Plasma-induced immobilization of poly(ethylene glycol) onto poly(vinylidene fluoride) microporous membrane

Poly(vinylidene fluoride) (PVDF) microporous membranes with surface-immobilized poly(ethylene glycol) (PEG) were prepared by the argon plasma-induced grafting of PEG. The PEG was pre-coated on the membrane surface, including the pore surfaces, by dipping the membrane in a PEG/CHCl3 solution prior to the argon plasma exposure. The microstructure and composition of the PEG-grafted PVDF (PEG-g-PVDF) membranes were characterized by attenuated total reflectance (ATR) FT-IR, X-ray photoelectron spectroscopy (XPS), and thermogravimetric (TG) analysis. A moderate radio-frequency (RF) plasma power and plasma treatment time led to a high concentration of the grafted PEG polymer. The morphology of the modified membranes was studied by scanning electronic microscope (SEM). The pore size and water flux of the modified membranes were also characterized. The flux decreased with increasing surface concentration of the grafted PEG polymer, while the pore size remained almost unchanged. Protein adsorption experiments revealed that the PEG-g-PVDF membranes with a PEG graft concentration, defined as the [CO]/[CF2] ratio above 3.2 exhibited good anti-fouling property.