Chemistry Commons^™

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 …

High-Temperature Resistant Water-Soluble Polymers Derived From Exotic Amino Acids, Sumant Dwivedi, Aniruddha Nag, Shigeki Sakamoto, Yasuyoshi Funahashi, Toyohiro Harimoto, Kenji Takada, Tatsuo Kaneko

Faculty Publications

© The Royal Society of Chemistry. High-performance water-soluble polymers have a wide range of applications from engineering materials to biomedical plastics. However, existing materials are either natural polymers that lack high thermostability or rigid synthetic polymers. Therefore, we design an amino acid-derived building block, 4,4′-diamino-α-truxillate dianion (4ATA²⁻), that induces water solubility in high-performance polymers. Polyimides containing 4ATA²⁻ units are intrinsically water-soluble and are processed into films cast from an aqueous solution. The resulting polyimide films exhibit exceptional transparency and extremely high thermal stability. In addition, the films can be made insoluble in water by simple post-treatment using …

Recent Progress In Enhancing Poly(Lactic Acid) Stereocomplex Formation For Material Property Improvement, Fuhong Luo, Alexander Fortenberry, Jie Ren, Zhe Qiang

Faculty Publications

The production and utilization of polymers have been widely implemented into diverse applications that benefit modern human society, but one of the most valuable properties of polymers, durability, has posed a long-standing environmental challenge from its inception since plastic waste can lead to significant contamination and remains in landfills and oceans for at least hundreds of years. Poly(lactic acid) (PLA) derived from renewable resources provides a sustainable alternative to traditional polymers due to its advantages of comparable mechanical properties with common plastics and biodegradability. However, the poor thermal and hydrolytic stability of PLA-based materials limit their potential for durable applications. …

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 …

Freshwater Endmembers Impacting Carbonate Chemistry In The Mississippi Sound, Allison Savoie

Master's Theses

Coastal ecosystems are highly dynamic areas for carbon cycling and are likely to be negatively impacted by increasing ocean acidification. This research focused on dissolved inorganic carbon (DIC) and total alkalinity (TA) in the Mississippi Sound in order to understand the influence of local rivers that supply alkalinity to the area and buffer against ocean acidification. This area receives large fluxes of freshwater from local rivers, in addition to episodic inputs from the Mississippi River through a human-built diversion, the Bonnet Carré Spillway. Sites in the Mississippi Sound were sampled monthly during August 2018 to November 2019 and at weekly …

Effect Of Different Phosphate Glass Compositions On The Process-Induced Macromolecular Dynamic Of Polyamide 66, Imane Belyami, Mohammad K. Hassan

Faculty Publications

The present study provides a fundamental understanding of the mechanism of action of special new phosphate glass (P-glass) systems, having different glass transition temperatures (T_g), in polyamide 66 (PA66). Dynamic mechanical analysis (DMA) revealed that the T_g of PA66/low T_g P-glass (ILT-1) was significantly shifted to a lower T_g (65 °C), and another transition appeared at high temperature (166 °C). This was supported by a drop in the melting point and the crystallinity of the PA66/ILT-1 hybrid material as detected by differential scanning calorimetry (DSC). The dielectric spectroscopic investigation on the networks’ molecular level structural …

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 …

Discriminating Azo Dyes: Conjugated Polymers, The Inner Filter Effect, And Array Sensors, Erin Crater

Honors Theses

Azo dyes are abundant pollutants that contaminate water supplies and threaten humans, biota, and ecosystem health. Their detection and discrimination are an incredible challenge due to the structural, chemical, and optical similarities between dyes, the complexity of the wastewater environment in which they are found, and their low environmental concentrations. In this work, the inner filter effect (IFE), combined with conjugated polymer array-based sensing, is utilized for the quantitative profiling of these pollutants. The array was constructed using three fluorescent, anionic conjugated polyelectrolytes whose varying spectroscopic properties led to distinct IFE patterns in the presence of the dyes. The unique …

Thiol-Ene Click Chemistry For Solid State Triplet-Triplet Annihilation Upconversion And Parts-Per-Billion Pyrophosphate Sensing In Artificial Seawater, Abagail K. Williams

Master's Theses

Thiol-ene click chemistry is a robust approach to molecularly engineering polymers for many applications. Within this work, thiol-ene click chemistry is used to fabricate thiol-ene networks for TTA-UC and to synthesize a conjugated polyelectrolyte (CPE) used as a pyrophosphate (PPi) sensor in complex aqueous media. Chapter I focuses on the synthesis and upconversion performance of rubbery networks fabricated using thiol-ene click photopolymerization. The advancement of triplet-triplet annihilation based upconversion (TTA-UC) in emerging technologies necessitates the development of solid-state systems that are readily accessible and broadly applicable. We demonstrate that thiol-ene click chemistry can be used as a facile cure-on-demand synthetic …

