Accurately controlling the hierarchical nanostructure of polyamide membranes via electrostatic atomization-assisted interfacial polymerization

Interfacial polymerization is a classical method for the preparation of thin-film composite (TFC) membranes. However, facile and controllable fabrication remains a grand challenge. Here, a dual-needle electrostatic atomization strategy is presented to atomize aqueous and organic phases into droplets respectively, and then a polymerization reaction occurs at interfaces. This method shows excellent controllability over the membrane nanostructure: the monomer ratio determines compactness and the monomer amount governs thickness. Particularly, a hierarchically structured IP layer is developed by regulating the monomer ratio, where the loose layer, a low-resistance region, supports the formation of an ultrathin dense layer for rejection. And the hierarchical nanostructure is proved by positron annihilation spectroscopy, CO2 adsorption, etc. We demonstrate that an IP layer with a 13.8 nm-thick dense layer readily realizes ultrafast solvent permeance (56.9 and 23.7 L m(-2) h(-1) bar(-1) for acetone and water, respectively) and complete rejection for acid yellow 14 (1.9 nm). Such a performance is superior to that of most reported TFC membranes and overcomes the general permeation-rejection trade-off effect. Moreover, this hierarchically structured membrane displays excellent operating stability, pressure stability and cycle stability, especially solvent resistance over 30 days. Briefly, such a strategy endows the membrane with accurate regulation from chemical components to the physical structure, paving the way for the design of next-generation TFC membranes.