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Release of small molecules from polymeric materials has wide applications in the delivery systems of active molecules such as drug, fragrance, and semiochemical. Rubber materials are good candidates for the excipients of those systems due to properties such as good flexibility, permeability, and biocompatibility. Factors like material properties, mechanical loading, and molecular interactions may affect the release of small molecules in those systems. Therefore, understanding how those factors affect the release is key to the formulation, design, and evaluation of those systems. To study the effects of materials properties, vulcanized natural rubber sheets with different crosslink densities, loaded with small molecules with different boiling points, molecular weights, and chemical moieties were prepared. Release experiments were performed to determine the mass transfer and diffusion coefficients of those molecules and corresponding numerical models were built. Good agreements between experiments and numerical simulation were observed. It was found that the mass transfer coefficients of those small molecules decreased with increasing boiling points but remained practically constant among rubber sheets with different crosslink densities. The diffusion coefficients did not show evident correlation with molecular weights but their relationships with crosslink densities indicated that there might be an optimal crosslink density where a small molecule reached its maximum diffusion coefficient. To study the effects of uniaxial tensile strain, silicone rubber sheets loaded with triacetin were stretched and held at different lengths up to 125% engineering strain. The mass transfer and diffusion coefficients of triacetin were determined experimentally. It was found that there was no significant change of diffusion coefficient as the applied strain increased, which might result from two microstructure changes that had conflicting effects on diffusion: chain orientation and free volume deformation. To study the effects of molecular interactions, the mass transfer and diffusion coefficients of three model molecules, octanol, octyl acetate, and octyl butyrate were determined from silicone rubber sheets loaded with only one or two of the three molecules. Differential scanning calorimetry and Fourier transform infrared spectroscopy were used to characterize molecular interactions. It was found that the release of octanol conformed to the Fickian diffusion pattern at low initial concentration but deviated as the concentration increased due to hydrogen bonding between octanol and the silanol group of the silica filler. When two small molecules were released simultaneously, different effects of one model molecule on the diffusion coefficient of another were observed and explained by the competing effects of plasticizing and hydrogen bonding/dipole-dipole interaction. In summary, the outcome of this work promoted the understanding on important influencing factors of the release of small molecules from rubber and other polymeric materials and can serve as support and reference for the formulation, design, and evaluation of such delivery systems.

Poly(lactic acid), or PLA, is an increasingly utilized bio-sourced polymer with increasing value as a semi-crystalline material with good processing capabilities, making it a versatile material used in many applications. The main drawback of PLA is its slow crystallization kinetics, which has been improved with a variety of processing techniques and the use of additives or nucleating agents. This study uses a method called Self-Nucleation (SN) to increase the nucleation and crystallinity of the polymer by heating it to a temperature below melting, causing most of the polymer crystals to relax into the melt. Some crystal fragments or melt memory remain in the melt which can then serve as nuclei upon further crystallization during conditions that favor this transition. This technique dramatically enhances nucleation density and overall crystallinity in the material and has potential as a simple, cost-effective method to increase nucleation in PLA. In this study, samples of various molecular weights and various D-isomer content in the PLA copolymer chain are studied using this technique to determine the range of the SN domain (Domain II) for each sample, and how this domain and the efficacy of the SN method changes with these variables. A non-isothermal protocol was utilized to minimize thermal degradation when kept at high temperatures and to show that SN can reasonably be utilized as a crystallization tool in a manufacturing environment where long isothermal treatments are impractical. Advisor: Lucia Fernandez-Ballester

Over the past 25 years, awareness of type 1 diabetes has significantly increased, leading to a comprehensive understanding of various aspects, including its genetics, epidemiology, and disease burden. According to the Type 1 Diabetic Index, about 8.7 million people around the world live with this long-term autoimmune disease characterized by insulin deficiency and resultant hyperglycemia. However, the increased availability and utilization of artificial pancreas systems could potentially save 673,000 lives by 2040. Although, the advancement of diabetes technology offers Type 1 diabetic patients more tools to enhance glycemic management and achieve effective outcomes, many patients are still hesitant to adopt these AP systems. This reluctance is attributed to the challenges associated with carrying various integrated parts alongside the insulin pumps on their bodies. Therefore, there is a pressing need for insulin delivery systems with smaller sizes and user-friendly features to promote wider acceptance of these devices among individuals with Type 1 Diabetes (T1D). As a potential solution, we propose a magnetorheological peristaltic micropump to offer a compact, lightweight, portable, wirelessly controllable, durable, and low-power insulin delivery system. This study introduces a magnetic actuation mechanism for a micro-fluidic pump with a flap valve. A Multiphysics-based simulation approach is carried out to evaluate the proposed idea. For this, a complex magneto-solid-fluid interactions are performed using a three-dimensional time-dependent computational model by COMSOL. Through the simulation, the velocity field in the pump channel as well as the deformation of the pump chamber's upper wall were evaluated. A replication of an existing literature study is also conducted to validate the simulation approach. The computational findings indicate that the pump can transfer up to 1.99 μL of fluid in a single pumping cycle, achieving this flow rate within 0.41 seconds. This wearable patch-integrated system has a flow chamber, sensors, drug reservoir, and a permanent magnet. Beyond insulin delivery for diabetic patients, the concept can be used to improve micro-cooling devices, move blood in artificial organs, and use organ-on-chip assemblies. This user-centric, small, and effective insulin delivery technology could be a possible solution for addressing the reluctance of T1D patients to adopt AP systems.

Self-consolidating, rapid-hardening concrete is a sought-after product in the market now, however the effects of admixtures on fresh and hardened concrete rheology are still uncertain. This study aims to create a self-consolidating concrete (SCC) using calcium sulfoaluminate (CSA) cement for its rapid-hardening properties, and tests two set time retarders and two viscosity-modifying admixtures (VMAs) to determine how they affect the properties of concrete. The properties studied in this thesis are workability, viscosity, set times, air content, compressive strength, and freeze-thaw resistance of self-consolidating concrete. It was found that tartaric acid creates a very workable SCC with consistent results regardless of VMA used while citric acid only works well with Hydroxypropyl Methylcellulose (HPMC) as a VMA and kills viscosity modifying properties of Welan Gum (WG).

Asphalt Concrete (AC) is a cross-anisotropic viscoelastic material. This study has developed a methodology to backcalculate the cross-anisotropic properties of the AC layer from the Falling Weight Deflectometer (FWD) sensor and pavement response data from embedded sensors inside a pavement section. This study has also developed a two-way coupled Multiscale Finite Element Model (MsFEM) with Phase Field Fracture (PFF) to study the microstructural heterogeneity and damage of the AC layer based on the actual field loadings. A Finite Difference Time Domain (FDTD) and Machine learning-based backcalculation algorithm were developed to determine the layer thickness and dielectric constant from air-coupled Ground Penetrating Radar (GPR) data. Using the developed methodologies and algorithms, it is possible to determine the in-situ cross- anisotropic viscoelastic properties of AC using non-destructive tests, determine the increment of strain at the microstructure RVE compared to the macroscale AC, and accurately predict the thickness of the AC layer.

