Nanoporous block copolymer membranes for ultrafiltration: a simple approach to size tunability.

Nanoporous structures were obtained by the self-assembly of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymers (BCP) where, in thick films, cylindrical microdomains were oriented normal to the substrate and air interfaces, and in the interior of the films, the microdomains were randomly oriented. Continuous nanopores that penetrated through the film were readily produced by a simple preferential swelling of the PMMA microdomains. The confined swelling and rapid contraction of PMMA microdomains generated well-defined uniform pores with diameters to 17.5 nm. The size selectivity and rejection of Au nanoparticles (NPs) for these ultrafiltration (UF) membranes were demonstrated, suggesting an efficient route to tunable, noncomponent-degradative UF membranes.