Engineering Commons^™

Harnessing Nanocellulose For Sustainable Carbon Capture: Synthesis, Processing, And Performance Evaluation, Jerred C. Wassgren

Doctoral Dissertations

Scientists and governments have recognized the need for environmental remediation, most notably with the adoption of the Paris Agreement in 2016. One of the major concerns is the production of greenhouse gases (GHGs). The major GHG is carbon dioxide (CO₂) in which humans emit over 36 gigatons yearly. Atmospheric CO₂ is responsible for 60% of the heat retained by the earth – resulting in rising temperatures, melting ice caps, and increasing ocean acidification. Therefore, a major goal of the Paris Agreement was to reduce GHG emissions as well as the capture of CO₂ from the atmosphere. …

Polyesters Derived From Biobased 1,5-Pentanediol For Coatings, Adhesives, And Biodegradable Plastics, Lei Zheng

Doctoral Dissertations

Biomass-derived polymers are drawing increased attention from researchers due to unique performance attributes, potential for biodegradability, new low-cost feedstocks, and improved sustainability. Biobased feedstocks are employed in both major applications of polymers thermosets and thermoplastics. For thermoset coatings and adhesives, biobased resins such as biobased alkyds, epoxy resins, benzoxazine resins, starch derivatives, and proteins from plants and animals, are promising candidates to replace petroleum-derived counterparts. Thermoplastics such as polyethylene are mainly produced from fossil resources, generally have poor degradability and are difficult to effectively recycle. Currently, in the United States, less than 10% plastics are recycled, and more than 70% …

Polymer Based Energy Storage And Thermal Management On Textile Devices, Wesley A. Viola

Doctoral Dissertations

Humans developed textiles to manage thermal energy transfer with the environment and support homeostasis in a wide range of climates. With the anticipation of wearable technologies to transform healthcare via early, pre-symptomatic detection of illness, there is now a demand for electrical energy storage to support such on-body devices. Finding energy materials to merge seamlessly with textiles is basic requirement to ensure widespread adoption of wearable health monitors. Here we use a vapor deposition process to conformally coat ordinary fabrics with the doped conjugated polymer poly(3,4 ethylenedioxythiophene) (PEDOT-Cl), a soft material which possesses electronic and redox capabilities. We demonstrate PEDOT-Cl …

Effect Of Chemical Identity And Morphology On Amphiphilic-Zwitterionic Block Copolymer Membranes, Ria Ghosh

Doctoral Dissertations

Amphiphilic block copolymers have gained a broad research interest attributed to their self-assembly properties over a range of pH, temperature, and ionic strength. Polyzwitterions have attracted special attention due to their hydrophilicity, charge sensitivity and coulombic attraction of the opposite charges over a range of environments making them a popular material of study in the field of stimuli responsive systems, for example in self-healing hydrogels, and water transport membranes. Combining the stimuli responsiveness and higher hydrophilicity of zwitterionic polymers with self-assembly behavior of amphiphilic block copolymers created an interest to study the effect of composition and identity of the zwitterionic …

Analysis Of Physicochemical Properties And Terrestrial Dynamics Of Mechanically Formed Micro-Nano Scaled Particles From Agricultural Plastic Mulches, Anton Friedrich Astner

Doctoral Dissertations

Release of microplastics (MPs) and nanoplastics (NPs) into agricultural fields is of great concern due to their reported ecotoxicity to organisms that provide beneficial service to the soil such as earthworms, and the potential ability of MPs and NPs to enter the food chain. Most fundamental studies of the fate and transport of plastic particulates in terrestrial environments employ idealized MP materials as models, such as monodisperse polystyrene spheres. In contrast, plastics that reside in agricultural soils consist of polydisperse fragments resulting from degraded films employed in agriculture. There exists a need for more representative materials in fundamental studies of …

Confinement And Interface Effects In Self Assembly Of Functional Block Copolymers, Jonathan P. Coote

Doctoral Dissertations

Functional block copolymers are of increasing interest for their ability to combine the functional properties of one polymer, such as a polymer electrolyte or semiconductor, with the mechanical properties of another polymer. Balancing properties in this way can be challenging, however, due to the complex relationship between self-assembled morphology and resulting properties. Interface effects in particular, whether due to confinement within a self-assembled domain or at macroscopic boundary, are poorly understood in such functional block copolymers. This dissertation consists of two main thrusts, each investigating confinement or interfacial effects in a different functional block copolymer system. The first thrust focuses …