This study presents a flexible sensor/harvester device to be used in both electromagnetic sensing and energy harvesting applications for smart grids. When a current passes through a wire, the sensor detects the magnetic field created by that current. The sensor magnet interacts with the wire magnetic field resulting in a transfer of energy through the piezoelectric cantilever. Piezoelectric, conductive, magnetic, and magnetostrictive composite thin films were prepared to fabricate this device. Initially, the magnet of the cantilever was optimized considering its shape, thickness, length, taper angle etc. via both simulations and experiments. Peak to peak voltage versus cantilever position graph was drawn for several different magnets. The triangular shape showed the widest sensing range around 18 mm. Experiments have been verified by COMSOL Multi physics software simulations constructing the magnetic flux density-position graphs. After the geometry optimization of the magnet, numerous 0-3 composite thin films were fabricated using piezoelectric, conductive, magnetic, and magnetostrictive powder in different polymers for comparison. After blending the materials, the spin coating method was used with various spin speeds to obtain different film thicknesses. Mainly, lead zirconate titanate (PZT), silver (Ag), neodymium (NdFeB), and Terfenol-D particles were used to create these functional films. After demonstrating that the functional thin films fabricated in this research can be successfully used to fabricate multilayered devices such as a micro-scale capacitor or a thin film energy harvester, thin film sensor/harvester versions of the bulk devices were fabricated and tested successfully. The broadest sensitivity region was obtained again from the piezoelectric thin film that has triangular thin film magnet positioned in such a way that its tip faces the free end of the cantilever. 40 wt.% concentration Ag-PI composites were used as electrodes. Finally, magnetostrictive thin films having various ball-milled Terfenol-D particle concentrations were fabricated to be used as a single layer sensor instead of using multiple layers of thin films. The thin film sensors were tested using a Helmholtz coil and their response were determined in terms of tip deflection and current gained.

The field of additive manufacturing (AM) has gained a significant amount of popularity due to the increasing need for more sustainable manufacturing techniques and the adaptive development of complex product geometries. The problem is that AM parts routinely exhibit flaws or weaknesses that affect functionality or performance. Over the years, surface treatments have been developed to compensate certain flaws or weaknesses in manufactured products. Combining surface treatments with the modularity of additive manufacturing could lead to more adaptable and creative improvements of product functions in the future. The current work evaluates the feasibility of pursuing a new research axis in the field of additive manufacturing for mechanical and chemical treatments during the making of polymers. The interest here is to investigate the effects of combining laser shock peening (LSP) in a multilayer AM product by introducing interlayer surface treatments that cold work the temporarily exposed layer. Shot peening has already proven effective at increasing mechanical strength of polymer materials in interlayer peening processes by locally inducing compressive residual stresses (CRSs). However, only few publications concern LSP on polymers, this could be due to the high-energy output of lasers that seems incompatible with the low tensile strength of polymers. In addition to evaluating this assumption, this project has the goal of exploring the effects of peening on different layers. Traditionally, each peened layer is separated by a fix number of unpeened layers, commonly referred to as fixed interval hybrid AM. However, ideal solutions for peening layer intervals are hypothesized to be irregular. Here, the aim was to study more diverse distribution patterns by comparing periodic and irregular intervals. Since the understanding of the effects of LSP on polymers is very limited, different aspects of thermo-mechanical behavior were evaluated. Advisor: Michael P. Sealy

While Carbon Fiber Reinforced Polymers (CFRPs) have exceptional mechanical properties concerning their overall weight, their failure profile in demanding high-stress environments raises reliability concerns in structural applications. Two crucial limiting factors in CFRP reliability are low-strain material degradation and low fracture toughness. Due to CFRP’s low strain degradation characteristics, a wide variety of interlaminar damage can be sustained without any appreciable change to the physical structure itself. This damage suffered by the energy transfer from high- stress levels appears in the form of microporosity, crazes, microcracks, and delamination in the matrix material before any severe laminate damage is observed. This research presents a novel Non- Destructive Evaluation (NDE) technique for assessing subsurface interlaminar interphacial health. A new self-sensing smart composite material is born by embedding microscopic magnetically activated sensors between CFRP ply. Magnetostrictive Carbon Fiber Reinforced Polymer (MagCFRP) is a self-sensing structural health composite material that is magnetically activated by an external magnetic field. This research merges the governing magnetoelasticity and general magnetization mechanics with analytical, experimental, and numerical results. For mode I and mode II fiber- matrix debonding, cracking, and shear delamination, there was an observed localized magnetic flux density gradient of more than 3 mT (2%) with a reversible flux of only 25% for low driving magnetic flux density (≈ 0.2 T) using the indirect magnetization stimulation method.

Around 40% of global energy consumption and 30% of worldwide carbon dioxide (CO2) emissions are attributed to buildings. Most of this consumption is dedicated to ensuring thermal comfort. The goal of this research was to develop and field validate retrofit solutions to improve the energy efficiency of buildings. Exterior cladding panels were designed and tested to ensure adequate thermal and structural performance. Sandwich panels (glass fibers reinforced polymer (GFRP) skins and polymeric foam cores) were fabricated using the vacuum assisted resin transfer molding (VARTM) process. Extruded polystyrene (XPS) and polyurethane (PU) foams were compared as core materials through a series of thermal and mechanical tests. Thermal resistances of 3.62-4.66 h.ft2.°F/Btu (0.64-0.82 K.m2/W) per inch were obtained for sandwich structures. XPS samples were 26% lighter, 24%-40% stronger, and 16%-28% more brittle than PU in quasi-static loading configurations. PU absorbed 11% more energy than XPS in a low-velocity impact (LVI) test. Flatwise tensile test showed that the bonding strength between XPS and GFRP was 47% higher than PU foam. Consequently, XPS was chosen as core material and further tests were conducted accordingly. Tensile testing performed on the GFRP material resulted in a 3,191 ksi (22 GPa) elastic modulus, 42,786 psi (295 MPa) tensile strength, and 0.165 Poisson’s ration. To predict the wind loads according to the American Society of Civil Engineers (ASCE) building standard, flexural tests were conducted on a 4 x 8 ft2 (121.92 x 243.84 cm2) sandwich panel. FEA simulations were also developed to accurately predict the behavior of the retrofit panels based on actual dimensions and connections. Less than 4% variation was noted between experimental and numerical data. The deflections were within the allowable limits set by the International Building Code (IBC). The panels were supposed to be used as an exterior application; therefore, it was important to understand the environmental effects. Discoloration of the GFRP skin due to v ultraviolet (UV) and moisture exposure was observed. Ceramic coating was applied to eliminate the discoloration effect. A fire simulation (ASTM E84) was conducted on a 2 x 24 ft2 (60.96 x 731.52 cm2) panel to obtain surface burning characteristics.

