Browsing by Author "Rupar, Paul A."
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Item Air-stable palladium(II) precatalysts: synthesis, properties, and applications in cross-coupling reactions(University of Alabama Libraries, 2017) Barnett, Kerry Lynn; Shaughnessy, Kevin H.; University of Alabama TuscaloosaPalladium catalyzed cross-coupling reactions are a versatile tool in organic chemistry to produce small molecules. Current research interests involve the development of new catalyst systems for various palladium catalyzed reactions. Previous work has suggested the active species for palladium-catalyzed cross-coupling reactions to be a mono-ligated palladium(0) species when sterically demanding ligands are used. Therefore, the my work focused on the synthesis of precatalysts with an established 1:1 L:Pd. Specifically, we were focused on the synthesis of mono-ligated palladium(II) precatalysts of general formula [(R_3P)PdCl_2]_2, using di-tert-butylneopentylphosphine (DTBNpP), tert-butyldineopentylphosphine (TBDNpP), and trineopentylphosphine (TNpP) as ligands. Under optimized conditions, both [(DTBNpP)PdCl_2]_2 and [(TNpP)PdCl_2]_2 were effective precatalysts for the Suzuki cross-coupling of a wide range of aryl bromides. Comparison studies with the air-stable precatalysts versus the in-situ generated catalyst showed the precatalysts to have improved conversions and higher rates of reaction under both inert and ambient atmospheres. The precatalyst activation pathways were investigated by 31P NMR spectroscopy. The spectra obtained from 31P NMR experiments revealed a side reaction resulting in a catalytically inactive palladacycle species. The results obtained from the mechanistic investigations led to further optimization of reaction conditions to decrease the amounts of catalytically inactive side products formed.Item The Anionic Polymerization of a tert-Butyl-Carboxylate-Activated Aziridine(MDPI, 2022) Giri, Chandan; Chang, Jen-Yu; Mbarushimana, Pierre Canisius; Rupar, Paul A.; University of Alabama TuscaloosaN-Sulfonyl-activated aziridines are known to undergo anionic-ring-opening polymerizations (AROP) to form polysulfonyllaziridines. However, the post-polymerization deprotection of the sulfonyl groups from polysulfonyllaziridines remains challenging. In this report, the polymerization of tert-butyl aziridine-1-carboxylate (BocAz) is reported. BocAz has an electron-withdrawing tert-butyloxycarbonyl (BOC) group on the aziridine nitrogen. The BOC group activates the aziridine for AROP and allows the synthesis of low-molecular-weight poly(BocAz) chains. A C-13 NMR spectroscopic analysis of poly(BocAz) suggested that the polymer is linear. The attainable molecular weight of poly(BocAz) is limited by the poor solubility of poly(BocAz) in AROP-compatible solvents. The deprotection of poly(BocAz) using trifluoroacetic acid (TFA) cleanly produces linear polyethyleneimine. Overall, these results suggest that carbonyl groups, such as BOC, can play a larger role in the in the activation of aziridines in anionic polymerization and in the synthesis of polyimines.Item Anionic polymerization of activated aziridines(University of Alabama Libraries, 2018) Mbarushimana, Pierre Canisius C.; Rupar, Paul A.; University of Alabama TuscaloosaPolyethyleneimine, also referred to as polyaziridine, is a polymer that has a repeat unit of (-CH2CH2NH-). Due to its high amine density, PEI finds application in several domains including gene transfection, antimicrobial/antibacterial medicine, CO2 capture, thin film metal deposition, industrial wastewater treatments, and more. Commercially, PEI is obtained via the uncontrolled polymerization of aziridine and the cationic ring opening polymerization (CROP) of oxazolines. However, the available cationic polymerization techniques of aziridines are poorly controlled. In order to synthesize well-defined PEIs, recent literature approaches have used the anionic ring opening polymerization (AROP) of various N-substituted aziridines. The present research, done at The University of Alabama, has focused on the synthesis and AROP of N-substituted aziridines, without the substitution at the 2-position of the aziridine ring. The studied monomers include three tert-butylcarboxy-protected aziridine monomers, specifically tert-butyl aziridine-1-carboxylate, tert-butyl 2-methylaziridine-1-carboxylate, tert-butyl 2-decylaziridine, and six 1-(alkylsulfonylsulfonyl) aziridine monomers, i.e. 1-(methylsulfonyl)aziridine, 1-(toluenesulfonyl)aziridine, 1-(octylsulfonyl)aziridine, 1-(sec-butylsulfonyl)aziridine, 1-((2-nitrophenyl)sulfonyl)aziridine, and 1-((4-nitrophenyl)sulfonyl)aziridine. After characterization, the synthesized monomers were homopolymerized by AROP using various nucleophilic initiators. Except for BOCDecAz, all the synthesized monomers were successfully converted into the corresponding polymers. However, only short oligomers of the resulting homopolymers were formed, as high molecular weight polymer chains were insoluble. The synthesized polymers can potentially be used as precursor to pure linear polyamines A single sulfonyl aziridine, namely1-((ortho-nitrophenyl)sulfonyl)aziridine (oNsAz) was found to produce high molecular weight poly(oNsAz) that was soluble in DMF and DMSO. This is significant as it is the first example of a soluble poly(1-sulfonylaziridine) homopolymer; prior examples were limited to random copolymer. The