Surface skin layer formation and molecular separation properties of asymmetric PEEKWC membranes

Asymmetric membranes based on a poly(ether ether ketone) with a phthalido group along the polymeric backbone (PEEKWC) were prepared by non-solvent induced phase separation. Three chlorinated solvents (i.e. chloroform, dichloromethane and 1,2-dichloroethane - TCM, DCM and DCE in the following), at fixed evaporation times between casting and coagulation in methanol, have been used to investigate the effect of different evaporation rates on the formation of the skin layer structure. The surface morphology of the membranes has been determined by AFM. Membranes prepared by using DCM and TCM as solvents are characterized by the presence of a dense skin layer with different grain size, whereas a porous skin layer is formed with DCE. These differences arise from the volatility (DCm > TCM > DCE) and the solvation ability (DCM < DCE