability against NaOCl solution. (PAH‐PSS)5 film was stable and had swelling/de‐swelling capability against methanol.