A series of polyvinylidene fluoride (PVDF) porous membranes with different pore structures were prepared from PVDF and sodium allyl sulfonate (SAS) via various phase inversion methods

such as non-solvent induced phase separation (NIPS)

vapor induced phase separation (VIPS)

and solvent evaporation induced phase separation (EIPS). A concept for membrane structure regulation was proposed on the basis of growth mechanism of polymer crystalline which controlled crystal growth by solvent evaporation time. The membrane was characterized by scanning electron microscopy (SEM)

Brunner-Emmet-Teller (BET)

X-ray diffraction (XRD)

differential scanning calorimetry (DSC)

as well as permeability of protons (H+)

tetravalent vanadium ions (VO2+)

and other ions. With the increase of solvent evaporation time

spherulites in cross-sectioned membrane was increased gradually till all spherulites grew into each other

such that membrane porous structure changed significantly as well as membrane crystalline percentage and morphology were altered. The decreased membrane pore size improved selectivity for H+ relative to VO2+ from 12 to 73

which demonstrated high separation properties of the naonporous membrane.