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Abstract: Plastics are the largest synthetic consumer product in the world, with an annual production of over 360 million metric tons annually. Despite the structural diversity enabled by modern advances in polymer synthesis, greater than 60% of world plastic production remains dominated by polyolefins. These high-volume, low-cost engineering thermoplastics are made from a small sub-set of petroleum derived monomers and demonstrate diverse thermomechanical properties, attractive chemical resistance, and excellent processability. Creating sustainable materials that compete with the performance and value proposition of polyolefins is a grand challenge for the field of polymer science. The goal of research in the Leibfarth group is to develop synthetic methods that transform readily available starting materials into functional and sustainable thermoplastics with molecular-level precision. This goal informs our two complementary approaches that seek to 1) leverage chemo- and regioselective C–H functionalization of polyolefins to enhance the properties of these venerable materials and 2) develop stereoselective polymerization methods that engender emergent polymer properties from simple chemical building blocks. These concepts have resulted in platform synthetic methods that enhance the thermomechanical, adhesion, and transport properties of polyolefins while also uncovering mechanistic insights that broadly inform synthetic method development.
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Abstract: Chemical analysis is an essential part of our search for life beyond Earth. The most sensitive, and least Earth-centric, way to perform a chemical search for life during a spaceflight mission is by coupling liquid-based sample handling and separation with mass spectrometry and other detectors. We have fundamentally advanced the readiness of this technology for potential robotic astrobiology missions, through the invention of a new generation of portable electrophoresis instrumentation. In the Atacama Desert, Chile we demonstrated “sample-in-data-out” function of a remotely operated rover-mounted microchip-based system using optical detection. More recently, at Mono Lake, California, we demonstrated a capillary-based system capable of interfacing with additional detector systems, including conductivity and mass spectrometry detection. These hardware systems serve as prototypes for future spaceflight mission instruments, and can be customized for terrestrial and marine investigations as well.
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ABSTRACT: The number of possible organic compounds is practically infinite, making it highly probable that an organic material with excellent properties can be found for any application. However, leveraging this potential requires a deep understanding of the relationship between the property of interest and molecular structure. Molecules and polymers with extended pi conjugation exhibit conductive and semiconducting properties once thought only possible in inorganic materials. Organic solar cells, light emitting diodes, transistors, thermoelectric devices, and printed electronics rely on pi-conjugated materials as their primary active material. Many of the early investigations on this class of materials focused on their electrochemical properties; their ability to transport ions from an electrolyte to facilitate a change in their oxidation state and hence material properties. This line of investigation has re-emerged at the frontier of basic research, owing to the development of biosensors, neuromorphic computing elements, and electrochromic devices. The common feature uniting these seemingly disparate applications is that they leverage the ability of organic materials to simultaneously transport both electronic and ionic charge carriers. We have used in-situ spectroscopy to develop a first-order description of device operation and have put forward a generalizable structure-property relationship that governs the rate of ion transport in pi-conjugated materials. The key insight is the importance of local field interactions, important in material solubility, for example. With the insights gained by this knowledge, my group is developing a novel organic dielectric material based on zwitterionic liquids. Interestingly, a collective switching behavior is observed, which provides these materials with capacitances comparable to electrolyte solutions.
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Abstract: The field of high entropy oxides (HEOs) flips traditional materials science paradigms on their head by seeking to understand what properties arise in the presence of profound configurational disorder. This disorder, which emerges as the result of multiple elements sharing a single crystalline lattice, can take on a kaleidoscopic character due to the vast numbers of possible elemental combinations and appears to imbue some HEOs with functional properties that far surpass their conventional analogs. However, the actual degree of configurational disorder, its role in stabilizing the HEO phase, and its effect on other physical properties such as magnetism all remain open questions. In my talk, I will discuss my group’s efforts towards addressing these questions using x-ray and neutron methods.
Monday, October 23
11:30 a.m.
Engineering Computer Science Building, Room 116
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Monday, October 16
11:30 a.m.
Engineering Computer Science Building, Room 116
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Abstract: Despite more than a century of modern organic chemistry research, the art and practice of synthesizing complex organic molecules is actually remarkably unchanged from how it was carried out in the early 1900s: reactions are optimized through an iterative and often Edisonian approach using single batch experiments carried out in round-bottomed flasks, varying one factor at a time, and then scaled-up using larger versions of small-scale equipment. While this has yielded world-altering insights and products that have improved the lives of billions, continued progress in the field requires new, more efficient techniques and tools to enable a deeper understanding of chemical space, and result in practical and robust methodology amenable to large-scale production.
The central theme of the Leitch lab research program is the exploration of uncharted chemical space, both in terms of new chemical matter and reactivity and mechanism, with the goal of addressing two of the most important problems facing organic chemistry:
1) How do we predict chemical reactivity in a quantitative manner, and use these predictions to develop more efficient transformations?
2) How can we efficiently synthesize complex organic molecules, especially those with novel structural features?
In the Leitch lab, we tackle these challenges by combining modern high-throughput tools and multivariate techniques with physical organic chemistry principles and organometallic chemistry. This talk will provide a progress update on how we have done since 2019 in meeting the goals set out in my 2017 proposal.