deprotection of poly(oNsAz) was also attempted in effort to synthesize linear PEI. Although evidence was found for the formation of linear PEI, satisfactory purification of the linear PEI was not achievable.Item The anionic ring-opening polymerization of cyclic imines(University of Alabama Libraries, 2019) Reisman, Louis; Rupar, Paul A.; University of Alabama TuscaloosaOne important class of polymers is polyimines. Polyimines have a wide range of applications such as CO2 capture and non-viral gene-transfection. Despite their many applications, the use of these polymers is limited due to difficulties in controlling the polymerization. To increase the feasibility of polyimines in the aforementioned high-value applications, the research in this dissertation focuses on controlled routes to produce linear polyimines using living anionic ring-opening polymerization (AROP). The early work of this dissertation focuses on an AROP route to linear polyethylenimine (LPEI). Due to the insolubility of p(N-sulfonylaziridine)s (i.e. non-2-substituted) in all common solvents, this was achieved using a copolymerization strategy. Utilizing two N-sulfonylaziridines, N-(methanesulfonyl)aziridine (MsAz) and N-(sec-butylsulfonyl)aziridine (sBsAz), with similar reactivities, a soluble random copolymer with narrow molecular weight distributions is produced. Removal of the sulfonyl groups of p(MsAz-r-sBsAz) affords the first example of LPEI by living, controlled AROP. The later work in this dissertation focuses on the AROP of N-sulfonylazetidines in route to linear poly(trimethylenimine) (LPTMI). Initially, the polymerization of N-(methanesulfonyl)azetidine (MsAzet) was investigated. The kinetics of this polymerization were studied, and the reaction found to be first order with respect to monomer and the number of active chain ends remains constant throughout the polymerization. Interestingly, activation occurs at the methanesulfonyl group, leading to polymer branching. This branching precludes p(MsAzet) from being a precursor to LPTMI. By more judicial selection of N-sulfonylazetidine monomers, a living, controlled AROP approach to LPTMI was achieved by copolymerizing two similar N-sulfonylazetidines, N-(p-tolylsulfonyl)azetidine (pTsAzet) and N-(o-tolylsulfonyl)azetidine (oTsAzet), to produce a statistical copolymer. Copolymerization was required as the homopolymers resulting from these monomers were insoluble in all common solvents. The copolymerization is living and controlled, producing polymers with narrow molecular weight distributions. The kinetics of the copolymerization, and the reactivity ratios of the two monomers, were studied and the sulfonyl groups of the polymer were removed to provide the first example of LPTMI by living, controlled AROP. Finally, the high barrier to polymerization of N-sulfonylazetidines was utilized to produce block copolymers, containing no homopolymer impurities, in a closed system in which all monomers are present in solution at the time of initiation.Item Borafluorenes and polyborafluorenes boron doped varients of fluorene(University of Alabama Libraries, 2017) Adams, Ian; Rupar, Paul A.; University of Alabama TuscaloosaA series of novel boron containing variants of fluorene were synthesized. Boron was incorporated synthetically via lithium halogen exchange and Grignard reaction pathways. Once incorporated, the borafluorene could be polymerized or undergo further functionalization via Yamamoto and Stille coupling reactions. This incorporation of boron into a conjugated system imparted Lewis acidic and electron deficient properties into a conjugated system. It is our hope that this will dope fluorene and create novel n-type semiconductors. A novel polymer of borafluorene, poly(9-borafluorene) (P9BF) was synthesized. HOMO and LUMO levels of P9BF were estimated by cyclic voltammetry. As predicted in prior DFT studies, P9BF has a reduced band gap and a lower lying LUMO compared with polyfluorene. To examine how the HOMO and LUMO levels of borafluorene systems could be tuned, copolymers of 9-borafluorene were synthesized. Four of the copolymers were a series of donor-acceptor (DA) type copolymers. A borafluorene-fluorene (P9BF-OF) copolymer and borafluorene-diketopyrrolopyrrole (P9BF-DPP), as an acceptor-acceptor (AA) copolymer were also synthesized. The series of DA copolymers showed higher energy HOMO and LUMO levels in correlation with the relative donating ability of the donor monomer. P9BF-OF has a reduced LUMO level in comparison with P9BF. P9BF-DPP has a very low band gap (1.8eV), with absorption well into the near-IR region. To examine ways to make borafluorene more air stable, a series of borafluorenes bearing bismethylmethoxyphenyl (BMMP) ligands were investigated. Interestingly, ii bismethylmethoxyphenyl-borafluorene (BMMP-BF) exhibits an exceptionally large Stokes shift of 16000 cm-1. To extend the conjugation and change the Stokes shift, thiophene containing derivatives BMMP-BF-T, BMMP-BF-2T, and BMMP-BF-3T were synthesized. These thiophene containing compounds exhibited anomalous two wavelength fluorescence. During our fluoride titration experiments, we noticed spectral impurities when using tetrabutylammonium fluoride (TBAF) as our fluoride source. Examining this more closely, we found that commercial samples of TBAF were found to absorb light at 295 and 370 nm and fluoresce as 435 nm. This was not expected for analytically