Systematic approach to real-time thickness prediction of polyelectrolyte multilayer modified nanoporous membranes using complementary surface-sensitive techniques

• Polyelectrolyte multilayer thickness is predicted prior to membrane modification. • QCM-D and MP-SPR are highly complementary to yield accurate predictions. • The approach is independent of the substrate material. • Modelling of the polyelectrolyte multilayer thickness is simple and straightforward. Nanoporous membranes modified with polyelectrolyte multilayers have emerged as powerful tools for membrane separations, where precise control over multilayer thickness is essential to optimize performance. In this study, we introduce a systematic approach for real-time prediction of multilayer thickness with high accuracy, utilizing complementary surface-sensitive techniques. By combining quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR), we demonstrate the ability to design nanoporous membranes with polyelectrolyte multilayers a priori. This approach, which is independent of substrate material and highly reproducible, reveals that for polyelectrolyte systems, the layer density alone suffices to model data obtained from both QCM-D and SPR. Our method proves particularly effective when modified membranes are subjected to pressure conditions, with the synergy of QCM-D and SPR providing a robust solution for multilayer thickness determination. This innovative approach significantly reduces both time and material consumption, offering a streamlined and highly efficient pathway for the systematic design of polyelectrolyte-modified membranes.