Highly Flexible Monolayered Porous Membrane with Superhydrophilicity–Hydrophilicity for Unidirectional Liquid Penetration

The ability to allow microliquid to penetrate in one direction but block in the opposite direction plays an irreplaceable role in intelligent liquid management. Despite much progress toward facilitating directional transport by multilayer porous membranes with opposite wettability, it remains difficult to achieve a highly multifunctional flexible membrane for highly efficient unidirectional liquid transport in different situations. Herein, a superhydrophilic-hydrophilic self-supported monolayered porous poly(ether sulfone) (PES) membrane with special nano- and micropores at opposite surfaces is demonstrated, which can be used for unidirectional liquid transport. The results reveal that the competition of liquid spreading and permeation is critical to achieve directional liquid transport. The porous PES membrane, transformed with 70 vol % of ethanol in water (E/W-PES-70%), exhibits continuous unidirectional liquid penetration and antigravity unidirectional ascendant in a large range of pH values and can be used as "liquid diode" for moisture wicking. Moreover, the PES membrane can be prepared in a large area with excellent flexibility at room and liquid nitrogen temperature, indicating great promise in harsh environments. This work will provide an avenue for designing porous materials and smart dehumidification materials, which have promising applications in biomedical materials, advanced functional textiles, engineered desiccant materials, etc.