Chemistry Commons^™

The Role Of Particle Surface Functionality And Microstructure Development In Isothermal And Non-Isothermal Crystallization Behavior Of Polyamide 6/Cellulose Nanocrystals Nanocomposites, Shahram Rahimi, Joshua U. Otaigbe

Faculty Publications

Polyamide 6 (PA6)/cellulose nanocrystal (CNC) and aminopropyl triethoxy silane (APS) - modified CNC nanocomposites were prepared by in situ anionic ring opening polymerization and subsequent melt extrusion. The morphological observation of these hybrid systems revealed that the non-modified nanocrystals developed a network-like fibrillar structure while the APS-modified CNCs were finely dispersed mostly as individual whiskers. The isothermal and non-isothermal crystallization kinetics was extensively studied with emphasis on the effects of CNC surface functionality and the subsequent microstructure development on crystallization behavior of these novel nanocomposite systems. The non-modified CNC particles with corresponding fibrillar microstructure were found significantly hinder the crystallization …

Design And Synthesis Of Dynamic Covalent Polymer Scaffolds With Controlled Architectures, Emily Annette Hoff

Dissertations

The design and synthesis of functional, controlled polymer architectures is essential to the development of new materials with precise and tailorable properties or applications. The work described in this dissertation focuses on the development of controlled polymer architectures with dynamic linkages for the design of multifunctional materials and surfaces via robust, efficient, and stimuli-responsive strategies.

In Chapter III, a post-polymerization modification strategy based on ambient temperature nucleophilic chemical deblocking of polymer scaffolds bearing N-heterocycle blocked isocyanate moieties is reported. Room temperature RAFT polymerization of three azole-N-carboxamide methacrylates, including 3,5-dimethyl pyrazole, imidazole, and 1,2,4-triazole derivatives, afforded reactive polymer scaffolds …

Electrogenerated Chemiluminescence Study Of Semiconductor Nanoparticles Towards Sensitive Detection Of Biomolecules, Yiliyasi Wusimanjiang

Dissertations

The main focus of this dissertation is to unfold the fundamental aspects of electrogenerated chemiluminescence (ECL) generation from semiconductor nanoparticles (also known as quantum dots or QDs) within different ECL systems. The ECL and photo-physical interactions between the CdTe QDs (λ_emission= ~760 nm) and the CdSe QDs (λ_emission= ~550 nm), as well as the effects of carbon nanotubes on ECL of QDs were separately investigated. Optimum experimental conditions for peptide bond formation on an electrode surface through EDC (1-ethyl-3-(-3-dimethylaminopropyl) carbodiimide hydrochloride)/NHS (N-Hydroxysulfosuccinimide) coupling were also revealed using cyclic voltammetry technique. Based on the information …

Structure-Property Relationships Of Polyisobutylene-Block-Polyamide Thermoplastic Elastomers, Morgan Dunn Heskett

Master's Theses

Thermoplastic elastomers (TPEs) are a class of polymer fit for a wide variety of applications due to their customizability. In the synthesis of these types of materials, an elastically-performing polymer, deemed the “soft block,” is combined with a stiffer “hard block” polymer, each of which can be selected based on their own specific properties in order to achieve desired material behavior in the final copolymer. Recently, the use of polyisobutylene as a soft block in combination with a polyamide hard block has been investigated for use in TPE synthesis. While the material showed some promising behavior, many properties were still …

Block Ionomer Complexes Consisting Of Sirna And ARaft-Synthesized Hydrophilic-Block-Cationic Copolymers Ii: The Influence Of Cationic Block Charge Density On Gene Suppression, Keith Hampton Parsons, Andrew Christopher Holley, Gabrielle A. Munn, Alex S. Flynt, Charles L. Mccormick

Faculty Publications

Block ionomer complex (BIC)–siRNA interactions and effectiveness in cell transfection are reported. Aqueous RAFT polymerization was used to prepare a series of hydrophilic-block-cationic copolymers in which the cationic block statistically incorporates increasing amounts of neutral, hydrophilic monomer such that the number of cationic groups remains unchanged but the cationic charge density is diluted along the polymer backbone. Reduced charge density decreases the electrostatic binding strength between copolymers and siRNA with the goal of improving siRNA release after targeted cellular delivery. However, lower binding strength resulted in decreased transfection and RNA interference pathway activation, leading to reduced gene knockdown. Enzymatic siRNA …

