NDSU Theses & Dissertations

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Research performed to achieve a formal degree from NDSU. Includes theses, dissertations, master's papers, and videos. The Libraries are currently undertaking a scanning project to include all bound student theses, dissertations, and masters papers.

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Advanced Electrochemical Methods for Characterizing the Performance of Organic Coatings
(North Dakota State University, 2012) Upadhyay, Vinod
Advanced electrochemical techniques such as electrochemical impedance spectroscopy (EIS), electrochemical noise method (ENM) and coulometry as tools to study and extract information about the coating system is the focus of this thesis. This thesis explored three areas of research. In all the three research areas, advanced electrochemical techniques were used to extract information and understand the coating system. The first area was to use EIS and coulometric technique for extracting information using AC-DC-AC method. It was examined whether the total charge passing through the coating during the DC polarization step of AC-DC-AC determines coating failure. An almost constant total amount of charge transfer was required by the coating before it failed and was independent of the applied DC polarization. The second area focused in this thesis was to investigate if embedded sensors in coatings are sensitive enough to monitor changes in environmental conditions and to locate defects in coatings by electrochemical means. Influence of topcoat on embedded sensor performance was also studied. It was observed that the embedded sensors can distinguish varying environmental conditions and locate defects in coatings. Topcoat could influence measurements made using embedded sensors and the choice of topcoat could be very important in the successful use of embedded sensors. The third area of research of this thesis work was to examine systematically polymer-structure coating property relationships using electrochemical impedance spectroscopy. It was observed that the polymer modifications could alter the electrochemical properties of the coating films. Moreover, it was also observed that by cyclic wet-dry capacitance measurement using aqueous electrolyte and ionic liquid, ranking of the stability of organic polymer films could be performed.
Advancing Plant Protein-Based Proteoposite Films Targeted for Food Packaging Applications. A Combined Computational and Experimental Approach
(North Dakota State University, 2021) Patnode, Kristen Lorraine
Demand for polymeric, plastic materials continues to grow each year. However, the limited supply of fossil-fuels and negative environmental impact caused by petrochemical products have led to an increased demand for bio-based plastic alternatives. While there is great interest in developing plant-based alternatives to plastic packaging products, industrial applications of such materials are limited and development of said products is time, cost, and resource consuming. For this reason, advanced, marketable plant-based bioplastics must be developed more efficiently. To achieve such a goal, this thesis outlines a combined computational and experimental approach which results in novel plant proteins-based (proteoposite) films, that demonstrate enhanced performance, developed via a time, cost, and resource-conscious, approach.
Amphiphilic Invertible Polymers: Self-Assembly into Functional Materials Driven by Environment Polarity
(North Dakota State University, 2012) Hevus, Ivan
Stimuli-responsive polymers adapt to environmental changes by adjusting their chain conformation in a fast and reversible way. Responsive polymeric materials have already found use in electronics, coatings industry, personal care, and bio-related areas. The current work aims at the development of novel responsive functional polymeric materials by manipulating environment-dependent self-assembly of a new class of responsive macromolecules strategically designed in this study, – amphiphilic invertible polymers (AIPs). Environment-dependent micellization and self-assembly of three different synthesized AIP types based on poly(ethylene glycol) as a hydrophilic fragment and varying hydrophobic constituents was demonstrated in polar and nonpolar solvents, as well as on the surfaces and interfaces. With increasing concentration, AIP micelles self-assemble into invertible micellar assemblies composed of hydrophilic and hydrophobic domains. Polarity-responsive properties of AIPs make invertible micellar assemblies functional in polar and nonpolar media including at interfaces. Thus, invertible micellar assemblies solubilize poorly soluble substances in their interior in polar and nonpolar solvents. In a polar aqueous medium, a novel stimuli-responsive mechanism of drug release based on response of AIP-based drug delivery system to polarity change upon contact with the target cell has been established using invertible micellar assemblies loaded with curcumin, a phytochemical drug. In a nonpolar medium, invertible micellar assemblies were applied simultaneously as nanoreactors and stabilizers for size-controlled synthesis of silver nanoparticles stable in both polar and nonpolar media. The developed amphiphilic nanosilver was subsequently used as seeds to promote anisotropic growth of CdSe semiconductor nanoparticles that have potential in different applications ranging from physics to medicine. Amphiphilic invertible polymers were shown to adsorb on the surface of silica nanoparticles strongly differing in polarity. AIP modified silica nanoparticles are able to adsolubilize molecules of poorly water-soluble 2-naphthol into the adsorbed polymer layer. The adsolubilization ability of adsorbed invertible macromolecules makes AIP-modified silica nanoparticles potentially useful in wastewater treatment or biomedical applications. Finally, the invertible micellar assemblies were used as functional additives to improve the appearance of electrospun silicon wires based on cyclohexasilane, a liquid silicon precursor. AIP-assisted fabrication of silicon wires from the liquid cyclohexasilane precursor has potential as a scalable method for developing electronic functional materials.
