Engineering Commons^™

Synthesis And Characterization Of Chemically Functionalized Shape Memory Nanofoams For Unattended Sensing Applications, Anna Paola Soliani

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The work in this dissertation is devoted to the synthesis and characterization of novel materials for off-line unattended sensing: shape-memory grafted nanofoams. The fabrication process and characterization of highly efficient, polymeric nanosensor element with the ability to selectively detect analytes and retain memory of specific exposure events is reported. These shape memory nanofoams could potentially act as efficient and highly sensitive coatings for evanescent waveguide-based optical monitoring systems. On exposure to specific analytes, the polymeric coatings locally change their internal structure irreversibly at the nanolevel, affecting the local optical properties such as refractive index. Currently, enrichment polymer layers (EPLs) are …

High-Productivity Membrane Adsorbers: Polymer Surface-Modification Studies For Ion-Exchange And Affinity Bioseparations, Heather Chenette

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This Dissertation centers on the surface-modification of macroporous membranes to make them selective adsorbers for different proteins, and the analysis of the performance of these membranes relative to existing technology. Traditional chromatographic separations for the isolation and purification of proteins implement a column packed with resin beads or gel media that contain specific binding ligands on their exposed surface area. The productivity of this process is balanced by the effective use of the binding sites within the column and the speed at which the separation can take place, in addition to the need to maintain sufficient protein purity and bioactivity. …

Drug Delivery With Feedback Control In Bioresponsive Hydrogels, Andrew Wilson

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Bioresponsive hydrogels are emerging with technological significance in targeted drug delivery, biosensors and regenerative medicine. The design challenge is to effectively link the conferred biospecificity with an engineered response tailored to the needs of a particular application. Moreover, the fundamental phenomena governing the response must support an appropriate dynamic range, limit of detection and the potential for feedback control. The design of these systems is inherently complicated due to the high interdependency of the governing phenomena that guide sensing, transduction and actuation of the hydrogel. The objective of the dissertation is to review the current state of bioresponsive hydrogel technology …

Uv-Assisted Stabilization Of Polyacrylonitrile-Based Carbon Fiber Precursors, Marlon Salvador Morales Sandoval

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Due to their high strength and stiffness coupled with low density, carbon fibers are the preferred reinforcing fibers used in high-performance polymer matrix composites. Consequently, the demand for carbon fibers is expected to grow from 40,000 metric tons to about 150,000 metric tons over the next decade. A large fraction of the increase is anticipated in the industrial sector that is cost-sensitive. Therefore, there is a need for the development of novel processes and precursors to reduce the carbon fiber production cost and expand the use of carbon fibers. This research focuses on the development of an alternative, rapid stabilization …

Effect Of Graphitic Carbon Nanomodifiers On The Electromagnetic Shielding Effectiveness Of Linear Low Density Polyethylene Nanocomposites, Byron Villacorta Hernandez

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Conductive polymer composites have become alternative materials for providing electromagnetic and electrostatic shielding where metals are not suitable. In this study, the effect of crystallinity, morphology, concentration and orientation of carbon nanomodifiers on shielding provided by their polyethylene-based composites has been investigated relative to their transport properties.

First, the electrical properties and EM SE of composites consisting of heat-treated carbon nanofibers (Pyrograf^® -III PR-19 CNF) in a linear low density polyethylene (LLDPE) matrix were assessed. Heat treatment (HT) of CNF at 2500°C significantly improved their graphitic crystallinity and intrinsic transport properties, thereby increasing the EM SE of the nanocomposites. …

Sulfonated Perfluorocyclobutyl (Pfcb) Aryl Ether Polymers: Synthesis, Reactivity, And Characterization For Polymer Electrolyte Applications, Jiyoung Park

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Perfluorocyclobutyl (PFCB) aryl ether copolymers are excellent candidates for proton exchange membrane (PEM) component in PEM fuel cells. Sulfonated PFCB copolymer membranes exhibit not only high chemical/thermal/mechanical stability but also high proton conductivity. In this regard, PFCB aryl ether copolymers were synthesized via thermal step-growth [2 + 2] cyclopolymerization from aryl bis-(trifluorovinyl ether) (TFVE) monomers and oligomers. Experimental and computational studies confirmed that copolymerization of relatively electron-rich and electron-poor TFVE monomers gave selective-segmented copolymers in an one-pot polymerization. After sulfonation, the PFCB copolymers comprising hydrophilic and hydrophobic segments gave membranes with high proton conductivity. Cross-linked membranes of the sulfonated PFCB …