A New Class Of Allosteric Hiv-1 Integrase Inhibitors Identified By Crstallographic Fragment Screening Of The Catalytic Core Domain, Disha Patel, Janet Antwi, Pratibha C. Koneru, Erik Serrao, Stefano Forli, Jacques J. Kessl, Lei Feng, Nanjie Deng, Ronald M. Levy, James R. Fuchs, Arthur J. Olson, Alan N. Engelman, Joseph D. Bauman, Mamuka Kvaratskhelia, Eddy Arnold

Faculty Publications

HIV-1 integrase (IN) is essential for virus replication and represents an important multifunctional therapeutic target. Recently discovered quinoline-based allosteric IN inhibitors (ALLINIs) potently impair HIV-1 replication and are currently in clinical trials. ALLINIs exhibit a multimodal mechanism of action by inducing aberrant IN multimerization during virion morphogenesis and by competing with IN for binding to its cognate cellular cofactor LEDGF/p75 during early steps of HIV-1 infection. However, quinoline-based ALLINIs impose a low genetic barrier for the evolution of resistant phenotypes, which highlights a need for discovery of second-generation inhibitors. Using crystallographic screening of a library of 971 fragments against the …

Correlation Of Polymer Performance And Hansen Solubility Parameters, Daniel Jobse Mania

Master's Theses

Ready-to-use (RTU) grout is becoming more important to the finish and remodeling construction industry. Market research shows it is a fast-growing product that not only is creating its own space, but is beginning to supplant existing technology.

The original intent of this research was to investigate formulation parameters and how they affect grout performance. It was learned that particle size and oil absorption (OA) value are important filler properties that affect performance as much as adequate packing density and optimal pigment volume concentration (PVC) without going beyond critical PVC (CPVC).

Polymer architecture was also determined to be extremely important, but …

Analysis Of The Intricacies Of Substrate Recognition Of High Mobility Group Proteins And Aminoacyl-Trna Synthetases Using Non-Cognate Substrates, Douglas Van Iverson Ii

Dissertations

The studies presented in section 1 (Chapters I-IV) focus on the design and development of nucleic acid four-way junctions (4WJs) to target a member of the high mobility group (HMG) proteins, the proinflammatory cytokine high mobility group box 1 protein (HMGB1). In the present study, hybrid PNA-DNA 4WJs based on a model DNA 4WJ were constructed to improve the thermal stability of 4WJs while maintaining strong binding affinity toward HMGB1. An electrophoretic mobility shift assay (EMSA) was used to examine the binding affinity of an isolated DNA binding domain of HMGB1, the HMGB1 b-box (HMGB1b), toward a set of PNA-DNA …

A Library Of Coumarin-Enaminone Chemodosimeters For The Detection Of Analytes, Aaron Berrell Davis

Dissertations

Many anions and metal ions are of biological and environmental importance. This work describes our attempts to synthesize molecular probes to specifically target cyanide, zinc, cadmium and mercury as these species can often result in negative effects to the environment and the human body.

The work in this dissertation, describes the synthesis of a family of coumarin-enamine chemodosimeters, in a straightforward synthetic procedure, the reaction between 7-(diethylamino)-4-hydroxycoumarin and a primary amine. The work presented in this dissertation demonstrates that these molecules can play dual roles and therefore the work is split into two distinct parts: Part 1 describes one role …

The Synthesis Of Chemosensors For Toxic Analytes, Johnathan Hugh Broome

Dissertations

A number of chemosensors have been designed and synthesized to target cations (Zn²⁺ions), neutral molecules (cathinones), charged molecules (aminoindanes), and anions. The Zn²⁺ ion sensor featured bistriazole designed binding unit and ferrocene signaling units. Characterization of Zn²⁺ ion binding was carried out with electrochemical techniques (CV and DPV), ¹H-NMR, mass spectrometry, and molecular modelling. It exhibited a 1:1 binding stoichiometry with Zn²⁺ and had an affinity for ZnCl₂ (Log K_1:1 = 4.1 ± 0.02) over other Zn²⁺ salts.

The cathinone probe was designed to selectively bind mephedrone over common street drugs …

Preparation And Characterization Of Singlet-Oxygen Generating Thiol-Ene Networks Containing Fullerene And Metallofullerene Derivatives, Emily Matthews Barker

Dissertations

This work explores the derivatization of C₆₀ and Sc₃N@C₈₀ with S-, P-, and C- centered radicals, and is the first exploration into the functionalization of Sc₃N@C₈₀ with sulfur and phosphorous. The number of addends bound to C₆₀, as a function of reaction time and molar ratios, as well as, structure-property relationships including thermal stability, solubility, and singlet oxygen generation were explored. Fullerene derivatives exhibiting enhanced solubility were incorporated into two different thiol-ene polymer matrices at varying thiol-ene monomer concentrations (1:1 or 1:0.75 molar equivalents) and at different C₆₀ loadings (0, …