The Application of Electroanalytical Techniques to the Study of Coating Systems
(North Dakota State University, 2015) Croes, Kenneth James
Electroanalytical techniques are often employed to augment standard practices utilized to study and characterize coating performance on metal substrates, yielding information that is not provided by standard coating analysis methods. Electrochemical impedance spectroscopy (EIS) was utilized to study epoxy-amine coatings incorporating oligomers and monomers of phenylenediamine in the coating structure; these results were compared to unusual EIS results obtained in previous studies of organic-inorganic hybrid sol-gel coatings attributed to the sol-gel structure. With a different coating structure, the unusual results were replicated in coatings containing phenylenediamine oligomers but not monomer. The results suggested the oligomers caused the coatings to act as osmotic membranes. Potentiodynamic polarization studies were utilized to study a highly alkaline chemical bath used for the deposition of magnetite on steel. The results were used to develop a working model of how the bath functions and explain the high temperature and pH required for proper bath function.
Corrosion Investigation of Structural Transition Joints Through Scanning Electrochemical Microscopy and the Characterization of High-Temperature Coatings at Different Temperatures
(North Dakota State University, 2021) Wiering, Luke Peter
Scanning electrochemical microscopy is a method that incorporates an ultramicroelectrode capable of facilitating electrochemical reactions paired with an XYZ positioning system capable of micron-level movements. This study investigates the corrosion behavior of structural transition joint clad material that contains steel, pure aluminum, and an aluminum alloy blast welded into a single joint. This study will characterize the corrosion response of the structural transition joint and identify the galvanic activity measured between its layers. High-temperature coatings in this study are designed to be used effectively up to 1400°F. In this study, we characterized several commercial high-temperature coatings exposed to different levels of heat. General trends of decreasing barrier performance were observed with the exception when these coatings are exposed to their rated temperature limit of 1400°F, at which the barrier increased slightly, indicated by their low-frequency impedance modulus. The cause is a combination of sintering and oxide formation.
Design of Polymer Materials with Lower Environmental Impact
(North Dakota State University, 2015) Popadyuk, Andriy
In today’s world of emerging advanced materials, environmental impact of new technologies, as well as already well-established products, is of utmost importance. Environmental safety is as crucial as performance/price ratio for new materials. Talking specifically about polymer materials, research efforts are dedicated to enhancing material biodegradability, sustainability, manufacturing process improvements etc. It starts to become an industrial standard – to eliminate solvents from polymer production routines, reduce number of chemicals, increase biobased content and generally move towards “green synthesis” concept (use of renewable and/or reclaimed resources throughout whole production process). The main goal of this work was to develop novel polymers and polymer materials to have potentially lower environmental impact, including new biobased polymer materials with properties and performance not sacrificed by the presence of renewable content, and demonstrate the feasibility of new polymers in industrial applications. For the purpose of achieving the goal of this work, several approaches were attempted. The first approach lies in the development of a new polymer - poly[n-(tert-butylperoxymethyl) acrylamide-co-maleic anhydride], which combines the features of both initiator and surfactant (the inisurf), to be applied in conventional emulsion polymerization. Use of the inisurf allows for synthesis of novel, in-situ functionalized (peroxidized) latex particles, while reducing the number of chemicals involved in the process. Another focus of this work was on the development of biobased polymer materials, from plant oils as a raw source, which would be used to substitute petroleum-based polymers. For this, soybean based polymer surfactants (amphiphylic copolymers) were synthesized, and their potential to be applied as surfactant ingredients in shampoos was evaluated. In addition, synthesis of novel biobased monomers from sebacic (castor oil) and caprylic (coconut, palm oils) fatty acids – dipropylene glycol acrylate caprylate and dipropylene glycol diacrylate sebacate is presented. Both monomers are shown to be applicable for development of thermosensitive latex particles for controlled encapsulation and release of fragrance in cosmetic products. Finally, a synthetic route for the fabrication of new soybean oil based acrylic monomer for free radical polymerization for making latexes for paints and adhesives is disclosed.
