Scientific leaders gather at the ACS fall meeting to discuss challenges and breakthroughs in chemistry
The American Chemical Society’s fall 2022 meeting took place in the McCormick Place Convention Center and featured experts in chemistry from UChicago’s Pritzker School of Molecular Engineering.
The American Chemical Society’s fall 2022 meeting recently took place in Chicago, 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:
Dean Matthew Tirrell was honored with the American Chemical Society Award in Colloid Chemistry
Prof. Laura Gagliardi delivered the Fred Kavli Innovations in Chemistry Lecture
Pritzker Molecular Engineering faculty and students delivered 36 presentations
The ACS’ biannual meeting draws thousands of chemistry professionals for the opportunity to share ideas and advance scientific knowledge. This year’s theme, “Sustainability in a Changing World” highlighted the critical role chemists play in addressing environmental challenges, both by solving the problems humanity faces today and developing sustainable processes for the future.
Awards and recognition
Two faculty members of Pritzker Molecular Engineering were honored at this year’s ACS meeting.
The ACS award in Award in Colloid Chemistry was established in 1952 and is supported by Colgate-Palmolive Company. (Photo by John Zich)
Tirrell was recognized for pioneering discoveries and applications of self-assembling peptide amphiphiles and for seminal contributions to the understanding of colloid modification with polymer brushes.
Tirrell’s broader research focuses on the manipulation and measurement of polymer surface properties. His transformative work has provided new insight into phenomena such as adhesion, friction, and biocompatibility, and contributed to the development of new materials based on self-assembly of synthetic and bio-inspired materials.
Laura Gagliardi, the Richard and Kathy Leventhal Professor in the Pritzker School of Molecular Engineering, was invited to give the Fred Kavli Innovations in Chemistry Lecture. The Kavli Lecture series recognizes groundbreaking discoveries by scientists tackling many of the world’s mounting challenges.
Her lecture, “Quantum Leaps: Chemistry and Creativity in a Changing World,” discussed how theoretical chemistry can address major environmental challenges such as water scarcity, global warming, and the need for clean energy. She explained how metal organic frameworks (MOFs) can help harvest water from the air, even in arid climates.
Gagliardi’s broader research aims to develop novel quantum chemical methods and apply them to study phenomena related to sustainable energies, with a special focus on chemical systems relevant to catalysis, spectroscopy, photochemistry, and gas separation. Her recent work includes research published in Science that demonstrates how to pull water from the air in environments where drinking water may not be readily available.
Chibueze Amanchukwu, Neubauer Family Assistant Professor of Molecular Engineering
Controlling electrochemical interfacial phenomena is vital for energy conversion devices. The conversion of carbon dioxide to fuels and chemicals is one such transformation that requires careful control of the interface. Current CO2 conversion systems suffer from poor product selectivity and low catalyst activity. In this work, we probe the influence of ion solvation at the bulk electrolyte and at the interface to determine the influence of electrolyte selection on modifying achievable current densities and product distribution. We combine multiple spectroscopic techniques to study bulk electrolyte properties as a function of cation-anion-solvent interactions. Finally, our work highlights the importance of understanding and controlling electrochemical interfaces through electrolyte design to enable efficient and selective electrochemical transformations
A series of dynamic covalent network films, which contain catalyst-free, room temperature dynamic thia-Michael bonds, were used to understand structure/property/processing relationships in materials that exhibit dynamic reaction-induced phase separation (DRIPS). The combination of dynamic bonds in a phase-separated system yielded materials with shape memory behavior and facile reprocessability. Interestingly, it was possible to use a tempering process to effectively ‘program’ the mechanical properties of the films, resulting in materials that could be readily converted from brittle to rubbery without changing the chemical composition of the network.