pure TBAF, so we concluded that there must be an impurity present in commercial TBAF. The source of this impurity was found to be I3- which occurs from the oxidation of I-.Item Carbohydrate sensing using boronic acid modified polymers(University of Alabama Libraries, 2019) Liang, Xiaoli; Bonizzoni, Marco; University of Alabama TuscaloosaPolyelectrolytes have attained a more prominent role in the design of supramolecular systems in recent years. In particular, commercially available poly(amidoamine) (PAMAM) dendrimers have been widely used because they have high loading capacities and good solubility in water. We focus here on using optical spectroscopy to investigate the application of PAMAM dendrimer derivatives as receptors in carbohydrate sensing, and to study the multivalent behavior of receptors covalently appended to the surface of these macromolecules. We then extended the design principles obtained from this work to linear water-soluble anionic polyelectrolytes developed in collaboration with the Kharlampieva group at the University of Alabama at Birmingham (UAB), using polymethacrylate-acrylamide co-polymers synthesized by their group. In chapters 2 and 3, we describe a carbohydrate sensing system that can operate in neutral water, using covalently modified polyelectrolytes as receptors, and common commercially available dyes as optical signaling units. Particularly, in chapter 2, boronic acid modified PAMAM dendrimers were used as receptors to differentiate common monosaccharides in water at millimolar concentration. This is a significant improvement in affinity and sensitivity over simple boronic acid receptors, particularly for work in aqueous environment, which is considered a challenging medium for carbohydrate detection. In chapter 3, these design concepts were also extended to using boronic acid modified polymethacrylate-acrylamide copolymers synthesized at UAB. Binding affinity trends of carbohydrates to boronic acid moieties were then investigated from a fundamental perspective. In chapter 4, the multivalent behavior of boronic acid moieties on surface-modified PAMAM dendrimers was characterized in detail to determine the factors influencing the onset of multivalent behavior, including the surface density of receptor sites and the overall size of the polymeric scaffold.Item Characterization and thermoelectric performance of polymer/inorganic hybrid films using spectroscopic and microscopic techniques(University of Alabama Libraries, 2019) Sutch, Tabitha Patricia; Szulczewski, Greg J.; University of Alabama TuscaloosaThe main goal of this dissertation was to investigate the thermoelectric performance of films of silver telluride (Ag2Te), bismuth sulfide (Bi2S3) and bismuth telluride (Bi2Te3) nanowires (NWs) dispersed in P(NDI2OD-T2). We hypothesize that the electrical properties of the films made with Ag2Te, Bi2S3, and Bi2Te3 will be n-type and behave like composite materials. Ag2Te was synthesized to make three different lengths of NWs. Powder x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS) confirmed that β-Ag2Te was synthesized with the anticipated stoichiometry. Scanning electron microscopy (SEM) of Ag2Te NWs in P(NDI2OD-T2) revealed that the longest Ag2Te NWs produced homogeneous composites whereas the shorter Ag2Te NWs phase-separated. Electrical conductivity and Seebeck coefficients for each composite film were determined and theoretical models were used to investigate charge-transport behavior. Seebeck coefficients confirmed that all composites were n-type. The longest Ag2Te NWs produced the highest electrical conductivities with parallel transport behavior and are promising to the field of thermoelectrics. Bi2S3 and Bi2Te3 NWs were synthesized, and their stoichiometry and structures were confirmed using XRD and EDS. SEM images of the NW/P(NDI2OD-T2) films revealed that both Bi2S3 and Bi2Te3 phase-separated. The electrical conductivity for each composite film was determined and theoretical models were applied. The electrical conductivity of the Bi2S3 and Bi2Te3 composites were slightly higher than pristine P(NDI2OD-T2), further indicating that the NWs phase-separated. Seebeck coefficients for both systems confirmed that the composites were n-type. Despite the various strategies for improving the film morphology, composites made with Bi2Te3 and Bi2S3 NWs did not produce promising results. The spin-dynamics of P(NDI2OD-T2) doped with cobaltocene were studied with continuous-wave electron paramagnetic resonance (EPR). Additionally, the electrical conductivity of cobaltocene doped P(NDI2OD-T2) films increased several orders of magnitude compared to pristine P(NDI2OD-T2). A sputter depth profile in conjunction with x-ray photoelectron spectroscopy was used to analyze how the dopant dispersed in the polymer matrix. Temperature-dependent pulsed EPR of two different doping concentrations suggested two different relaxation rates. Overall, this study investigated the temperature-dependent spin dynamics of cobaltocene doped P(NDI2OD-T2) films and lays the foundation for further investigations on n-doped polymer system.Item Development of Novel Solvents for Efficient CO2 Absorption Through Glycerol Derivatization(University of Alabama Libraries, 2022) Qian, Shuai; Bara, Jason E.; University of Alabama TuscaloosaThis dissertation demonstrates the development of novel, glycerol-derived compounds enabled by value-added