Development of Ice Releasing Epoxy-Siloxane Marine Coatings
(North Dakota State University, 2022) Hagerott, Morgen
In this study, epoxy-siloxane coatings were prepared and modified using various polysiloxane oil additives with the goal of developing an ice releasing epoxy-siloxane coating. Contact angle, surface energy, and ice adhesion tests were conducted to study the effect each oil additive had on the surface properties of the coatings. Additionally, antifouling and fouling release properties were assessed using two micro-organisms, Cellulophaga lytica and Navicula incerta, and one macro-organism, Amphibalanus Amphitrite (barnacles). The goal of which was to compare the ice and fouling releasing properties of the coatings to see if any correlations could be made between the two. One of the coating formulations yielded lower ice adhesion and barnacle adhesion. The 5% PMDM-010s, coating with oil containing 8-12% phenylmethylsiloxane and 88-92% dimethylsiloxane, showed improved properties compared to the base coating and outperformed the other coating formulations that containing oils of different composition.
Development of Novel Kraft Lignin Resin for Use in Thermoset Materials
(North Dakota State University, 2019) Krall, Eric
Video summarizing a Ph.D. dissertation for a non-specialist audience.
The Effect of Fatty Acid Unsaturation on Properties and Performance of Monomers and Latex Polymers from Plant Oils
(North Dakota State University, 2020) Demchuk, Zoriana
The interest in renewable natural resources, including plant oils, has become increasingly appealing due to the oil abundance, availability, and wide range of applications for polymers and polymeric materials thereof. In this dissertation, a library of plant oil-based acrylic monomers (POBMs) with a broad range of unsaturation was synthesized using a one-step transesterification. It is demonstrated that the unsaturation degree of plant oil remains preserved during the synthesis and determines the structure and properties of POBMs. The life cycle assessment (LCA) was conducted in this study to evaluate the environmental impact of soybean oil-based acrylic monomer (SBM) production. LCA was applied to provide guidance for SBM synthesis optimization, including the type of catalyst, the ratio between reactants, renewable sources (soybean oil/biodiesel), and solvent recycling. The performed LCA shows the positive effect of the inclusion of the solvent recycling step in the SBM synthesis. This study shows that POBMs behave as conventional vinyl monomers in free radical polymerization and copolymerization. The monomer unsaturation impacts polymerization rate and molecular weight of resulted polymers decreasing as follows: poly(OVM) > poly(SFM) > poly(SBM) > poly(LSM), due allylic termination presented during polymerization. A series of stable POBM-based latexes with high solid content (40-45 %) and monomer conversion (95-97 %) were synthesized using miniemulsion process. The incorporation of POBMs fragments provides the plasticizing effect on the resulting latex polymers, as seen by a noticeable decrease in their glass transition temperature (Tg). The crosslink density of POBM-based latex films follows the linear dependence vs. monomer feed unsaturation, providing a tool for controlling latex mechanical properties, including hardness, toughness, Young's modulus, etc. Besides, the presence of highly hydrophobic POBM fragments enhances water resistivity of latex coatings and films. Following the "greener" vector of research, a variety of stable latexes from high oleic soybean oil-based monomer (HOSBM) and cardanol, eugenol, and guaiacol derivatives were synthesized in miniemulsion. Resulting polymeric materials advantageously combine flexibility provided by HOSBM fragments with strength facilitated by aromatic biobased units.
