▎ 摘　　要

Stimuli-responsive membranes exhibit a flexible adjustment in response to environmental stimuli and have been established many applications. In this paper, dual-stimuli-responsive ultrafiltration membranes were designed by stacking graphene oxide (GO) nanosheets cross-linked with poly(vinyl alcohol) (PVA) onto the surface of a porous substrate. The membrane showed a significant response to the direction of hydraulic pressure, where water flux varied by 11 times and rejection varied between 9.8 and 79.3% under normal/reverse filtration modes at a liquid pressure of 0.1 MPa. The pressure response was based on the reversible jacking-up and pressing-down of the GO nanosheets under different filtrate flow directions and feed liquid pressures and the state change of chemical groups and free ends of PVA macromolecules inserted between GO nanosheets. In addition, the membrane also responded to water and ethanol filtration differently as a result of the reversible stretching and shrinking of cross-linked PVA macromolecules in water and ethanol, respectively. The water-stretched PVA macromolecules among GO nanosheets shrunk into rigid aggregates when water molecules surrounding PVA chains were expelled by ethanol, thereby affecting the interspace among GO nanosheets. The cross-linking of GO nanosheets with flexible PVA macromolecules provided a means to tune the GO nanosheet interspacing.