The gut microbiome has myriad effects on both mucosal and systemic health. Resident commensal bacteria play a critical role in the maintenance of mucosal homeostasis, in part through their production of short-chain fatty acids, especially butyrate. Although butyrate is known to play important roles in regulating gut immunity and maintaining epithelial barrier function, its clinical translation is challenging due to its offensive odor and quick absorption in the upper gastrointestinal tract. Here, we designed two block copolymers that contain a high content of butyrate and self-assemble into water-suspendable micelles. These two copolymers consist of a hydrophilic block, poly(N-(2-hydroxypropyl) methacrylamide) or poly(methacrylic acid), with a hydrophobic block, poly(N-(2-butanoyloxyethyl) methacrylamide), thus connecting a backbone sidechain to butyrate with an ester bond. These two copolymers form micelles with either a neutral charge (NtL-ButM) or a negative charge (Neg-ButM). Each micelle releases butyrate from their polymeric core in the ileum or the cecum, respectively, after intragastric administration to mice. These polymer formulations mask the foul smell and taste of butyrate and act as carriers to release the active ingredient (butyrate) over time as the micelles transit the GI tract. Treatment with NtL-ButM in germ-free (and thus butyrate-depleted) mice up-regulated genes expressing antimicrobial peptides in the ileal epithelium. We show that these butyrate-containing micelles, used in combination, restored a barrier-protective response in mice treated with either antibiotics or dextran sodium sulfate (DSS), a chemical perturbant that induces epithelial barrier dysfunction. Twice daily intragastric administration of our butyrate-prodrug micelles ameliorates an anaphylactic response to peanut challenge in a mouse model of peanut allergy and increases the abundance of bacteria in a cluster (Clostridium Cluster XIVa) known to contain butyrate-producing taxa. By restoring microbial and mucosal homeostasis, these butyrate-prodrug polymeric micelles may function as a new, antigen-agnostic approach to the treatment of food allergy.
Juan De Pablo, the University of Chicago’s executive vice president for science, innovation, national laboratories, and global initiatives; Liew Family Professor of Molecular Engineering at Pritzker Molecular Engineering; and senior scientist at Argonne National Laboratory.
There is considerable interest in designing the sequence of polyampholites for specific applications. In this presentation, I will summarize recent theoretical and computational developments that provide a framework with which to engineer the phase behavior and the rheological properties of polyampholites. The capabilities and limitations of such a framework will be discussed in the context of several classes of materials, including flexible and semiflexible macromolecular materials, as well as composites with charged colloids.
Electrocatalytic carbon dioxide reduction reaction (CO2RR) has the potential to use renewably generated electricity to convert waste carbon dioxide (CO2) to carbon monoxide (CO) under ambient temperature and pressure. This produced CO can then be used in existing Fischer-Tropsch synthesis reactions to generate fuels and chemicals. Recent advances in CO2RR to CO have focused either on the design of intricate Au, Ag nano-catalysts or 2D catalysts for room temperature aqueous CO2 to CO or on the design of high-temperature solid oxide electrolysis cells. Unfortunately, ambient CO2 to CO in aqueous systems suffer from parasitic hydrogen evolution reaction (HER). In this work, we explore the effect of electrolyte design in enabling simple monometallic catalysts for ambient CO production. Using a dry aprotic acetonitrile electrolyte, we are able to eliminate proton availability and increase the faradaic efficiency for CO. More importantly, we show that cheap earth-abundant metals such as tin, indium, and zinc can enable FEs close to 100 percent. The earth-abundant catalysts have lower onset potentials and higher current densities in this electrolyte than gold. Finally, we show that these catalysts are robust enough to maintain high CO FE even when water is added to the aprotic electrolyte. Hence, electrolyte design strategies especially with aprotic systems provide another avenue to suppress HER with cheap catalysts, enable high CO production, and further our understanding of CO2 reduction reactions
Laura Gagliardi, Richard and Kathy Leventhal Professor at the Pritzker School of Molecular Engineering, the Department of Chemistry, and the James Franck Institute.
Addressing the energy challenges that we face globally requires the coordinated efforts of scientists, engineers, and policymakers. Chemistry has the potential to drive quantum leaps in technology. With theory, computation, and machine intelligence we can accelerate the search for solutions to water scarcity, decarbonization, and clean energy. I will discuss the challenges and opportunities facing theoretical chemists, and how, as a community, we can make lasting, sustainable change in our world.
Giulia Galli, Liew Family Professor of Molecular Engineering at the Pritzker School of Molecular Engineering (PME) and the Department of Chemistry at the University of Chicago and senior scientist at Argonne National Laboratory.
We discuss a quantum embedding theory to study spin-defects and impurities in solids, which is scalable to large systems. We compare the theory (which we call quantum defect embedding [QDET]) with other embedding frameworks, pointing out differences and similarities and target applications. We also present calculations on classical and quantum computers of the electronic structure of qubits performed with QDET.
