Chemistry Commons^™

Development Of High-Performing Polydimethylsiloxane-Based Membranes For Carbon Dioxide Separation, Tao Hong

Doctoral Dissertations

Membrane separation is highlighted as one of the most promising approaches to mitigate the excessive CO₂ [carbon dioxide] emission, due to its significant reduction of energy cost compared with many conventional separation techniques. Unfortunately, the separation performance of current membranes does not meet the practical CO₂/N₂ [nitrogen] separation requirements. And due to the huge volume of industrial flue gas, membranes with exceptionally high permeability are needed for practical reasons.

Currently, the separation mechanism of most polymeric membranes is based on size-sieving. However, this method is not sufficient for CO₂/N₂ separations due to the …

Development And Implementation Of Redox-Active Olefin Polymerization Catalysts, William Curtis Anderson Jr.

Doctoral Dissertations

Investigating homogeneous polymerization catalysts has been a thriving area of chemistry in the academic realm for several decades now, and has helped drive the development of a range of materials, from designer plastics to cheap commodity polymers. Billions of pounds of these materials are produced every year, which ensures that continuing research in the area will be necessary to improve current processes and enable more economic use of our resources.

This dissertation showcases the Long group’s research in homogeneous polymerization catalysis and our impact on the field thus far. We show that intelligent design of redox-active catalysts allows for a …

Polyorganosiloxanes: Molecular Nanoparticles, Nanocomposites And Interfaces, Daniel H. Flagg

Doctoral Dissertations

Five research projects described. First, a reproducible, lab-scale synthesis of MQ silicone copolymers is presented. MQ copolymers are commercially important materials that have been ignored by the academic community. One possible reason for this is the difficulty of controlling and reproducing the preparative copolymerizations that have been reported. A reproducible method for lab-scale preparation was developed that controls molecular weight by splitting the copolymerization into the discrete steps of sol growth from silicate precursor and end-capping by trimethylsiloxy groups. Characterization of MQ products implicates that they are composed of highly condensed, polycyclic structures. The MQ copolymers prepared in the first …

Synthesis And Characterization Of Imidazole-Containing Conjugated Polymers, Jared D. Harris

Doctoral Dissertations

Semiconducting conjugated polymers hold tremendous promise as active layers for transformative electronic devices. This materials class benefits from the structural variety provided by organic chemistry such that highly tunable band structures are attainable for as-synthesized polymers. This dissertation describes the synthesis and characterization of novel imidazole-containing conjugated polymers for the purposes of (de)protonating the as-synthesized materials gaining conjugated poly(ionomer)s. (De)protonation easily enables band structure modification through manipulation of the materials’ ionization potential and electron affinity. Controlled exposure to acids and bases led to reversible (de)protonation observable via UV-visible and photoluminescence spectroscopies. (De)protonation’s effects on polymeric band structures was empirically and …

Synthesis, Characterization, And Reactive Modification Of 2-Vinyl-4,4-Dimethyl Azlactone Polymers, Bethany Michelle Aden

Doctoral Dissertations

Polymeric materials possessing specific functionality have been designed for use in applications such as membranes, biocompatible coatings, lubricants, and tissue engineering. Because the chemical nature of the repeat units set the properties offered by the polymer, the ability to reactively modify polymer chains to integrate specific functionality expands the range of potential applications. Thus, reactive modification of polymer thin films provides a useful route to confer new properties to the underlying material, with the range, strength and type of interaction across the interface dictated by the display of functional groups decorating the surface. To address the links between design, in …

Stimuli Responsive Polymeric Nanogels For Hydrophobics & Hydrophilics Delivery, Kishore Raghupathi

Doctoral Dissertations

Stimuli responsive nanoparticles have gained significant interest in the drug delivery research. The essential goal of drug delivery is to improve the efficacy of drugs by increasing their stability and bioavailability. Small molecule hydrophobic drugs face limited bioavailability due to their poor water solubility. Biologic drugs on the other hand, lack bioavailability because of their degradation by various enzymes encountered during blood circulation. For a systemic delivery approach, depending on site of drug action, delivery vehicles must pass through several contrasting micro environments before delivering the cargo selectively at the target site. Therefore, it is essential that a delivery vehicle …

Effect Of Crosslinking On Carbon Nanotube Materials Through Chemical Treatment And Irradiation, Xinyi Lu

Doctoral Dissertations

Carbon nanotubes (CNTs) exhibit a variety of exceptional properties, especially their ultrahigh tensile strength on the order of 100GPa show promise for constituting the next-generation carbon fiber. However, challenges remain to translate these properties into useful technology, primarily due to the sliding of the tubes past one another under tensile loading. The work presented in this dissertation is focused on enhancing the interaction between the CNTs and their bundles in a macro-assembly, in order to improve the tensile properties of the material.