Electrically Conductive Polymers and their Use as Novel Pigments in Advanced Coatings
(North Dakota State University, 2018) Byrom, Joseph Robert
With the push to more environmentally friendly materials to solve some of the biggest challenges in the coatings industry, electrically conductive polymers (ECPs) are seen as a flexible solution due to their unique properties. ECPs are seen as an attractive substitute to the current metallic materials used in applications such as printable electronics, anti-static protection, and corrosion mitigation. Polypyrrole (PPy) is seen as a popular class of ECPs due to its inherent high electrical conductivity, resistance to environmental degradation, and ease of synthesis. The first part of this work was to study the ability of polypyrrole to be synthesized through a novel photochemical process. This method eliminated the need to stabilize particles in a suspension and deposit an electrically conductive film onto a variety of substrates. The second part of this work was to synthesize functional versions of PPy that could further be crosslinked into the coating matrix to improve bulk physical properties through better interaction between the functional filler and the organic coating matrix. The last part of this work is based off prior work at NDSU on AL-flake/PPy composites. This study took the development of these pigments further by incorporating organic anions known to inhibit corrosion and study their efficacy. Advanced analytical methods such as Conductive Atomic Force Microscopy was used to study the electrical properties of PPy. In addition, advanced electrochemical tests such as Electrical Impedance Spectroscopy (EIS), Scanning Vibrating Electrode Technique (SVET), Linear Polarization (LP), and Galvanic Coupling (GP) were conducted alongside traditional accelerated weathering techniques such as ASTM B117 and GM 9540 to determine the corrosion resistance of the synthesized coatings.
Electrochemical and Mechanical Properties Studies of Flexible Mg-rich Primers
(North Dakota State University, 2010) Chen, Tiantian
The coating systems for military aircraft must protect the aluminum skin and frame, and associated fastening and joining from corrosion in a variety of aggressive environments. Excessive grinding is often needed to remove the corrosion products at the cracks formed around the seams and fasteners on the aircraft resulting from poor system flexibility of coatings, which causes high maintenance cost and damages the integrity of the aircraft's body. Thus the U.S. Air Force wants to develop an advanced performance coating system with a primer that can provide superior flexibility and good corrosion protection. Currently commercialized magnesium-rich corrosion protection primers were initially developed from some epoxy-amine coating systems, the most common polymer system for aircraft primer use. But the primers were developed under the old specification, which cannot meet the "ideal" goals of the Air Force. Thus, as a carefully selected alternate, polysulfide modified polymers, which have lowest gas permeability, outstanding oil resistance and UV resistance, and especially great flexibility, are being examined as candidate materials. In this research, a number of accelerated laboratory testing methods were applied to measure the electrochemical and mechanical properties of the modified Mg-rich primers which are based on polysulfide modified polymer as binder. Electrochemical measurement results and visual inspections show that the Mg-rich flexible primer has better or equal corrosion protection performance versus a standard epoxy-based Mg-rich primer with the same PVC. The flexibility of the newly formulated Mg-rich primer was also indicated by the results of a variety of empirical testings and instrumental characterizations. Meanwhile, the weathering impact introduced by the laboratory accelerated exposure cannot compromise the superiority of the flexible Mg-rich primers. Based on the results found, future work will be focused on creating a new formulate method or making some modification of the sulfur-containing polymer's structure to achieve a really low VOC.
Electrochemical Investigation of Powder Coatings and Their Application to Magnesium-Rich Primers For Corrosion Protection
(North Dakota State University, 2015) Orgon, Casey Roy
Corrosion is the decomposition of metal and metal alloys which threatens the integrity of manmade structures. One of the more efficient methods of delaying the corrosion process in metals is by coatings. In this work, the durability of two polyester powder coatings were investigated for corrosion protection of AA-2024-T3. Polyester powder coatings crosslinked by either triglycidyl isocyanurate (TGIC) or β-hydroxyalkyl amide (HAA) compounds were prepared and investigated for barrier protection of metal substrates by electrochemical impedance spectroscopy (EIS). Polyester-TGIC coatings were found to provide better long-term protection, which can be attributed to the increased mechanical strength and higher concentration of crosslinking in the coating films. Additionally, the polyester powder coatings, along with a fusion bonded epoxy (FBE) were investigated for their compatibility as a topcoat for magnesiumrich primers (MgRP). Under proper application conditions, powder topcoats were successfully applied to cured MgRP while corrosion protection mechanisms of each system were maintained.
Electrochemical Method for Characterization and Ranking of Corrosion Inhibitors
(North Dakota State University, 2017) Kelly, Brett
One of the most cost-effective methods in mitigating corrosion effects is through the use of corrosion inhibitors. This work studied the performance of eight organic inhibitors on mild steel substrate through electrochemical characterization techniques, with the primary goal of incorporating a screening process to sift through the large selection of potential inhibitors without having to fully characterize them. The test methodology developed was successful at screening the potential corrosion inhibitors through linear polarization resistance (LPR) testing in NaCl electrolyte, narrowing the collection of inhibitors to the three most-promising chemicals, adrenalone, 3,4-dihydroxyphenylacetic acid and dopamine. The screened inhibitors proved effective in HCl electrolyte, reducing the corrosion rates of mild steel by over 85%. X-ray photoelectron spectroscopy (XPS) and quartz crystal microbalance (QCM) testing were used to confirm surface adsorption of the molecules to the substrate, indicating the formation of a protective barrier film as the means of corrosion protection.
