Nanoporous Films with Superior Resistance to Protein Adsorption by Selective Swelling of Polystyrene-block-poly(ethylene oxide)

Poly(ethylene oxide) (PEO) is well-known for its excellent resistance to the nonspecific adsorption of proteins. However, it remains challenging to fabricate surfaces with uniform and robust coverage of PEO chains in a simple and efficient way. Simply by treating the block copolymer polystyrene-block-poly(ethylene oxide) (PS-b-PEO) in ethanol, we obtain nanoporous polymeric films with superior resistance to protein adsorption. The pores are nondestructively formed via the selective swelling-induced pore generation mechanism in which PEO microdomains embedded in PS matrix are selectively swollen in ethanol and collapsed in the subsequent air drying. Pore sizes and porosities can be typically tuned in the ranges ∼20-50 nm and ∼20-70%, respectively, by changing swelling durations and temperatures. Interestingly, the PEO chains are simultaneously migrated on the film surface and pore walls in the selective swelling-induced pore forming process. Atomic force microscopy examinations reveal that PEO chains are solvated when the film is wetted with water, closing the pores in the film. Thus, produced SEO films adsorb much less proteins than PS films without PEO on the surface, and also demonstrate a better fouling resistance than many reported PEO-covered surfaces prepared by other methods.