Preparation of protein-resistant surfaces on poly(vinylidene fluoride) membranes via surface segregation

Self-organizing blends of an amphiphilic comb polymer having a poly(methyl methacrylate) (PMMA) backbone and poly(ethylene oxide) (PEO) side chains in poly(vinylidene fluoride) (PVDF) have been examined as a means to create foul-resistant, self-healing surfaces on polymer membranes. X-ray photoelectron spectroscopy (XPS) analysis of phase inversion membranes prepared from these blends indicates substantial surface segregation of the amphiphilic component, which occurs both during the coagulation step of the phase inversion process and in subsequent annealing of the membranes in water. With annealing, a near-surface coverage of nearly 45 vol % comb polymer is produced on a membrane with a bulk comb concentration of only 3 vol %. Surface enrichment of the hydrophilic comb polymer is shown to impart significant resistance to the adsorption of bovine serum albumin (BSA). XPS analysis of membranes treated with concentrated acid shows that hydrophilic surface layers removed by acid exposure may be regenerated by further surface segregation during a subsequent heat treatment in water, resulting in partial recovery of protein adsorption resistance.