The influence of polymer purity and molecular weight on the synthesis of integrally skinned polysulfone membranes

Polysulfones (PSf) from 10 different origins were chosen to prepare solvent resistant nanofiltration (SRNF) membranes by the non-solvent induced phase separation method via immersion precipitation. Besides synthesis of membranes with only one type of PSf, polymer blends were also synthesized. The effects of PSf molecular weight (MW), purity and polydispersity (PDI) on the structure and performance of the prepared asymmetric membranes were investigated by means of scanning electron microscopy (SEM) and SRNF experiments, the latter obtained by measuring Rose Bengal (RB) rejections from iso-propanol (IPA) solutions. Polymers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) and thermogravimetric analysis (TGA) and the polymer casting solutions by viscosity and cloudpoint measurements.