Selective Transport through Membranes with Charged Nanochannels Formed by Scalable Self-Assembly of Random Copolymer Micelles

Membranes that can separate compounds based on molecular properties can revolutionize the chemical and pharmaceutical industries. This study reports membranes capable of separating organic molecules of similar size based on their electrostatic charge. These membranes feature a network of carboxylate-functionalized 1-3 nm nanochannels, manufactured by a simple, scalable coating process: a porous support is coated with a packed array of polymer micelles in alcohol, formed by the self-assembly of a water-insoluble random copolymer with fluorinated and carboxyl functional repeat units. The interstices between these micelles serve as charged nanochannels through which water and solutes can pass. The negatively charged carboxylate groups lead to high separation selectivities between organic solutes of similar size but different charge. In single solute diffusion experiments, neutral solutes permeate up to 263 times faster than negatively charged compounds of similar size. This selectivity is further enhanced in experiments with mixtures of these solutes. No permeation of the anionic compound was observed for over 24 h. In filtration experiments, these membranes separate anionic and neutral organic compounds while exhibiting water fluxes comparable to that of commercial membranes. Furthermore, carboxylate groups can be functionalized, creating membranes with nanopores with customizable functionality to enable a broad range of selective separations.