Embedded Reference Electrodes for Corrosion Potential Monitoring, Electrochemical Characterization, and Controlled-Potential Cathodic Protection
(North Dakota State University, 2012) Merten, Bobbi Jo Elizabeth
A thin wire Ag/AgCl reference electrode was prepared using 50 μm Ag wire in dilute FeCl3. The wire was embedded beneath the polyurethane topcoat of two sacrificial coating systems to monitor their corrosion potential. This is the first report of a reference electrode embedded between organic coating layers to monitor substrate health. The embedded reference electrode (ERE) successfully monitored the corrosion potential of Mg primer on AA 2024-T3 for 800 days of constant immersion in dilute Harrison’s solution. Zn primer on steel had low accuracy in comparison. This is in part due to short circuiting by Zn oxidation products, which are much more conductive than Mg corrosion products. Data interpretation was improved through statistical analysis. On average, ERE corrosion potentials are 0.1 to 0.2 V and 0.2 to 0.3 V more positive than a saturated calomel electrode (SCE) in solution for AA 2024-T3 and steel coating systems, respectively. Further research may confirm that ERE obtains corrosion potential information not possible by an exterior, conventional reference electrode. The ERE is stable under polarization. AA 2024-T3 was polarized to -0.95 V vs ERE to emulate controlled potential cathodic protection (CPCP) applications. Polarizations of -0.75 V vs ERE are recommended for future experiments to minimize cathodic delamination. The ERE was utilized to analyze coating mixtures of lithium carbonate, magnesium nitrate, and Mg metal on AA2024-T3. Corrosion potential, low frequency impedance by electrochemical impedance spectroscopy (EIS), and noise resistance by electrochemical noise method (ENM) were reported. Coating performance ranking is consistent with standard electrochemical characterization and visual analyses. The results suggest anti-corrosion resistance superior to a standard Mg primer following 1600 hours of B117 salt spray. Both lithium carbonate and magnesium nitrate are necessary to achieve corrosion protection. Unique corrosion protective coatings for aluminum could be designed through continued mixture optimization. The Ag wire ERE has been utilized for the characterization and ranking of experimental coatings on metal substrates. Structural health monitoring and corrosion potential feedback of cathodic protection systems are additional uses. There is some indication that CPCP may be applied by ERE to control the substrate polarization for an organic coating system.
Enhanced Bone Tissue Regeneration Enabled with Tissue-Engineered Interlocking Nanoclay Scaffolds and Bone Morphogenic Proteins
(North Dakota State University, 2022) Kundu, Krishna
About 6 million bone fractures occur annually in the US; 30% require bone grafting transplants to aid bone healing. Well-established clinical therapy techniques for bone regeneration suffer from limited availability, higher infection risk, donor site morbidity, and poor transplant integration. Delay in healing or nonunion of critical-sized defects is another concern in orthopedics. This dissertation focuses on constructing an interlocking scaffold structure to speed bone regeneration. In this thesis, a BMP-2 & 7 coated PCL-nanoclay-hydroxyapatite interlocking scaffold was developed to accelerate bone regeneration. Developed nano clay polymer interlocking scaffolds retain the scaffold's structural integrity and provide a large surface area while allowing for media interaction. Mesenchymal stem cells (MSCs) and osteoblast cells seeded at a 1:1 ratio boost cell viability and enable calcium deposition on day three and collagen production on day 7 with BMP-2 and BMP-7 coated scaffolds. In addition, BMPs, interlocking, and co-culturing of osteoblasts and MSCs promote osteogenic differentiation. In this dissertation, The long-term effect of BMP-2/BMP-7 on in-vitro utilizing interlocking scaffold blocks was evaluated. Changes to the nanomechanical properties of scaffolds and bone tissue during osteogenesis with the progression of ECM formation were reported. Gene expression results and Alizarin Red S staining images indicate a significant increase in mineralized bone nodules with BMPs coated samples compared with uncoated samples. Results suggest BMPs played a critical role in mineralized ECM production, which increased the scaffolds' elastic modulus. This research provides valuable insight into understanding how BMPs affect bone growth. In this dissertation, polymer clay nanocomposites fibers were constructed utilizing a pressured gyration setup and observed improved cell viability, osteogenic differentiation, ECM development, and collagen formation for PCL HAP MMT-Clay nanocomposite fiber scaffolds compared to pure PCL fibers. In this dissertation, the in-silico design of the unnatural amino acids modified clays and fabricated unnatural amino acids modified scaffolds were reported for application as cancer testbeds. This dissertation also reported the design of the in situ hydroxy apatite and tri-calcium phosphate incorporated nano clays polymer scaffolds for bone tissue engineering applications. These studies represent a new opportunity to design manufacturable composite nanoclay polymer scaffolds for bone tissue engineering applications.
