Issues surrounding water scarcity and quality have led to a global water crisis. A potential solution to remove contaminants from wastewater is polymeric membranes, due to their reliability and versatility. Two membrane materials, polyvinylidene fluoride (PVDF) and copolymer polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), are often selected for membrane fabrication due to their favorable qualities: thermal stability and mechanical strength. The purpose of this study was to successfully fabricate a bilayer membrane using PVDF-HFP and polysulfone (PSf) in eco-friendly solvents, while being able to utilize polydopamine to chemically bind layers together. Once complete, the membranes and layer adhesion were characterized. Bilayer membranes are preferred over single layer membranes due to their increased stability and permeability. The effects of polydopamine were tested due to its favorable qualities: adhesiveness and high hydrophilicity. The compatibility of polydopamine, the polymers, and environmentally friendly solvents Rhodisaolv® PolarClean and gammavalerolactone (GVL) were calculated utilizing Hansen Solubility Parameters. These “green” solvents typically offer reduced toxicity compared to traditional solvents such as petroleum-derived N-methyl-2-pyrrolidone (NMP). Dope solutions were created using nonsolvent induced phase separation (NIPS) and cast simultaneously with differing coating gaps on two doctor blades to fabricate bilayer membranes. These membranes were characterized via ternary phase diagrams, XPS scans, Young’s Modulus values, and pure water flux, then compared to single layer membranes lacking polydopamine. SEM imagery was used to visually determine gaps between membranes and was paired with tensile strength data to evaluate the effectiveness of polydopamine addition. Polydopamine addition improved the thermodynamic stability of fabricated membranes, while also improving the mechanical strength by increasing Young’s modulus values.
