Ceria (cerium oxide) nanomaterials, or nanoceria, have commercial catalysis and energy storage applications. The cerium atoms on the surface of nanoceria can store or release oxygen, cycling between Ce3+ and Ce4+, and can therefore act as a therapeutic to relieve oxidative stress within living systems. Nanoceria dissolution is present in acidic environments in vivo. In order to accurately define the fate of nanoceria in vivo, nanoceria dissolution or stabilization is observed in vitro using acidic aqueous environments. Nanoceria stabilization is a known problem even during its synthesis; in fact, a carboxylic acid, citric acid, is used in many synthesis protocols. Citric acid adsorbs onto nanoceria surfaces, capping particle formation and creating stable dispersions with extended shelf lives. Nanoceria was shown to agglomerate in the presence of some carboxylic acids over a time scale of up to 30 weeks, and degraded in others, at pH 4.5 (representing that of phagolysosomes). Sixteen carboxylic acids were tested: citric, glutaric, tricarballylic, α-hydroxybutyric, β-hydroxybutyric, adipic, malic, acetic, pimelic, succinic, lactic, tartronic, isocitric, tartaric, dihydroxymalonic, and glyceric acid. Each acid was introduced as 0.11 M, into pH 4.5 iso-osmotic solutions. Controls such as ammonium nitrate, sodium nitrate, and water were also tested to assess their effects on nanoceria dissolution and stabilization. To further test stability, nanoceria suspensions were subject to light and dark milieu, simulating plant environments and biological systems, respectively. Light induced nanoceria agglomeration in some, but not all ligands, and is likely to be a result of UV irradiation. Light initiates free radicals generated from the ceria nanoparticles. Some of the ligands completely dissolved the nanoceria when exposed to light. Citric and malic acids form coordination complexes with cerium on the surface of the ceria nanoparticle that can inhibit agglomeration. This approach identifies key functional groups required to prevent nanoceria agglomeration. The impact of each ligand on nanoceria was analyzed and will ultimately describe the fate of nanoceria in vivo. In addition, simulated biological fluid (SBF) exposure can change nanoceria’s surface properties and biological activity. The citrate-coated nanoceria physicochemical properties such as size, morphology, crystallinity, surface elemental composition, and charge were determined before and after exposure to simulated lung, gastric, and intestinal fluids. SBF exposure resulted in either loss or overcoating of nanoceria’s surface citrate by some of the SBF components, greater nanoceria agglomeration, and small changes in the zeta potential. Nanocomposites are comprised of a polymer matrix embedded with nanoparticles. These nanoparticles can alter material and optical properties of the polymer. SR-399 (dipentaerythritol pentaacrylate) is a fast cure, low skin irritant monomer that contains five carbon-carbon double bonds (C=C). It is a hard, flexible polymer, and also resistant to abrasion. It can be used as a sealant, binder, coating, and as a paint additive. In this case, metal oxide nanoparticles were added to the monomer prior to polymerization. Titania nanoparticles are known to absorb UV light due to their photocatalytic nature. Titania nanoparticles were chosen due to their high stability, non-toxicity, and are relatively quick, easy, and inexpensive to manufacture. Channels in thin monomer films were created using a ferrofluid manipulated by magnetic fields. The mechanical properties of a microfluidic device by rapid photopolymerization is dependent on the crosslinking gradient observed throughout the depth of the film. Quantitative information regarding the degree of polymerization of thin film polymers polymerized by free radical polymerization through the application of UV light is crucial to estimate material properties. In general, less cure leads to more flexibility, and more cure leads to brittleness. The objective was to quantify the degree of polymerization to approximate the C=C concentration and directly relate it to the mechanical properties of the polymer. Polymerization of C=C groups was conducted using a photoinitiator and an UV light source from one surface of a thin film of a multifunctional monomer. The C=C fraction in the film was found to vary with film depth and UV light intensity. The extents of conversion and crosslinking estimates were compared to local mechanical moduli and optical properties. A mathematical model linking the mechanical properties to the degree of polymerization, C=C composition, as a function of film depth and light intensity was then developed. For a given amount of light energy, one can predict the hardness and modulus of elasticity. The correlation between the photopolymerization and the mechanical properties can be used to optimize the mechanical properties of thin films within the manufacturing and energy constraints, and should be scalable to other multifunctional monomer systems.

