Doctor of Philosophy, The Ohio State University, 2022, Chemistry

Two-dimensional materials are a huge field of study owing to the many uses of the materials and the utility they offer in being easily tunable through processes such as functionalization, alloying, and exfoliation. Herein several families of 2D materials will be discussed regarding how altering the base materials can result in the controlled tuning of properties and emergence of new phenomena. One such family of materials are the Xenes. This large family of materials in unique in that a terminal ligand on every atom in the framework is required for stability. The identity of the terminal ligand can be used to control the optical, electrical, and thermal properties of the Xene. Chapter 1 discusses the developed chemical methods used to functionalize Xenes. Additionally, the significant influence of the ligand identity on electronic structure, optical properties, and thermal stability is discussed in detail. The Xene family allows for the systematic exploitation of properties and phenomena resulting from use of surface functionalization with 2D materials. Further exploration of the group 14 graphene analogues Xene materials is examined in Chapter 2. All these analogue materials require surface ligand termination on every atom for stability. In this chapter it is explored how altering the ligand identity can result in nonobvious interactions with other chemical species. Using x-ray diffraction, Fourier transform infrared spectroscopy, and thermal gravimetric analysis it is shown that the reversible intercalation of water occurs in methyl-terminated germanane, GeCH3, but not with hydrogen-terminated germanane, GeH. Molecular dynamics and density functional theory simulations predict that a dative interaction occurs between water and the Ge−C σ* pocket of the Ge framework resulting in local structural distortions. An above bang gap 1.87 eV luminescence with an average lifetime of hundreds of picoseconds is a result of the distortion in the Ge framework. The intercalatio (open full item for complete abstract)

Committee: Joshua Goldberger (Advisor); Casey Wade (Committee Member); Patrick Woodward (Committee Member) Subjects: Chemistry

Doctor of Philosophy, Miami University, 2021, Chemistry and Biochemistry

Construction of well-defined polyurethane dendrimers is challenging due to the high reactivity of externally added or in-situ formed isocyanates leading to the formation of side products. For this reason, the synthesis of dendritic polyurethanes is limited to very few reports. With a primary focus of dendrimer research on the interaction of the periphery and the core, we report the synthesis of a common polyurethane dendron, which allows for late-stage variation of both the periphery and the core. The periphery can be varied simply by installing a clickable unit in the dendron and then attaching to the core and vice-versa. Thus, a common dendron allows for varying both the periphery and the core in the final two steps. To accomplish this, protecting-group-free one-pot multicomponent Curtius reaction was utilized to afford a robust and versatile AB2 type polyurethane dendron employing commercially available simple molecules 5-hydroxyisophthalic acid, 11-bromoundecanol, and 4-penten-1-ol (or 4-pentyn-1-ol). Subsequent late-stage modification of either dendrons or dendrimers via thiol-ene or azide-alkyne click reaction gave surface-functionalized alternating aromatic-aliphatic polyurethane homodendrimers to generation-three (G3). A bifunctional AB2 type dendritic monomer demonstrated this approach's versatility by undergoing a click reaction followed by attachment to the core or attachment to the core followed by click reaction at the periphery to generate surface-functionalized polyurethane dendrimers. This approach enables the incorporation of functionalities at the periphery and the core that may not withstand the dendrimer growth for the synthesis of polyurethane dendrimers and other dendritic macromolecules. While 1-octanethiol was used in the late-stage modification of G1-G3 dendrimers using thiol-ene click chemistry, organic azides (7-diethyl-3-azidocoumarin, 9-azido-2,3,5,6-tetrahydro-1H, 4H-11-oxa-3a-aza-benzo[de]anthracene-10-one, and 4-azido-N-ethyl-1, (open full item for complete abstract)

Committee: Richard Taylor PhD, Professor (Advisor); C. Scott Hartley PhD, Professor (Committee Chair); Dominik Konkolewicz PhD, Associate Professor (Committee Member); David Tierney PhD, Professor (Committee Member); J. Andrew Jones PhD, Assistant Professor (Other) Subjects: Organic Chemistry

Master of Science in Biomedical Engineering, Cleveland State University, 2020, Washkewicz College of Engineering