Pyrene Oligomers: Their Isolation, Molecular Characterization, And Phase Behavior, David Esguerra Taborda

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Carbonaceous pitches can serve as attractive precursors for advanced carbon materials such as high thermal conductivity fibers or carbon-carbon composites. Yet the effects of composition and molecular structure on the bulk properties (e.g., mesophase content and melting point) of these precursors remain only partly known, mainly because of the difficulties associated with the isolation, identification, and quantification of the large (i.e., molecular weight (mol wt) > 350-400 Da) polycyclic aromatic hydrocarbon (PAH) oligomers comprising these pitches. In this study, oligomeric fractions were isolated via supercritical extraction (SCE) from two representative pitches: a petroleum pitch (M-50) produced by the thermal polymerization of …

A Localized Controlled Delivery System Utilizing A Block Copolymer To Improve The Current Paradigm Of Chemotherapy, Jason Olbrich

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The goal of the field of Bioengineering has always been to bring about a better standard of care for patients. As a field encompassing a broad array of researchers and talents, such improvements often are brought about through the integration of different fields. This work advances the integration of controlled delivery and chemotherapy. The use of cytotoxic chemotherapy has become and will continue to be a powerful tool for the treatment of solid malignancies. Conventional dose scheduling of cytotoxic agents and newer biological response modifiers are investigated under a clinical paradigm initially designed to identify a drug dose that elicits …

Perfluorocyclobutyl Polymer Thin-Film Composite Membrane Fabrication, Plasticization And Physical Aging, Jinxiang Zhou

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Membrane technologies have been used widely in industrial practices such as waste water treatment, sea water desalination, gas separations, pharmaceutical separations, and food and beverage processing to name a few. Among the features that make them attractive are that they are cost effective, highly efficient, scalable, and environmentally benign. The focus of this dissertation is to contribute to the understanding and use of polymeric membranes for carbon dioxide separations.
Currently, the largest carbon capture demand lies in the natural gas industry. However, since global warming has become a severe concern for human existence, flue gas cleaning is potentially another very …

A Computational Approach For The Rational Design Of Bimetallic Clusters For Ethanol Formation From Syn-Gas, Ming He

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There is currently a growing interest in the catalytic synthesis of ethanol from syn-gas (2CO + 4H2 --> C2H5OH + H2O). A major challenge associated with this direct route is an inability to find a low-cost catalyst that promotes the proper combination of CO dissociation and CO insertion steps, so as to yield ethanol as the primary reaction product. Bimetallic catalysts, in which one metal promotes hydrocarbon production and the other oxygenate production, may exhibit a synergistic effect that can facilitate the formation of ethanol. Given the complexity of this reaction system, a simple trial-and-error approach to catalyst design is …

Advanced Biomaterials From Renewable Resources: An Investigation On Cellulose Nanocrystal Composites And Co2 Extraction Of Rendered Materials, Jose Orellana

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The annual global consumption of petroleum-based plastics is approximately 280 million tons and is impacting the sustainability of our planet and prosperity of future generations. One solution is the development of bio-based polymer materials with advanced properties for commercial applications. Therefore, the ultimate goal of this dissertation is to investigate the properties of new bio-based materials for broader applications. This dissertation includes two research areas: cellulose nanocomposites, and CO₂ extractions of rendered fat. In the first half, cellulose nanocrystals (CNCs), which exhibit excellent mechanical and optical properties, were investigated for the reinforcement of a biodegradable polymer. The properties of …

Novel Ceria-Zirconia-Yttria Mesostructures: Synthesis, Characterization, Diffusional Studies And The Effects Of Morphology On Their Properties, Alma Cordova Morales

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Ceria-zirconia-yttria (CZY) mixed oxides are used as catalyst supports for three-way catalysts for automotive exhaust emission control and in solid oxide fuel cells. By improving the morphology of CZY mesopores it is possible to reduce the sintering of supported noble metals and enhance overall catalyst lifetime and performance. However, limited studies have been published on the synthetic control of the morphology of CZY materials and the effects that CZY pore geometry has on catalyst operation.
To create optimized CZY catalyst supports, novel mesoporous CZY oxides were synthesized via classical sol-gel and evaporation induced self-assembly (EISA) methods, obtaining mesostructures that exhibited …