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 …

Investigation On The Morphology Of Charge-Transfer Complexes In Low Density Polyethylene, Wade Korf

Master's Theses

Fillers are used ubiquitously throughout the fields of polymer and material science to overcome many inherent limitations to polymeric materials (i.e. poor stiffness or strength) and to expand their potential applications. There is a need to develop controllable particle architectures to better understand fundamental structure-property relationships in particle reinforced polymer composites. Charge-transfer complexes (CTCs) can assemble in situ into various needle and dendritic shapes via simple fabrication processes and at low loading levels. In this study, the effect of tetrathiafulvalene (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) CTC crystallites of various shapes and sizes on composite mechanical properties was investigated in an LDPE …

A Game-Theoretic Approach To Deciphering The Dynamics Of Amyloid-Beta Aggregation Along Competing Pathways, Preetam Ghosh, Pratip Rana, Vijayaraghavan Rangachari, Jhinuk Saha, Edward Steen, Ashwin Vaidya

Faculty Publications

Aggregation of amyloid-β (Aβ) peptides is a significant event that underpins Alzheimer's disease (AD). Aβ aggregates, especially the low-molecular weight oligomers, are the primary toxic agents in AD pathogenesis. Therefore, there is increasing interest in understanding their formation and behaviour. In this paper, we use our previously established results on heterotypic interactions between Aβ and fatty acids (FAs) to investigate off-pathway aggregation under the control of FA concentrations to develop a mathematical framework that captures the mechanism. Our framework to define and simulate the competing on- and off-pathways of Aβ aggregation is based on the principles of game theory. Together …

Synthesis, Characterization, Dna Binding, Topoisomerase Inhibition, And Apoptosis Induction Studies Of A Novel Cobalt(Iii) Complex With A Thiosemicarbazone Ligand, Stephen J. Beebe, Michael J. Celestine, Jimmie L. Bullock, Shayna Sandhaus, Jessa Faye Arca, Donald M. Cropek, Tekettay A. Ludvig, Sydney R. Foster, Jasmine S. Clark, Floyd A. Beckford, Criszcele M. Tano, Elizabeth A. Tonsel-White, Raj K. Gurung, Courtney E. Stankavich, Yuk Ching Tse-Dinh, William L. Jarrett, Alvin A. Holder

Faculty Publications

In this study, 9-anthraldehyde-N(4)-methylthiosemicarbazone (MeATSC) 1 and [Co(phen)₂(O₂CO)]Cl·6H₂O 2 (where phen = 1,10-phenanthroline) were synthesized. [Co(phen)₂(O₂CO)]Cl·6H₂O 2 was used to produce anhydrous [Co(phen)₂(H₂O)₂](NO₃)₃ 3. Subsequently, anhydrous [Co(phen)₂(H₂O)₂](NO₃)₃ 3 was reacted with MeATSC 1 to produce [Co(phen)₂(MeATSC)](NO₃)₃·1.5H₂O·C₂H₅OH 4. The ligand, MeATSC 1 and all complexes were characterized by elemental analysis, FT IR, UV–visible, and multinuclear NMR ( …

Granulins Modulate Liquid-Liquid Phase Separation And Aggregation Of Prion-Like C-Terminal Domain Of The Neurodegeneration-Associated Protein Tdp-43, Anukool A. Bhopatkar, Vladimir N. Uversky, Vijay Rangachari

Faculty Publications

Tar DNA binding protein 43 (TDP-43) has emerged as a key player in many neurodegenerative pathologies including frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Hallmarks of both FTLD and ALS are the toxic cytoplasmic inclusions of the prion-like C-terminal fragments of TDP-43 (TDP-43 CTD), formed upon proteolytic cleavage of full-length TDP-43 in the nucleus and subsequent transport to the cytoplasm. Both full-length TDP-43 and its CTD are also known to form stress granules (SGs) by coacervating with RNA in the cytoplasm during stress and may be involved in these pathologies. Furthermore, mutations in PGRN gene, leading to haploinsufficiency …

Adsorption Of Polyisobutylene-Based Dispersants Onto Carbon Black, Travis Paul Holbrook

Dissertations

The formation of carbonaceous by-products (e.g. soot) during the operation of an internal combustion engine is unavoidable and the aggregation of this soot leads to deleterious effects including abrasive wear of the engine, increased oil viscosities, and sludge deposition. Dispersants, which are composed of a hydrophobic tail and a polar headgroup, are used as oil additives to aid in the suspension and stabilization of the soot particles. Polyisobutylene succinimide (PIBSI) is the most well-studied class of dispersants and is characterized by a linear architecture and polyamine headgroup that interacts with soot by acid-base and dipole-dipole interactions. As such, there remains …

