Hydrophilisation of polysulphone ultrafiltration membranes by incorporation of branched PEO-block-PSU copolymers

Polysulphone (PSU) is a popular and versatile material, which is extensively used for the manufacturing of ultrafiltration (UF) and microfiltration (MF) semi-permeable membranes. However, the hydrophobic character of this material causes PSU membranes to be susceptible to adsorptive fouling. Although the use of poly(ethylene-oxide) (PEO) to increase the hydrophilicity of PSU membrane surfaces remains popular, the methods available to add PEO to these surfaces are not without disadvantages. The incorporation of a membrane-modifying, PEO-containing copolymer with a branched architecture directly into the membrane formulation solves many of the problems associated with conventional membrane surface modification techniques. In addition to conventional dynamic contact angle (DCA) determinations and energy dispersive spectrometry (EDS), digital pulsed force mode–atomic force microscopy (DPFM–AFM) was used to prove evidence of the decrease in the hydrophobic character of modified PSU membrane surfaces. Our results strongly indicate that the optimisation of membrane surface hydrophilisation depends on membrane precipitation kinetics as well as the amount of modifying copolymer added to the membrane formulation. Annealing, often used as a post-treatment to membrane manufacturing, appears to have little or no influence regarding this membrane surface hydrophilisation process.