glycerol derivatives initially from biomass for the sake of abundant resources, improved regioselectivity and tailorability to allow the possibility of production in large scale with precise modifications in glycerol backbones to form symmetric and/or asymmetric structures. Compounds obtained include neutral small molecules (including glycerol mono-, di-, and tri-ether) and ionic liquids (ILs). A screening of physical properties (i.e., density, viscosity, vapor pressure, miscibility with common solvents) was conducted with the realization of temperature dependence to set up a database for comparisons with analogues in literature. The structure-property relationship was illustrated by quantum chemical simulations. Besides, the property characterization results also indicate potential applications. Some solvents showed good performance in CO2 capacity along with reduced viscosity and vapor pressure compared to common solvents used in industries, and thus making those compounds competent candidates as novel solvents in CO2 capture. Apart from carbon mitigation, continued research on task-specific glycerol derivatives is introduced in the last chapter for extensive applications in fields of fuel additives, electrolytes, lithium extraction from brines, polymer membranes, 3D printing, among many other possible applications.Item Electron-deficient conjugated materials(University of Alabama Libraries, 2018) Cao, Hongda; Rupar, Paul A.; University of Alabama TuscaloosaThe development of new conjugated materials with tailored properties is in high demand for applications in organic electronics. This has led to conjugated materials receiving a great deal of research attention over the last few decades. One efficient method to prepare these novel conjugated small molecules and polymers is the incorporation of p-block elements into conjugated systems. In Chapter 2, a new phosphafluorene is synthesized and copolymerized to produce a donor-acceptor (D-A) conjugated copolymer PPF-BDTT. Direct post-polymerization modification of PPF-BDTT was performed on the phosphorus center to prepare the phosphine sulfide polymer PPF-BDTT-S and phosphine gold chloride polymer PPF-BDTT-Au. These D-A polymers have been fully characterized, and their applications in organic solar cells was also investigated. In Chapter 3, three air-stable difuran small molecules were synthesized by the incorporation of phosphorus, germanium, and silicon. The good stability is partially due to the σ*-π* conjugation interaction between p-block elements and the pi systems. These molecules show strong absorption in the UV region and intense emissions. The phosphorus bridged difuran was also copolymerized with fluorene to produce a D-A conjugated polymer. In Chapter 4, bithiazole (BTz) was functionalized with a 9-borabicyclononane (BBN) moiety to produce a boronium molecule BTz-BBN. With similar synthetic methods, two conjugated organoboronium polymers PFOBPy-BBN and PFOBTz-BBN were developed, which demonstrated a novel method to prepare conjugated boronium polymers in high yield. PFOBPy-BBN and PFOBTz-BBN were studied optically and electrochemically. In Chapter 5, benzothiophene dioxide was selected to prepare the non-fullerene acceptor ITBC with an acceptor-donor-acceptor structure. The strong electron-withdrawing sulfonyl acceptor units lead to extended UV-Vis absorption and low frontier molecular orbital energy levels with a narrow bandgap. A power conversion efficiency of 4.17 % was achieved by fabricating organic solar cells with polymer FTAZ as the donor and ITBC as the acceptor. In Chapter 6, a chlorinated bifuran small molecule ClBF was synthesized, and a series of random copolymers (PNDI-ClBFx) using ClBF and naphthalene diimide were prepared. These polymers exhibit strong and broad absorption, and the low-lying frontier energy levels of PNDI-ClBFx are suitable as polymer acceptors in all-polymer solar cells applications.Item Electron-deficient heterofluorene conjugated polymers and small molecules(University of Alabama Libraries, 2018) Cassidy, Stephen Joel; Rupar, Paul A.; University of Alabama TuscaloosaA series of heterofluorene polymers, containing electron-deficient heteroatoms, were designed for investigation. Indium was first chosen for heteroatom substitution, due to the known Lewis acidity of Group-13 elements, and supermesityl (2,4,6-tri-tert-butylphenyl) was used as a protective substituent to reduce unwanted hydrolysis of indafluorene by sterically protecting the vacant p-orbitals of the indium heteroatom. An indafluorene small molecule was synthesized as a model system; however, 1H NMR analysis showed the compound demonstrated poor stability when exposed to air, so an indafluorene polymer based on this design was not pursued. A novel borafluorene was investigated, featuring an OCO pincer-type ligand as the protective substituent, which stabilizes the boron heteroatom through weak B-O dative bonds. A borafluorene small molecule (BMMP-BF) was synthesized as a model system, and demonstrated robust stability under ambient conditions. Surprisingly, BMMP-BF also exhibited an extraordinarily large Stokes shift, and the cause behind this intriguing optical behavior was investigated. The borafluorene was then functionalized as a monomer and incorporated into two copolymer systems in order to examine the effects that extended conjugation and comonomer electron affinity would have on the