Impacts of support membrane structure and chemistry on polyamide–polysulfone interfacial composite membranes

Herein, we discuss the properties of polyamide thin films formed via identical interfacial polymerization conditions over porous polysulfone supports with different physical and chemical properties. Polysulfone supports were formed by nonsolvent induced phase separation (i.e., immersion precipitation) employing several casting solution and precipitation bath chemistries. Hand-cast polysulfone films (and a commercial polysulfone membrane) exhibited a wide range of pure water permeabilities, dextran rejections, water contact angles, and surface roughness statistics. These results, combined with FTIR spectra and SEM images, confirm that each support offered a different skin layer pore morphology and chemistry. Polyamide composite membranes formed thereon displayed widely varying film morphology, separation performance, and interfacial properties. More permeable, hydrophilic supports produced low permeability polyamide–polysulfone interfacial composite membranes, whereas highly porous, relatively hydrophobic supports produced more permeable composite membranes. A conceptual model was proposed to explain the potential impacts of polysulfone support membrane properties during the polyamide interfacial polymerization reaction and the resulting characteristics of polyamide–polysulfone interfacial composite membranes.