Physical Sciences and Mathematics Commons^™

Controlling Degradation With Force And Light, Brad Davis

Dissertations

Stimuli-responsive polymers respond to changes in their environment by altering their physical and chemical properties. Their responsiveness allows them to be used as sensors, mechanical actuators, delivery systems, and can yield either elongated lifetimes through healing mechanisms or shortened lifetimes through triggered degradation. Still a growing field in polymer science, researchers seek to expand the capabilities of these materials by improving their specificity, range, and mechanisms of both the stimuli and the response. The work presented explores stimuli-responsive materials, focusing on mechanical and light stimuli, and how to gain control of the response by specific changes in the polymeric material. …

Synthesis And Characterization Of Novel Organic Ligands With Their Complexes Of Platinum, Copper And Uranium, Mustafa Adnan Yasin Aldulaimi

Dissertations

Transition metal complexes of symmetrical and asymmetrical Schiff bases have played a significant role in the field of coordination, inorganic, and bioinorganic chemistry as models for biological, analytical, industrial, and pharmaceutical applications. Over recent years a great deal of interest has developed in new transition metal complexes of Schiff base ligand. The preparation of novel organic ligands is the most important step in the development of metal complexes that exhibit unique properties and novel reactivity. To highlight the presentation of this dissertation and to provide more detailed investigations, the dissertation was separated into six chapters according to the sequence of …

Doping Of Conjugated Polymers: Preparation, Characterization And Device Fabrication, Kan Tang

Dissertations

Semiconducting conjugated polymers (CPs) as emerging materials for advanced electronic applications such as sensors, OPVs, and OEFTs has become an intriguing research topic in the past decades. It opens a new avenue of “flexible” electronics, which has shown great potential in next-generation electronic devices.

However, due to the nature of CP materials and related solution processing techniques, unlike almost perfectly crystalline silicon materials, CPs in the solid-state often exhibit much lower crystallinity if it is not complete amorphous, which severely hinder the electronic property and optical property of the materials. The crystallinity of CPs in a film is often uniquely …

Photopolymer Networks With Tunable Command Destruct Properties, William Walker

Dissertations

Photoinduced thiol-catalyzed hydrogen abstraction and beta-scission of acyclic benzylidene acetals is demonstrated as a new route to “command-destruct” polymer thermosets. Using this approach, we show that poly(thioether acetal) networks synthesized via thiol-ene photopolymerization rapidly degrade to alkyl benzoate byproducts when triggered with light, transitioning from solid to liquid within seconds. The light-driven construction and destruction processes, accessible via distinct differences in kinetics, are readily amendable for photopatterning, additive/subtractive manufacturing, and wavelength-selective applications.

The first chapter of this dissertation details the development of command-destruct poly(thioether acetal) networks via a previously unexplored mechanism for polymer degradation. The degradation mechanism is confirmed via …

Stereocontrolled Mannosylation By Hydrogen-Bond-Mediated Aglycone Delivery, Catherine Alex

Dissertations

Stereocontrolled Mannosylation by Hydrogen-Bond-Mediated Aglycone Delivery

Carbohydrates are the essential bio-molecules of life as they form the forefront of interactions with receptors, proteins, pathogens, or neighboring cells. On cell-surfaces, carbohydrates are mostly found as linear or branched glycoconjugates, and a majority of them are linked via either 1,2-cis or 1,2-trans O-glycosidic linkages. There is no template-driven pathway for achieving the synthesis of glycans unlike other biomolecules like proteins and nucleic acids. The synthesis of 1,2-trans glycosides can be reliably achieved via the neighboring group assistance. The synthesis of 1,2-cis glycosides is difficult because, beyond weak anomeric effects, there are …

Reconstituting The Cyanobacterial Circadian Clock In Vitro, Pyong Hwa Kim

Dissertations

Cyanobacteria are photosynthetic organisms that are known to be responsible for oxygenating Earth’s early atmosphere. Having evolved to ensure optimal survival in the periodic light/dark cycle on this planet, their genetic codes are packed with various tools, including a sophisticated biological timekeeping system. Among the cyanobacteria is Synechococcus elongatus PCC 7942, the simplest clock-harboring organism with a powerful genetic tool that enabled the identification of its intricate timekeeping mechanism. The three central oscillator proteins—KaiA, KaiB, and KaiC—drive the 24 h cyclic gene expression rhythm of cyanobacteria, and the "ticking" of the oscillator can be reconstituted inside a test tube just …

