Determination of fouling tendency, salt stability and viscoelastic properties of the multilayered functional coatings

Fouling caused by the retention of salt ions within functional coatings remains a major challenge for long-term performance. Here, our endeavor is to investigate the multiple parameters, including layer stability, fouling tendency and swelling properties of the polyelectrolyte multilayers (PEMs) as a function of the coating structure and ionic strength of the salt solution. The behavior of multilayered coatings composed of poly(vinylamine hydrochloride) (PVA), poly(allylamine hydrochloride) (PAH), poly(sodium 4-styrene sulfonate) (PSS) and poly(acrylic acid) (PAA) against synthetic seawater, NaCl and MgCl 2 solutions is monitored using Quartz Crystal Microbalance with Dissipation (QCM-D). None of the PEMs show degradation against synthetic seawater. Nevertheless, 6 M NaCl causes multilayer disintegration in PAH-PSS, PAH-PAA, and PVA-PSS coatings while 2 M MgCl 2 leads to disassembly in PVA-PSS. Notably, PVA-PAA coating does not lose its layer stability against salt solutions and retained a certain amount of salt (18% NaCl and 14% MgCl 2 ) within the multilayers after rinsing, potentially enhancing fouling. We show that the void fraction (𝜙 void ) of PAA-containing PEMs is bigger than that of PSS-containing PEMs, reaching 0.19. The significant swelling reversibility of PAH-PSS and PVA-PAA during salt solution exposure may benefit applications such as membrane, drug release, or non-fouling adsorption systems.