The aim of this work is to study different various softwood lignins and manufacture and characterize neat ABS-lignin composites. This involved characterizing deodorized and non-deodorized softwood lignins using techniques such as differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, and principle component analysis. These techniques are used to determine the similarities and differences among the various softwood lignins at the functional group level. Neat ABS-lignin is blended in different weight fractions and analyzed for thermal and mechanical properties. A microscopic analysis of the blends is completed to study the interfacial properties of neat ABS-lignin. This effort was a collaboration among the Center for Renewable Carbon (CRC) and the Civil and Environmental Engineering Department, and Prisma Renewable Composites, LLC. The ABS-lignin blends showed a range of tensile strength of 33.0-40.6 MPa and a tensile modulus of 2.01-2.64 GPa. All ABS-lignin blends showed superior tensile and flexural strength and modulus, but showed lower impact resistance than neat ABS. These results are a result of the higher modulus of the lignin increasing the overall modulus and strength of the blends. The brittle nature of lignin reduces the impact resistance of the ABS-lignin blends as well as the ultimate strain. Microscopic analysis shows uneven spatial distribution of lignin in ABS resin.

Polylactic acid (PLA) is a biopolymer made from renewable resources such as sugar and corn. PLA filament is a popular material used in Fused Deposition Modeling (FDM) 3D-printing. While this material has many advantages, all the failed parts, support structures, rafts, nozzle tests, and the many prototype iterations during the 3D-printing process contribute to the plastic pollution and release of greenhouse gases. Although PLA is biodegradable, it can take years to degrade in landfills. Instead of throwing away PLA waste and buying new filaments, PLA can be recycled. Amongst the different recycling technologies, mechanical recycling is the most environmentally friendly. In this project, PLA filaments were mechanically recycled. One of the goals in this study was to identify the barriers to recycling and to introduce a more detailed recycling process. To achieve this goal, three different recycling extruders were tested to find the most user-friendly, which was the Noztek Pro Desktop extruder. Moreover, a new and more detailed material preparation process was introduced. In this method, PLA was first shredded. Then liquid nitrogen was added to make the material more brittle and easier to crush, and finally, it was ground. Additionally, the most effective process parameters for extrusion were presented. These parameters included temperature of 200 ºC, a pulley speed of 1.5 m/min, and using fans to cool the extruded filament before winding. The next goal was to evaluate the process with the added details and find the impacts of successive mechanical recycling on the properties of PLA. Therefore, a comprehensive testing was done including thermal (TGA and DSC), chemical (FTIR), and mechanical tests (tensile). Filaments could be recycled for three generations however after the third recycling, the filament no longer printed reliably. The test results demonstrated degradation of PLA. The UTS decreased from 44.7 MPa to 40.5 MPa, strain at break decreased from 10.4% to 7.5%, and the modulus, E, decreased from 1.603 GPa to 1.055 GPa. The FTIR results suggested that all samples had the same chemical structure of PLA. However, decreased intensity peaks around 920/cm show a decrease in crystallinity. In addition, a decrease in the absorbance band in the carbonyl region around 1750/cm, an intensity change from 700/cm to 2000/cm regions, and an intensity decrease around the 1180/cm-1240/cm were also observed. The DSC analysis showed that the Tg values were between 61.97 ℃ and 62.95 ℃, the cold crystallization temperatures had a range from 117.87 ºC to 128.81 ºC, and the melting temperatures ranged from 158.48 ºC to 161.28 ºC. Moreover, The TGA results showed that the decomposition temperatures were between 311.33 and 337.5 ºC. The recycling process was initially successful, however, after the third generation the filament became unprintable. This was due to decrease in crystallinity and molecular weight which caused brittleness, lower strength, and nozzle clogging. This research provided important design data regarding performance and limitations of recycled PLA.

The current most efficient solution to fighting liquid pool fires involves the use of firefighting foams containing fluorinated surfactants. The physiochemical properties of these foams are considerably different to all other currently available firefighting foams. Fluorinated surfactants lower the surface tension to a point where the foam solution draining from the foam structure forms a continuous aqueous film on the surface of a volatile hydrocarbon fuel, adding an additional barrier to fuel vapor diffusion to the burning fire. For this reason, these foams qualify as aqueous film forming foams (AFFFs). However, fluorinated compounds are extremely harmful for the environment due to their chemical stability and resulting bioaccumulation. There are currently several industrially produced non-fluorinated firefighting foams available, but these foams possess gaps in their performance in comparison to AFFFs. In this research, we grafted poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) brushes of different oligo(ethylene glycol) side chain lengths to the surface of hollow glass bubbles (GBs), prepared concentrated aqueous suspensions with these GBs, and used the suspensions to extinguish heptane pool fires. We investigated the effects the parameters of the grafted layer such as side chain length, graft density, molecular weight, and hydrophobic side chains have on the suspension properties—such as viscosity and surface and interfacial tension—and the firefighting performance of the suspensions. It was determined that, out of the GB suspensions studied, GBs with loosely grafted, high molecular weight POEGMA chains with large polyethylene glycol side chains (at least 19 ethylene glycol repeating units) on the surface provided suspensions (in conjunction with a low surface energy siloxane surfactant) with low viscosities, complete spreading over a liquid hydrocarbon (hexadecane) surface, and low heptane fire extinguishment times. The extinguishment times of these low-viscosity GB suspensions were approximately equivalent to the AFFF extinguishment time, but the suspensions offer highly superior protection against reignition of the fire following extinguishment. Overall, this dissertation provides insight into the utilization of a new class of materials for extinguishment of liquid hydrocarbon fires. The GB suspensions reported herein represent fluorine-free fire extinguishing materials which offer the opportunity for reuse following extinguishment. Our understanding of these suspensions and the specific physiochemical properties which contribute to their effectiveness in fire extinguishment lays the groundwork for further exploration of low-density aqueous suspensions for extinguishment of liquid hydrocarbon fires.

Automotive industry at large is focused on vehicle light-weighting since a 6%-8% increase in fuel efficiency can be achieved with a 10% reduction in vehicle weight [1]. With the growing demand for cost-effective and sustainable light weighting of automobile structures, interest has increased in the application of fiber reinforced plastic (FRP) composites for use in the Body-in-White (BiW), which can account for up to 40% of the total vehicle weight. Traditional FRP composite manufacturing processes like vacuum assisted resin transfer molding, autoclave consolidation or use of automated fiber placement have been successfully used for marine and aerospace applications. However, these processes are not suitable for the automotive industry due to the low production rate, need for highly skilled labor for manufacturing and quality control, and poor joining with traditional structural materials like steel. This necessitates the use of higher throughput outof-autoclave (OOA) processes like high pressure resin transfer molding (HP-RTM), wet compression molding (WCM) or even fiber reinforced thermoplastics (FR-TP) forming. The transition to these OOA processes face two major challenges: a) the time-consuming iterative design and thermal profiling process required for metal tools which increases cost; and b) the lack of a low-cost, scalable, and sustainable multi-material joining pathways that can enable integration of FRP composite parts with traditional metal structures. This is because existing composite joining methods necessitate significant redesign of existing OEM infrastructure, incur high capital costs, and produce weak joints between metal and composite components. iii To address the first challenge, a new paradigm where additive manufacturing of thermoplastic filament reinforced with continuous fiber is used to develop a low-cost and sustainable composite tool, is investigated. Furthermore, additive manufacturing can enable faster tool design turn-around times and allows for designing of complex tool geometries with embedded sensors and conformal cooling channels. This opens greater avenues for process and design optimization and will enable manufacturers to gain a better understanding of the process based on sensor data gathered in real time from the embedded sensors. To address the later challenge, a highly integrated multi-material, FRP-intensive BiW design was developed using unique multi-material transition joints which retain existing OEM joining infrastructure [2]. It incorporates multi-material transition joints where continuous dry fibers are laid through machined looped channels in a metal substrate and additional metal layers are additively manufactured on top of the looped fiber and metal substrate to embed the fibers within the metal and create a strong metal – fiber mechanical interlocking bond. The fibers are then infused with a thermoset matrix that fills out the loops as well, forming a string FRP-metal transition [3]. Thus, the resulting CFRP component with metal tabs can be spot welded to other metal components without piercing, drilling, or punching holes - significantly increasing the mechanical performance of the multi-material joints. To ascertain the advantages of these multi-material designs and the use of state-of-the-art additively manufactured smart tools, their life cycle impact must be investigated and compared with existing technology. The results from the LCA can provide vital understanding of the energy requirements of the new processes methodologies and can help iv quantify the benefits offered by transitioning to this new proposed paradigm of composite design and manufacturing from a sustainability and emission reduction standpoint. To best of the authors knowledge there have been no studies that address the LCA for each of the proposed solutions. Thus, this work, conducts two comparative life cycle analyses on the proposed additively manufactured smart composite tool for OOA processes and for the multi-material designs for automotive structural components. Different scenarios are studied for both the LCAs to consider the existing FRP production processes as well as the production process of traditional materials.