optoelectronic properties. Optical characterization showed that both copolymers had a change in their optical behavior, relative to BMMP-BF, as demonstrated by smaller Stokes shifts, and CV analysis revealed that both copolymers possessed low lying LUMOs and narrow optical bandgaps. It is our hope that this research will lead to the development of novel n-type semiconductors. A novel carbazole-based polymer was explored, featuring a cationic ammonium functional group incorporated in the conjugated polymer backbone. A quaternized carbazolium small molecule was synthesized through an intramolecular cyclization mechanism, and served as a model system. The small molecule was characterized by NMR and XRD, and exchange of the counter ion was effectively demonstrated. We intended to synthesize a carbazole polymer and characterize the polymer in a non-ionic state, then quaternize the monomer sub-units during a post-polymerization phase to achieve a carbazolium polyelectrolyte. However, the non-ionic polymer had poor solubility in common organic solvents, which restricted access to the desired polyelectrolyte, and several efforts to form a soluble polymer were ultimately unsuccessful.Item Explosive dissolution and trapping of block copolymer seed crystallites(Nature Portfolio, 2018) Guerin, Gerald; Rupar, Paul A.; Manners, Ian; Winnik, Mitchell A.; University of Toronto; University of Bristol; University of Alabama TuscaloosaEnhanced control over crystallization-driven self-assembly (CDSA) of coil-crystalline block copolymers has led to the formation of intricate structures with well-defined morphology and dimensions. While approaches to build those sophisticated structures may strongly differ from each other, they all share a key cornerstone: a polymer crystallite. Here we report a trapping technique that enables tracking of the change in length of one-dimensional (1D) polymer crystallites as they are annealed in solution at different temperatures. Using the similarities between 1D polymeric micelles and bottle-brush polymers, we developed a model explaining how the dissolving crystallites reach a critical size independent of the annealing temperature, and then explode in a cooperative process involving the remaining polymer chains of the crystallites. This model also allows us to demonstrate the role of the distribution in seed core crystallinity on the dissolution of the crystallites.Item In-Depth Analysis of the Effect of Fragmentation on the Crystallization-Driven Self-Assembly Growth Kinetics of 1D Micelles Studied by Seed Trapping(MDPI, 2021) Guerin, Gerald; Rupar, Paul A.; Winnik, Mitchell A.; East China University of Science & Technology; University of Toronto; University of Alabama TuscaloosaStudying the growth of 1D structures formed by the self-assembly of crystalline-coil block copolymers in solution at elevated temperatures is a challenging task. Like most 1D fibril structures, they fragment and dissolve when the solution is heated, creating a mixture of surviving crystallites and free polymer chains. However, unlike protein fibrils, no new nuclei are formed upon cooling and only the surviving crystallites regrow. Here, we report how trapping these crystallites at elevated temperatures allowed us to study their growth kinetics at different annealing times and for different amounts of unimer added. We developed a model describing the growth kinetics of these crystallites that accounts for fragmentation accompanying the 1D growth process. We show that the growth kinetics follow a stretched exponential law that may be due to polymer fractionation. In addition, by evaluating the micelle growth rate as a function of the concentration of unimer present in solution, we could conclude that the micelle growth occurred in the mononucleation regime.Item Investigation of protein dynamics in glycosyltransferases with the GT-B structural fold(University of Alabama Libraries, 2019) Chen, Wen; Frantom, Patrick A.; University of Alabama TuscaloosaCarbohydrate transfer reactions are significant for organisms and are involved in a variety of functions in cells. This complicated system is controlled by enzymes including glycosyltransferases (GTs). GTs catalyze sugar transfer reactions. There are mainly two structural folds adopted by GTs, GT-A and GT-B. Structures of the GT-B enzymes are well conserved, especially in the C-terminal domain. GT-Bs are believed to undergo a conformational change upon binding substrates. This indicates that protein dynamics of GT-B members is a key for the study of the whole family. To better understand the commonly shared conformational change by GT-B enzymes, backbone amide hydrogen-deuterium exchange monitored by mass spectrometry (HDX-MS) is utilized to characterize protein motion in solution. We report results of HDX-MS experiments to determine conformational changes of two representatives of GT-B enzymes, MshA from Corynebacterium glutamicum (CgMshA) and Heptosyltransferase I (HepI). HDX-MS analysis of CgMshA suggests a third conformation of CgMshA in solution with uridine 5′-diphospho-N-acetylglucosamine (UDP-GlcNAc) bound. It indicates that the UDP-GlcNAc complex might be in a loose form compared with UDP complex, and the UDP release step might be rate determining for the reaction. Moreover, structural and dynamic studies are combined with bioinformatic results for CgMshA to predict the sequence/structure/dynamic relationships