Synthesis And Assembly Of Polymer Materials At Interfaces, Xiaoshuang Wei

Doctoral Dissertations

The overarching goal of the thesis is to understand growth and assembly of polymer materials at interfaces. Chapter 2 and Chapter 3 study simultaneous polymer growth and assembly at fluid interfaces, where in-situ photopolymerization and vapor phase deposition were utilized to grow polymers, respectively. Chapter 4 leverages capillary condensation to pattern polymer growth at solid substrates. Chapter 1 provides background information on polymer materials at interfaces, and vapor phase deposition method (initiated chemical vapor deposition, iCVD) to grow polymers. This chapter also reviews polymer thin film wetting, and colloidal assemblies at interfaces. In Chapter 2, we demonstrate the preparation …

Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian

Doctoral Dissertations

The self-assembly of charged macromolecules forms the basis of all life on earth. From the synthesis and replication of nucleic acids, to the association of DNA to chromatin, to the targeting of RNA to various cellular compartments, to the astonishingly consistent folding of proteins, all life depends on the physics of the organization and dynamics of charged polymers. In this dissertation, I address several of the newest challenges in the assembly of these types of materials. First, I describe the exciting new physics of the complexation between polyzwitterions and polyelectrolytes. These materials open new questions and possibilities within the context …

Functional Bottlebrush Polymer Additives For Thin Films And Coatings, Travis S. Laws

Doctoral Dissertations

Bottlebrush polymers are a class of highly branched polymers consisting of polymeric side chains that are densely grafted to a linear backbone. Their highly branched architecture results in surface enrichment across a broad range of materials. The goal of my research has been centered around the design of functional bottlebrush polymers and their use as surface active additives in blend films and coatings.

In the first chapter, we examine the segregation behavior of polystyrene bottlebrushes that are blended with linear polystyrene. We systematically vary the lengths of the bottlebrush backbone (Nb), side-chain (Nsc), and the linear matrix (Nm) in order …

Crowd Control: Regulating The Spatial Organization Of Biopolymers And Gene Expression By Macromolecular Crowding, Gaurav Chauhan

Doctoral Dissertations

The intracellular environment is crowded with macromolecules that can occupy a significant fraction of the cellular volume. This can give rise to attractive depletion interactions that impact the conformations and interactions of biopolymers, as well as their interactions with confining surfaces. We used computer simulations to study the effects of crowding on biologically-inspired models of polymers. We showed that crowding can lead to attractive interactions between two flexible ring polymers, and we further characterized the adsorption of both flexible and semiflexible polymers onto confining surfaces. These results indicate that crowding-induced depletion interactions could play a role in the spatial organization …

Biomass Conversion To Bio-Derived Materials And Their Applications, Luna Liang

Doctoral Dissertations

Nowadays, fossil fuels still serve as the primary global energy resource. Replacing fossil fuels with renewable sources of energy and developing efficient energy storage technology is an urgent problem to solve. Lignocellulosic biomass has been investigated as a promising alternative for the production of biofuels, chemicals, and materials. In this dissertation, we studied the thermochemical biomass conversion strategies via different pretreatments strategies (e.g. dilute acid, ethanol, tetrahydrofuran, gamma-valerolactone) and genetic modification to overcome the biomass recalcitrance and achieve efficient conversion process. The biomass component structure of lignin and cellulose after thermal treatments were characterized and analyzed.

To further explore the …

Oligodimethylsiloxanes With Charged Chain Ends: Synthesis, Characterization, And Properties, Tianyu Li

Doctoral Dissertations

Charged polymers have been intensively studied because of their scientific and industrial importance. In certain cases, a single charged group in the chain end can alter the structure and properties of a polymer dramatically. On the other hand, oligomers, which are different from both discrete small molecules and higher molecular weight polymers, have become an emergent class of materials. There are several charged chain-end functionalized oligomers reported, but this area has been largely unexplored. The work described in this dissertation is aimed at using well-characterized end-group functionalized oligodimethylsiloxane (oDMS) as model materials to understand the effects of charged end groups …