Carbon fibers possess ultra-high specific strength and modulus. Therefore, the material is popular in aerospace, automotive, and sports industries. Approximately 95% of all carbon fibers are spun from a high-cost precursor, polyacrylonitrile (PAN). There is a need for a cheaper grade of carbon fiber for low-cost applications because about half of carbon fiber cost is associated with precursor cost. A promising alternative to the high-cost PAN precursor is petroleum-based asphaltene. Asphaltenes are highly aromatic and have a high carbon content but lack the purity of the PAN precursor. Processes like the molten- sodium desulfurization upgrading have been used to harvest impurities such as sulfur and produce a cleaner asphaltene. The goal of this study was to utilize such refined Athabasca oil-sand-asphaltenes to produce precursor fibers and convert them into carbon fibers. Various such grades were investigated to determine the effect of impurities and thermal treatment on the processing and properties of carbon fibers. The samples used for this study were provided by Alberta Innovates as a part of the Carbon Fiber Grand Challenge (CFGC). Two types of samples were studied: (i) asphaltenes removed as vacuum tower bottoms (VTB) from the oil-sand refining process and subsequently desulfurized, and (ii) VTBs that were also heat-treated (HT-VTB) by a proprietary process that too were desulfurized. These precursors had sulfur contents ranging between 0.3 and 7.0 wt%. The asphaltenes were characterized by using softening point and thermogravimetric analysis to determine the volatile content and melting characteristics of the asphaltenes. Several of these asphaltenes grades could be melt-spun into precursor fibers that werethermo-oxidatively stabilized and successfully carbonized at 1000°C, 1500°C or 2000°C. The microstructure was analyzed with Raman microscopy, EDX and SEM. The tensile strength and electrical resistivity were also measured for various fibers produced using different carbonization temperatures for different impurity contents. The results showed that for untreated VTB group, a small increase of softening point was observed, 188°C to 203°C, when samples were desulfurized and refined (sulfur content reduced from 1.7wt% to 0.3wt%). In contrast, the heat-treated vacuum-tower- bottoms (HT-VTB) asphaltenes without sulfur removal had the highest softening point of 280°C (sulfur concentration of 7 wt%). When subjected to the desulfurization refining step, the softening point decreased significantly to 208°C (about 1.4 wt% S). However, due to its high softening point, HS-VTB could be thermo-oxidatively stabilized in about 24 hours at a high temperature and fast rate. In contrast, untreated VTBs had a lower softening temperature and needed 72 hours to be adequately stabilized as a slower rate had to be used. Because the softening point of untreated VTBs was not significantly different, no trend between sulfur concentration and stabilization time could be inferred. The VTB asphaltenes showed a char yield of approximately 50%, whereas the HT- VTB asphaltenes had char yields between 55-65%. For both types of asphaltenes, the graphitic content moderately increased with carbonization temperature. The disordered to graphitic carbon ratio (ID/IG) ratio from Raman spectroscopy was measured at 1.2 for carbonization at 2000°C. The EDX analysis of the VTB and HS-VTB asphaltenes showed a reduction in sulfur concentration when carbonization temperature was increased from 1000 to 1500°C and further from 1500 to 2000°C. For all carbon fibers obtained at 2000°C, he sulfur concentration was undetectable The HS-VTB asphaltene-based fibers had the highest tensile strength of 1.1 GPa when carbonized at 1000°C. The strength reduced to 0.3 GPa for a carbonization temperature of 2000°C. The tensile strength for all asphaltene-based fibers decreased with increasing carbonization temperature but was largely unaffected by the sulfur concentration. Electrical resistivity decreased from 60 to 40 µΩ-m as carbonization temperature was increased from 1000°C to 2000°C. This corresponds to an increase in electrical conductivity, which is consistent with increasing graphitic content inferred from Raman spectroscopy. In summary, several Athabasca oil-sand-asphaltenes were successfully melt spun, stabilized, and carbonized into carbon fibers. It was found that fibers obtained from heat- treated asphaltenes (HT-VTBs) stabilize faster and have higher tensile strength than those from untreated VTB asphaltenes. It was found that 1000°C was the optimal carbonization temperature for asphaltene-based carbon fibers with tensile strength reaching 1 GPa. Also, these asphaltene-based carbon fibers are electrically conducting (in contrast to insulating glass fibers), which makes them useful for applications where electrostatic dissipation and electromagnetic shielding is necessary.

The petrol-based polymer has been widely applied in current daily life. The end-of-life of polymeric products has drawn environmental concerns. One of the solutions to such issues is to use bio-renewable materials to replace or reduce the use of petrol-based materials. Lignocellulosic materials are one of the potential candidates. Along with the features of 3D printing and the unique properties of biomass, 3D-printed biomass-based materials could be promising in preparing sustainable alternatives. In this dissertation, lignin and other biomass were applied to various 3D printing techniques for sustainable composites. Stereolithography (SLA) was first used, and the kraft softwood lignin was incorporated into the commercial clear resin. The printed composites showed a reinforcing effect after fully curing. Inspired by such a reinforcement, wood flour, where lignin is isolated, was also applied as a biomass filler. The 3D-printed wood flour composites showed a unique stress-whitening phenomenon, which displayed a potential for stress indicators. To further improve the loading amount of lignin in 3D printing, fused depositional modeling (FDM) was also involved. To improve the interfacial interaction between lignin and the polymer matrix, organosolv hardwood lignin was demethylated with improved phenolic hydroxyl groups. Enriched phenolic hydroxyl structures improved the interfacial interaction, thereby promoting tensile performance. A similar demethylation was executed on the softwood lignin. Due to the inherent difference in the functional groups, the obtained enriched polyphenol structures showed different but positive influences on tensile properties. In addition, the enhanced phenolic structures also showed great anti-aging performance, which brings more functions to the resultant composites, making lignin/polymer composites a promising functional and renewable material for the sustainable materials world.