Synthesis And Self-Assembly Of Amphiphilic Block Copolymers For The Fabrication Of Non-Spherical Polymersomes, Tamuka Chidanguro

Dissertations

Polymersomes, also known as polymer vesicles, have gained a lot of interest over the past two decades. These hollow spherical systems are made via the self-assembly of amphiphilic block copolymers and have found use in a range of areas from drug delivery, to cellular models, to nanoreactors. Their hollow nature allows them to carry hydrophilic cargo in their inner compartment and hydrophobic cargo in their membrane. Over the last decade, increasing efforts have focused on controlling the morphology of polymersomes. Research has shown that polymersome morphology plays an important role for instance in drug delivery, where tubular or rod-like vesicles …

The Power Of Sulfur: A Study Of An Isothiocyanate Chiral Derivatizing Agent, Thioamide Based Chiral Solvating Agents, And The Geometry Of Sulfonamides, Emily B. Crull

Dissertations

This three-part dissertation is connected by the thread of utilizing sulfur-based functional groups, hence the power of sulfur. The first project was the development of a pentafluorobenzene based isothiocyanate chiral derivatizing agent (CDA), a class of compounds that differentiate enantiomers through covalent bond formation. This project, which was addressed using a combination of synthetic and computational methods and NMR analysis, gave rise to an CDA that was highly selective for amines and computationally predictable. Branching off of that, the second project demonstrated the use of two thioamide chiral solvating agents (CSAs), which had never been reported as a core functional …

Data-Driven Approaches To Complex Materials: Applications To Amorphous Solids, Dil Kumar Limbu

Dissertations

While conventional approaches to materials modeling made significant contributions and advanced our understanding of materials properties in the past decades, these approaches often cannot be applied to disordered materials (e.g., glasses) for which accurate total-energy functionals or forces are either not available or it is infeasible to employ due to computational complexities associated with modeling disordered solids in the absence of translational symmetry. In this dissertation, a number of information-driven probabilistic methods were developed for the structural determination of a range of materials including disordered solids to transition metal clusters. The ground-state structures of transition-metal clusters of iron, nickel, and …

Design And Modeling Of Bioinspired Polyelectrolytes With Controlled Architectures For Gene Delivery Applications, Kelli Stockmal

Dissertations

This dissertation focuses on the development of a range of bioinspired polyelectrolytes with controlled architectures for gene and drug delivery applications. Glycans are ubiquitous in biological systems, and understanding the role of saccharide stereochemistry, as well as cationic charge, on polymer behavior in aqueous solution and the interactions with nucleic acids can provide insight into how synthetic polyelectrolytes can be used for non-viral gene delivery and other biological applications. The first chapter provides an introductory overview on how cationic polyelectrolytes can be used to aid the delivery of RNA for controlling gene expression in a variety of cell types, how …

Atomic Oxygen Resistant Low Earth Orbit Stable Polymer Matrix Composites Employing Phenylphosphine Oxide Epoxy-Amines, Witold Fuchs

Dissertations

Atomic oxygen (AO) attacks polymer matrix composites (PMC’s) on the surfaces of spacecraft in low earth orbit (LEO) and threatens safe spacecraft operation and service life. Incorporating phenylphosphine oxide (PPO) groups into polymer chains offers a self-regenerating method of protection from AO but remains poorly understood. Herein, epoxies containing PPO groups were synthesized with increasing concentrations of phosphorus [P] from 0 to 8 wt % to investigate their AO resistance. Measurements confirmed the exposure of these materials to AO produces a passivation phosphate (POx) layer on the surface of the sample and the efficacy of the resultant layer was directly …

Development Of Small Molecule Inhibitors Of Therapeutic Target Enzymes: Paths To Discover Novel Antimicrobials, Thahani Shifna Habeeb Mohammad

Dissertations

The rising antimicrobial resistance to antibiotics is a major global problem, which has been exacerbated by the inappropriate use of antibiotics. The effectiveness of frequently prescribed penicillin derivatives and β-lactamase inhibitors are compromised by the evolution of bacterial β-lactamases and antibiotic-resistant bacteria. Consequently, design and synthesis of small-molecule inhibitors of identified novel antibiotic targets is an urgent unmet medical need. We previously demonstrated that N-functionalized α-aminocyclobutanones can act as peptidomimetic enzyme inhibitors, including inhibition of a key esterase in Francisella Tularensis. The carbonyl of a cyclobutanone is electrophilic due to ring strain, therefore cyclobutanone derivatives can serve as transition state …

