Controlled pore collapse to increase solute rejection of modified PES membranes

Pore collapse upon drying is a well-known phenomenon in ultrafiltration PES membranes. Here we demonstrate how alteration of membrane surface chemistry can be used to control the extent of pore collapse and ultimately to tailor membrane properties. Commercial hollow-fiber PES membranes were modified via surface-initiated ATRP to obtain different polymer-grafted membranes and were subsequently dried to facilitate pore collapse. The different polymer grafts could be used for controlling the water flux and solute rejection characteristics of the membranes. Controlled membrane pore collapse could be exploited to obtain higher rejection of sodium chloride, magnesium sulfate and calcein. Calcein as the largest solute showed almost full rejection (98.9 ± 0.3%) on the membrane. The chemical nature of the grafted polymer was directly reflected in the water flux-to-rejection ratio and the extent of pore collapse.