High Flux Membranes with Ultrathin Zwitterionic Copolymer Selective Layers with ∼1 nm Pores Using an Ionic Liquid Cosolvent

We report membranes with ultrathin <200 nm zwitterionic copolymer selective layers exhibiting ∼1 nm size cutoff and permeances as high as 50 L/m2·hr·bar. The thin layer is formed by the deposition of random zwitterionic copolymers in trifluoroethanol/ionic liquid mixtures onto a porous support. The resultant membranes have the same low molecular weight cutoff of ∼1000 Da and narrow pore size distribution but fluxes up to 10 times higher than membranes prepared without ionic liquid and 20 times higher than commercial membranes of similar pore size, making them promising for wastewater treatment and pharmaceutical purification.