Aqueous Suspensions Of Polymer Coated Magnetite Nanoparticles: Colloidal Stability, Specific Absorption Rate, And Transverse Relaxivity, Steven Saville

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The design, functionalization, characterization, and applications of magnetic nanoparticles have garnered significant interest over the past several decades. While this area has garnered increasing attention, several questions remain unanswered about the stability of these systems and it's influence on their biomedical applications. To help answer these questions about the stability of these, a novel tri(nitroDOPA) terminated polymer based ligand has been developed for the stabilization of magnetite nanoparticles. The synthesis involves a process in which ethylene oxide is polymerized using a trivinyl initiator, modified with carboxylic acid using a free radical addition of mercaptoundecanoic acid, and then functionalized with nitroDOPA …

Application Of Carbon Dioxide Towards The Development Of Smart Materials, Green Reaction Schemes And Metallic Nanoparticle Synthesis, Fiaz Mohammed

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Global carbon dioxide (CO₂) emissions have steadily risen over the last 50 years, with 34 billion tons of CO₂ released in 2009 alone. Its potential as a greenhouse gas has negatively affected of our lives and environment by the resulting ocean acidification and climate change. To mitigate atmospheric CO₂, various strategies have been implemented for CO₂ separation, capture, storage and use as a chemical feedstock. The use of CO₂ in various chemical industries is attractive as its non-flammable, non-toxic, and relatively inert properties have made it an inherently safer alternative to traditional organic …

Design Of Advanced Fouling-Resistant And Self-Cleaning Membranes For Treatment Of Oily And Impaired Waters, Daniel Wandera

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The overall goal of my Doctor of Philosophy (PhD) research was to design and develop advanced anti-fouling and self-cleaning membranes for treating impaired waters. Initial work focused on the development of membranes to treat produced water, which is oily wastewater that is co-produced during oil and gas exploration. Economical, environmentally sustainable treatment of the large volumes of produced water is a grand challenge for oil and gas companies. While membranes offer many advantages over more conventional treatment methods, membrane-based treatment processes for oily waters often fail due to membrane fouling. Therefore, the primary objective of my doctoral research was to …

Modeling And Synthesis Of Functionalized Meta-Poly(Phenylene Ethynylene) Helical Structures, Ha Nguyen

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The ability of meta-poly(phenylene ethynylene) (mPPE) materials to undergo random coil to helix conformational changes under select conditions affords many opportunities for their use in sensor, separation, catalysis, and bio-related applications. Thus, to advance the development of these materials, a modeling procedure based on replica exchange molecular dynamics (REMD) simulation was developed to reliably assess factors affecting the folding behaviors of functionalized mPPE variants in solution. A combinational modeling study of 20 functionalized mPPEs in five solvent conditions provided insight into how mPPE secondary structure is impacted by the complex relationship between mPPE functional groups and solvent moieties. Further, these …

Pitch-Based Activated Carbon Fibers: The Effect Of Precursor Composition On Pore Structure, Halil Tekinalp

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Although researchers have previously investigated the effect of precursor differences on the final properties of activated carbon fibers (ACFs), those precursors were not well-characterized. In particular, detailed information about their molecular composition and anisotropy was not available.
In this study, seven oligomeric fractions, each of well-defined composition and molecular weight (mol wt) distribution, were isolated from a commercially produced isotropic petroleum pitch (i.e., Marathon M–50) and used for the production of ACFs. Four of these precursors of varying oligomeric composition were fully isotropic and three contained different levels of mesophase, so that the effects of molecular composition and molecular order …

Light-Emitting Nanocomposites And Novel Amorphous Polymers For Optical Applications, Kyle Gipson

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Polymeric optical materials generally are comprised of amorphous polymers that are transparent in at visible wavelengths but exhibit strong absorption bands in the near-infrared making them less useful for many optical applications. Attenuation, which is the absorption per unit length, largely results from the high vibrational energy associated with carbon-hydrogen bonds contained in the polymer backbone. Attenuation can be mitigated by optical amplification utilizing light emitting additives. Investigated in this dissertation are synthesis techniques for the fabrication of light-emitting polymer nanocomposites and their resultant thermal and rheological characteristics for potential use as polymer optical fibers or films.
Inorganic nanocrystals doped …

