Physical Sciences and Mathematics Commons^™

Elucidating The Importance Of Structure, Surfaces, And Interfaces In Polymer Nanoparticles And Nanocomposites, Jacob E. Fischer

Doctoral Dissertations

This dissertation details research conducted to elucidate the importance of structure, surfaces, and interfaces in both polymeric nanoparticles and polymer nanocomposites. The fundamental understanding that is garnered in these studies provides a foundation to rationally develop nanocomposites tailored for unique functionalities, performance and applications.

Soft polymeric nanoparticles, have shown to imbue non-traditional diffusive properties, the strength of which decreases with crosslinking density of the nanoparticle. The crosslinking dependent morphology of these nanoparticles is first characterized in a dilute solution of good solvent (Chapter 2). The scattering results revealed that the structure ranges from a swollen polymer in good solvent (0% …

Controlling Polymer Molecular Structure And Morphology: From Illumination Of Conjugated Polymers To Polymer Chain Depolymerization, Josh Moncada

Doctoral Dissertations

Polymers remain a prominent component of our lives, and finding methods to control their structure or morphology are needed to tune material properties. This dissertation reports methods to alter the conformation, morphology, or structure of polymeric materials. Chapter two describes the impact of exposure to white light during annealing of conjugated polymer blends on their morphology and optoelectronic performance. The observed changes in the morphology correlate strongly to the variation in photoluminescence (PL) with illumination, including that the PL varies less with illumination at higher Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] loadings, offering foundational understanding to guide the structure and optoelectronic performance of conjugated polymer …

Intra-Skeletal Variation In Stable Isotopes Through Non-Destructive Approaches: Applications Of The Patterns Of Skeletal Remodeling To Biological Anthropology, Armando Anzellini

Doctoral Dissertations

Stable isotope analysis is a well-established method in biological anthropology used to deliver data on residence, diet, and life history. Samples for these analyses are often collected from the diaphyses of long bones with an assumption of an expected rate of turnover between five and ten years, depending on the skeletal element. However, the biological foundations of this assumption are still uncertain, especially concerning the intra-skeletal and intra-element variation of isotopic signatures that may relate to patterns of remodeling. Exploring these gaps in intra-element isotopic variation requires fine-grained work using multiple bones from multiple individuals, but such work is limited …

Light Matter Interactions: A Study Of Soft Materials Using Linear And Nonlinear Spectroscopy, Muhammad Redwan Hassan

Doctoral Dissertations

The adoption of complex fluids for various industrial applications is becoming normal. Complex fluids offer tunability, wide range solubility, and chemical and thermal stability which are the factors that conventional polar and non-polar solvents often lack. However, fundamental studies of these fluid systems are still lacking which is limiting the appropriate use of these complex fluids in many applications. The goal of this dissertation was to study and characterize complex fluids for application in electrolytes for redox flow batteries. Chapter 3 and chapter 4 feature the study of microemulsions and deep eutectic solvents (DES) by fluorescence techniques. Fluorescence studies of …

Analytical Techniques For The Analysis Of Uranium Bearing Materials, Nathaniel D. Fletcher

Doctoral Dissertations

The interest in the use of nuclear power has increased drastically in recent years. This is due to significantly increased efficiency at producing energy when compared to fossil fuels. With the increased use of nuclear power comes an increased need to for monitor for uranium bearing materials outside of regulatory control. This dissertation covers four projects aimed at improving the analysis of these materials. The first projects aims to develop a method that allows for the analysis of elements that exist in nature as anions by triple quadrupole ICP – MS. This would allow for the ability to measure more …

Transition Metal Computational Catalysis: Mechanistic Approaches And Development Of Novel Performance Metrics, Brett Anthony Smith

Doctoral Dissertations

Computational catalysis is an ever-growing field, thanks in part to the incredible progression of computational power and the efficiency offered by our current methodologies. Additionally, the accuracy of computation and the emergence of new methods that can decompose energetics and sterics into quantitative descriptors has allowed for researchers to begin to identify important structure-function relationships that predict the properties of unexplored subspaces within the overall chemical space. Catalytic descriptors have been used frequently in data driven high-throughput computational screenings. With the use of machine learning, a large portion of the chemical space an be predicted in matter of minutes or …

Tethered Axial Coordination As A Control Modality In Rhodium(Ii)-Catalyzed Carbene Transfer Reactions, Anthony Dean Abshire

