Design and performance of foul-resistant poly(vinylidene fluoride) membranes prepared in a single-step by surface segregation

Immersion precipitated membranes with enhanced fouling resistance are prepared from blends of poly(vinylidene fluoride) (PVDF) and a free-radically synthesized amphiphilic comb polymer having a methacrylate backbone and poly(ethylene oxide) side chains. X-ray photoelectron spectroscopy analysis indicates substantial surface segregation of the comb polymer during membrane coagulation, providing an integrated near-surface coverage of up to 50 vol.% comb for a membrane containing 10 wt.% (14.6 vol.%). The surface coverage increases with comb molecular weight, providing hydrophilic surfaces with excellent stability and substantiating a proposed mechanism for surface localization. Separation surface porosities for comb-modified membranes are up to an order of magnitude higher than PVDF controls. With the combined benefits of fouling resistance and increased porosity, a membrane containing 10 wt.% comb is over 20 times as permeable as a PVDF-only membrane with equivalent separation characteristics after 3 h of filtration of a foulant protein solution.