Accelerated Catalyst Diffusion In Chemically Amplified Resists, Christopher M. Bottoms

Doctoral Dissertations

Quantitative reaction-diffusion models are critical for the development of high-resolution lithographic processes based on chemically amplified resists (CARs). CARs consist of a glassy polymer resin with a photoacid generator. Patterns are formed through a coupled reaction-diffusion process. It is known that reaction kinetics is controlled by the slow diffusion of acid-anion pairs (catalysts), and catalyst diffusion lengths partly control the pattern resolution and uniformity. However, it is difficult to quantify the diffusivity during reaction, let alone examine the roles of polymer-ion and ion-ion interactions on catalyst mobility, using direct measurements. This work presents a concerted experimental and computational effort to …

Modeling Chain Packing In Complex Phases Of Self-Assembled Block Copolymers, Anugu Abhiram Reddy

Doctoral Dissertations

Block copolymer (BCP) melts undergo microphase seperation and form ordered soft matter crystals with varying domain shapes and symmetries. We study the con- nection between diblock copolymer molecular designs and thermodynamic selection of ordered crystals by modeling features of variable sub-domain geometry filled with individual blocks within non-canonical sphere-like and network phases that together with layered, cylindrical and canonical spherical phases forms “natural forms” of self- assembled amphiphilic soft matter at large. First, we present a model to revise our understanding of optimal Frank-Kasper sphere-like morphologies by advancing the- ory to account for varying domain volumes. We then develop generic …

New Isomeric Silicones: Synthesis, Compositions And Surface Properties, Yan Cong

Doctoral Dissertations

This dissertation presents research performed in the field of silicone polymer science, which refers to polymers with alternating silicon-oxygen backbones. Three research topics will be explored. The first topic involves the synthesis of trimethylsiloxysilsesquioxane (MT) copolymers with vinyl and hydride functionalities as reactive liquid silicone precursors. The second topic describes titration of dimethylsiloxy (D) composition into trimethylsiloxysilsesquioxane (MT) copolymers for the purpose of controlling the mechanical properties and thermal stabilities of the material. The last topic explores the modification of hydrophobic silicone surfaces with oxygen plasma to form silica-like, hydrophilic surfaces and the behaviors of hydrophobic recovery. The first chapter …

Development Of Crosslinking Technologies For Waterborne & Powder Coatings, Mengfei Huang

Doctoral Dissertations

Waterborne coatings and powder coatings are fast-growing sectors of the world coating market due to their environmentally friendliness as they have low or zero volatile organic compounds (VOCs) emission. However, compared with solventborne coatings, significant limitations need to be overcome to enable their broad applications. My dissertation will discuss several novel crosslinking strategies for waterborne and powder coating that could enable curing on-demand at ambient conditions, with facile polymerization and easy processing, and ultimately, exhibit a high degree of crosslinking and excellent performance that is comparable to solventborne coatings. We introduced and demonstrated the anionic polymerization mechanism and the high …

Structural Stability Of Thermosets During Material Extrusion Additive Manufacturing, Stian K. Romberg

Doctoral Dissertations

Over the past decade, the scale of polymer additive manufacturing has been revolutionized with machines that print massive thermoplastic parts with greater geometric complexity than can be achieved by traditional manufacturing methods. However, the heat required to print thermoplastics consumes energy and induces thermal gradients that can reduce manufacturing flexibility and final mechanical properties. With the ability to be extruded at room temperature and excellent compatibility with fibers and fillers, thermoset resins show promise to decrease the energy consumption, expand the manufacturing flexibility, and broaden the material palette offered by large-scale polymer additive manufacturing. However, structural instability in the uncured …

Advanced Materials Design Using Application-Based Processing Techniques, Daniel S. Camarda

Doctoral Dissertations

This dissertation pertains to generating advanced materials using application-based processing techniques. First, billets consisting of PTFE sintering powders are evaluated using Thermomechancal Analysis. It was found that both shape change and volume change are associated with enthalpic and entropic recoil, respectively. These phenomena, due to melting and stored energy during the powder compaction process, were found to be molecular weight dependent. Additionally, kinetics of the recovery and sintering process were found to be slower in blended specimens than pure samples. Next, the creation of graft copolymers by selectively grafting a second polymer to the amorphous fraction of a semi-crystalline polymer …