Doctoral Dissertations

Rhodium(II) paddlewheels are versatile carbene transfer catalyst that are broadly applied in insertion reactions, cycloadditions, and ylide transformations. The effects of axial coordination in rhodium(II)-catalyzed carbene transfer reactions are still little understood due to compounding factors that are difficult to isolate. Traditionally, researchers study axial coordination by addition of Lewis base additives. To ensure interaction between the Lewis base and catalyst, high molar equivalents are used. This can also have the undesired effect of hampering the activity of the catalyst and suppressing the yield of the reaction. We have developed ligands with a tethered Lewis base to overcome these issues. …

Development Of Raman Spectroscopic Methods For Detection Of Molecules Indicating Life In Extraterrestrial Environments, Grace Sarabia

Doctoral Dissertations

Mineral analysis is of great importance to the understanding of the world around us and worlds beyond. Geology, chemistry, and environmental studies all benefit from characterization of the structure and properties of minerals. While various techniques have been applied towards the study of minerals, we propose that Raman spectroscopy is specifically suited for the detection and study of minerals under various conditions, including for terrestrial and space applications.

In our terrestrial studies, we explored the polymorphs of calcium carbonate within freshwater mollusk shell matrices with Raman spectroscopy. We found that aragonite was the main calcium carbonate polymorph present in the …

Vapor Deposition Strategies For Tuning Surface And Interface Chemistry For Optoelectronics And Biosensors, Kwang-Won Park

Doctoral Dissertations

Ordered assemblies of molecular semiconductors have been of particular interest for their integral role in organic optoelectronics, originating from interesting optical and charge transport properties. Compared with disordered films, organized nanostructured organic semiconductors display enhanced optoelectronic characteristics. However, past studies using template layer and self-assembly strategies are not applicable to molecular heterointerfaces and cannot be practically integrated into existing device fabrication routines to achieve large-area optoelectronic devices. This dissertation demonstrates unprecedented strategies to create one-dimensional (1D) nanostructures of molecular semiconductors using vapor deposition techniques. We begin this work by investigating how the interplay between dipole-dipole and van der Waals interactions …

Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian

Doctoral Dissertations

The self-assembly of charged macromolecules forms the basis of all life on earth. From the synthesis and replication of nucleic acids, to the association of DNA to chromatin, to the targeting of RNA to various cellular compartments, to the astonishingly consistent folding of proteins, all life depends on the physics of the organization and dynamics of charged polymers. In this dissertation, I address several of the newest challenges in the assembly of these types of materials. First, I describe the exciting new physics of the complexation between polyzwitterions and polyelectrolytes. These materials open new questions and possibilities within the context …

Intracellular Delivery Of Therapeutic Biomolecules Through Versatile Polymer Nanotechnology, David C. Luther

Doctoral Dissertations

Advancing pharmaceutical technology has made it possible to treat diseases once considered ‘undruggable.’ Access to these new pharmaceutical targets is possible thanks to the advent of protein and nucleic acid therapeutics. Responses to the COVID-19 pandemic, as well as cutting-edge treatments for cancer and multiple sclerosis have centered on these biologic therapies, promising even greater value in the future. However, their utility is limited at a cellular level by inability to cross the plasma membrane. Nanocarrier technologies encapsulate therapeutics and facilitate uptake into the cell but are often trapped and degraded in endosomes. Arginine-functionalized gold nanoparticles (Arg-NPs) provide efficient, direct …

Elucidating The Function Of Ions In Hybrid Perovskite Photovoltaics, Emily C. Smith

Doctoral Dissertations

Perovskite solar cells (PSCs) have risen to the forefront of versatile thin-film technologies with power conversion efficiencies rivaling traditional silicon and the potential to be fabricated at a fraction of the cost. However, one crucial drawback to PSCs is their instability to illumination, which is likely due in part to mobile ions during operation. It is difficult to predict the influences of ion dynamics in devices, and the exact nature and impact of these ions remain elusive. In this dissertation work, I have set out to unravel the complex interplay between ions and device operation in PSCs. Through the development …

Formation Of Doped Semiconductor Nanocrystals From Doped Molecular Clusters, Jillian E. Denhardt

