Selective Ion Transport in Hydration-Limited sub-nm pores of Polymer Membranes - Chinedum Osuji - Davidson School of Chemical Engineering - Purdue University

Ion transport under nanoscale confinement and in the presence of charge is poorly understood from a fundamental perspective. Under the conditions of dielectric saturation that arise in nanoscale pores, the classical ideas that guide our understanding of electrostatic interactions break down, and new principles that account for the role of pore geometry and chemistry on water structure and ion interactions are needed. At the same time, our ability to develop such principles is hindered by the challenge of generating relevant well-defined geometries that enable experimental studies over statistically meaningful volumes such that experimental data can be more confidently considered alongside data from computational efforts. Beyond the fundamental implications, new understanding is needed to drive the rational design of materials for ion separations in critical minerals production and resource recovery, among other examples, where the need to distinguish between ions of the same valency and charge imposes a severe challenge. Here, we examine transport of ions in polymer membranes with well-defined sub-1 nm pores. The membranes are charged, modestly hydrated nanoporous polymers produced by crosslinking self-assembled lyotropic mesophases with direct hexagonal and gyroid nanostructures. This work addresses the roles of hydration, pore geometry and ion identity on transport using a combination of electrochemical and NMR measurements, and molecular simulation. Our results highlight the roles of hydration, solubility, pore size, and ion-pore wall interactions in dictating transport in the pores. They provide new insight regarding transport under nanoscale confinement in the presence of charge and that we suggest could be relevant for the development of materials for challenging ion separations.

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Dr. Osuji is the Eduardo D. Glandt Presidential Professor, and Chair, in the Department of Chemical and Biomolecular Engineering, and a secondary member of the faculty in Materials Science and Engineering, at University of Pennsylvania. He is an Associate Editor for Macromolecules and was a member of the Board of Directors of the Materials Research Society (2021-2024). He leads an experimental research group focused on structure and dynamics of soft materials and complex fluids. Topics of interest include structure-property relationships in ordered soft materials, directed self-assembly of block copolymers and molecular materials, and rheology of dense, disordered systems.

Prof. Osuji received his undergraduate degree in Materials Science and Engineering from Cornell followed by his Ph.D., also in Materials Science and Engineering from MIT in 2003. From 2003-2005 he was a Senior Scientist at a startup company, Surface Logix Inc., before moving to Harvard as a Postdoctoral Associate in Applied Physics (2005-2007). He was a member of the faculty at Yale University in the Department of Chemical and Environmental Engineering from 2007-2018 before moving to the University of Pennsylvania.

Prof. Osuji is a Fellow of the American Physical Society, and a recipient of a CAREER award from the National Science Foundation (2008). He received an Office of Naval Research's Young Investigator award and a 3M Nontenured Faculty award in 2012. He is the recipient of the Dillon Medal of the American Physical Society (2015), the Hendrick C. Van Ness Award (2019), and the Nano Research Young Investigator Award (2019). In 2022 he received the Prince Sultan Bin Abdulaziz International Prize for Water (PSIPW)