Controlled degradation of polymers finds various applications in fields ranging from the design of functional soft materials to recycling of polymers. In several of these applications, the characteristic length scale at which relevant processes occur ranges from nanometers to microns, typically referred to as the mesoscale. Although analytical models and continuum approaches inform our current understanding, analysis of degradation at the mesoscale is exceptionally limited. For modeling degradation at the mesoscale, we use the Dissipative Particle Dynamics (DPD) technique and the LAMMPS simulation software. Within the DPD framework, we model controlled degradation or the breaking of covalent bonds within a polymer as a stochastic process that reproduces first order degradation reaction kinetics. A known limitation of the DPD approach is polymer chains crossing through each other. Previous researchers had developed a modified segmental repulsive potential (mSRP) framework which prevents such crossing of polymers by introducing extra repulsion between the bonds of polymer chains. We modified the existing model in LAMMPS to enable switching off the extra repulsion when a bond is broken. We implemented this feature within the LAMMPS framework, and it is now available for the general scientific community as a part of the online open-source project. Later, we extended this feature to introduce the extra repulsion when a bond is formed to simulate the hydrosilylation reaction used in the synthesis of polymer derived ceramics. As a model polymer network for studying degradation, we use the tetra-arm polyethylene glycol (tetra-PEG) based hydrogel films. Tetra-PEG networks have a uniform network structure and hence superior mechanical properties. We tracked the degradation iii of these networks by measuring the evolution of the weight average molecular weight and dispersity during degradation. By tracking the fraction of degradable bonds broken, we identified the “reverse gel point”, the point where the polymer network dissolves into the surrounding solvent. Additionally, we tracked the erosion or mass loss from the degrading network by accounting for polymer fragments which dissociate and diffuse away from the network. We identified that the mass loss from the network depends on the initial thickness of the hydrogel films. As a second system, we modeled the controlled degradation of nanogels that are either suspended in a single solvent or adsorbed onto a liquid-liquid interface. Controlled degradation of nanogels at an interface provides a dynamic approach to control interface topography at the nanoscale. We tracked the degradation of these particles by analyzing the evolution of their shape and size along with the molecular weights and dispersity in the system. In bulk, the particles swell almost homogenously while at the interface, the particles spread and cover the interface as degradation occurs. We found that the reverse gel point for these particles varies with the total initial number of precursors. The evolution of particle shape and size is significantly affected by the surrounding solvent and the surface tension between the two liquid phases. The final part of this dissertation focuses on developing an initial framework to extend the above approach to model degradation of polyolefin melts under a local temperature gradient. The long term goal of this project is to study thermal degradation of polyolefins caused by introducing microwave absorbing nanosheets and subjecting the polymer to microwave irradiation.

The use of lignin in the fabrication of soft composites has become an emerging area of research in polymer science and polymer chemistry. These lignin-based materials present numerous benefits, notably, a reduction in the use of petroleum-based precursor, improved structural benefits to otherwise soft host polymers, as well as the inherent antimicrobial and antioxidant properties of lignin, making it suitable for biomaterials. Herein, we present two chemical reaction pathways of incorporating lignin that was fractionated and cleaned using the Aqueous Lignin Purification with Hot Agents (ALPHA) process into poly(vinyl alcohol) (PVA) hydrogel composites for aqueous-based separations. By leveraging the ALPHA process, we can obtain lignins of prescribed molecular weights (MWs) with narrow dispersity (Ð) and low ash content – i.e., low concentrations of sodium and potassium. In one reaction pathway, lignin was first functionalized with vinyl-containing acrylate groups that enabled free radical chemical crosslinking of lignin chains. Notably, both the lignin MW and chemical functionality had an impact on the permeability of methylene blue (MB), where the breakthrough time of the MB across the membrane was significantly longer for lignin with higher hydroxyl content. Further, the permeability of MB was seen to decrease by over two orders of magnitude with the introduction of just 20 wt % lignin. In addition, the importance of leveraging lignin of narrow Ð in the development of structure–processing–property relationships for these materials was underscored by the consistent, repeatable permeation experiments obtained for these membranes versus their counterparts made with unfractionated lignins. In the second reaction pathway, both the lignin and PVA chains were chemically crosslinked via a condensation reaction using glutaraldehyde (GA). In general, increases in the GA content and lignin MW resulted in improved mechanical properties, including increases in ultimate tensile strength, storage modulus, and Young’s modulus, which was attributed to a tightening of the hydrated network structure and supported by decreases in equilibrium water uptake and molecular weight between crosslinks. Enhanced mechanical properties were also observed in hydrogel composites containing ALPHA-fractionated lignin as compared to unfractionated, stock lignin, underscoring the impact of the ALPHA process on the resulting properties.

Carbon fiber reinforced plastics (CFRP) are widely used throughout the aerospace industry where a weight reduction remains the highest priority with less emphasis on cost. Textile grade carbon fiber (TCF) and other low cost carbon fiber (LCCF) alternatives have recently emerged for use in the automotive market where emissions regulations have pushed automotive manufacturers and research institutions to look for cost effective light weight materials. Fiber reinforced thermoplastics provide an effective solution that align with automotive design including low cost, high processing rates, high impact toughness, unlimited shelf life, and recyclability. TCF and Zoltek_PX35 fibers are two LCCF aimed at the automotive, wind energy and commercial markets that are helping to push the cost of CF down to approximately $5 per lb. In combination with a hot melt thermoplastic pultrusion impregnation technique, an intermediate low cost composite tape can be produced that is shown to have good mechanical performance when consolidated through hot compression molding (CM). Automation is critical to the required rapid part production and process control within the automotive industry. Research was conducted into the manufacturing process parameters of LCCF composite tapes through in-situ consolidation with an automated tape placement (ATP) or automated fiber placement (AFP) robotic system. This research focuses on the manufacturing of low-cost continuous polypropylene composites and explores the mechanical and morphological properties associated with compression molding and automated tape placement.

The progress in materials engineering and the ability to make various models possible have made soft robotics a popular alternative to traditional robotics. Still, soft robots need various parts, like Printed Circuit Boards (PCBs), batteries, cables, fittings, and more, to work correctly or to get attached to other complex parts. These parts can have different material properties, like elastic moduli, strength, etc. Because of these differences, mechanical failures happen at the points where two materials meet, making soft robots less durable and less lasting in real-life situations due to failure. Conventionally, the fabrication of soft robot parts is through moulding. The advent of additive manufacturing has given much potential for manufacturing soft robot parts such as grippers. The extrusion additive manufacturing approach, precisely the direct ink writing (DIW) additive manufacturing technology approach, has been considered to have the highest potential to manufacture soft robot parts due to its wide range of material capabilities, simplicity, and ability to combine diverse materials in a single process. However, this approach is still in its early stage of development, giving it a good prospect in manufacturing soft robots. This work conducted a pilot investigation to enhance the interfacial property of 3d printed parts that incorporate both soft and hard phases by DIW of a silicone-polyurethane resin hybrid material. The interfacial adhesion was tested by conducting T-peel tests, showing improved peeling strength. INDEX WORDS: Silicone, Polyurethane resin, Direct ink writing, Peel test.