Doctoral Dissertations

Transition metal doping of semiconductor nanomaterials, particularly magnetic dopant ions, is of great interest for the synthesis of diluted magnetic semiconductors (DMS) with spintronic-based applications. The incorporation of magnetic ions into quantum dots (QDs) would be particularly useful since the quantum confinement of these materials is theorized to enhance magneto-optical related properties. One major challenge in this field is the segregation of dopant ions towards the outer regions of the QD due to the exclusion of dopants during the nucleation process, thereby inhibiting the magneto-optical properties. In this dissertation, we address the dopant segregation challenge by exploring the underlying mechanisms …

Expanding The Polymer Zwitterion Library – Novel Phosphonium-Based Polymer Zwitterions And Analogous Structures, Marcel U. Brown

Doctoral Dissertations

This dissertation encompasses the synthesis, characterization and application of novel polymer zwitterions that significantly expand the library of available zwitterionic polymers. Their facile synthesis is facilitated by the preparation of a novel functional sultone precursor molecule, which can be ring-opened by commercially available phosphine, amine and sulfide nucleophiles, affording phosphonium, ammonium or sulfonium sulfonate monomers, respectively. Most notably, this work describes the invention of phosphonium-based polymer zwitterions, establishing a new class of zwitterionic polymer structures with unique solution and interfacial properties. Furthermore, the incorporation of these phosphonium sulfonates into block copolymer architectures with conventional polymer zwitterions, and the resulting switchable …

Enabling Nanoimprint Lithography Techniques Across Multiple Manufacturing Processes, Vincent Einck

Doctoral Dissertations

Advanced nanooptics in the areas of flat lenses, diffractive elements, and tunable emissivity require a route to high throughput manufacturing. Nanooptics are often demanding of high refractive index materials, nanometer precision and ease of fabrication. Nanoimprint lithography (NIL) is a low-cost, high throughput manufacturing technique beginning to be realized in commercial industry.^1,2 The NIL process is an ideal manufacturing candidate due to its ability to have a fast process time, efficient use of materials, repeatability and high precision while also having wide diversity of potential structures and material choices. Appling NIL techniques to other facets of manufacturing enable the …

Driving Piezochromism And Metallicity In Van Der Waals Materials Under Compression, Nathan Harms

Doctoral Dissertations

Complex chalcogenides provide an important platform to explore the interplay between structure, charge, and spin across pressure-induced phase transitions. Where much of the previous research has been focused on tuning these materials towards the single-layer limit, we instead explore the modification of bond lengths and bond angles under compression. In the first project we revealed piezochromism in MnPS₃. We combined high pressure optical spectroscopy and first-principles calculations to analyze the dramatic color change (green → yellow → red → black) that takes place as the charge gap shifts across the visible and into the near infrared region, moving …

Functional Bottlebrush Polymer Additives For Thin Films And Coatings, Travis S. Laws

Doctoral Dissertations

Bottlebrush polymers are a class of highly branched polymers consisting of polymeric side chains that are densely grafted to a linear backbone. Their highly branched architecture results in surface enrichment across a broad range of materials. The goal of my research has been centered around the design of functional bottlebrush polymers and their use as surface active additives in blend films and coatings.

In the first chapter, we examine the segregation behavior of polystyrene bottlebrushes that are blended with linear polystyrene. We systematically vary the lengths of the bottlebrush backbone (Nb), side-chain (Nsc), and the linear matrix (Nm) in order …

How Dynamic Bond Results In The Unique Viscoelastic Behavior Of The Associating Polymers, Sirui Ge

Doctoral Dissertations

Associating polymer is a special kind of polymer possessing transient reversible bonds in addition to the conventional covalent bonds. The reversible bonds provide unique dynamics and fascinating viscoelastic properties, resulting in attractive applications for these polymers, such as self-healing and shape memory materials. Despite many years of studies, the understanding of dynamics of polymers with reversible bonds, especially on molecular level, is still in the rudimentary stage, preventing the rational design of the potential novel functional materials based on associating polymers. In this dissertation, we provide a detailed and quantitative understanding of the dynamics and viscoelastic properties of associating polymers. …

Elucidating Molecular Structure And Interactions Of Disease-Related Noncovalent Assemblies Through Ion Mobility Spectrometry - Mass Spectrometry, Amber Leann Hope Gray

Doctoral Dissertations

Ion mobility spectrometry – mass spectrometry (IMS-MS) is a powerful gas-phase technique that is routinely employed in the investigations of amyloid oligomers and conformational studies due to its ability to separate isobaric and isomeric species with the same mass-to-charge ratio (m/z). The goal of this dissertation is to use IMS-MS as a primary platform to probe the conformational landscape of a macrocyclic protein, Cyclosporin A (CycA), and to characterize interactions of amyloidogenic assemblies. Through five independent studies presented within document, the limits of IMS-MS are pushed by employing conditions which mimic biological environments.