Epoxidized Sucrose Soyate and Derivatives as Bioderived Crosslinkers in Various Thermosets
(North Dakota State University, 2019) Silbert, Samantha Danielle
Throughout the world, alternatives to petrochemically-derived materials are being sought. Aside from petrochemical feedstocks with precarious futures, materials that are derived from renewable resources such as crops are attractive. Epoxidized sucrose soyate is a material made from soybean oil and sucrose. Its rigid sucrose core, flexible aliphatic chains, and many modifiable epoxy sites make it an attractive candidate to replace petrochemically derived materials in a multitude of thermosets. This dissertation encompasses studies of ESS and its derivatives for the development of thermosets in a variety of processes. Namely, ESS-derived polycarbamates for use in ambient-curing polyurethane coatings produced via carbamate-dialdehyde crosslinking, ESS-derived acrylic resins for their use in stereolithographic printing, and UV-curable epoxy coatings from both ESS and adhesion-promoting derivatives. The incorporation and effect of strengthening and/or processing additives were also assessed in the mentioned ESS-containing thermosets. Each topic involves a unique area where formulations use resins derived from petrochemicals; several posing health and/or environmental concerns. Investigations to match or exceed the performances of conventional formulations with alternatives made with ESS further demonstrate the remarkable tunability and versatility of this material, as well as the assets available to lessen reliance on petrochemicals with the use of a renewable resource.
Features of Highly Hydrophobic Plant Oil-Based Vinyl Monomers in Cationic and Free Radical Polymerization
(North Dakota State University, 2019) Kingsley, Kyle
The demand for polymeric materials, which have traditionally been produced from petroleum-based resources over the last century, continues to grow each year. However, the supply of fossil fuels is limited. This, along with price volatility, harmful effects on the environment, and stricter regulations, have led to a surge in the exploration of suitable replacements, namely renewable resources such as plant and vegetable oils. In this work, newly synthesized highly hydrophobic plant oil-based vinyl monomers were polymerized using different mechanisms and processes to obtain polymer coatings and crosslinked films. First, novel vinyl ether monomers derived from soybean oil were copolymerized with vinyl ether counterparts derived from poly(ethylene glycol) (PEG) via cationic polymerization to prepare alkyd-type coatings. Soybean oil-derived polymer coatings and free films were formed by autoxidation of the unsaturation provided by the parent soybean oil moieties. Studies revealed that mechanical and viscoelastic properties, hydrophobicity, and morphology of coatings were dependent on copolymer composition and even more strongly on molecular weight and molecular weight distribution. The soybean oil-derived polymer coatings exhibited Tg values below room temperature, and it was shown that their thermomechanical properties were dependent on crosslink density. Next, plant oil-based acrylic monomers (POBMs) from soybean, high oleic soybean, and olive oils were copolymerized with styrene, methyl (meth)acrylate, and vinyl acetate to yield latexes and prepare polymer films with tailorable thermomechanical properties. Feasibility of the emulsion process was realized with regard to parent plant oil structure (unsaturation amount), POBM content and comonomer aqueous solubility, by determining copolymerization kinetics, mode(s) of latex particle nucleation, and molecular weight of resulting latex copolymers. POBM-emulsifier interactions, competing modes of latex particle nucleation, and effect of comonomer radical reactivity have all been investigated. Total monomer conversion and molecular weight of latex copolymers were enhanced by incorporation of an amphiphilic oligosaccharide (methyl-β-cyclodextrin) within the reaction system, which increases the availability of the POBMs and simultaneously diminishes degradative chain transfer reactions that are triggered by POBM fatty acid unsaturation fragments.