C60 And Sc3N@C80(Tmb-Ppo) Derivatives As Constituents Of Singlet Oxygen Generating, Thiol-Ene Polymer Nanocomposites, Emily M. Barker, Ashli R. Toles, Kyle A. Guess, J. Paige Buchanan

Faculty Publications

Numerous functionalization methods have been employed to increase the solubility, and therefore, the processability of fullerenes in composite structures, and of these radical addition reactions continue to be an important methodology. C₆₀ and Sc₃N@C₈₀ derivatives were prepared via radical addition of the photodecomposition products from the commercial photoinitiator TMB-PPO, yielding C₆₀(TMB-PPO)₅ and Sc₃N@C₈₀(TMB-PPO)₃ as preferred soluble derivatives obtained in high yields. Characterization of the mixture of isomers using standard techniques suggests an overall 1PPO:6TMB ratio of addends, reflecting the increased reactivity of the carbon radical. Although, a higher …

Crystal Structure Of Di-Aqua-Bis-(7-Di-Ehtyl-Amino-3-Formyl-2-Oxo-2h-Chromen-4-Olato-Κ(2) O (3), O (4))Zinc(Ii) Dimethyl Sulfoxide Disolvate, Aaron B. Davis, Frank R. Fronczek, Karl J. Wallace

Faculty Publications

The structure of the title coordination complex, [Zn(C₁₄H₁₄NO₄)₂(H₂O)₂]·2C₂H₆OS, shows that the Zn^II cation adopts an octa­hedral geometry and lies on an inversion center. Two organic ligands occupy the equatorial positions of the coordination sphere, forming a chelate ring motif via the O atom on the formyl group and another O atom of the carbonyl group (a pseudo--diketone motif). Two water mol­ecules occupy the remaining coordination sites of the Zn^II cation in the axial positions. The water mol­ecules are each hydrogen bonded to …

Wrinkled1 Rescues Feedback Inhibition Of Fatty Acid Synthesis In Hydroxylase-Expressing Seeds, Neil D. Adhikari, Philip D. Bates, John Browse

Faculty Publications

Previous attempts at engineering Arabidopsis (Arabidopsis thaliana) to produce seed oils containing hydroxy fatty acids (HFA) have resulted in low yields of HFA compared with the native castor (Ricinus communis) plant and caused undesirable effects, including reduced total oil content. Recent studies have led to an understanding of problems involved in the accumulation of HFA in oils of transgenic plants, which include metabolic bottlenecks and a decrease in the rate of fatty acid synthesis. Focusing on engineering the triacylglycerol assembly mechanisms led to modest increases in the HFA content of seed oil, but much room for …

Automated Data Acquisition Of Deet Time-Dependent Concentration Profiles, Ryan D. Coleman

Honors Theses

Spatial insect repellents must maintain a sufficient concentration in the vapor phase to successfully deter pests. However, little is known regarding correlation of concentration to efficacy nor does there exist a standard testing protocol to measure efficacy in air. Among existing spatial repellents, DEET is the most common active ingredient. This research focuses on application of sensor-based technologies to monitor the concentration levels of DEET under static conditions.

Metal oxide semiconductor sensors feature conductivity variance in response to absorption and desorption of volatile organic compounds. Advantages of these sensors include cost, versatility, and sensitivity. Metal oxide semiconductor sensors were chosen …

Using Intrinsic Properties Of Polyaniline To Sense Expression Of The Microrna Let-7, Jared N. Gloria

Honors Theses

MicroRNAs are approximately 22-nucleotide long RNA molecules that function through decay and translational repression of messenger RNA. The microRNA let-7 is found to play a role in maintaining the fate of differentiated cells in humans. Thus, expression level of this microRNA is a reliable biomarker of tumor cell phenotype. However, there are significant limitations in the current profiling techniques of microRNA. The current methods like northern blotting, microarrays, RT-PCR, or using locked nucleic acid (LNA) for in-situ hybridization are either laborious, semi-quantitative, or expensive. In this research we try to address this issue by developing a fast, specific, and inexpensive …

The Effect Of Acrylic Acid On Ring Formation In Polyacrylonitrile, Elisha Cade Willis

Honors Theses

The addition of comonomers into carbon fiber precursor, polyacrylonitrile (PAN), has shown to have effects on the extent of stabilization and thermal behavior.1 Acrylic Acid (AA) was added at varying initial apparent weight percent and added via semibatch reaction to copolymerize with acrylonitrile to form carbon fiber precursor. Accompanying batch reactions were synthesized for comparison. Degradation was found to be greater in the semibatch reactions although overall was comparable to the batch reactions. Differential scanning calorimetry (DSC) confirmed the addition of higher concentrations of AA into the reaction resulted in a less intense exotherm upon cyclization, along with a greater …

