Pressure-driven membrane processes such as reverse osmosis and ultrafiltration are commonly
leveraged to purify drinking water; however, modern commercial membranes are manufactured using
toxic organic solvents which pollute the environment. We propose the implementation of sustainably
fabricated polyelectrolyte complex (PEC) coacervate membranes. A PEC coacervate is a single-phase
aqueous ionic solution concentrated with polymers of opposite charge, and during aqueous phase
separation (APS), water draws salt ions from the complex, resulting in a polyelectrolyte precipitate with a
porous structure, namely, a membrane. Previously, the PEC consisting of poly(sodium 4-styrenesulfonate)
(PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) in a 1:1 ratio was shown to yielded
mechanically stable antifouling membranes with a cationic surface after undergoing APS. In this study,
the stoichiometric ratio of PSS to PDADMAC was tuned to determine its effect on separation
performance and stability. Additionally, emphasis was placed on determining the polyelectrolyte ratio for
a neutral surface charge membrane. Pure water permeance (PWP) tests confirmed the mechanical stability
of the nonstoichiometric membranes. Dye rejection tests using methylene blue and methyl orange
unveiled insights into the membranes’ surface chemistry and charge. Neutral poly(ethylene glycol) (PEG)
rejection tests at varying molecular weights (600, 1000, 2000 Da) coupled with gel permeation
chromatography characterized the selectivity of the membranes. Ultimately, our work established the
tunability of nonstoichiometric polyelectrolyte membranes, paving the way for the production of
specialized membranes tailored for exact process requirements.