Fouling Release Marine Coatings: Effect of Surface Abrasions on Fouling Release Performance of Self-Stratified Siloxane-Polyurethane Coatings and Novel Isocyanate-Free Glycidyl Carbamate Technologies
(North Dakota State University, 2017) Pade, Madhura
Video summarizing a Ph.D. dissertation for a non-specialist audience.
Functional Colloids from Amphiphilic Polymer Assemblies and Peptides/Polypeptides
(North Dakota State University, 2019) Zholobko, Oksana
The use of responsive polymers, where even minor changes in one of the macromolecular characteristics triggered by the external stimuli can cause drastic changes in the material function or performance, is widely studying area of research. Formation of the thermodynamically stable polymer-peptide colloids, such as mixed micellar assemblies or polymer-enzyme conjugates, loading capacity of the colloids, and cargo activity all depend on the macromolecular interactions within the peptide/polypeptide-polymer system. The goal of this work is to investigate interactions between range of new polymers and various cargo molecules and determine whether those interactions affect the physicochemical properties of the resulted colloids. For this purpose, two types of colloid systems were explored: i) peptide-loaded invertible micellar assemblies (IMAs), formed using hydrophobic interactions between amphiphilic invertible polymers (AIP) and peptides (HA, V5, or peptide-based vaccine), and ii) polymeric cellulosomes made from polymer ligand (PL), copolymer of glycidyl methacrylate (GMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) and mixture of cellulases, using covalent bonding. The purpose of the research was to evaluate if colloids properties are affected by changes in responsive polymer characteristics as well as if the developed macromolecular structure and composition need further synthetic modification/optimization. AIP-related part of this dissertation is focused on i) understanding of interaction between peptides and AIPs, and formation of mixed micellar assemblies; ii) further behavior of cargo peptide molecules in the micellar interior under the AIP conformational changes, triggered by IMAs localization at polar and nonpolar interface; iii) evaluation of the impact of IMAs on model lipid membrane diffusivity and permeability. Besides, AIP-peptide assemblies were tested in vitro and in vivo in order to evaluate the cargo delivery, antibody response, and immunity protection in vaccinated pigs against Swine influenza viruses (SIV). To explore the feasibility of covalent bonding in formation of responsive polymer-based colloids, enzyme-polymer conjugates (EPCs) were designed and their enzymatic catalytic activity for the biomass hydrolysis was further tested. The effect of conjugation on catalytic activity, conjugation efficiency, glucose inhibition effect, type of substrate, and type of biomass pretreatment were evaluated and compared to free enzymes.
High Performance Bio-Based Thermosets for Composites and Coatings
(North Dakota State University, 2016) Ambeg Paramarta, Adlina
In the recent decade, there has been increasing interest in using renewable feedstocks as chemical commodities for composites and coatings application. Vegetable oils are promising renewable resources due to their wide availability with affordable cost. In fact, the utilization of vegetable oils to produce composite and coatings products has been around for centuries; linseed oil was widely used for wide variety of paints. However, due to its chemical structure, the application of vegetable oils for high-performance materials is limited; and thus chemical modification is necessary. One of the modification approaches is by substituting the glycerol core in the triglycerides with sucrose to form sucrose esters of vegetable oil fatty acids, in which this resin possesses a higher number of functional group per molecule and a more rigid core. In this research, thermosets of highly functionalized sucrose esters of vegetable oils were developed. Two crosslinking methods of epoxidized surcrose soyate (ESS) resins were explored: direct polymerization with anhydride moieties for composite applications and Michael-addition reaction of acrylated-epoxidized sucrose soyate (AESS) for coatings applications. In the first project, it was shown that the reaction kinetics, thermal and mechanical properties of the materials can be tuned by varying the molar ratio between the epoxide and anhydride, plus the type and amount of catalyst. Furthermore, the toughness properties of the ESS-based thermosets can be improved by changing the type of anhydride crosslinkers and incorporating secondary phase rubbers. Then, in the second system, the epoxy functionality in the ESS was converted into acrylate group, which then crosslinked with amine groups through the Michael-addition reaction to produce coatings systems. The high number of functional groups and the fast reactivity of the crosslinker results in coatings that can be cured at ambient temperature, yet still possess moderately high glass transition temperatures.

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