Copolymer Nanofilters with Charge-Patterned Domains for Enhanced Electrolyte Transport

The further advancement of membrane separation processes will require the development of more selective membranes. In this study, membranes that take inspiration from the mosaic structure of cell walls and use multiple functionalities of unique chemical design to control solute transport through chemical factors as well as steric factors are detailed. Specifically, a polyfacrylonitrile-co-[oligo (ethylene glycol) methyl ether methacrylate]-co-(3-azido-2-hydroxypropyl methacrylate)} copolymer tailor-made for the generation of nanofilters, which possess a high density of well-defined pores that are lined by azido moieties, allowed for the generation of chemically patterned mosaic membranes in a rapid manner through the use of printing devices. By engineering the composition of the reactive ink solutions printed on the membrane to allow for the rapid, one-to-one covalent attachment of alkynyl-functionalized groups to the azido moieties, we generated large areas of patterned membranes in seconds rather than hours as detailed in previous reports. Charge mosaic membranes, in particular, were used as an example of this novel platform. These membranes possess distinct cationic and anionic domains that traverse the membrane thickness, which results in the emergence of negative osmosis. As demonstrated through transport testing, this novel transport mechanism results in the preferential permeation of electrolytes over neutral molecules and solvents. For example, a negative rejection of -15% was observed for an aqueous feed solution containing 0.1 mM potassium chloride. The versatile and precise control over membrane chemistry at the nanoscale provided by the technique suggests that it could be engineered to prepare a variety of highly selective mosaic membranes.