Synthesis And Application Of (R)-3-Methylpyrrolidine-3-Carboylic Acid, Shelby D. Dickerson

Honors Theses

L-Proline is an amino acid widely used in pharmaceutical and biotechnological research due to its catalytic activity and biological relevance. L-Proline has been recognized and utilized as an organocatalyst, which allows cleaner, more sustainable reactions. However, one issue with L-proline is its low solubility in organic systems, limiting its reactivity and efficiency, especially when considering industrial research. Two reactions that utilize L-Proline are the Michael and Aldol but require 100 mol% of L-Proline and 30 mol% of L-Proline, respectively. This research will focus on the synthesis of an analogue of L-Proline utilizing inexpensive, commercially available reagents. A variety of organic …

A Chemical Sensor For Cyanide, Rachel E. Lambert

Honors Theses

The cyanide ion and its gaseous form, hydrogen cyanide, are extremely toxic. Cyanide impairs cellular respiration by inhibiting cytochrome c oxidase, an enzyme in the electron transport chain, leading to cell death.

In a previous study, we synthesized an optical sensor that detects cyanide selectively. The aim of this project is to increase the sensitivity of this sensor. This can be achieved by utilizing the unique spectroscopic properties of lanthanide ions.

The lanthanide metal (europium or terbium) was added to a coumarin-glycine chemodosimeter in a DMSO solvent system. The sensor was titrated with several monodentate analytes including, nitrate, octylamine, 1-pentanethiol, …

Investigation Of How Hydrogen Bonding Affects The Enantiomeric Excess Of Pig Liver Esterase Promoted Hydrolysis Of Pro-Chiral Substrates, Jacob E. Pruett

Honors Theses

Pig Liver Esterase is a cost effective enzyme for ester hydrolysis. In our group, it is vital for creating chiral molecules for the synthesis of unnatural amino acids of potential biological importance. It has been previously found that the enantiomeric excess (%ee) of the PLE hydrolysis reaction increases drastically with the addition of co-solvents that are able to both accept and donate hydrogen bonds. This research endeavors to see if substrates of enhanced hydrogen bonding ability also increase the stereoselectivity of PLE hydrolyses. Diester malonate was covalently linked with a furan ring in both the third and second position from …

Synthesis Of Acceptors For Use In Donor-Acceptor Copolymers And Characterization Of These Polymers, William D. Walker

Honors Theses

In this thesis, a selenium-derivatized acceptor was synthesized to examine the heavy atom effects of selenium on the position of the frontier molecular orbitals (HOMO/LUMO band gap) as opposed to sulfur in a donor-acceptor copolymer for use in light harvesting and detection applications. Over the course of this research, standard operating protocols for ultraviolet-visible (UV-Vis-NIR) and Fourier transform infrared (FT-IR) spectroscopies, as well as cyclic voltammetry (CV) characterization techniques were established. Once synthesized, the polymers were characterized through use of the established characterization protocols. The selenium-derivatized polymer exhibited a bathochromic shift compared to the sulfur analogue, with a solid-state absorption …

Functionalizing Β-Cyano Oligo(P-Phenylene Vinylene) Chromophores For Use In Mechanochromic Materials, Alexander J. Wink

Honors Theses

Mechanochromic materials are materials that change color upon mechanical deformation. This concept can be applied in areas of quality control, since the knowledge of damaged parts will easily be detected due to a color change in the material that has undergone deformation. Typically these types of materials are enabled by employing functional small molecules. Often, these are conjugated organic molecules or chromophores, which fluoresce different colors determined by the stimulus (or lack thereof) acting upon the material. In this work, we explore a new avenue to elicit color changes in polymeric materials based on the process of restriction of intramolecular …

Synthesis And Characterization Of "Click Inspired" Thiol-Ene-Fullerene Nanocomposites, Amber Danielle Windham

Dissertations

This work explores the covalent incorporation of C₆₀ and Sc₃N@C₈₀ fullerenes into thiol-ene networks by a facile, one-pot photochemical reaction with multifunctional thiol and alkene monomers. Synthesis of disulfide bonds within the tri-functional thiol monomer served to photochemically initiate the reaction when cleaved. This was followed by thermal curing of the pre-polymer for preparation of fullerene-containing thiol-ene films. Films were characterized by standard techniques including infrared spectroscopy, gel percent, and thermogravimetric analysis. The role of C₆₀ and Sc₃N@C₈₀ as suitable alkenes for free-radical reaction with multifunctional thiols was investigated by preparing a …

Addressing The Issues Of Drug Delivery Via Advanced Macromolecular Design, Brooks Allen Abel

Dissertations

The work described in this dissertation focuses on the development of synthetic approaches toward novel polymer architectures that specifically address the issues of in vivo drug delivery. Successful implementation of the synthetic methodologies described herein required fundamental investigations into the underlying chemistries in ways that now provide greater insights into the nature of the these chemical reactions.