Decades of use of per- and polyfluoroalkyl substances (PFAS) in a multitude of consumer and industry-based products have led to a devastating amount of soil and water contamination. Although these chemicals and compounds possess advantageous qualities – such as that of PFAS in the role of fire-fighting foams that have no doubt saved countless lives and homes, we must take responsibility for the anthropogenic hazards that threaten our global health. This entails being able to cost-effectively remediate problems created in the past from overuse of toxic substances that could negatively impact our future, and in this case, the future of clean water availability. The chemical and thermal stability of PFAS have proved them to be an especially daunting challenge from an environmental remediation standpoint. Presently, the only full-scale water treatment separates via sorption and uses non-selective materials such as activated carbon (AC) or mineral media which are extremely difficult and/or costly to regenerate. Research focused on selective adsorption is becoming a more practical route for capture and removal from contaminated water systems. The work presented here investigates the development and effectiveness of polymer-based sorbents that have affinity toward PFAS through incorporation of various monomers that possess cationic and/or fluorinated functionalities. In some instances, composite systems were created with the inclusion iron oxide nanoparticles during the synthesis process. Although the main route of PFAS sorption occurs via ionic and hydrophobic interactions, several approaches were explored: (1) Thermoresponsive hydrogel expansion and contraction to drive contaminant into gel for sorption on functionalized sites; (2) Magnetic polymer composites allow for contaminant binding via sorption to cationic sites of quaternary amine functionalized polymers and removal via magnetic decantation; (3) Linear, non-crosslinked systems drive contaminant binding through flocculation with functionalized thermoresponsive polymers. The affinity of the synthesized materials for PFAS was evaluated at equilibrium conditions using a liquid chromatography coupled to mass spectrometer detection (LCMS) for quantification purposes, and the data was used to determine removal efficiency in both spiked and real-world environmental samples. Binding studies were conducted by subjecting 2.5 mg/mL of each sorbent to 500 ppb of aqueous PFAS for up to 24 h at room temperature for crosslinked systems and 1 h at 50 ºC for linear systems. Cationic crosslinked polymers showed high affinity for PFOA (>80%) and PFOS (>90%) across a range of aqueous pH (4 – 10). Linear polymers that included both cationic and fluorinated monomers showed improved flocculation and contaminant removal as compared to those systems with isolated functionality. Furthermore, upon exposure of the magnetic composites to an alternating magnetic field (AMF) for a period of 30 minutes, release of bound PFAS is realized in minor amounts depending on regeneration solvent selection. Overall, we have provided strong evidence that the materials presented here have a promising application as sorbents for PFAS contaminants in polluted water sources providing high binding affinities, a low-cost regeneration technique and are capable of withstanding use under environmental conditions offering a cost-effective alternative to current remediation approaches.

Soft, slippery surfaces have gained increasing attention due to their wide range of potential applications, for example in self-cleaning, anti-fouling, liquid collection, and more. One design approach in creating slippery surfaces is using a swollen elastomer, which is a polymer network swollen with a lubricant. This type of surface may be beneficial for longer-term use than standard lubricant-infused surfaces, and provides a versatile surface with tunable mechanical properties. Hence, understanding the physics of soft surface interactions is important for fundamental soft matter physics, biomaterials, adhesives, and coatings. This research experimentally investigates wetting on soft infused networks, with the aim of providing insight towards a physical description of wetting on a low-modulus, swollen elastomer. In principle, when a water drop is deposited on a soft surface, the surface tension of water can pull up the surface and form a wetting ridge at the drop periphery. However, when the soft material surfaces are also swollen with a fluid, the imbibed fluid may separate from the surface at the drop periphery to minimize the elastic energy that is caused by network stretching. Although significant efforts have been put into understanding the wetting ridge formation on soft crosslinked solids, as well as designing slippery, lubricant-infused porous surfaces (SLIPS), there is limited knowledge on soft and swollen surfaces. We bridge soft crosslinked solids and SLIPS by studying how infusing a soft crosslinked network with lubricant affects drop interactions, with a focus on low modulus elastomers (e.g. ~100 kPa or less). Specifically, by using silicone oil–swollen polydimethylsiloxane (PDMS) elastomers, we investigate situations of both static and dynamic wetting. My research is mainly divided into two integrated sections, briefly described below. In the first part of this work, we present an approach to visualize a crosslinked network and its swelling fluid separately by employing fluorescent molecules and confocal microscopy. We can vividly see the PDMS network and the oil phases separately at the contact line. We systematically investigate how the degrees of crosslinking and swelling affect fluid separation and network deformation during wetting on swollen networks. The degree of swelling is varied from =1 (dry) to saturation (maximum swelling) for four different degrees of crosslinking. Upon swelling the network to lower swelling ratios, the height of the wetting ridge increases due to the decreased modulus from swelling. As the degree of swelling increases further however, fluid clearly separates from the network. By continuing to increase the degree of swelling towards saturation, the amount of fluid separation increases. Qualitatively, the general trend of an initially increasing wetting ridge height followed by fluid separation is universal, regardless of the degree of crosslinking. Our experiments reveal that the static wetting ridge of a soft and swollen network can comprise both a region of network pullup and a region of pure fluid; this suggests that the swelling fluid, commonly found in soft networks, can play a critical role on surface wetting properties. In the second part, we transfer our focus from static wetting to dynamic wetting conditions to investigate the slippery properties of soft, swollen elastomers. In the dynamic wetting state, we study how the polymer network density and degree of swelling related to the pinning force and friction of a water drop. We first study when a water drop sticks or slides on a vertical, silicone oil–swollen PDMS elastomer, where gravity drives the drop to slide down while surface interactions promote drop sticking. Hence, a critical drop volume exists directly when gravity overcomes drop-surface adhesion forces. We find that the critical water drop volume for sliding decreases when increasing the degree of swelling, nearly independently from crosslinking for very soft elastomers. This is likely associated with oil separating from the bulk substrate when it encounters a water drop, lubricating the surface and decreasing the pinning force. Additionally, we develop a cantilever-based approach to measure lateral friction forces between drops and soft surfaces, while observing the water-elastomer contact line with confocal microscopy. Results show the friction force decreases when increasing the degree of swelling, which is a function of velocity. In summary, the results demonstrate the importance of considering the fluid inside of gels when investigating wetting of soft surfaces, offering fundamental insight into soft wetting, and into the slippery properties of soft, oil-swollen elastomers.

