An EVAl membrane with polyionic complex (PIC) as a skin layer has been prepared by in situ polyionic complexation between the cationically modified surface of EVAl membrane and the corresponding polyanion solutions.Two types of polyanions like sulfonated EVAl and phosphorylated EVAl

as well as quaternary ammonium modified EVAl membrane were synthesized and used for polyionic complexation.To reach the complete complexation

the amount of polyanion must be well above the cations on the surface of EVAl.The x-ray photoelectron spectron spectroscopy and elemental analysis revealed that the complexation mainly occurred on the surface of EVAl membrane.An asymmetric membrane with more condensed skin layer and porous inner alyer was obtained

which mya find new applications in biologi field.