Zwitterionic polymers have been widely promoted as effective antifouling agents due to the often-observed resilience of surfaces modified with zwitterionic moieties to the adhesion of proteins and microbial organisms. Nevertheless, a deep understanding of the relationship between zwitterion structure and fundamental properties, such as the degree of hydration or solubility, remains lacking. This project entails a systematic study of the interactions between zwitterionic polymers and surrounding water molecules, as conveyed by the chain dimensions of polyzwitterions in aqueous environments, measured via Small Angle X-ray Scattering (SAXS) and Dynamic Light Scattering (DLS). By extracting and contrasting the effective solvent quality of polyzwitterions with different side chain chemistries, a clear relationship between zwitterion structure and solvent interactions will be established. Following comparison with observations from foulant adhesion studies will elucidate the connection between surface hydration and foulant repulsion, allowing for better design of anti-biofouling materials.
Stretchable electroluminescent (EL) polymers are the key components for realizing skin-like displays and optical bio-simulations, which can offer unique functionality for information visualization, wirelessly signal/power transmission, and medical therapies. However, in contrast to other types of stretchable devices, such as sensors and transistors, stretchable EL devices have lagged behind in terms of combining high stretchability with high EL efficiency. All stretchable emitters reported to date have been based on “first-generation” EL polymers that can only harness the singlet excitons with a theoretical quantum yield of 25%. In this work, we present a material design concept for imparting the stretchability onto “third-generation” EL polymers that can harness all the excitons through thermally activated delayed fluorescence (TADF), thereby with a theoretical near-unity quantum yield. Our novel design concept for such stretchable light-emitting polymers is the backbone insertion of flexible, linear units between TADF units, which, as shown both experimentally and theoretically, provides very effective strain dissipation for stretchability without causing any sacrifice to the EL performance. Therefore, enabled by the highly efficient TADF processes and extraordinary stretchability, record-high external quantum efficiency (EQE) is achieved even at 100% strain. Demonstrated by the fully stretchable organic light-emitting diodes (OLEDs), the stretchable TADF polymers provide an unparalleled path towards achieving all the desired EL and mechanical characteristics, including high efficiency, brightness, switching speed, stretchability, and low driving voltage.
Cellulose nanocrystals (CNCs) are bio-based nanofillers that allow access to sustainable composites with enhanced property profiles. However, incorporating these rigid nanorods into most polymer matrices causes significant embrittlement, which limits the applicability of the resulting composites. By grafting polymer chains to CNCs, we can tune matrix-filler interactions, thus limiting the degree of embrittlement. In this work, we attach polymers of various molecular weights at various grafting densities to the CNC surface to examine how the resulting brush conformations impact composite mechanical properties.
The current developments in the understanding of transport phenomena in the nanoscale have the potential to overcome the limitations of the traditional methods for osmotic energy harvesting.
This work summarizes observations made over various asymmetric single-pore molecular dynamics simulations, from conical to asymmetrically charged pores. We discuss the physical limits for optimizing the total power output, ionic selectivity, and ionic current rectification. We further analyze the effect of pore charge, pore size, and electrolyte concentration on the membrane's performance.
Beyond revealing the optimal solutions within the explored parameter space for the design of energy extraction pores, we will also emphasize the need for redefining many of the frequently used scientific terms that shape the discussions in this field.
Selective CO2 capture and conversion is an important tool in the fight against climate change. Industrially, CO2 is captured using a variety of aprotic solvents due to their high CO2 solubility and good thermal stability. Therefore, the electrochemical upgrade of CO2 to high value-added products in an aprotic medium could then boost the overall CO2 capture effectiveness. However, the effect of ion solvation and solvent selection in the CO2 reduction selectivity and current density within nonaqueous electrolytes remains unclear. Here, we show that bulk solvation behavior controls the CO2 reduction reaction and product distribution occurring at the catalyst-electrolyte interface. We investigate the ion solvation behavior and its effect on the CO2 reduction performance in glyme ethers and dimethyl sulfoxide (DMSO), which present relatively low and high dielectric constants respectively. Using spectroscopic techniques, we show that ion pair formation is prevalent in a low dielectric medium and is dependent on anion type. More importantly, we show as ion pair formation decreases within the electrolyte, CO2 current densities increases, and a higher CO Faradaic efficiency is observed at low overpotentials. Meanwhile, electrolytes dissolved in a high dielectric constant medium show small population of ion pairs and similar electrochemical behavior. By directly coupling bulk solvation to interfacial reactions and product distribution, we showcase the importance and utility of controlling the reaction microenvironment intuning electrocatalytic reaction pathways. This combined approach could enable novel electrolyte design for efficient and selective CO2 capture and conversion.