In recent years, organic-inorganic metal halide perovskites (HP) have garnered tremendous attention in photovoltaic research. This attention is attributed to their low cost and excellent optoelectronic properties, including large absorption coefficients, tunable bandgaps, long charge-carrier diffusion lengths, and low densities of deep trap states. Inverted p-i-n architecture perovskite solar cells (PSCs) are of intense interest and are generally regarded as more amenable to low-temperature solution processing. Nevertheless, the development of inverted PSCs is lagging the conventional architecture devices. Imperfect energy level alignments and charge carrier recombination, especially at the interface between perovskite and electron transport layers (ETLs), are two main factors suppressing the power conversion in inverted PSCs. More and more efforts are focused on manipulating the interface to improve PV devices. Organic semiconductors (OSCs), including π-conjugated polymers and small molecules, display distinct advantages in terms of low-cost, lightweight, diverse structures, easy solution-processed manufacturing, as well as excellent mechanical flexibility. However, the performance of OSCs-based devices is lagging behind their inorganic counterparts, in part due to lower mobility and electrical conductivity. Molecular doping provides a route to significantly enhance electronic properties, and as a result, is progressively attracting more attention. My Ph.D. research interest is focused on the applications of photoelectron spectroscopies to the study of perovskite solar cells and organic semiconductor-based electronics. The first work carried out is how surface ligands impact interfacial energetics and charge carrier dynamics at methylammonium lead iodide (MAPbI3)/C60 interfaces. The frontier electronic energy levels at perovskite/C60 interfaces are directly probed by ultraviolet photoelectron spectroscopy (UPS) and low energy inverse photoelectron spectroscopy (IPES), providing evidence of interfacial energetic reconstruction caused by surface ligands with differing dipoles. Ultrafast absorption/reflectance spectroscopies and transient photovoltage/photocurrent are utilized in comprehensively picturing the charge dynamics in films and devices. The following work reports the doping mechanism in the photoactivated p-doping of hole-transporting material (HTM) to enhance hole extraction for perovskite/textured silicon tandem solar cells, making the device performance less sensitive to the variation of hole transport layer thickness. Lastly, several collaborative works on doping of organic semiconductors are discussed, with applications in organic solar cells and thermoelectrics.

Additive manufacturing technologies have been enhanced throughout the years yet have surprised the manufacturing industry due to their high-end surface finish and dimensional accuracy. Different experiments have been done to identify a specific phenomenon known in the vat-polymerization field. Distortion and dimensional inaccuracy tend to affect the overall properties of the process, either physical or chemical. This approach allows the understanding of how the physical properties have been affected and how to study the chemical properties to avoid this type of phenomenon. The chemical reaction between polymer and UV light has been studied and experimented with to the point that certain parameters must be altered to avoid photodegradation. Photodegradation or photooxidation is the process where 3D-printed polymer specimens become brittle, and their mechanical properties tend to fail faster than a healthy specimen. Experimentation was done by allocating 3 different levels into 4 parameters, each parameter was investigated to be a cause to either enhance or affect the overall prints by LCD/SLA printing. Oxygen Concentration, Oligomer Concentration, Stabilizer Concentration, and Exposure Time were the parameters chosen to run these experiments, each having 3 different levels to be tested with. ASTM standard specimens were used to provide parts for 3 different characterization and mechanical testing: Tensile Testing, Compression Testing, and Hardness Testing. Results showed higher mechanical properties around Oxygen Concentration, Stabilizer Concentration, and Exposure Time. Various One-way ANOVA Tests were provided to check if the results retrieved statistically significant data. It was analyzed that each parameter provided statistically significant data, calculating a p-value less than 0.05 for each analysis of variance done. This data allowed the comparison between the current experiment in hand with external research, providing aspiring results for this new approach.

This research investigates the fabrication of hybrid nano Ultra-high molecular weight polyethylene (UHMWPE) fibers and their composites. The solution spinning method was used in the study to fabricate three different types of fibers: UHMWPE fibers, UHMWPE + 2 wt.% SWCNT fibers and UHMWPE + 10 wt.% PVP/PVDF coated fibers. Strain hardening was performed on the produced fibers, and mechanical testing was performed in order to determine the properties of fibers. The mechanical properties of the fibers involved the ultimate tensile strength, young’s modulus, fracture strain, and modulus of toughness. The focus was determining the effect of the inclusion of nanotubes on their mechanical properties. Neat UHMWPE fibers have an average stress and strain of 561.88 MPa and 106.67% respectively. The fiber properties decrease with the addition of nanotubes at low concentrations. The inclusion of 2 wt% nanotubes decrease the average stress and strain to 209 MPa and 68 % respectively. However, the inclusion of nanotubes as high as 10wt% significantly increases the toughness, young’s modulus, and ultimate strength of the fibers. The produced fibers were used to fabricate composites. The fibers involved in the production of the composites were not strain hardened. The maximum average stress-strain values of the composites were used to determine the following: the ultimate tensile strength, young’s modulus, fracture strain, and modulus of toughness of the composites. The experiment results showed that the composite made of 3:1 epoxy hardener, without any fiber, had higher tensile strength and young’s modulus compared to the other type of composites. Composite UHMWPE had higher tensile strength, modulus, fracture strain, and energy absorption compared to the composites with the inclusion of nanotubes. Composite with the presence of surface modifier (POSS) on the surface of the fibers had the lowest tensile strength and young modulus compared to the other type of composites but had about the same fracture strain as composite UHMWPE, and higher energy absorption compared the two other types of composites with the inclusion of nanotubes. An improper bounding between the fibers and the polymer matrix reduces the properties of the composite significantly compared to their respective fibers.

An original design and photolithographic fabrication process for poly(3-hexylthiophene-2, 5-diyl) (P3HT) based organic thin-film transistors (OTFTs) is presented. The structure of the transistors was based on the bottom gate bottom contact OTFT. The fabrication process was efficient, cost-effective, and relatively straightforward to implement. Current–voltage (I-V) measurements were performed to characterize the primary electronic properties of the transistors. The measured mobility of these transistors was significantly higher than most results reported in the literature for other similar bottom gate bottom contact P3HT OTFTs. The higher mobility is explained primarily by the effectiveness of the fabrication process in keeping the interfacial layers free from contamination, as well as the proper annealing of the P3HT. An interface engineering method is investigated to further enhance the performance of the OTFTs. Three interfacial materials were used for this purpose: graphene oxide (GO), poly(oligo (ethylene glycol) methyl ether methacrylate- glycidyl methacrylate- lauryl methacrylate) (P(OEGMA-GMA-LMA)) or POGL, and a composite of GO and P(OEGMA-GMA-LMA) or GO-POGL. The OTFTs with a GO interfacial layer were observed to have a higher drain current and field-effect mobility than the OTFTs with no interfacial layer. The enhanced drain current and mobility are associated with the particular structure of the P3HT layer on the dielectric surface and the reduction in the contact resistance between the GO-covered electrodes and the P3HT. The OTFTs with a POGL interfacial layer were observed to have a smaller threshold voltage than the OTFTs with no interfacial layer. The POGL OTFTs were also observed to have much more ideal drain current saturation characteristics with very small I-V curve slope. This is explained by the deep trap states on the POGL surface and the reduction of the contact resistance at the electrode/organic semiconductor interface. The OTFTs with a GO-POGL composite layer were observed to have a higher drain current and mobility, and a smaller threshold voltage than the OTFTs without an interfacial layer, which is the optimum case for these two device parameters. The higher drain current and field-effect mobility are attributed to the larger interconnecting grains of the P3HT that is deposited onto the GO-POGL surface and the smaller interfacial tension between the GO-POGL and the P3HT. The smaller threshold voltage is attributed to the deep trap states on the GO-POGL layer and the smaller contact resistance between the GO-POGL modified electrodes and the P3HT. Furthermore, experiments that could be performed to advance this research work and enhance the performance of the OTFTs even further are proposed.

