Solvent-resistant nanofiltration membranes based on multilayered polyelectrolyte complexes

Alternating deposition of oppositely charged polyelectrolyte (PEs) can create stable solvent-resistant nanofiltration (SRNF) membranes with very high flux and selectivity. A new combination of PEs (poly(diallyldimethylammonium chloride) and sulfonated poly(ether ether ketone) is reported from which supported membranes consisting of 5, 10, 15, and 20 bilayers are prepared via the layer-by-layer method. The morphology of the membranes was studied in detail by SEM and AFM, showing rougher membrane surfaces with increasing bilayer number. For the first time, polyelectrolyte complex (PEC) based membranes were also applied in the filtration of organic solvents, where they form an excellent new tool to study the role of charges in solvent filtrations. Due to Dolman exclusion, the multilayered PEC membranes showed very good retentions up to 99% for charged solutes in the pressure-driven filtration of isopropanol solutions. Moreover, they were found to show excellent prospective use in polar aprotic solvents, like dimethylformamide and tetrahydrofuran, which have been extremely troublesome so far for most existing SRNF membranes.