Diblock Thin Films with Densely Hexagonally Packed Nanochannels

Films, 2μm thick, with hexagonally packed and uniformly sized nanochannels with a diameter of ∼17 nm and at a density of ∼5 × 1010 cm–2 were prepared. These channels were partially filled with poly(acrylic acid) (PAA) and the structural change of PAA chains with variations in pH, ionic strength, and ion type caused water permeability to change by several orders of magnitude. These membranes with “chemical valves” should be useful in controlled drug release or chemical sensing. In cyclopentane, the PAA chains probably collapse onto the channel walls and the channel centers should open up. The channels allowed the separation of species according to their difference in size and this property should be useful for future studies of polymer chain reptation through the nanochannels.