for the GT4 family. In addition, protein dynamics of HepI in the apo form is studied and compared to CgMshA. HDX-MS analysis of HepI suggests that the regions in the outer layer of HepI exhibit flexibility, which predicts a slight domain rotation in HepI. The flexible regions of HepI might participate in the potential conformational change. Other contributions of an additional domain are investigated in this dissertation in terms of protein activity and mechanism. By studying isopropylmalate synthase and citramalate synthase from Methanococcus jannaschii (MjIPMS and MjCMS, respectively), the role of the LeuA dimer regulatory domain in substrate selectivity is determined. Overall, we report a more complex role for the LeuA dimer regulatory domain in substrate selectivity through catalytic modulations rather than selectivity through differential binding as a result of extensive co-evolution between the catalytic and regulatory domains.Item Investigation of structural changes in vanadium containing transition metal oxides(University of Alabama Libraries, 2020-12) Davenport, Matthew Austin; Allred, Jared M.; University of Alabama TuscaloosaWe have completed an experiment to obtain diffuse scattering data for use in a comprehensive study of the local-structure changes as a function of molybdenum composition and have made large strides in interpreting some of the major changes found in this study. For these experiments, single crystals of molybdenum substituted VO2 with the formula V1-xMoxO2 were synthesized, with molybdenum compositions up to x = 0.60, using a novel, two-step chemical vapor transport synthesis. Using these large single crystals for total scattering experiments, we report the discovery of the sudden collapse of three-dimensional order in the low-temperature phase of V1-xMoxO2 at x = 0.17 and the emergence of a novel frustrated two-dimensional order at x = 0.19, with only a slight change in electronic properties. Single crystal diffuse x-ray scattering reveals that this transition from the 3D M1 phase to a 2D variant of the M2 phase results in long-range structural correlations along symmetry-equivalent (11L) planes of the tetragonal rutile structure, yet extremely short-range correlations transverse to these planes. Additionally, we report a combined study using single crystal X-ray diffraction, powder X-ray diffraction, and representational analysis to examine both the local and crystallographically averaged atomic structures simultaneously near x = 0.50. Between about x = 0.50 and 0.60, the average structure of V1-xMoxO2 is the parent rutile phase, but the local symmetry is broken by atomic displacements that are best described by an orthorhombic cell in the spacegroup Fmmm. This model is locally identical to the two-dimensionally ordered 2D-M2 phase except the correlation length is much shorter in the 2D plane, and longer in the frustrated one, making it more isotropic.Item Ionic liquids and chitinous biomass: materials, synthesis, and applications for uranium sequestration(University of Alabama Libraries, 2016) Griggs, Christopher Scott; Rogers, Robin D.; University of Alabama TuscaloosaThe mining of Uranium (U) ore, processing, and applications in weapons manufacturing and nuclear fuel have resulted in a legacy of contamination that require the creation of innovative methods that provide waste to volume minimization. Therefore a major objective of this research was to combine the reactivity of chitosan with the toughness and insolubility of chitin by surface modifications with UO22+ selective moieties. Thus the IL platform consisting of the 1-ethyl-3-methyl-imidazolium cation [C2C1im]+ paired with the acetate anion [OAc]- was selected and demonstrated to overcome solubility limitations of the biomass. This strategy was successful in producing the first report of electrospinning fibers directly from chitinous biomass in ILs. Concurrent to these results, supercritical carbon dioxide was explored as an alternative solvent to high boiling point coagulation baths to reduce economic and engineering challenges of using ILs at scale. With the successful efforts producing high surface area fibers from chitinous biomass, both qualitative and quantitative analysis supported functionalization of fibers with the amidoxime functional group for aqueous uranyl ions. While these research efforts have demonstrated chitin as a versatile polymer back-bone for fiber applications for U recovery, complexity of the waste derived feedstock is challenging and other chemical components that remain in the processed shell waste are key variables. Further characterization of the feedstock led to the discovery that metabolically inactive shrimp shell has the intrinsic ability to mineralize and reduce aqueous metal ions. This represents a new alternative to promote stable secondary U(VI) phosphate U(VI) and insoluble U(IV) phases, providing an effective strategy for immobilizing U. In addition the rediscovery of the simple but understudied salt [NH3OH][CH3COO] not only demonstrates OAc- is an excellent ligand for U(VI) coordination, but its protic ionic liquid properties suggest a much broader application space. Therefore future work is warranted to determine the influence of carboxylic acids in the reduction of U(VI) and the speciation and stability of the U(IV) phase. However these results provide considerable improvements that address constraints of current