Identification Of New Pathways For Co Oxidation On Rh(111) & Spatial And Structural Control Of O-Induced Reconstruction Of Ag(111), Marie Turano

Dissertations

Understanding the fundamentals of oxygen surface structures under a variety of conditions is pivotal to determining reactivity of heterogeneous catalysis. Exposure of catalytically active metal surfaces to high oxygen coverages results in a myriad of surface structures. A further complication is the formation of subsurface oxygen (Osub) or oxygen present in the near subsurface region of the metal. It is known to form in transition metals yet the absorption of oxygen and resultant formation of Osub is not equivalent across all catalytically relevant metals. As a result, it is difficult to predict the stability and efficacy of the formation of …

Molecular Mechanism Of Cyanobacteria Circadian Clock Oscillator And Effect Of Co Factors On Its Oscillation, Manpreet Kaur

Dissertations

The circadian rhythms arise as an adaptation to the environmental 24-hour day and night cycle due to Earth's rotation. These rhythms prepare organisms to align their internal biological activities and day to day behavior or events with the environmental change of the 24-hour day and night cycle. Circadian rhythms are found widely in all living kingdoms of life on Earth. Cyanobacteria are photosynthetic prokaryotes which first used to study these circadian rhythms. Among cyanobacterial species, Synechococcus elongatus PCC 7942 (henceforth, S. Elongatus) is the simplest organism with a durable and sturdy circadian clock and is study as a model organism. …

The Aging And Impacts Of Atmospheric Soot: Closing The Gap Between Experiments And Models, Ogochukwu Yvonne Enekwizu

Dissertations

The main goal of this dissertation is to generate data and parameterizations to accurately represent soot aerosols in atmospheric models. Soot from incomplete combustion of fossil fuels and biomass burning is a major air pollutant and a significant contributor to climate warming. The environmental impacts of soot are strongly dependent on the particle morphology and mixing state, which evolve continuously during atmospheric transport via a process known as aging. To make predictions of soot impacts on the environment, most atmospheric models adopt simplifications of particle structure and mixing state, which lead to substantial uncertainties. Using an experimentally constrained modeling approach, …

Modeling Mass Transfer And Chemical Reaction In Industrial Nitrocellulose Manufacturing Processes, Francis Patrick Sullivan

Dissertations

A series of models are proposed to describe the production of military grade nitrocellulose from dense cellulose materials in mixtures of nitric acid, sulfuric acid, and water. This effort is conducted to provide a predictive capability for analyzing the rate and extent of reaction achieved under a range of reaction conditions used in the industrial nitrocellulose manufacturing process for sheeted cellulose materials. Because this capability does not presently exist, nitrocellulose producers have historically relied on a very narrow range of cellulose raw materials and resorted to trial and error methods to develop processing conditions for new materials. This tool enables …

Novel Applications Of Mass Spectrometry For Quantitation And Reaction Mechanism Elucidation, Pengyi Zhao

Dissertations

Mass spectrometry (MS) has been growing as one of the most widely used tools in the field of analytical chemistry. Various applications have been developed to harness the high sensitivity and specificity of mass spectrometric analysis. In this dissertation, two major challenges are addressed. By developing mass spectrometric-based methods, absolute quantitation of proteins/peptides have been achieved. Elucidation of various reaction mechanisms are also enabled. These are the focuses of this dissertation.

In Chapters 2 to 4, a novel quantitation method is developed, titled as coulometric mass spectrometry (CMS). The strength of this method is that no reference standard or isotope-labeled …

Development Of Novel Membranes For Nanocarbon Enhanced Separation With Application In Biofuels And Solvent Recover, Oindrila Gupta

Dissertations

Pharmaceutical industries historically have had one of the highest amounts of solvent waste generated per unit of drug manufactured. Energy requirements and carbon footprint of current solvent recycling processes tend to be quite high, and the incineration of the solvents for waste disposal produces toxic air emissions. Also, rapidly increasing demand for energy and strict regulation on engine pollutant emissions have necessitated the use of alcohol as carbon-neutral fuels. Thermal distillation is one of the most common methods for the separation of alcohol-water mixtures. However, its application is limited due to energy requirements and high operating costs, and heating to …

A Library Of Low Molecular Weight Fluorescent Probes For The Detection Of Cu(Ii) And Fe(Iii) Ions, Ashley Johnson