In Section I, the synthesis of tunable pH- and CO₂-responsive sulfonamide-containing polymers using reversible addition-fragmentation chain transfer (RAFT) polymerization is described. Initially, poor polymerization control of methacryloyl sulfonamide (MSA) monomers was observed using traditional RAFT polymerization conditions. Ultimately, reducing the polymerization …

Energy Management Mechanisms Employed At The Human-Material Interface Of Traditional And Minimalist Shod Running, Nadine M. Lippa

Dissertations

From recreational to elite athletes, greater than 50% of runners sustain overuse injuries each year, prompting substantial research efforts to identify causes of—and solutions to—the high injury rate. Different shoe types and material property degradation have been related to injury. Two popular footwear types are traditional shoes with thick graded soles and minimalist running footwear with thinner foam and/or non-graded soles. Notwithstanding 45 years of significant modifications to shoe design features, gained knowledge in kinesiology, and advanced technologies in polymer science, runner injury rates have not decreased and EVA foam has remained the primary running shoe midsole material since the …

Curing Of Polymer Thermosets Via Click Reactions, Mark Richard Brei

Dissertations

In the first project, an azide functional resin and tetra propargyl aromatic diamines were fabricated for use as a composite matrix. These systems take already established epoxy/amine matrices and functionalize them with click moieties. This allows lower temperatures to be used in the production of a thermoset part. These new systems yield many better mechanical properties than their epoxy/amine derivatives, but their T_gs are low in comparison.

The second project investigates the characterization of a linear system based off of the above azide functional resin and a difunctional alkyne. Through selectively choosing catalyst the linear system can show …

Surface And Interfacial Design And Control Of High Performing Thermoplastics: Polysulfones And Beyond, Katrina Marie Knauer

Dissertations

The study of a class of materials almost always begins with the development of an understanding of properties in the bulk state. However, it is the study of surface critical phenomena that has led to a number of new important insights into polymer behavior. A systematic understanding of physical properties in the immediate vicinity of surface and interfacial layers, which cannot be deduced by simple extrapolation of bulk properties, is of significant importance for advancements in polymer applications where the interface drives performance, such as in membranes, coatings, drug-delivery systems, medical devices, and composites.

First, the surface and interfacial modification …

Polymer Chain Dynamics In Epoxy Based Composites As Investigated By Broadband Dielectric Spectroscopy, Mohammad K. Hassan, Samuel James Tucker, Ahmed Abukmail, Jeffrey S. Wiggins, Kenneth A. Mauritz

Faculty Publications

Epoxy networks of the diglycidyl ether of bisphenol A (DGEBA) were prepared using 3,3′- and 4,4′-diaminodiphenyl sulfone isomer crosslinkers. Secondary relaxations and the glass transitions of resultant networks were probed using broadband dielectric spectroscopy (BDS). A sub-T_g γ relaxation peak for both networks shifts to higher frequencies (f) with increasing temperature in Arrhenius fashion, both processes having the same activation energy and being assigned to phenyl ring flipping in DGEBA chains. A β relaxation is assigned to local motions of dipoles that were created during crosslinking reactions. 4,4′-based networks exhibited higher T_g relative to 3,3′-based …

Molecular Scale Cure Rate Dependence Of Thermoset Matrix Polymers, Christopher Harold Childers, Mohammad K. Hassan, Kenneth A. Mauritz, Jeffrey S. Wiggins

Faculty Publications

This manuscript demonstrates the molecular scale cure rate dependence of di-functional epoxide based thermoset polymers cured with amines. A series of cure heating ramp rates were used to determine the influence of ramp rate on the glass transition temperature (Tg) and sub-Tg transitions and the average free volume hole size in these systems. The networks were comprised of 3,3′-diaminodiphenyl sulfone (33DDS) and diglycidyl ether of bisphenol F (DGEBF) and were cured at ramp rates ranging from 0.5 to 20 °C/min. Differential scanning calorimetry (DSC) and NIR spectroscopy were used to explore the cure ramp rate dependence of the polymer network …