Quantitative Analysis And Structural Characterization Of Carbonaceous Pitches, Sourabh Kulkarni

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Both petroleum pitches and pitches derived from pure polycyclic aromatic hydrocarbons (PAHs) are oligomeric materials that can serve as precursors for a wide variety of advanced carbon materials. The goal of this study was the structural characterization and quantitative analysis of the dominant constituent oligomers and species present in these pitches.
A key requirement for such work is the ability to fractionate these complex mixtures into samples of narrow molecular weight distribution (mol wt; MWD) that can be used as standards. To this end, semicontinuous (or semibatch) dense-gas/supercritical extraction (DGE/SCE) was used to produce monomer, dimer, and trimer fractions of …

Effects On Hydrogen Adsorption And Activation On Platinum In A Fuel Cell Catalyst, Jack Zhang

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Proton exchange membrane fuel cells are a highly efficient source of power generation that is needed to sustain the energy demands of today's more environmentally conscience society. However, the presence of impurities in the hydrogen fuel stream, such as CO, H₂S, and NH₃ from the steam reforming/partial oxidation of hydrocarbons/methanol, can severely poison the Pt electrocatalyst present in the fuel cell electrode causing degradation in the fuel cell performance. To counter these poisoning effects, fuel cell manufacturers are forced to use higher Pt loadings, which dramatically increases material costs and prevents the successful commercialization of the technology. …

Oxygenate Synthesis During Co Hydrogenation On Cocuzno- Based Catalysts, Yu-Tung Tsai

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The research of catalytic synthesis of methanol and other higher alcohols from CO hydrogenation has received great attention since 1980s. The focus of this research is to establish a better fundamental insight into heterogeneous metal catalysts for oxygenate (especially alcohol) synthesis by CO hydrogenation.
Co-based catalysts have been reported widely as the high-performance Fischer-Tropsch Synthesis (FTS) catalysts. The solid base, hydrotalcite (HT), using as a support for Co catalysts resulted in higher activity for CO hydrogenation comparing to other supports (pre-calcined hydrotalcite, MgO and Al₂O₃). The activities of Co/HT reduced at different reduction temperatures (300-600oC) were …

Cellulose Nanocrystals Properties And Applications In Renewable Nanocomposites, Esteban Urena Benavides

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Development of novel bio-based nanocomposites is fundamental to reduce the dependence on fossil resources and provide a sustainable future. In light of this global problem, cellulose nanocrystals (CNCs) have raised interest due to their remarkable mechanical properties. Adequate design of nanocomposites requires a fundamental understanding of how the structure affects the mechanical properties of the material. However, contradictory results in the literature have revealed a lack of comprehension of this relationship for CNC based composites. Consequently, this work provides an explanation to unusual results for CNC nanocomposites presented in the literature and demonstrates the ability to achieve property enhancements in …

Design Of Advanced Ion-Exchange Membranes And Their Performance Assessment For Downstream Chromatographic Bioseparations, Bharatkumar Bhut

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This doctoral research focuses on the design, development and characterization of advanced ion-exchange membranes and their performance evaluation as process chromatography media for downstream bioseparations. Chromatography is a widely used unit operation in the biopharmaceutical industry for the downstream purification of protein therapeutics. The rapid developments in biotechnology and the pharmaceutical potential of biomolecules have increased the worldwide demand for protein therapeutics dramatically. Considering that 50−90% of the total cost of bioprocesses is due to the downstream recovery and purification, high-productivity and high-resolution separation techniques that will enable cost-effective production are essential to the biopharmaceutical industry. In recent years, membrane …

Catalysis Of Ethanol Synthesis From Syngas, Jia Gao

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Catalytic synthesis of ethanol and other higher alcohols from CO hydrogenation has been a subject of significant research since the 1980s. The focus of this research is to establish a better fundamental insight into heterogeneous catalysis for CO hydrogenation reactions, in an attempt to design the best catalysts for ethanol synthesis.
It has been reported widely that promoted Rh-based catalysts can exhibit high selectivity to C2+ oxygenates during CO hydrogenation. The doubly promoted Rh-La-V/SiO2 catalysts exhibited higher activity and selectivity for ethanol and other C2+ oxygenates than singly promoted catalysts. The better performance appears to be due to a synergistic …

