Multifunctional PVDF nanofiber materials for high efficiency dual separation of emulsions and unidirectional water penetration

Multifunctional fibrous materials are desirable for smart garments, dual separation of oil-in-water (O/W) and water-in-oil (W/O) emulsions, and membrane filtration, however, the contradictory permselectivity and sophisticated preparation method impede the large-scale manufacture and their wide applications. Herein, the multifunctional polyvinylidene fluoride (PVDF) nanofibrous materials were fabricated by the facile washing treatment of electrospun PVDF-polyvinylpyrrolidone nanofiber membrane (WPVDF). The WPVDF nanofiber membranes with hierarchical and porous structure illustrated interesting wettability, such as superamphiphilic in air, underoil superhydrophobic, and underwater superoleophobic. Consequently, the WPVDF membranes achieved intriguing dual separation performance towards both O/W and W/O emulsions, involving separation efficiency >98.5% and permeation flux >12940.1 L m-2h−1 towards O/W emulsions, separation efficiency >99.5% and permeation flux >8264.3 L m-2h−1 towards W/O emulsions, and good reusability within 20 cycles. Furthermore, the WPVDF/PVDF composite membranes exhibited intriguing unidirectional water penetration performance and long-term stability, the water can only penetrate from hydrophobic PVDF layer to hydrophilic WPVDF layer and cannot occur in reverse direction. The fabrication of such multifunctional PVDF nanofibrous materials could be potentially applied in the field of smart garments, water treatment, and flow control devices.