The Antimicrobial Activity And Cellular Targets Of Plant Derived Aldehydes And Degradable Pro-Antimicrobial Networks In Pseudomonas Aeruginosa, Yetunde Adewunmi

Dissertations

Essential oils (EOs) are plant-derived products that have been long exploited for their antimicrobial activities in medicine, agriculture, and food preservation. EOs represent a promising alternative to conventional antibiotics due to the broad-range antimicrobial activity, low toxicity to human commensal bacteria, and the capacity to kill microorganisms without promoting resistance. Despite the progress in the understanding of the biological activity of EOs, many aspects of their mode of action remain inconclusive. The overarching aim of this work was to address these gaps by studying molecular interactions between antimicrobial plant aldehydes and the opportunistic human pathogen Pseudomonas aeruginosa. We initiated …

Towards The Synthesis Of An Artificial Fluorescent Siderophore, Ashley Burns

Honors Theses

Siderophores are molecules capable of binding ferric ions with high affinity (Ka = 1052). This thesis outlines our attempts to synthesize an artificial siderophore, which incorporates a signaling group to help monitor the uptake of ferric ions. The artificial siderophore is a tripodal molecular receptor synthesized in a five-step procedure with a proposed final sixth step. Rhodamine 6G azide (95.0% yield) was formed from rhodamine 6G and the synthesis of 2-azidoethanamine was modified from the literature. The tripodal arm portion of the sensor was successfully synthesized by protecting the catechol of 2,3-dihydroxybenzaldehyde to form 3-formyl-1,2-phenylene dimethanesulfonate (98.8% yield). The reduction …

Stretchable Self-Healable Semiconducting Polymer Film For Active-Matrix Strain-Sensing Array, Jin Young Oh, Donghee Son, Toru Katsumata, Yeongjun Lee, Yeongin Kim, Jeffrey Lopez, Hung-Chin Wu, Jiheong Kang, Joonsuk Park, Xiaodan Gu, Jaewan Mun, Nathan Ging-Ji Wang, Yikai Yin, Wei Cai, Youngjun Yun, Jeffrey B.-H. Tok, Zhenan Bao

Faculty Publications

Skin-like sensory devidces shoud be stretchable and self-healable to meet the demands for future electronic skin applications. Despite recent notable advances in skin-inspired electronic materials, it remains challenging to confer these desired functionalities to an active semiconductor. Here, we report a strain-sensitive, stretchable, and autonomously self-healable semiconducting film achieved through blending of a polymer semiconductor and a self-healable elastomer, both of which are dynamically cross-linked by metal coordination. We observed that by controlling the percolation threshold of the polymer semiconductor, the blend film became strain sensitive, with a gauge factor of 5.75 x 10⁵ at 100% strain in a …

Melt Electrospinning Designs For Nanofiber Fabrication For Different Applications, Yasseen S. Ibrahim, Essraa A. Hussein, Moustafa M. Zagho, Ghada G. Abdo, Ahmed A. Elzatahry

Faculty Publications

Nanofibers have been attracting growing attention owing to their outstanding physicochemical and structural properties as well as diverse and intriguing applications. Electrospinning has been known as a simple, flexible, and multipurpose technique for the fabrication of submicro scale fibers. Throughout the last two decades, numerous investigations have focused on the employment of electrospinning techniques to improve the characteristics of fabricated fibers. This review highlights the state of the art of melt electrospinning and clarifies the major categories based on multitemperature control, gas assist, laser melt, coaxial, and needleless designs. In addition, we represent the effect of melt electrospinning process parameters …

Modifying Inhibited Primer Performance Via Control Of Epoxy-Amine Matrix Structure And Composition, Steven Wand

Dissertations

This research represents an effort to deliver a new fundamental understanding of how polymer matrix characteristics influence corrosion protection of organic coatings, in particular the performance of corrosion inhibitor-containing primers. By modifying the structure and composition features of epoxy-amine matrices which commonly serves as the binder for protective coatings, the thermal/mechanical, adhesion, and transport properties which govern coating performance and inhibitor release were altered in such a way that directly influenced protection efficacy. This research is composed of three distinct approaches towards systematically varying thermoset network characteristics and observing the resulting impact on transport behaviors and corrosion prevention, with an …

“Polysoaps” Via Raft Copolymerization To Form Well-Defined Micelles For Water Remediation And Targeted Drug Delivery Applications, Phillip Pickett