This thesis describes a comprehensive study on the complexation of single-wall carbon nanotubes (SWCNTs) with biopolymers via noncovalent and covalent approaches as well as the characterization of the resulting complexes. SWCNTs are unique, one- dimensional nanocylinders that are highly attractive for surface modification because all their atoms comprise a surface. Specifically, single-chirality SWCNTs functionalized with biomolecules are excellent candidates for applications in bioimaging, biochemical sensing, and drug delivery. Here, we investigated the complexation affinity of recognition sequences of single-stranded DNA (ssDNA) with SWCNTs. We utilized the optical modulation of ten chirality-pure SWCNTs to study the kinetics of the coating displacement of ssDNA by a strong surfactant. Unique changes were observed for DNA- SWCNTs hybrids upon surfactant exchange, including distinct reaction time constants ranging from 9 s to 230 s and an increase in photoluminescence ranging from 1.3 to 14.7- fold. Additionally, DNA-wrapped SWCNTs showed unique interaction behavior and stability in cell culture medium. The CTC3TC-(7,6) hybrid exhibited the largest time constant upon surfactant-exchange and was the only hybrid to show an increase in near- infrared (NIR) fluorescence intensity in serum-containing cell culture medium. Moreover, we explored covalent functionalization of chirality-pure SWCNTs via oxygen doping and oriented immobilization of disaccharide lactose-containing glycopolymers. We observed a strong dependence on oxygen doping on surface-coatings of nanotubes when exposing various aqueous dispersions of SWCNTs to short wavelength ultraviolet (UV) light. Our results provide a foundation for future development of applications for chirality-pure SWCNTs in biochemical sensing and imaging advancement. Successful completion of the covalent functionalization of SWCNTs with lactose-containing glycopolymers will lead to the creation of engineered multicolor, fluorescen (open full item for complete abstract)

Committee: Geyou Ao (Advisor); Xue-Long Sun (Committee Member); Moo-Yeal Lee (Committee Member) Subjects: Biomedical Engineering; Chemical Engineering

Master of Science (MS), Ohio University, 2020, Mechanical Engineering (Engineering and Technology)

This study evaluated the functionalization of bituminous and sub-bituminous coals via acid and hydrogen peroxide routes to improve interfacial adhesion in coal-plastic composites. Three coals were studied, including Pittsburgh No. 8, Kittanning, and Powder River Basin. Boehm analysis and Fourier-transform infrared spectroscopy were used to study coal surface chemistry. Additionally, the interactions (esterification) between the coal's hydroxyl functional groups and graft-maleic anhydride on four different coupling agents were studied. An investigation of the effect of coal filler content (0-60 wt.%) and coupling agent content (0-3 wt.%) on the tensile and flexure properties of the material was conducted. When the coupling agent was added, the greatest improvement in mechanical properties occurred at 60 wt.% coal content and 3 wt.% coupling agent (maleic anhydride grafted-polypropylene) content.

Committee: Jason Trembly (Advisor); Kerrti Kappagantula (Committee Member); Frank Kraft (Committee Member); Peter Harrington (Committee Member) Subjects: Materials Science; Mechanical Engineering

Doctor of Philosophy, University of Akron, 2019, Polymer Science

Scale-up of end-functionalized poly(propylene fumarate) for academic and industrial research. Scale-up of poly(propylene maleate) (PPM) and poly(propylene fumarate) (PPF) was investigated to examine the control of polymer molecular mass properties, adverse side reactions, and end-group fidelity. Two batches of PPM were synthesized at reaction sizes greater than 100 grams using a round-bottom flask with yields exceeding 90% and narrow molecular mass distributions (DM) below 1.3. Polymerization and isomerization conditions were developed for increasing the reaction size to 5000 grams using a 20-liter process reactor, and yields remained above 80% and DM below 1.4. 1H NMR spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS) confirmed end-group fidelity and preservation of the propargyl alcohol initiator under scale-up conditions. This project demonstrates the feasibility of the scale-up and commercialization of PPF and provided material to collaborators for research. Surface availability and dispersal of Bioglass 45S5 in 3D printed poly(propylene fumarate) for bone tissue regeneration. Poly(propylene fumarate) (PPF) shows potential as a material in implantable devices for bone defect repair as it can be 3D printed into degradable scaffolds. The mild hydrophobicity, lack of cell attachment moieties, and osteogenic signals of untreated PPF scaffolds hinders their well-studied osteoinductive properties to aid in bone tissue regeneration. To address this issue, these scaffolds may be coated with both serum albumens and functionalized with tethered whole growth factors or bioactive short peptides ligands. We have previously presented a method of tethering ligands that requires a bioactive ceramic (45S5 Bioglass) be incorporated into PPF resins. However, for this surface functionalization strategy to have success, sufficient Bioglass must present at the surface of 3D printed PPF scaffolds. Our Bioglass-based surface (open full item for complete abstract)

Committee: Matthew Becker (Advisor); Junpeng Wang (Committee Chair); Chrys Wesdemiotis (Committee Member); Eric Amis (Committee Member); Rebecca Willits (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Chemistry; Materials Science; Plastics; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2019, Polymer Science