Prediction Of Liquid Crystalline Content And Molecular Structures Present In Carbonaceous Pitches, Ward Burgess

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ABSTRACT
Previous research at Clemson has shown that multistage, packed column, supercritical extraction (also called dense-gas extraction, or DGE) of petroleum pitches is a promising technique for the production of carbonaceous precursors that can be processed into a variety of carbon products, including activated carbons and high thermal conductivity carbon fibers. As the existence (or lack thereof) of a liquid crystalline phase, or mesophase, plays a key role in establishing the suitability of a potential precursor material for a given application, we developed the SAFT-LC (liquid crystal) equation of state by combining Maier-Saupe theory for multicomponent mixtures with the SAFT …

Isolating Petroleum Pitch Oligomers Via Multistage Supercritical Extraction, Eduardo Cervo

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Petroleum pitches are carbonaceous materials that serve as precursors for advanced carbon products. Because of their highly graphitic nature, such pitches are of particular interest for producing high thermal conductivity carbon fibers for thermal management applications, such as microelectronics packaging for hybrid and plug-in vehicles.
Even though the properties of the final carbon products are impacted by the molecular composition of the starting pitch precursor, a fundamental understanding of this relationship has yet to be established. To this end, dense-gas extraction (DGE), a fractionation technique that allows for the production of pitches of controlled composition for both analytical and rheological …

The Rheology, Degradation, Processing, And Characterization Of Renewable Resource Polymers, Jason Conrad

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Renewable resource polymers have become an increasingly popular alternative to conventional fossil fuel based polymers over the past couple decades. The push by the government as well as both industrial and consumer markets to go 'green' has provided the drive for companies to research and develop new materials that are more environmentally friendly and which are derived from renewable materials. Two polymers that are currently being produced commercially are poly-lactic acid (PLA) and polyhydroxyalkanoate (PHA) copolymers, both of which can be derived from renewable feedstocks and have shown to exhibit similar properties to conventional materials such as polypropylene, polyethylene, polystyrene, …

Novel Techniques For The Synthesis Of Three-Way Catalytic Converter Support Materials, Prince Anyaba

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Current automobiles use catalytic converters, consisting of noble metals on an oxide support, to convert noxious engine exhaust pollutants into less harmful species. The development of mesoporous oxide supports with optimal pore geometries could enable these devises to decrease in size and weight and significantly reduce the metal loadings required to achieve optimal performance. Thus, in this work, I investigated a wide range of techniques for the synthesis of mesoporous oxides to determine if they could be adapted to ceria-zirconia-yttria mixed oxide (CZY) systems, which are the industry standard for the optimal oxide support for catalytic converter applications. Additionally, I …

Surface And Bulk Modification Of Poly(Lactic Acid), Rahul Rasal

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The major drawbacks of PLA are its poor toughness and lack of readily reactable groups. Unfortunately, typical methods of PLA toughening are associated with significant modulus and/or ultimate tensile strength (UTS) loss. The main objective of this research was to toughen PLA, with minimal modulus and/or UTS loss, and introduce reactive groups into the PLA matrix in one step. Initially, this objective was divided into two separate parts: PLA surface modification followed by toughening.
PLA film was solvent cast from chloroform solution and was surface modified using a sequential two-step photografting approach. Benzophenone was photografted onto the film surface in …

Synthesis And Analysis Of Nano-Thin Polymer Films For Separation Applications, Azadeh Samadi-Dezfouli

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This dissertation focuses on the fabrication of uniform polymer nanolayers using surface-initiated polymerization. The kinetics of low temperature surface-initiated atom transfer radical polymerization (ATRP) is discussed in detail. The work is then extended to the surface modification of polymeric membranes to tune the physical and chemical properties of the membranes for gas separations. I discuss how atom transfer radical polymerization might be advantageous compared to some of the techniques that have been proposed in the literature for preparing polymeric membranes for CO2 separation.
The first part of this dissertation describes the synthesis of polystyrene (PS) nanolayers by surface-initiated ATRP at …