Characterization Techniques And Cation Exchange Membrane For Non-Aqueous Redox Flow Battery, Kun Lou

Doctoral Dissertations

The motivation of this work comes from one of the major problems of emerging non-aqueous flow battery (NAFB) that a separator or membrane which facilitates conductivity and blocks redox species crossover does not exist. Although many aspects of principles can be mirrored from mature fuel cell and aqueous flow battery, it is found that some well-defined membrane properties in aqueous systems such as swelling, transport and interactions are different in non-aqueous solvents to some extent. However, the approach of this work does follow the way perfluorosulfonate ion exchange membrane (PFSA) facilitated development of fuel cell and aqueous flow battery in …

Direct Printing/Coating/Plating Of Key Components For Electronic Devices, Xiyu Hu

Doctoral Dissertations

Miniaturization has been a technological trend for several decades for electronic devices. From the practical point of view, the successful miniaturization of fully integrated systems mainly depends on their components. This dissertation examines the inkjet printing of copper oxide inks on flexible substrates for applications in microfluidic valving systems. We expand the knowledge of low-cost and high-performance electrowetting valves and fabricate the microfluidic device for fluidic control, which is necessary to enable the next-generation microfluidic devices. In addition, we also study the electromagnetic interference (EMI) shielding material, which is a crucial part of electronic devices. The basic theory of EMI …

Surface Modification Of Cellulose Nanocrystals: Imparting Non-Native Properties On Sustainable Substrates, Allen C. Chang

Doctoral Dissertations

Governments and scientists all over the planet have recognized the importance of pursuing and achieving sustainability. As the human population grows and technologies advance, the planet’s limited resources become less and less able to support our taxing demands. In 2015, the United Nations set forth 17 Sustainable Development Global Goals. Goal 12 “Responsible Production and Consumption” can be addressed quite readily by the integration of sustainable materials into advanced technologies; however, such materials have yet to be developed. Cellulose nanocrystals (CNCs) – an abundant, well-known sustainable nanomaterial hydrolyzed from bulk cellulose with high surface functionality and high strength properties – …

Stretching The Applications Of Biomass: Development Of Lignin Based Thermoplastic Elastomers And Composite Materials, Anthony Stephen Bova

Doctoral Dissertations

Bio-based plastics and composites have seen increased industry adoption in recent years due to growing demand for materials with a low carbon footprint. The use of lignin as a feedstock for polymers has seen growing interest as the concept of an integrated cellulosic biorefinery gains traction and advances the need to use all components of separated biomass for value-added applications. Historically, use of lignin in thermoplastic and elastomeric copolymers and blends has been bottlenecked by the inability to introduce lignin content above 30 weight percent due to difficulties with interfacial adhesion of lignin with other soft segments. Efforts to overcome …

Unraveling The Effects Of Molecular Confinement On The Dynamics Of Polymeric Systems: I. Block Copolymer Architecture Ii. Silica Nanopores, Thomas P. Kinsey

Doctoral Dissertations

In this dissertation, broadband dielectric spectroscopy (BDS) is employed as an experimental tool to probe dipolar relaxations in polymeric systems under two types of molecular confinement. First a series of miktoarm star copolymers are used to explore how branching block copolymer architectures constrain polymer relaxations within self-assembled domains in relation to linear systems. Secondly, the effects of hard spatial confinement on the dynamics of polymer chains and of ions in polymerized ionic liquids (PILs) are studied after infiltration into silica nanochannels. Complementary techniques such as transmission electron microscopy, small angle x-ray scattering, and Raman spectroscopy are used to determine various …

Synthesis Of Inorganic Porous Materials With Tunable Morphology For Molecular Adsorption And Separation, Sanket Sabnis

Doctoral Dissertations

Global industrial and economic development over the past century has largely relied on combustion of non-renewable fossil fuels, such as petroleum, coal, and natural gas, which are also harmful to environment because of the release of CO₂, responsible for global warming and climate change. Establishing eco-friendly, energy-efficient and cost-effective processes to reduce environmental impact is currently one of the most urgent issues for the sustainable development of our society. Inorganic porous materials have found applications in the fields of renewable energy and environmental protection such as biomass conversion, fuel cells, thermal energy storage, CO₂ capture and conversion, …