bioremediation and abiotic precipitation techniques to provide a long term sink for one of the most abundant radionuclides released into the environment.Item Metal organic frameworks as sorbents for volatile organic compounds(University of Alabama Libraries, 2021) Shankwitz, Jennifer Elizabeth; Szulczewski, Gregory J.; University of Alabama TuscaloosaMetal organic frameworks (MOFs) are a class of highly porous materials with large surface areas, large pore volumes, and chemical tunability. These features make MOFs desirable as sorbents for applications such as gas storage, gas separation, and gas sensing. In this work, MOF thin films of UiO-66-R, where R = -H, -NH2, and-NO2, were fabricated onto Au-coated Si wafers and Au-coated quartz crystal microbalance surfaces using a vapor-assisted conversion method. The films were then characterized by scanning electron microscopy, powder x-ray diffraction, x-ray photoelectron spectroscopy, reflection absorbance infrared spectroscopy, and Raman spectroscopy. The spectroscopy reveals that the films of UiO-66-H, UiO-66-NH2, and UiO-66-NO2 are polycrystalline and 1 – 3 µm thick. The diffraction patterns reveal that the UiO-66-NO2 film potentially has the most missing linker defects. The UiO-66-R films grown on quartz microbalance crystals were activated by heating under high vacuum and exposed to a known pressure of benzene, toluene, ethyl benzene, and the xylene isomers (BTEX). The Henry’s constant, which describes the adsorption capacity for each MOF, was calculated from the mass change during the adsorption isotherm at 30°C, 25°C, and 20°C. The enthalpy of adsorption and entropy change was determined by plotting the logarithm of Henry’s constants versus the reciprocal of temperature. The results reveal the Henry’s constant for BTEX increased in the following order: UiO-66-H < UiO-66-NH2 < UiO-66-NO2. The results suggest that the functional groups on the organic linker and missing linkers influence adsorption behavior. The Henry’s constant of the films UiO-66-H were an order of magnitude smaller than those obtained for UiO-66-NH2 and UiO-66-NO2 films, largely due to the large pore size and lack of any functional group. The results suggest that UiO-66-NO2 films contain more missing linker defects than UiO-66-NH2 films. As a result, the heat of adsorption and entropy change for BTEX molecules in UiO-66-NH2 films is more negative than UiO-66-NO2. In contrast, due to a large pore size caused by the missing linkers, the adsorption capacity of UiO-66-NO2 films is larger than UiO-66-NH2 films.Item The Modification and Characterization of Internally Plasticized, Reconditioned, and Elastomerized Poly(Vinyl Chloride)(University of Alabama Libraries, 2024) McEachern, David Furman; Rupar, Paul A.Poly(vinyl chloride)(PVC) is a structurally simple polymer composed of a chain of [-CHCl-CH2-] repeat units. This material is used worldwide for a vast array of applications that include the automotive industrie, water delivery, children's toys, etc. PVC can be divided into two distinct categories that include hard and soft materials. Hard PVC includes items such as pipes or siding and gains rigidity from fillers like calcium carbonate and silicon dioxide. Soft PVC is created by the addition of plasticizers, commonly dioctyl phthalate, into the polymer matrix that allow polymer chains to slide past each other more freely. Plasticizer migration out of the material causes a loss of mechanical properties and exposes users to a toxicant. In chapter 2 of this dissertation, we describe our investigation into the covalent tethering of thioethers to the PVC backbone to create an internally-plasticized PVC material. Chapter 3 will outline a method to create a thermoplastic elastomer from PVC that can be implemented with waste materials. By utilizing Diels-Alder cycloadditions, thermally reversible crosslinking networks can be created throughout the polymer matrix. We showed that adding furan functionality to the PVC backbone in small amounts is sufficient to create crosslinking sites with bismaleimide crosslinkers. Combined with plasticizing molecules, these materials exhibited rubber-like qualities. Finally, chapter 4 will discuss our efforts at reconditioning dehydrochlorinated PVC by using the double bonds in the degraded material as a foundation for chemical modification. The first method investigated was to simply rehydrochlorinate the material with HCl. We showed that the mechanical properties of the material could be restored to pre-dehydrochlorinated levels could be attained by rehydrochlorinating the double bonds in the presence of a catalyst. Other methods investigated were thiol-ene click reactions to add thioethers to the double bonds and the dichlorination of the double bonds utilizing a triphenyl phosphine (Ph3P) and n-chlorosuccinimide (NCS) system. The latter of which proved to be the most efficient at shortening the conjugated segments which was confirmed by UV-Vis spectroscopy. The last method utilized the double bonds as a reaction site for thiol-ene click reactions with 1-dodecanethiol (C12H25SH) and azobisisobutyronitrile (AiBN) as a radical initiator.Item Observation and electronic properties of reactive intermediates from measurement and electronic structure calculations(University of Alabama Libraries, 2018) Lightcap, Johnny Clement; Dixon, David A.; University of Alabama TuscaloosaElectronic structure calculations