Dissertations

This dissertation reports the synthesis and photophysical properties of a family of rhodamine dyes (compounds 3.9-3.13 and 4.6). The rhodamine dyes are prepared in two steps, and fully characterized by ESI-MS (Low and High resolution), X-Ray crystallography, NMR spectroscopy, and FT-IR spectroscopy. The coordination environment of the low molecular weight fluorescent probes (LMFPs) was systematically changed to investigate the thermodynamic behavior between the LMFPs and an array of metal ions (Cu²⁺, Fe²⁺, and Hg²⁺ ions) in protic and aprotic solvent systems. Upon coordinating to metal ions, the π-conjugation of the LMFPs changed, resulting in …

Practical Adhesion Measurements In Organic Coatings; Advancing Understanding And Mechanical Methods Development, Diana Gottschalk

Dissertations

“Adhesion” can be considered either a mechanical or chemical phenomenon. The mechanical interpretation describes the difficulty of separating surfaces and is useful for quantifying performance within applications that depend on bulk and interfacial properties. Chemical adhesion describes interfacial resistance to chemical attack and does not depend on bulk properties. Predicting chemical failure through mechanical measurement is confounded by the influence of bulk properties. However, the prospect is attractive because of the robust tolerance for sample geometries, allowing experiments to resemble an end-use system. The present work's primary goal was to elevate mechanical methods to provide a detailed interfacial characterization of …

Synthesis Of Biologically Active Phosphorus Heterocycles, Giri Gnawali

Dissertations

This dissertation work is divided into two parts. The first part is focused in the development of methodology for the synthesis of phostones and phosphonosugars and advancement thereof. The second part is focused in the development of affinity probes based on analogs of natural products cyclophostin and the cyclipostins.

Phostone (3) and phosphonosugars are cyclic phosphonates. The anomeric carbon of sugar is replaced by a phosphorus atom. The synthesis of phostones has been achieved starting form the key intermediate, γ,δ-epoxy vinyl phosphonate (1). The palladium catalyzed ring opening of γ,δ-epoxy vinyl phosphonates by a nucleophile results …

Embedded Gold Nanoparticles For Metal Enhanced Photoluminescence, Hasna Alali

Dissertations

Noble metal nanoparticles (MNPs) have attracted great attention in electronics, solar cells and catalysis. Their unique optical properties and biocompatibility makes them useful in biological applications like imaging, drug delivery, therapy and diagnostic. At the surface of MNPs the collective oscillation of free electrons resonates with a particular wavelength of incident light, generating the Localized Surface Plasmons Resonance (LSPR). LSPR results in absorption and scattering of incident light. Scattering results in reflecting photons and absorption leads to enhanced photoluminescence and quenching of fluorophores, if the fluorophore is in the vicinity of MNPs.

Most of the studies in this regard have …

Synthesis Of Alpha-Methylselenocysteine, Its Relevant Analogues, And An Unnatural Glutathione Disulfide Core, Robert J. Wehrle

Dissertations

Selenoproteins, such as glutathione peroxidase, have gained interest for their ability to act as antioxidants, and their potential to act as anti-cancer agents. Synthesizing and studying selenoproteins can be problematic, however, due to their propensity to degrade from over-oxidation. The degradation from over-oxidation can be avoided by the incorporation of the unnatural amino acid, alpha-methylselenocysteine. A synthesis utilizing methyl malonic esters was used to synthesize protected (R)-alpha-methylselenocysteine efficiently (46% over four steps) and in high enantio-purity (88% enantiomeric excess). Using similar procedures, the (S)-enantiomer was also synthesized as well as a beta-analogue.

The use of enzymes …

Machine Learning Approaches For Improving Prediction Performance Of Structure-Activity Relationship Models, Gabriel Idakwo

Dissertations

In silico bioactivity prediction studies are designed to complement in vivo and in vitro efforts to assess the activity and properties of small molecules. In silico methods such as Quantitative Structure-Activity/Property Relationship (QSAR) are used to correlate the structure of a molecule to its biological property in drug design and toxicological studies. In this body of work, I started with two in-depth reviews into the application of machine learning based approaches and feature reduction methods to QSAR, and then investigated solutions to three common challenges faced in machine learning based QSAR studies.