Electrospinning Fibers Via Complex Coacervation, Xiangxi Meng

Doctoral Dissertations

Electrospun fibers are high-surface-area materials widely used in applications ranging from batteries to wound dressings. Typically, an electrospinning precursor solution is prepared by dissolving a high-molecular-weight polymer in an organic solvent to form a sufficiently entangled solution. Our approach bypasses the requirement for entanglements and completely avoids toxic chemicals by focusing on using an aqueous complex coacervates solution. Coacervates are a dense, polymer-rich liquid phase resulting from the associative electrostatic complexation of oppositely charged macroions. We were the first to demonstrate that liquid complex coacervates could be successfully electrospun into polyelectrolyte complex (PEC) fibers. A canonical coacervate system was formed …

Nano- And Micro-Structured Temperature-Sensitive Hydrogels For Rapidly Responsive Devices, Qi Lu

Doctoral Dissertations

This thesis aims to extend the understanding and explore the application of temperature-responsive hydrogel systems by integrating microelectromechanical systems (MEMS). Stimuli-responsive hydrogel systems are immensely investigated and applied in numerous fields, and interfacing with micro- and nano-fabrication techniques will open up more possibilities. In Chapter 2, the first biologically relevant, in vitro cell stretching device based on hydrogel surface instability was developed. This dynamic platform is constructed by embedding micro-heater devices under temperature-responsive surface-attached hydrogels. The fast and regional temperature change actuates the stretching and relaxation of the seeded human artery smooth muscle cell (HASMC) via controllable surface creasing instability. …

Sequence Control Of Complex Coacervation, Li-Wei Chang

Doctoral Dissertations

Complex coacervation is a liquid-liquid phase separation driven by the complexation of oppositely charged polyelectrolytes. The resulting coacervate phase has been used for many applications, such as underwater adhesives, drug delivery, food and personal care products. There also has been increasing interest in coacervate-like droplets occurring in biological systems. The majority of these “membraneless organelles” involve a combination of intrinsically-disordered proteins and RNA, and phase separate due to long-range charge effects and short-range hydrophobic effects. While evolution has optimized the self-assembly of these types of biological polymers, our ability to design such materials remains limited, in part because the relevant …

Kinetics Of The Crystal-Melt Phase Transformation In Semicrystalline Polymers, Kiran Subramaniam Iyer

Doctoral Dissertations

The assembly of long-chain polymers into an ordered state is a process that has puzzled polymer scientists for several decades. A process that is largely controlled by the strength of intermolecular attractions in small molecular systems, this crystallization in the case of polymers is controlled by a competition between the aforementioned force of attraction between monomers and the formidable conformational entropy of polymer chains. Any factor that affects this conformational entropy, whether that is an equilibrium thermodynamic factor or a kinetic factor, has the ability to control polymer crystallization. In this thesis, we focus on understanding the underlying kinetic processes …

Characterizing Non-Linear Structural, Mechanical, And Volumetric Properties Of Aliphatic And Aromatic Thermosets, Brendan Robert Ondra

Doctoral Dissertations

A unifying theme throughout this dissertation employs advanced experimental mechanics, including the design and development of new instruments, testing techniques, and analysis strategies. Chapter 1 covers the design and development of a new instrument for polymer and composite characterization. More specifically, a bi-fluidic, confining-fluid, pressurizable dilatometer (referred to herein as the BFCF-PVT). Whereas both classical and contemporary confining-fluid type pressurizable dilatometers utilize a bellows and / or piston system along with a Linear Variable Displacement Transducer to apply pressure and track volume changes, the BFCF-PVT that was designed and built utilizes a fluid-fluid interface (composed of two immiscible fluids that …

Surface Driven Flows : Liquid Bridges, Drops And Marangoni Propulsion, Samrat Sur

Doctoral Dissertations

Molecules sitting at a free liquid surface against vacuum or gas have weaker binding than molecules in the bulk. The missing (negative) binding energy can therefore be viewed as a positive energy added to the surface itself. Since a larger area of the surface contains larger surface energy, external forces must perform positive work against internal surface forces to increase the total area of the surface. Mathematically, the internal surface forces are represented by surface tension, defined as the normal force per unit of length. One common manifestation of surface tension is the difference in pressure it causes across a …