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

Abstract

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.

Ultra‐Fast Click Modification of Self‐Assembled Zwitterionic Copolymer Membranes for Enhanced Ion Selectivity

“…This layer thickness could potentially be further decreased by improving the coating processes, resulting in higher membrane permeances by up to 50 times, as demonstrated with other ZAC membrane chemistries. [ 52,63 ]…”

“…This layer thickness could potentially be further decreased by improving the coating processes, resulting in higher membrane permeances by up to 50 times, as demonstrated with other ZAC membrane chemistries. [52,63] Membrane was immersed in TFE, a solvent that readily dissolves un-cross-linked P(AM-r-SBMA). The fact that the selective layer is visually unchanged shows that cross-linking improves the solvent stability of this layer.…”

“…This novel chemical approach enables us to tune membrane selectivity and ion separations in a matter of seconds, decreasing processing time by over an order of magnitude compared with both past post‐processing times used with ZACs [ 19 ] and with other reports of thiol‐ene post‐processing of various membranes. [ 20,23,52 ] We show that the resultant membranes not only exhibit high and tunable monovalent/divalent ion selectivity, but also excellent fouling resistance. These novel membranes feature selective layers fabricated from the cross‐linkable ZAC poly(allyl methacrylate‐random‐sulfobetaine methacrylate) (P(AM‐ r ‐SBMA)), [ 19 ] whose chemical structure is shown in Figure 1B.…”

Ultrafiltration Membranes Coated by Amphiphilic Copolymers Containing Superhydrophilic Zwitterionic and Hydrophobic POSS Moieties Showing Improved Fouling Resistance/Release Properties

“…This is in agreement with results from our previous study on amphiphilic copolymers containing high proportions of hydrophobic moieties. [ 10b ]…”

“…[ 3b,3c,4a,5a,9 ] Since zwitterions can impart superhydrophilicity, amphiphilic copolymers having zwitterionic moieties have been also developed. However, since many of the polymers having zwitterionic moieties have poor solubility in most of the organic solvents, [ 3a,10 ] their application in the surface coating process, the most efficient way to modify the membrane surface, [ 3c ] has been limited.…”