The American Chemical Society’s Spring 2023 meeting takes place this week in Indianapolis, hosting international leaders in chemistry from industry, government, and academia. Researchers from the University of Chicago’s Pritzker School of Molecular Engineering (PME) had a significant presence at the event.
The ACS biannual meeting draws thousands of chemistry professionals for the opportunity to share ideas and advance scientific knowledge.
PME presentation highlights
Electrolyte and solvation effects for nonaqueous CO2 electrochemistry
Chibueze Amanchukwu, Neubauer Family Assistant Professor of Molecular Engineering
Carbon dioxide (CO2) conversion is vital because it provides a pathway to efficiently valorize CO2 and incentivize CO2 capture. Electrocatalytic CO2 conversion is of great interest because it is scalable and can be done at ambient temperature and pressure. However, these reactions are typically performed in water which suffers from undesired hydrogen evolution reaction (HER) from water breakdown. Furthermore, catalyst selection is often determined by the ability of the catalyst to favor CO2RR over HER. Aprotic nonaqueous electrolytes can suppress HER and enable a wider range of catalysts for CO2RR. Here, we study the influence of aprotic electrolyte solvent on CO2RR. Firstly, we probe the ability of aprotic electrolytes to enable earth-abundant catalysts for CO2RR to CO. Secondly, we understand the influence of dissolved water and water solvation in aprotic electrolytes and the ability of aprotic electrolytes to enhance or suppress HER. Our work pushes the field in the understanding of electrolyte solvent and water effects for electrochemical transformations such as CO2RR and HER.
Riccardo Allesandri, postdoctoral researcher (de Pablo Group)
The increasing societal need for energy storage, currently essentially relying on the lithium-ion battery technology, presents pressing challenges that include the full life cycle of the batteries, their carbon footprint, and their reliance on scarce metals. Among emerging technologies, organic-based batteries that are degradable or recyclable may offer metal-free solutions to energy storage. One example of such emerging battery technologies are solid-state devices that use nonconjugated radical-containing polymers. A fundamental understanding of how the chemical structure of such polymers impacts their charge transport performance is still lacking. To enable the rational design of such polymers, there is a need of accurate and efficient multiscale models that incorporate both mesoscale morphological features and electronic structure information.
Using our recently developed method that combines machine learning and coarse-grained modeling to predict electronic properties at large spatiotemporal scales, we investigate radical-containing polymers and their charge transport properties. Coarse-grained modeling allows to probe relevant polymeric material length- and timescales. At the same time, electronic structure information is retained, allowing for the retrieval of conformationally-averaged electronic property distributions as a function of material morphology and processing conditions. The impact of polymer backbone, radical sites, and solvent swelling are investigated. The derived morphology-electronic structure relationships inform the design of radical-containing polymers with improved characteristics for all-organic battery materials.
Chuting Deng, PhD student (De Pablo Group)
Grafting a mix of side chains onto a polymer electrolyte introduces additional functionalities beyond Li+ conduction. This study investigates how Li+ are solvated and transported in materials having a contrast in their side-chain polarities and mobilities. We employ MD simulations to compare Li+ solvation and transport behaviors in POEM versus in its copolymers with the cyclic carbonate-containing PGCMA. Although the PGCMA side chain is more polar than the POEM side chain, Li+ is favorably solvated by the latter, due to its relatively low entropic penalty. Due to a similar argument on solvation entropy, the presence of PGCMA side chain also switches the favorable solvation motif from two-chain solvation to single-chain solvation, and thereby altering its hopping mechanism. Finally, compared to PGCMA-r-POEM, the less-mixed block copolymer PGCMA-b-POEM shows decreased Li+ transport. The observed trend is explained by further analysis on solvation site network connectivity. The discussions on entropic driving forces for ion solvation preferences and on effects of mixing on long-range Li+ transport are insightful for future mixed SPE designs.
Engineering metal-organic framework functionalities for water harvesting and catalysis
Laura Gagliardi, Richard and Kathy Leventhal Professor in the Pritzker School of Molecular Engineering. Director of the Chicago Center for Theoretical Chemistry.
High-throughput methods and computational modeling play a fundamental role in understanding metal-organic frameworks (MOFs) at the level of individual atoms, molecules, and extended frameworks. Interplay between theory and experiment is indispensable to advance the field. I will overview the latest theoretical and computational achievements of our community and present our recent modeling studies combined with data science of MOFs as catalysts and as adsorbents for water harvesting.
Self-healing directed self-assembly of block copolymers for lithographic applications
Whitney Loo, postdoctoral researcher (Nealey Group)
The directed self-assembly (DSA) of block copolymers (BCPs) is a lithographic process with significant promise for patterning sub-10nm features and for the use of pattern rectification in EUV lithography. Patterning at these small length scales will require both the design of new polymers that follow specific materials design requirements and tailored approaches to DSA. Here we utilize BCPs with A-b-(B-r-C) copolymer architecture which decouple thermodynamic and surface energy properties to allow for DSA via thermal annealing with low defectivity. Through the use of a high throughput, post synthetic modification, we are able to synthesize a library of A-b-(B-r-C) copolymers based on polystyrene-block-poly(glycidal methracylate) copolymers with copolymer periodicities, L0, between 16-19 nm. While a full set of polymer mat and brushes for conventional DSA is not readily accessible to this new family of A-b-(B-r-C) polymers, we have developed a new, self-brushing chemoepitaxial DSA workflow. The B-r-C random block contains chemical functionality that allows for self-brushing to Si substrates. Through sequential rounds of DSA, the B-r-C domain of the copolymer grafts to the substrate and registers the B-r-C copolymer domain to the pre-pattern with incremental improvement at each DSA cycle, which results in “self-healing” of the DSA defects and a large increase in the DSA processing window. We hope this work will uncover a new understanding between copolymer molecular properties and characteristics of the final pattern such as line edge and line width roughness.
Investigating composites of functionalized cellulose nanocrystals
Stuart Rowan, Barry L. MacLean Professor for Molecular Engineering Innovation and Enterprise
Cellulose nanocrystals (CNCs) have attracted attention in recent years as potential green nanomaterials. CNCs are highly crystalline nanofibers that can be isolated from a variety of renewable biosources, including cotton, sisal, wood, and sea tunicates. The diameters range from 5 to 30 nm and the lengths range from 100 nm to several micrometers depending on the biosource and method of isolation. CNCs have several advantages as a nanomaterial, including bio-sustainability, bio-renewability, relatively low production cost, and low cytotoxicity. They generally have high surface area, low density, low coefficient of thermal expansion as well as high elastic moduli of about 80-150 GPa, depending on the biosource. We have been investigating the use of CNCs to access mechanically-dynamic composites, as reinforcing agents for polymers and aerogels and to access stable nano-emulsions and latexes. More recently we have exploring how functionalizing the CNC surface impacts the properties of the resulting nanocomposites and our latest work in this area will be discussed.