Self‐Assembled Asymmetric Block Copolymer Membranes: Bridging the Gap from Ultra‐ to Nanofiltration

Abstract

The self‐assembly of block copolymers is an emerging strategy to produce isoporous ultrafiltration membranes. However, thus far, it has not been possible to bridge the gap from ultra‐ to nanofiltration and decrease the pore size of self‐assembled block copolymer membranes to below 5 nm without post‐treatment. It is now reported that the self‐assembly of blends of two chemically interacting copolymers can lead to highly porous membranes with pore diameters as small as 1.5 nm. The membrane containing an ultraporous, 60 nm thin separation layer can fully reject solutes with molecular weights of 600 g mol−1 in aqueous solutions with a water flux that is more than one order of magnitude higher than the permeance of commercial nanofiltration membranes. Simulations of the membrane formation process by dissipative particle dynamics (DPD) were used to explain the dramatic observed pore size reduction combined with an increase in water flux.

Block Copolymer Membranes for Aqueous Solution Applications

“…The minimum pore size depends on the length of the stretchable pH-responsive block and the size of the pre-formed pores. Recently 115 we found out that by blending PS-b-P4VP with small molecular weight PS-b-PAA copolymers nanofiltration membranes could be obtained with pore size as small as 1.5 nm, rejecting solutes of 600 g/mol at neutral pH with remarkably high flux of 432 L m -2 h -1. bar -1 . This was demonstrated for one blend system, but we anticipate that this approach would be successful with a variety of still unexplored copolymer compositions.…”

Nanofiltration membranes with narrowed pore size distribution via pore wall modification

“…[1][2][3] It has been widely applied in the fields of seawater desalination, 4 waste water treatment, 5 chemical product purification 6 and food engineering. 7,8 Nanofiltration membranes (NFMs) are the critical part of nanofiltration processes.…”

Recent Advances in Preparation of Porous Polymeric Membranes by Unique Techniques and Mitigation of Fouling through Surface Modification

“…The isoporous upper layer followed by the asymmetric spongy structure (Figure ) is the characteristics of SNIPS membranes. Interestingly, reduction of the pore size is not lowering the water permeability, but in reality it increases the water permeability due to the increased pore density . Hence, cylindrical shaped cross‐sectional pores allow high water permeability and narrow the borderline between the nanoporous and ultrafiltration membranes.…”