Highly permeable nanoporous block copolymer membranes by machine-casting on nonwoven supports: An upscalable route

Block copolymer (BCP) membranes are distinguished for their well-defined porosities, tunable pore geometries, and functionable pore walls. However, it remains challenging to produce robust BCP membranes by affordable, convenient methods. Herein, we demonstrate a facile and easily upscalable approach to produce highly permeable BCP membranes in large areas. The membranes possess a bi-layered composite structure with nanoporous polystyrene-block-poly(2-vinylpyrdine) BCP layers directly supported on macroporous nonwoven substrates. The BCP layers are machine-cast on the water-prefilled nonwoven, and interconnected nanoporosities are created in the BCP layers by ethanol swelling. The nanoporous BCP layers exhibit a thickness of ~10 µm and are tightly adhered to the nonwoven. Changes in the swelling temperatures and durations modulate both pore sizes and surface hydrophilicity of the BCP layers, and consequently the permselectivity of the membranes. By increasing swelling duration from 15 min to 12 h, the permeability of the membrane swollen at 65 °C can be increased from ~100 to ~850 L m⁻² h⁻¹ bar⁻¹ with the retention to 15-nm gold nanoparticles reduced from ~93% to ~54%. Moreover, we demonstrate that the composite membrane can efficiently fractionate nanoparticles and narrow down their size distribution from ~3–20 nm to ~3–10 nm.