Dissertations

Amphiphilic copolymers have become increasingly important for environmental and biological applications due to their behavioral characteristics in aqueous solution. For example, structurally-tailored statistical amphiphilic copolymers or “polysoaps” can self-assemble into micelles or other architectures in water at various concentrations. Polysoaps may be differentiated from small molecule surfactant micelles in their capability to self-assemble into unimolecular associates (unimolecular micelles) with no dependence on concentration. Such micelles offer enormous potential for dispersion of hydrophobic species in water at high dilution. Importantly, each polymer chain forms its own micelle and upon dilution, these micelles remain intact and capable of dispersing hydrocarbon material in …

Engineering Multifunctional And Morphologically Diverse Polymer Brush Surfaces, Cassandra M. Reese

Dissertations

The combination of surface-initiated polymerization (SIP) and post-polymerization (PPM) serves as a powerful approach to fabricate complex, multifunctional polymer films, which can be precisely tuned for desired surface engineering applications. Careful manipulation of PPM parameters such as reaction conditions, the tethered brush parameters, and the physical properties of the unbound post-modifier greatly influence the depth of penetration of the post-modifier and the polymer brush compositional heterogeneity. This dissertation focuses on engineering polymer brush surfaces with multifunctional chemistries and tunable morphologies by investigating the PPM parameters that dictate the distribution of post-modifiers on grafted polymer brush surfaces.

The first chapter of …

Manipulation Of Noncovalent Interactions For The Synthesis And Use Of Natural Product Synthons, Alison P. Hart

Dissertations

Natural products are widely used in the pharmaceutical industry, in agriculture, and as specialty chemicals. Methodology development focuses on optimizing the key organic reactions to access these natural products while trying to limit the overall number of synthetic steps. Key bond forming strategies are sought to provide new ways to address carbon-carbon or carbon-heteroatom bonds. The advancement of new asymmetric reactions to generate enantiopure products from achiral starting materials is a vital area of research. The objectives addressed in this dissertation include: 1) the development of a general reductive conversion of esters to ethers with a broad substrate scope accessing …

Evaluating Corrosion Altering Properties Of Thiophene Based Copolymers, Robert Peterson

Dissertations

There is an important and ongoing debate on how or whether conductive polymers (CP) alter corrosion performance with some researchers reporting that CPs ultimately accelerate corrosion and others saying CPs, if understood could possibly replace the world’s best standard for corrosion prevention, i.e., chromium based inhibitors. The primary project goal was to improve our understanding of how CPs alter corrosion chemistry by 1) controlling the polymer structure and 2) in-turn the properties and then 3) targeting the best protocol for fast corrosion kinetic evaluation.

We detail the copolymer synthesis results and shift in corrosion protection properties for …

Molecular Packing Control Enables Excellent Performance And Mechanical Property Of Blade-Cast All-Polymer Solar Cells, Baojun Lin, Lin Zhang, Heng Zhao, Xianbin Xu, Ke Zhou, Song Zhang, Lu Guo, Baobing Fan, Lei Zhang, Hongping Yan, Xiaodan Gu, Lei Ying, Fei Huang, Yong Cao, Wei Ma

Faculty Publications

All-polymer solar cells (all-PSCs) are the most promising power generators for flexible and portable devices due to excellent morphology stability and outstanding mechanical property. Previous work indicates high crystallinity is beneficial to device performance but detrimental to mechanical property, therefore identifying the optimized ratio between crystalline and amorphous domains becomes important. In this work, we demonstrated highly efficient and mechanically robust all-PSCs by blade-coating technology in ambient environment based on PTzBI:N2200 system. By controlling the aggregation in solution state and ultrafast film formation process, a weakly ordered molecular packing morphology as well as small phase separation is obtained, which leads …

A High-Spin Ground-State Donor-Acceptor Conjugated Polymer, Alex E. London, H. Chen, M.A. Sabuj, Joshua Tropp, M. Saghayezhian, Naresh Eedugurala, B.A. Zhang, Y. Liu, Xiaodan Gu, B.M. Wong, N. Rai, M.K. Bowman, Jason D. Azoulay

Faculty Publications

Interest in high-spin organic materials is driven by opportunities to enable far-reaching fundamental science and develop technologies that integrate light element spin, magnetic, and quantum functionalities. Although extensively studied, the intrinsic instability of these materials complicates synthesis and precludes an understanding of how fundamental properties associated with the nature of the chemical bond and electron pairing in organic materials systems manifest in practical applications. Here, we demonstrate a conjugated polymer semiconductor, based on alternating cyclopentadithiophene and thiadiazoloquinoxaline units, that is a ground-state triplet in its neutral form. Electron paramagnetic resonance and magnetic susceptibility measurements are consistent with a high-to-low spin …