Surface zwitterionicalization of poly(vinylidene fluoride) porous membranes by post-reaction of the amphiphilic precursor

► A facile method to endow porous membranes with coverage of zwitterion was described. ► PDMAEMA was transited to zwitterion by using 3-bromopropionic and 1,3-propanesultone. ► The modified membranes showed increased protein retention while decreased water flux. A facile method to endow porous membranes with high coverage of zwitterionic components on surface was described. The amphiphilic precursor poly(vinylidene fluoride)- graft- N, N-dimethyl aminoethyl methacrylate (PVDF- g-PDMAEMA) was firstly synthesized via ATRP method and then blended with PVDF to prepare flat membranes. The 3-bromopropionic and 1,3-propane sultone were then used as quaternization agent to transit the PDMAEMA into poly(zwitterions) through an surface reaction by treating membranes under a mild condition. The reaction kinetics was investigated, finding that 1,3-propane sultone was more reactive than the 3-bromopropionic. The X-ray photoelectron spectroscopy (XPS) confirmed that nearly 70% of PDMAEMA had been quaternized in 48 h for the 1,3-propane sultone, while only 62% of PDMAEMA was transited for the 3-bromopropionic in 96 h. The porosity determination indicated that the specific area had decreased obviously after the membranes being modified. Morphology changes were found to be responsible for the decreased water fluxes and increased retentions when zwitterions were formed. The successful modification was confirmed by the nice biocompatibility that no platelets adhesion as well as proteins deposition was observed on modified membranes.