Stuart Rowan, Barry L. MacLean Professor for Molecular Engineering Innovation and Enterprise
The concept of a pluripotent material is best explained by analogy to stem cells, which are pluripotent as they can give rise to different cell types. Thus, a “stem plastic” has the capability of being converted into different classes of plastic material. Given weight limitations when traveling in space the concept of pluripotent plastics that can be converted into very different materials depending on need, is an attractive one. The question, therefore, is “how can we design pluripotent materials?”
The mechanical properties of cellular carbon foams depend on strut dimension, node density and strut design (solid vs. hollow). There is a need for low-density-high-strength carbon foams that exceed the current mechanical performance of synthetic foams and can also be fabricated on a large scale. Among the challenges to large scale fabrication are the limitations imposed by the significant pyrolysis-induced volume shrinkage (>98%) of the polymeric precursors. This work demonstrates scalable synthesis of low-density-high-strength 3D porous carbon foams with deterministic control over density (0.05-0.5 g cm-3) through the pyrolysis of a low char-yielding porous polymer template coated with a high char-yielding conjugated polymer layer. The carbons synthesized though this new framework exhibit remarkably low pyrolytic shrinkage and record high strength to density ratio among reported carbon foams derived from stochastic polymer templates. Owing to the design of mismatch in degradation and carbonization properties between the template and coating, it is possible to access scalable, low-density-high-strength 3D porous carbons with (1) hierarchical pore distribution, small strut diameter and large node density, resulting from mismatched carbonization temperature, and (2) hollow strut architecture resulting from mismatched degradation temperature.
Matthew Tirrell, Dean of the Pritzker School of Molecular Engineering
Nature exploits all available covalent and non-covalent interactions for unparalleled spatiotemporal control over hierarchical length scales of macromolecular and supramolecular structure. The complex interplay of electrostatic and other non-covalent interactions of charged macromolecules still poses many open questions that will require broad collaboration among the life and physical sciences, as well as input from the engineering disciplines to drive toward new solid-state structures and useful materials. Scientific questions related to the physics of electrostatic self-assembly and to its role in biology will be discussed. Recent advances in understanding and biomedical applications of polyelectrolyte complex micelles will be presented.
Cationic polymers have found increased use in biomedicine as endosomolytic drug and gene delivery systems, engineered tissues, and antimicrobial coatings, among other applications. Despite the promise of these materials, many fail clinical trials due to unpredictable systemic toxicity and/or immunogenic responses. High positive charge density, tendency to form nanoparticles, and ability to form charge-based interactions with proteins cause such polymers can disrupt cellular and organelle membranes and/or activate innate immune receptors such as the NLRP3 inflammasome, yet the precise biophysical interactions underpinning these responses have failed to be screened in a comprehensive manner. In this work, we seek to understand the physicochemical properties of polymers which result in a toxic or immunogenic response. 107 polymers varied in charge density, hydrophobicity, and molecular weight using RAFT polymerization in a process chemistry approach and screened for their toxicity and ability to activate the NLRP3 inflammasome. Based on the results of this screen, we use confocal microscopy to identify how physicochemical properties modulate polymer-cell interactions. We show that positive charge and hydrophobicity synergize to induce cell membrane disruption or lysosomal rupture and inflammasome activation. Finally, by developing a “Trojan Horse” approach to screen immunotoxic positive charge, we demonstrate the efficacy of our immunogenic polymer adjuvants for use in vaccination.
Redox-active particles (RAPs) consist of poly(glycidyl methacrylate) particles crosslinked with redox-responsive bis(5-amino-l,3,4-thiadiazol-2-yl) disulfide demonstrated reversible 2-e- charging/discharging capability. Cyclic voltammetry showed 30% reduced peak spacing indicating improved electrochemical reversibility of disulfides anchored on particles compared to small molecules disulfide due to spatial confinement. Particles stability and specific capacity was investigated by galvanostatic cycling and dimethyl sulfoxide and magnesium triflate electrolyte were chosen as the best electrolyte combination for its electrochemical reversibility and specific. Size of particles was also investigated and smaller particles was favorable for higher specific capacity. Overall, this work demonstrates a modular RAP platforms for the design and study of organic battery materials, and spatially-confine redox moieties on particles systems proved promising for improved electrochemical properties.