Organic materials are promising candidates for future electronic devices compared to the complementing inorganic materials due to their ease of processability, use, and disposal, low cost of fabrication, energy efficiency, and flexible nature toward implementation as flexible and non-conformal devices.With that in mind, electrochemical materials have been widely demonstrated with commercial use as sensors, displays, and a variety of other electronic devices. As Moore's law predicts the increase in the density of transistors on a chip, the requirement to create either smaller transistors or the replacement of the transistor device entirely is apparent. Memory resistors, coined ``memristor", are variable resistive tuning devices that are capable of information processing and data storage in one device. This work focuses on the embodiment of a non-volatile conjugated polymeric electrochemical memristor. Three-terminal memristive systems are fabricated and studied using various electrochemicals (a self-doped PEDOT derivative, a polypyrrole, and a dithienopyrrole derivative) and are tested for their electronic properties and biomimicking capabilities. Optical absorbance properties are studied in order to verify the electrochemical material's redox tuning potential for their respective oxidized and reduced chemical forms. The three-terminal device employed a post-synaptic ``read'' channel where conductivity of the electrochemical material was equated to synaptic weight and was electronically decoupled from the pre-synaptic programming electrode by means of a polymeric gel electrolyte. Basic electronic characteristics are exhibited for these three devices such as state stability and retention, non-volatile voltage-driven conductivity tuning, input parameter characteristic trends, and power consumption per input program. Biological synapses consume, on the order of, 1 - 100 fJ of energy per synaptic energy. The electrochemical materials used in this study, at their most optimized input parameters, were capable of demonstrating a 4.16 fJ/mm2 power consumption per input pulse and lead to a promising candidate for implementation as future artificial neural networks. Biological mimicry was displayed for these devices in the form of paired-pulse facilitation and paired-pulse depression, both a form of short term memory which observes the effect the timescale between two incoming inputs has on the change in the final output signal. Toward the indication for the replacement of transistors with three-terminal memristors, basic circuit operations are achieved and demonstrated for these devices. These operations include both Boolean and elementary algebra, key features that demonstrate data processing and storage in-memory where the physical states of the conjugated polymer film represent either logical statements or arithmetic counting variables. The Boolean algebra demonstrated the use of a single memristive device equal to a variety of single logic gates (AND, NAND, OR and NOR) where, by wiring several devices in series, more advanced combinational logic gates can be achieved. Furthermore, each device was capable of displaying elementary algebra for the basic arithmetic functions of addition, subtraction, multiplication, and division. In regards to thin film deposition techniques, the self-doped PEDOT device employed roll-to-roll gravure printing, a high speed and high resolution commercially used deposition technique. The polypyrrole device was fabricated implementing an in-situ polymerization technique, referred to as vapor phase polymerization, and demonstrated the use of this technique toward non-conformal devices. The dithienopyrrole derivative was polymerized through the same vapor phase polymerization technique as the polypyrrole and used in tandem with screen printing in order to construct the final device, including the oxidant film, the silver electrodes, and the polymeric gel electrolyte.

CO2 released by the combustion of fossil fuels is driving significant changes to the earth’sclimate. The natural cycle for removing CO2 from the atmosphere, namely photosynthesis, cannot keep up with the rate at which it is being added. Developing engineering approaches to remove CO2 from the atmosphere is becoming essential to reduce these effects. Removal leads to further issues of carbon sequestration and favorable CO2 reuse strategies, including the electrochemical transformation of recovered CO2 to useful products such as fuels and materials. Copper is an important electrocatalyst for the CO2 reduction reaction (CO2RR) because of its unique capability for producing a wide range of organic compounds, from carbon monoxide to multi-carbon products such as ethanol, acetate, and ethylene. This research aims to study several aspects of integrated electrochemical CO2 reduction systems, including the effects of catalyst structure and the use of sacrificial oxidative species for converting CO2 to energetic organic molecules. We show that the structure of dendritic copper foam electrocatalysts prepared by high current density electrodeposition can be controlled by the composition of the electrodeposition solution. Multiscale structural characterization shows that simple chemical controls can significantly affect the structure from the nanoscale to the macroscale. Furthermore, we have demonstrated that these structural and morphological differences can affect the product selectivity of the catalyst. In addition, these morphological differences affect the mechanical aspects of electrocatalytic activity, including bubble formation mechanics and detachment, which are important factors in large-scale electrolysis. Towards understanding integrated CO2RR systems, we have also studied electrolysis reactions with reduced overall cell potentials by replacing the water oxidation reaction typically paired with CO2RR and hydrogen evolution with sacrificial glycerol electrooxidation. We have shown that a trimetallic Au-Pt-Bi anode can be used over extended periods to perform two-electron oxidation reactions on glycerol to glyceraldehyde and dihydroxyacetone. We have demonstrated that these reactions reduce the required potential of the electrochemical cell by 1.1 V at practical current densities when compared to a system using the oxygen evolution reaction. Furthermore, by using bipolar membranes to separate the cathode and anode compartments, the advantages of glycerol electrooxidation can be extended to operate opposite a wide range of cathodic reactions. This allows the electrochemical environment for the cathode to be chosen independently from the glycerol electrooxidation environment.

Current orthopedic implants are overwhelmingly composed from metallic materials. These implants show superior mechanical properties, but this can additionally result in stress shielding due to a modulus mismatch between the bone tissue and implanted device. Polymeric implants reduce this stress shielding effect but have much lower mechanical properties, limiting their use. Polylactic acid (PLA) is a widely used biodegradable thermoplastic polymer, however, its use has been limited by the polymer’s mechanical properties and rapid loss of strength during degradation in vivo. Polyether-ether-ketone (PEEK) is another common biocompatible polymer , with chemical and mechanical properties which make it a popular alternative to metallic implants. The ability to 3D print carbon fiber-reinforced PEEK (CFR-PEEK) components with the relatively cheap fused filament fabrication (FFF) process furthers the favorability of this polymer. By incorporating the stronger CFR-PEEK as a reinforcing lattice structure, the properties of biodegradable polymer can be improved. The 3D-printed lattices have been extensively researched, but they have yet to be investigated as the reinforcing component of an overmolded composite. The purpose of this work is to develop a novel overmolded lattice (OML) composite. This was accomplished by first optimizing the print parameters to maximize interlayer adhesion (ILA) using a proposed redesigned tensile specimen. These results were then used to print CFR-PEEK gyroid and then injection overmolded with PLA and characterized via flexural testing. The results of the parameter optimization showed increases in ILA with increased print temperature, print speed, and reduced layer height. The flexural results of the OML showed specific flexural strength (SFS), specific flexural modulus (SFM), and specific energy absorption (SEA), compared to the PLA and the CFR-PEEK gyroid lattice. The overmolded composite was found to have properties comparable to CFR-PEEK and had a SFM (4.3GPa/g) which exceeded all other materials tested. This composite structure has the potential to be integrated in a number of applications to provide highly tailored reinforcement of a weaker polymer matrix.