Machine learning has been gaining popularity over the past few decades as computers have become more advanced. On a fundamental level, machine learning consists of the use of computerized statistical methods to analyze data and discover trends that may not have been obvious or otherwise observable previously. These trends can then be used to make predictions on new data and explore entirely new design spaces. Methods vary from simple linear regression to highly complex neural networks, but the end goal is similar. The application of these methods to material property prediction and new material discovery has been of high interest as many researchers have begun using the structure-property relationships of materials in conjunction with computational modeling to discover new materials with novel chemical and physical properties. One such class of materials is that of emulsion polymers, which are heavily used in the coatings industry as they serve as the binder in many waterborne coating systems. The great advantage of these materials is that they are synthesized in water at high solids (30-70%) and therefore are largely compliant with stringent environmental regulations. The chemistry of these polymers is highly variant, but the predominant chemistries include copolymers of styrene and acrylic monomers such as n-butyl acrylate or copolymers of only acrylic monomers. Due to the high degree of complexity and variability of these systems, modeling their behavior according to structure-property relationships is currently impractical. Instead, this thesis will demonstrate the use of supervised machine learning methods in conjunction with genetic algorithms to predict and optimize emulsion polymer performance based on recipe composition. These emulsion polymers will also be evaluated for use in concrete coatings meant to be applied with minimal preparation work, i.e. no etching.

Rapid battery exchange systems were built for an electric van and pedal assist electric bike as a method of eliminating the need to recharge the vehicles batteries in order to increase the feasibility of using electric propulsion as a method of efficient student transportation. After selecting proper materials it was found that the systems would need a protective coating to ensure consistent operation. 1020 cold rolled steel samples coated with multiple thicknesses of vinyl resin paint, epoxy resin paint, and powder coating were subjected to environmental wear tests in order to determine if the type and thickness of common protective coatings has an effect on the durability of the system over its lifetime. The tests consisted of a 2400 hour extended salt spray test, coating delamination testing, and modified impact testing. The extended salt spray test, delamination test, and deformation tests of the coatings all found that the type of coating and the thickness of the coating to have a significant effect on the measured outputs. The significant effect shown in the deformation test could not determine the proper material without the aid of microscopic studies of the surface geometry change due to the induced deformation. Powder coating the rapid battery exchange systems would result in proper performance if coupled with epoxy paint for repairs. Testing of the Rapid battery exchange system indicated that the use of mechanical aiming was not suitable for the application, a further adaptation of the system indicated that the system may be better suited toward personal bicycles as there was a large increase in transportation efficiency.

Research was conducted to observe bacterial growth on the surface of metals in a static bioreactor. Metal and non-metal samples were subjected to bacterial exposure (1 day and 9 days). The metal samples were surface treated prior to bacterial exposure. The microstructures of the surface treated samples were analyzed by optical microscopy. After exposure, the microstructures of the samples were analyzed by scanning electron microscopy (SEM). The analysis suggested that microbial attachment on the surface was related to the underlying microstructure of steel. The preferential attachment of microbes could potentially be influenced by cathodic and anodic regions created by the electrolytic cells.