Applying inter-tube crosslinks has been predicted to significantly enhance the stress transfer between the CNT components. We developed …

Design-Structure-Property Relationships Of Purine-Based Copolymers And Chromophores, Graham Smith Collier

Doctoral Dissertations

Understanding the relationship between monomer design and polymer properties is imperative for developing polymeric systems that can find applicability in targeted technologies. Purines have been extensively studied across many scientific disciplines and are useful due to the diverse properties they possess, which is due in part to the broad scope of precise synthetic transformations that are used to tailor their properties. The overarching goal of my dissertation involves developing the synthesis of “poly(purine)s” and investigating the effect of purine monomer design on polymer properties. In this vein, poly(purine)s and purine-based donor-acceptor small-molecules are synthesized via Stille cross-coupling reactions with a …

Thermally Robust And Redox Active Catalysts: Studying Their Behavior For Ethylene And L-Lactide Polymerization, Lauren Ashley Brown

Doctoral Dissertations

The development of homogenous single-site catalysts has significantly impacted the field of organometallic chemistry. The well-defined structures of homogenous catalysts make it less cumbersome to understand and develop methods to tailor these compounds for specific catalytic processes. Currently, polymerization catalysis is a major division in organometallic chemistry due to the global demand for polymeric materials such as polyethylene (PE) and polypropylene (PP), based on their low-cost feedstock, remarkable mechanical properties, and their use in a wide range of applications. However, bioplastics have become a highly sought-after alternative to conventional petrochemical-based plastics due to their biodegradability and derivatization from renewable resources. …

Hetero-Atom Containing Functional Polymers: Synthesis, Characterization And Applications, Hongbo Feng

Doctoral Dissertations

A mission to manage ever increased energy demands and reduce carbon foot print has challenged scientists and engineers to develop new materials with superior characteristics. In this scenario, lithium-ion batteries have been the dominating technology for not only applications in consumer electronics but also are essential for clean energy storage. On the other hand, the capture and separation of CO₂ [carbon dioxide] in power generation and in industrial processes is considered to be a key to reduce the carbon footprint.

Living anionic polymerization along with controlled polymerization techniques has realized the preparation of a wide variety of functional polymers …

Development Of High Performance Gas Separation Membranes Through Intelligent Catalyst And Monomer Design, Kevin Richard Gmernicki

Doctoral Dissertations

Polymer membranes are a valuable tool for separating components of liquid and gas mixtures. Heavily inspired by biological systems, the idea of using the intrinsic properties of polymers to perform otherwise energy-intensive tasks is attractive for applications such as water desalination, natural gas sweetening, and post-combustion carbon capture. Of particular interest to our research group, post-combustion carbon capture is a promising potential solution aimed at reducing the carbon footprint involved with production, transportation, and storage of electrical energy generation.

Every year, the United States produces close to seven billion metric tons of carbon dioxide, of which a significant portion is …

Impact Of Macromolecular Design On Self-Assembly Properties Of Block Copolymers: Effect Of Tunable Chain Flexibility And Chain Topology, Kamlesh Ramesh Bornani

Doctoral Dissertations

The generation of well-ordered complex structures from constituent block copolymeric building blocks by the spontaneous process of self-assembly is useful in various technologies. The well-defined 3D structures are dictated by complex energetic interplays and their shape is controllable by both preparative conditions and macromolecular design. This dissertation work aims at exploring the effect of chain flexibility and chain topology design changes on phase behavior of block copolymers in solution. Further, we exploit the tunable flexibility of the semiflexible polymers in studying dispersion and controlling macroscale thermal properties in polymer nanocomposites.

The experimental design is based on two model systems: The …

All Acrylic Based Thermoplastic Elastomers: Design And Synthesis For Improved Mechanical Performance, Wei Lu

Doctoral Dissertations

Thermoplastic elastomers (TPEs) have been widely studied because of their recyclability, good processability, low production cost and distinct performance. Compared to the widely-used styrenic TPEs, acrylate based TPEs have potential advantages including exceptional chemical, heat, oxygen and UV resistance, optical transparence, and oil resistance. However, their high entanglement molecular weight lead to “disappointing” mechanical performance as compared to styrenic TPEs. The work described in this dissertation is aimed at employing various approaches to develop the all acrylic based thermoplastic elastomers with improved mechanical performance.

The first part of this work focuses on the introduction of acrylic polymers with high glass …

Thiol-Ene Chemistry As An Enabler Of New Polymer Structures And Architectures, Joel M. Sarapas

Doctoral Dissertations

This dissertation focuses on two distinct projects: the synthesis and design of novel cell penetrating peptides mimics (CPPMs), and the implementation of the thiol-ene click reaction to generate new polymer architectures and chemistries. Guanidinium-rich CPPMs were generated through both ROMP and RAFT polymerizations, allowing for a comparison to be made across polymer backbone chemistries with respect to both siRNA and protein cellular internalization. A particularly effective methacrylate derived block copolymer was able to deliver siRNA to nearly an entire Jurkat T cell population. The thiol-ene reaction was implemented initially within the context of improving material design for solid polymer electrolytes …