Chapter 2 focused on how …

Polynorbornenes For Advanced Applications And Processes, Xinyi Wang

Doctoral Dissertations

Polynorbornenes have dramatically different properties and various applications depending on their chemical structures. The modular nature of norbornene-based systems provides a facile route toward synthesizing diverse polymeric materials, thus making them ideal materials for systematic structure-property investigations. Herein, their application as gas separation membranes and the correlation between their gas-transport properties and polymer structures will be investigated. Though many valuable correlations between gas-permeability and polynorbornene structure have been studied previously, many of these efforts have focused heavily on designing materials with various chemical structures to achieve high permeabilities. In contrast, the influence of molecular structure on: a) polynorbornene chain packing …

Molecular Vibrations And Shape-Selectivity: A Computational Model Of Biofuel Precursors In Zeolites, Babgen Manookian

Doctoral Dissertations

We have used Density Functional Theory (DFT) to model acyclic and cyclic olefins in acidic zeolites. We have studied the impact of host-guest interactions between adsorbed molecules and zeolite frameworks through the lens of molecular vibrations and shape-selectivity. This work considered three zeolite frameworks with varying pore structures and environments: large pore zeolite HMOR and medium pore zeolites HZSM-5 and HZSM-22. A key finding is that for acyclic olefins in acidic zeolites there exists two regimes of host-guest interaction: a strong interaction leading to protonation and a weak interaction between charged guest and zeolite framework. We found that these interactions …

Designing Polymer-Protein Complexes For Intracellular Delivery, Hazel Davis

Doctoral Dissertations

Previous work in the Tew group has demonstrated polymer cell-penetrating peptide mimics (CPPMs) as effective transporters of biological agents, including proteins and antibodies. These synthetic polymers non-covalently bind to cargo, offering a mechanism to deliver proteins in a way that does not alter protein secondary structure. However, correlations of the protein binding-delivery relationship or the role of polymer-protein complexation on intracellular activity of protein cargo are understudied. The work presented herein connects a fundamental understanding of polymer-protein complexation with intracellular internalization and cargo activity. Characterization and quantification of polymer-protein binding relationships were established using fluorescence quenching assays. In particular, the …

Experimental Chronology And Investigation Of Yttrium Aluminum Garnet Nanoparticle Syntheses, Matthew Mcdonald

Doctoral Dissertations

Yttrium aluminum garnet (YAG) has been a material of intense interest since its discovery in 1964. Recently, efforts have been made to find alternate ways of producing YAG and other analogous oxides as dense materials for applications in lasers, scintillators, and optics. Methods of densification necessitate the use of nanomaterials as the building blocks for their development.

The production of nano-oxides is a diverse field with numerous methods, each with its own benefits and drawbacks. Methods like ball milling and solution combustion were chosen because of their projected simplicity, meanwhile flame spray pyrolysis and precipitation were chosen because of the …

Design Of Polymeric Membranes For Large-Scale Energy Storage, Michelle L. Lehmann

Doctoral Dissertations

Many countries have enacted renewable energy targets of 32% or more by 2040 to reduce their carbon footprint. However, due to the intermittent nature of renewable energy sources, long-duration energy storage systems are vital for providing a secure electricity supply. To meet this demand, new battery technologies utilizing earth-abundant and low-cost components are necessary. Among them, non-aqueous redox flow batteries represent a transformative energy storage system due to their flexible material selection and wide operating voltage window. A membrane plays a critical role in these next-generation energy storage technologies as it separates the anode and cathode while allowing for facile …

The Exploration Of Small Molecules, Lanthanide Complexes, And Catalysis Using Electronic Structure Theory, Dynamics, And Machine Learning, Gavin Mccarver