This thesis describes the synthesis and application of a new series of amphiphilic graft copolymers with a hydrophobic polyolefin backbone and pendent hydrophilic poly(ethylene glycol) (PEG) grafts. These copolymers are synthesized by ruthenium benzylidene-catalyzed ring-opening metathesis polymerization (ROMP) of PEG-functionalized cyclic olefin macromonomers to afford polycyclooctene- graft -PEG (PCOE- g -PEG) copolymers with a number of tunable features, such as PEG graft density and length, crystallinity, and amphiphilicity. Macromonomers of this type were prepared first by coupling chemistry using commercially available PEG monomethyl ether derivatives and a carboxylic acid-functionalized cycloctene. In a second approach, macromonomers possessing a variety of PEG lengths were prepared by anionic polymerization of ethylene oxide initiated by cyclooctene alkoxide. This methodology affords a number of benefits compared to coupling chemistry including an expanded PEG molecular weight range, improved hydrolytic stability of the PEG-polycyclooctene linkage, and a reactive hydroxyl end-group functionality for optional attachment of biomolecules and probes. The amphiphilic nature of these graft copolymers was exploited in oil-water interfacial assembly, and the unsaturation present in the polycyclooctene backbone was utilized in covalent cross-linking reactions to afford hollow polymer capsules. In one approach, a bis -cyclooctene PEG derivative was synthesized and co-assembled with PCOE-g-PEG at the oil-water interface. Upon addition of a ruthenium benzylidene catalyst, a cross-linked polymer shell is formed through ring-opening cross-metathesis between the bis -cyclooctene cross-linker and the residual olefins in the graft copolymer. By incorporating a fluorescent-labeled cyclooctene into the graft copolymer, both oil-water interfacial segregation and effective cross-linking were confirmed using confocal laser scanning microscopy (CLSM). In a second approach, reactive functionality capable of chemical cross-linking was incorporated directly into the polymer backbone by synthesis and copolymerization of phenyl azide and acyl hydrazine-functional cyclooctene derivatives. Upon assembly, these reactive polymers were cross-linked by photolysis (in the phenyl azide case) or by addition of glutaraldehyde (in the acyl hydrazine case) to form mechanically robust polymer capsules with tunable degradability ( i.e. non-degradable or pH-dependent degradability). This process permits the preparation of both oil-in-water and water-in-oil capsules, thus enabling the encapsulation of hydrophobic or hydrophilic reagents in the capsule core. Furthermore, the assemblies can be sized from tens of microns to the 150 nm - 1 µm size range by either membrane extrusion or ultrasonication techniques. These novel capsules may be well-suited for a number of controlled release applications, where the transport of encapsulated compounds can be regulated by factors such as cross-link density, hydrolytic stability, and environmental triggers such as changes in pH.

Utilizing the diverse functionality of amino acids, a new class of amphiphilic graft copolymers has been synthesized, characterized, and explored for applications in biomaterials and nucleic acid delivery. This thesis research focused on the syntheses of oligopeptide-functionalized polyesters and polyolefins. Polyester functionalization was geared towards applications in biomaterials, tissue engineering, and drug delivery by incorporating sequences that promote cell-adhesion. These polyester- graft -oligopeptide materials were prepared by a 1,3-Huisgen cycloaddition reaction, "click" chemistry, of an azide-terminated oligopeptide (prepared by Fmoc-based solid phase peptide synthesis (SPPS)) and alkyne-containing polyester (synthesized by ring-opening polymerization). Following the syntheses of these materials, they were analyzed by nuclear magnetic resonance (NMR) and organic gel permeation chromatography (GPC). The oligopeptide-functionalized polyolefins were designed for nucleic acid complexation, and therefore the oligopeptide sequences were intended to incorporate positively-charged moieties ( e.g. , oligolysine) for DNA and short interfering RNA (siRNA) complexation. These graft copolymers, prepared by SPPS followed by ring-opening metathesis polymerization, have highly tunable structures that enable control over charge density and polymer backbone rigidity. Moreover, non-ionic hydrophilic grafts such as polyethylene glycol were integrated into these polyelectrolytes such that the charges along the polymer backbone are spaced accordingly while maintaining the hydrophilicity of the polymer. While numerous applications for such charged, "bio-tailored" materials can be envisioned, this work is geared towards positively-charged polyelectrolytes for their potential application in nucleic acid therapy, specifically the delivery of plasmid DNA and siRNA. These graft copolymers were characterized ( 1 H, 13 C NMR, organic and aqueous GPC), studied for their solution properties (static and dynamic light scattering), and investigated as polyplexes with plasmid DNA.