First, to improve the prediction accuracy of learning …

An Atomistic Study Of The Effects On Mechanical Properties And Bonding Interactions Of Carbon Nanofillers In Nylon 6 Nanocomposites, Michael Roth

Dissertations

Polymers have potential for a wide range of applications. The effectiveness of polymers can be further enhanced through the addition of nanofillers that improve thermal, mechanical, and electrical properties of the polymer. Carbon based nanofillers such as carbon nanotube (CNT), graphene, and carbon nanofibre (CNF) are of particular interest due to their high properties and high aspect ratios. However, limited understanding of the governing interactions of these nanofillers with polymers limits the effectiveness of the final nanocomposite.

The first facet of this dissertation focuses on determining the dominating interactions between pristine CNT and graphene with nylon 6 monomer and the …

Effect Of Selfsame Microparticles On Epoxide Amine Network Formation And Matrix Mechanics, Travis Palmer

Dissertations

Epoxide amine matrices are widely utilized in aerospace carbon fiber reinforced polymer (CFRP) composites having engendered significant reductions in weight and fuel consumption. This dissertation focuses on the effect of constrained space during network formation on the matrix mechanics of these highly complex composite systems. Precipitation polymerization conditions are developed to prepare epoxide amine microparticles (EMs) based on tetraglycidyl-4,4’-methylenedianiline (TGDDM) and isophorone diamine (IPDA). Surface functionality of EMs is tuned via control of epoxide to reactive amine hydrogen ratio, where unreactive, amine- and epoxide-functional EMs are prepared. We demonstrate that EMs are polydisperse, but can be filtered, yielding low dispersity …

Huisgen 1,3-Dipolar Azide-Alkyne Cycloaddition “Click” Reaction In Polymer Synthesis And Curing, Jie Wu

Dissertations

This dissertation’s key focus is on utilizing Huisgen 1,3-dipolar azide-alkyne cycloaddition (AAC) reaction in copolymer synthesis and modification, including thermoplastic block copolymer and commercially available two-component polyurethane system. It can be divided into two major projects, introduced as follows.

The first project involves the development of a modular synthetic approach toward polyisobutylene (PIB)-based triphasic pentablock thermoplastic elastomer with enhanced moisture permeability. This terpolymer consists of a poly(styrene-b-isobutylene-b-styrene) (SIBS) core and appended hydrophilic polymer blocks (HBs). The SIBS core was synthesized via living cationic polymerization (LCP) of isobutylene followed by sequential addition of styrene. AAC was utilized …

Geochemical Tracers Of Arctic Ocean Processes: A Study Of Gallium, Barium, And Vanadium, Laura M. Whitmore

Dissertations

The Arctic Ocean is linked to the global oceans and climate through its connectivity with the North Atlantic Ocean and the regional thermohaline deep water formation sites. It’s also a region undergoing rapid environmental change. To inform the community of potential changes in geochemical and biogeochemical cycles, this dissertation addresses three dissolved geochemical tracers (gallium, barium, and vanadium) as indicators of Arctic Ocean processes. Gallium is tested as a replacement for nutrient-type tracers in an effort to deconvolve Pacific and Atlantic derived waters in the Arctic Ocean basins. These water masses carry different heat and salt content and can influence …

New Catalytic Reactions In Carbohydrate Chemistry, Scott Geringer

Dissertations

Carbohydrates or sugars are some of the most diverse and abundant biological molecules. They are involved in a multitude of processes in the body such as fertilization, cell-cell communication, and cancer metathesis. Because of these vital functions, the study of sugars is rapidly growing field. The field however is limited due to the complex nature of sugars which results in difficulties in obtaining large quantities for study.

Protecting group manipulation is a large emphasis area in carbohydrate chemistry due to the need to selectively protect different functional groups of each molecule during synthesis. Catalytic and selective cleavage of protecting groups …

Metal Ions Impact On Shewanella Oneidensis Mr-1 Adhesion To Ito Electrode And The Enhancement Of Current Output, Aisha Awad Alshahrani

Dissertations

The goal of this study is to enhance the efficiency of bacterial extracellular electron transfer (EET) in Shewanella oneidensis MR-1 by enhancing adhesion to the electrode's surface. Our results clearly show a major difference in the attachment and behavior of Shewanella oneidensis MR-1 for Ca2+, Pb2+, Cd2+, and Mg2+, compared to the control. the final microbial coverage, as measured by confocal microscopy and cathodic peak charge in cyclic voltammetry (Qpc), increases with increasing metal ion concentrations. We found the cells attached to the electrode increased more with the addition of metal ion concentrations in the following order of metals: Ca2+ …