Doctoral Dissertations

With the ever increasing availability of computational resources, more challenging chemical systems can be studied. Among these challenges are the rotational and vibrational spectra of diatomic molecules within spectroscopic accuracy, the environmental perturbations induced on a rotating water molecule, the prediction of free binding energies of lanthanide complexes using machine learning, and the study of catalytic mechanisms through a theoretical framework. High levels of electronic structure theory were combined with a rigorous treatment of either the anharmonic vibrational wave functions to study diatomic molecules or the rotational wave functions to study H₂O-pH₂ interactions. The former was initially …

Influence Of Tethered, Axially Coordinated Ligands On Rh(Ii,Ii)-Catalyzed Carbene Transfer Reactions, Cristian E. Zavala

Doctoral Dissertations

Dirhodium (II,II) paddlewheel complexes have become ubiquitous in diazo-mediated carbene transfer reactions. The Rh(II,II)-carbene intermediate is capable of a large variety of transformations such as cyclopropanation, C-H and X-H (O, N, S, Si, B) insertion reactions, cyclopropenations, and ylide transformations. Cyclopropanation reactions resulting in the formation of functionalized cyclopropane structures has always been a major focus in Rh(II,II)-carbene chemistry. Improvements on catalytic performance in cyclopropanations has largely focused on the modification of the bridging ligands and has resulted in Rh(II,II) catalysts that exhibit high reactivity and selectivity in cyclopropanation reactions. However, high enantio- and diastereoselectivity is not easily achieved with …

Experimental Physical Chemistry Applications For Material Science: The Neutron Vibrational Spectrum Of Biaxially-Oriented Pet And Hkust-1 As A Qcm-Based Ethylene Sensor, Zachary D. Stroupe

Doctoral Dissertations

This work is divided into two comprehensive subjects exploiting fundamental properties of physical chemistry to understand applied materials. The two subjects will be: the inelastic neutron scattering of thin polyethylene terephthalate (PET) films and the design and development of a quartz crystal microbalance-based ethylene detector. For the work involving the thin films, the inelastic neutron scattering (INS) was accomplished using the high flux of the VISION vibrational spectrometer at the Spallation Neutron Source yielding the highest quality data currently available. The torsional vibrational modes of biaxially-oriented PET (bPET) will be reported with the help of DFT calculations to aid in …

Optimization And Development Of Sodium-Based Electrolytes For Energy Storage Devices, Jameson L. Tyler

Doctoral Dissertations

Energy storage devices have undergone development for decades. Much of the research is focused on the improvement of energy density by developing existing electrodes and investigating novel electrode materials. This has led to the overall improvement of traditional lithium-ion batteries, but also the discovery of new energy storage devices such sodium-ion batteries, redox flow batteries, solid electrolyte-based batteries, and many more. As the field expands, fundamental research is necessary to fully ascertain the validity of these novel systems for long term success. One of the most important components to all electrochemical energy storage devices such as batteries and supercapacitors is …

The Development Of Photoinduced Initiation Of Olefin Polymerization And Its Applications, Justin M. Burroughs

Doctoral Dissertations

Polyolefin synthesis is an ever-growing field due to the low cost of monomer feed stocks and the wide range of applications of the resulting polymeric material. Polyolefins are most commonly polymerized through coordination-insertion polymerization. One area this field of research has progressed is the development of complex ligand scaffolds to achieve various levels of control over polymerization. For example, researchers have been able to control molecular weight, branching density, and tacticity of various olefin polymerizations. As a result of complex ligand scaffolds, the catalytic systems become more expensive and less industrially applicable. On the other hand, little research efforts have …

Chiral Mesogen-Free Liquid Crystalline Polyethers With Sulfonylated Side Chains And Patchy Brush Nanoparticles, Caleb A. Bohannon

Doctoral Dissertations

Ferroelectric liquid crystalline polymers (LCPs) hold promise for various applications driven by low electric fields, e.g., electrocaloric materials, because of the higher molecular motion in the liquid crystalline (LC) state. However, traditional chiral smectic C (SmC*) LCPs exhibit small spontaneous polarizations due to the bulky aromatic mesogens and weak polar groups. This dissertation research is focused on the design of mesogen-free sulfonylated LCPs with a goal of seeking the ferroelectric SmC* phase. Such LCPs are expected to exhibit high polarizations owing to the sulfonyl’s large dipole moment. A series of poly(oxypropylene)s (POPs), with chirality being introduced into either the backbone …