The phase behavior of chiral block copolymers (BCPs*), namely, BCPs with at least one of the constituent block is formed by chiral monomers, is studied both experimentally and theoretically. Specifically, the formation of a unique morphology with helical sense, the H* phase, where the chiral block forms nanohelices hexagonally embedded in the matrix of achiral block, is investigated. Such unique morphology was first observed in the cast film of polystyrene-b-poly(L-lactide) (PS-b-PLLA) from a neutral solvent dichloromethane at room temperature with all the nanohelices being left-handed, which would switch to right-handed if the PLLA block changes to PDLA. Further studies revealed that such morphology only forms when the chiral PLLA block possesses certain volume fraction (from 0.32 to 0.36), and the molecular weight exceeds certain critical value (around 20,000 to 25,000 g/mol). Achiral phases such as lamellae, gyroid, cylinder, and sphere will form if the above criteria are not satisfied. Even though the unique H* phase has been extensively studied and utilized for many applications, many fundamental and important questions remain unanswered for such BCP* system. Specifically, how does the molecular level chirality transfer from the several-angstrom scale of the lactide monomer to the tens-of-nanometer size scale of the H* domain morphology? Why is the chirality transfer not automatic for this BCP* system? Is H* phase a thermodynamic stable or metastable phase? Are there other novel phases other than the H* phase that could form within the BCP* system? We aimed at providing answers to the abovementioned questions regarding the formation of chiral H* phase, which is no longer limited to the PS-b-PLLA/PDLA system. We divided our studies into both experimental and theoretical parts. In the experiments, we studied the effect of solvent casting conditions, including solvent removal rate and polymer-solvent interactions, on the formation of the H* phase in PS-b-PLLA/PDLA BCPs*. In addition, we monitored the morphological evolution during solvent casting using time-resolved x-ray scattering technique. We found that good solubility towards both PS and PLLA/PDLA blocks are required for the formation of the H* phase, and microphase separation has to happen prior to crystallization of chiral block. Most importantly, we found that crystalline ordering is not necessary for the H* phase formation. This result led us to propose melt-state twisted molecular packing as the underlying driving force for such helical phase to form, and began our work on the theory for BCPs*. First we built the theoretical tool by incorporating the orientational segmental interactions into the self-consistent field theory (SCFT) for BCPs. As a demonstration, we constructed the phase diagrams for one-dimensional (1D) and two-dimensional (2D) phases, for achiral BCPs with different orientational stiffness. We found that orientational stiffness could serve as another parameter to introduce asymmetry into BCP systems, in addition to conformational and architectural asymmetry. This model was further applied to study the phase behavior of BCPs*, and two phase diagrams were constructed. Another chiral phase, wavy lamellae (L* phase), was observed for BCPs*. The H* phase was found to be a thermodynamic stable phase, as long as the segregation strength ����and chiral strength ��! exceed certain critical values. Energetically favorable cholesteric texture was observed for the chiral segment packing inside the H* phase, which is believed to drive such unusual morphology to form. A simple geometrical argument based on bending of cylindrical microdomain and twisted packing of the bended microdomain can be given to explain the nonlinear chiral sensitivity of BCP* morphology, which further explains the non-automatic feature of chirality transfer in such system.

<p>Multilayer polymer decorative films are showing a growing presence in the automotive industry, substituting conventional paint applications while maintaining similar aesthetic appeal. However for certain film constructions that have distinct layer properties, the polymer film laminates have shown to form wrinkles on application of heat during thermoforming. In this study, attempts were made to identify the factors influencing wrinkling and to predict the variation in the wrinkle parameters under changing forming conditions using existing theoretical models. A new modified thermoforming technique is proposed for producing thermoformed parts without wrinkles and thereby achieving a <em>Class A</em> finished surface.</p> / Master of Applied Science (MASc)

This thesis proposes an algorithm that determine the geometry of 3D-printed, custom-designed spring element bands made of thermoplastic elastomer (TPE) for use in a wearable orthotic device to aid in the physical therapy of a human hand exhibiting spasticity after stroke. Each finger of the hand is modeled as a mechanical system consisting of a triple-rod pendulum with nonlinear stiffness at each joint and forces applied at the attachment point of each flexor muscle. The system is assumed quasi-static, which leads to a torque balance between the flexor tendons in the hand, joint stiffness and the design force applied to the fingertip by the 3D-printed spring element. To better understand material properties of the spring element’s material, several tests are performed on TPE specimens printed with different infill geometries, including tensile tests and cyclic loading tests. The data and stress-strain curves for each geometry type are presented, which yield a nonlinear relationship between stress and strain as well as apparent hysteresis. Polynomial curves are used to fit the data, which allows for the band geometry to be designed. A hypothetical hand is presented along with how input measurements might be taken for the algorithm. The inputs are entered into the algorithm, and the geometry of the bands for each finger are generated. Results are discussed, and future work is noted, providing a means for the design of a customized orthotic device.

Abstract An experimental method was developed that demonstrated the size effects in forming thin sheet metals, and a finite element model was developed to predict the effects demonstrated by the experiment. A universal testing machine (UTM) was used to form aluminum and copper of varying thicknesses (less than 1mm) into a hemispherical dome. A stereolithography additive manufacturing technology was used to fabricate the punch and die from a UV curing resin. There was agreement between the experimental and numerical models. The results showed that geometric size effects were significant for both materials, and these effects increased as the thickness of the sheets decreased. The demonstration presents an inexpensive method of testing small-scale size effects in forming processes, which can be altered easily to produce different shapes and clearances.