were performed to understand the properties of reactive intermediates generated from experiment. Aluminum, manganese and iron nitrate anions were generated in the gas-phase via electrospray ionization (ESI) and were observed to decompose into metal oxides under collision induced dissociation (CID). Aluminum-oxygen bonds were formed after each consecutive loss of NO2•, which possess significant radical character localized to the oxygen ligands. These oxygen radicals facilitate the decomposition of Al(NO3)4- by abstracting neutral oxygen atoms and then undergoing loss of O2. Neutral oxygen atom abstraction was also observed in the decomposition of Mn(NO3)3-, however loss of NO• occurs immediately after, resulting in the rearrangement of a nitrate ligand to provide two oxygen substituents. Both MnO(NO3)2- and MnO2(NO3)- were observed to decompose under CID into the permanganate anion, MnO4-, which occurs through a pair of spin forbidden surface crossings. Fe(NO3)4- can also decompose into a tetroxide, FeO4-, however this occurs through 4 consecutive losses of NO2•, and no nitrate ligand rearrangement was observed. Oxidation of the metal center continues until MnO4- and FeO4- exist in the +VII oxidation state. Density functional theory (DFT) was used to optimize the structures for the ions and neutrals generated by ESI, and coupled cluster methods were used to calculate accurate electronic energies. DFT studies were also performed to interpret the emission spectrum of the 4-methyl-3-azabenzyl radical which was generated in a corona excited supersonic expansion source to understand how substituting a nitrogen atom into the benzene ring can change the electronic properties of aromatic radicals. Although it is possible for an electron in the nitrogen lone pair to be promoted via a charge transfer excitation, the observed emission spectrum of the 4-methyl-3-azabenzyl occurs from an unpaired electron relaxing from an antibonding orbital in the π system to a p orbital localized on the CH2 substituent. Several vibrational energies were measured and the calculated energies agree with experiment.Item Photopolymerization of coordinated and non-coordinated ionic liquid monomers(University of Alabama Libraries, 2016) Whitley, John; Bara, J. E.; University of Alabama TuscaloosaPhotopolymerization is an industrially important polymerization technique that has numerous advantages in comparison to other radical based processes. Previous work has shown that ionic liquid media can improve the efficiency of these reactions; however, the applicability of these solvents is limited by the challenging separation processes required to isolate polymer products. In this work, we present a new method of radical polymerization in which coordinated ionic liquids were synthesized from salts containing bulky, non-coordinating anions and polar vinyl monomers that functioned as coordinating ligands. These polymerizable coordinated ionic liquids offer many of the benefits of conventional ionic liquid media in radical polymerizations with the additional advantage of allowing for relatively simple product separations. This reaction technique was shown to be useful in the photopolymerization of both common and niche vinyl monomers using multiple bistriflimide salts. In addition, composite materials containing ionic liquids and polymerized ionic liquids have found increasing applications and we were also interested in the reaction behavior of the systems used in their preparation. To this end, we examined the polymerization kinetics of polymerizable ionic liquids in a non-polymerizable imidazolium ionic liquid using infrared spectroscopy. The reaction kinetics of the monomers in these systems were found to be affected by a combination of intermolecular interactions that likely affect the behavior of a variety of reactive systems in which ionic liquids are present.Item Rapid synthesis of functional poly(ester amide)s through thiol-ene chemistry(Royal Society of Chemistry, 2023) Qu, Taoguang; West, Kevin N.; Rupar, Paul A.; University of Alabama Tuscaloosa; University of South AlabamaPoly(ester amide)s (PEAs) bearing various side chains were synthesized by post-polymerization modification of PA-1, a vinylidene containing PEA. The thiols 1-dodecanethiol (1A-SH), 2-phenylethanethiol (1B-SH), 2-mercaptoethanol (1C-SH), thioglycolic acid (1D-SH), furfuryl mercaptan (1E-SH) and sodium-2-mercaptoethanesulfonate (1F-SH) were reacted with PA-1 to form PEAs PA-1A through PA-1F respectively. PEAs containing non-polar thiol side chains (PA-1A, PA-1B, PA-1E), showed little change in solubility compared to PA-1, while PEAs with more polar side chains improved solubility in more polar solvents. PA-1F, functionalized with sodium-2-mercaptoethanesulfonate, became water-soluble. The introduction of pendant functional groups impacted the thermal behaviors of PEAs in a wide range. The PEAs were thermally stable up to 368 degrees C, with glass transition temperatures (T-g) measured between 117 to 152 degrees C. Moreover, to demonstrate the versatility of the PEAs, thermal reprocessable networks and polyurethanes were successfully fabricated by reacting with a bismaleimide (1,6-bis(maleimido)hexane, 1,6-BMH) and a diisocyanate (4,4'-diphenylmethane diisocyanate, 4,4'-MDI), respectively. This study paves the way for the facile synthesis of functional poly(ester amide)s with great potential in many fields.