Isoporous
membranes which have narrow pore size distributions and straight pore profiles
promise sharp selectivity at no expense of permeability. However, it remains
challenge to produce isoporous membranes in an affordable and efficient way. In
this work, we report on the facile preparation of isoporous membranes based on
the nondestructive creation of straight pores in block copolymers of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP).
Thin films of PS-b-P2VP are annealed
to induce the perpendicular orientation of the P2VP cylinders, and then
transferred to macroporous supporting membranes to form mechanically robust
composite structures. The copolymer films are treated in hot ethanol to convert
the P2VP cylinders into straight pores following the selective swelling-induced
pore generation mechanism. The perpendicular alignment of the P2VP cylinders in
the PS matrix facilitates the swelling-induced pore generation process, making
the membrane highly permeable. Because of its ultrathin thickness, high porosity,
and strong hydrophilicity, the membrane exhibits a water flux as high as 1686 L·m^-2·h^-1·bar^-1, which is about 10-times higher than
commerical membranes and also much higher than other isoporous membranes with
similar effective pore sizes. Furthermore, the membrane has an inherent
reversible pH-responsive functionality because of the enrichment of
protonizable P2VP chains on the pore wall and membrane surface.