Polysulfone-AN69 blend membranes and its surface modification by polyelectrolyte-layer deposit-Preparation and characterization

The thermodynamic behavior of phase inversion in membrane formation was studied by measuring the cloud points of polysulfone (PSf)/solvent/water ternary systems and PSf/AN69/N-methyl pyrrolidone/water quaternary system. AN69 is an ionomer made of acrylonitrile-methallylsulfonate copolymer. The polysulfone-AN69 blend membranes were prepared by the phase inversion technique using N-methyl-2-pyrrolidinone (NMP) and water as solvent and coagulant, respectively. AN69 was added in the casting solution to create sulfonic negative charges on the formed membranes, which were modified by simple contact of the blend membranes with solutions of a cationic polyelectrolyte, polyethylenimine (PEI) or polydiallyl-dimethylammoniumchloride (PDADMAC). The obtained membranes were characterized by scanning electron microscopy, dye-staining tests, contact angle, thermogravimetry and ultrafiltration measurements. It was found that the blending of partially miscible AN69 and PSf polymers led to increased membrane wettability and larger pores in the membranes. The ultrafiltration process was used to characterize the filtration properties of the prepared membranes, and the quartz crystal microbalance technique to study the polycation immobilization on the blend membranes. The results show that water permeability, PEG rejection and the resistance of PEG adherence of the modified membranes were enhanced due to the presence of hydrophilic polyelectrolyte adsorbed onto the charged membrane pores.