Effect of surface chemistry on chondrocyte phenotype maintenance using molecular concentration gradients. Tissue-engineered cartilage has the potential to address many of the issues surrounding osteoarthritis. However, a significant remaining challenge is the development of a feasible cell expansion process that preserves the chondrogenic phenotype. Chondrocytes rapidly undergo dedifferentiation during the ex vivo expansion in monolayer cultures. Herein, we have investigated the effects of various concentrations of surface chemical groups on chondrocyte behavior. The proliferation and phenotype maintenance of primary human chondrocytes were measured on continuously variable one-dimensional gradients substrates. The gradient approach provides a fast, efficient, and reliable strategy by incorporating a series of concentrations in a single substrate. Primary human chondrocyte density and viability were studied on amine- and hydroxyl-terminal functional groups. After 7 days of culture, cell numbers were found to reach maximum density at higher surface concentrations on hydroxyl-functionalized gradients, while the maximum density was related to lower surface concentrations on amine-functionalized gradients. Both functional groups were found to maintain phenotype after 14 days of culture, but chemical concentrations did not have significant impact on phenotype. Enhancing Schwann cell migration using concentration gradients of laminin derived-peptides. Neuroregeneration following peripheral nerve injury is largely mediated by Schwann cells (SC), the principal glial cell that supports neurons in the peripheral nervous system. Axonal regeneration in vivo is limited by the extent of SC migration into the gap between the proximal and distal nerve, however, little is known regarding the principle driving forces for SC migration. Engineered microenvironments, such as molecular and protein gradients, play a role in the migration of many cell types, including cancer cells a (open full item for complete abstract)

Committee: Matthew Becker (Advisor); Rebecca Willits (Committee Member); Chrys Wesdemiotis (Committee Member); Yu Zhu (Committee Member); Nic Leipzig (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Neurobiology; Polymers

Doctor of Philosophy, University of Akron, 2019, Polymer Engineering

Polymeric materials have been used in the healthcare and medical industry for decades, with advantages from design flexibility to cost-effective manufacturing. Despite the wide adoption of polymeric materials in the field, challenges remain, including i) the capability to integrate a roll-to-roll (R2R) process to fabricate bio-functional devices and ii) the ability to harness and understand the properties associated with any mechanical or thermal history during device fabrication. The research herein focuses on fundamental molecular-level understanding of the structure development of bio-functional polymers during mechanical and thermal processes, and continuous R2R processes for post-functionalization with surface attached bio-functionalities. The first part of the research utilizes a real-time birefringence measurement system to study the stress-optical relationships a series of α-Amino acid-based poly(ester urea)s (PEUs). PEUs are a new class of materials that have shown promise for biomedical applications due to their biodegradability, biocompatibility and enhanced mechanical properties. The hydrogen bonding species associated with the urea groups in the structure provides a nonchemical method to strengthen their physical properties and to impart unique performance characteristics including shape memory properties. The molecular structure evolution of PEUs during a complex shape memory cycle was studied by real time mechano-optical, Fourier transform infrared spectroscopy (FTIR) and wide-angle X-ray scattering (WAXS) measurements over a range of temperatures. A characteristic temperature, defined as the liquid–liquid (Tll) transition (rubbery–viscous transition), was found at about 1.05 Tg (K) (at Tg + 15 °C), at which temperature the mean relaxation time and shape recovery ratio for the polymer were also maximized. The hydrogen bonding strengthened supramolecular packing, the rearrangement of which associated with the deformation history was revealed to ultima (open full item for complete abstract)

Committee: Matthew Becker (Advisor); Mukerrem Cakmak (Advisor); Nicole Zacharia (Advisor); Younjin Min (Committee Chair); Rebecca Willits (Committee Member) Subjects: Engineering; Materials Science; Polymers

Doctor of Philosophy, University of Akron, 2018, Polymer Science

Incorporating chemical functionality into polymer systems allows for material properties and interactions to be more precisely controlled, expanding their scope for use/improvement in biomedical and other applications. In this body of work, several polymer platforms, including polyethylene glycol (PEG)-based hydrogels and thermoplastic polyurethanes (TPUs), are chemically modified with functional reagents, e.g. quaternary ammonium compounds (QACs), and their ability promote specified properties and/or interactions are examined. Post-Fabrication, QAC-Functionalized Thermoplastic Polyurethanes for Contact-Killing Catheter Applications: Catheter-related infections are an estimated $2.3 billion annual burden to the U.S. healthcare system, and result in approximately 28,000 deaths per year. To combat these infections, a TPU containing an allyl ether side-chain functionality (allyl-TPU) that allows for rapid and convenient surface modification with antimicrobial QACs is explored. A series of quaternary ammonium thiol compounds (Qx-SH) possessing various hydrocarbon tail lengths (8 – 14 carbons) are synthesized and attached to the allyl-TPU surface using thiol-ene “click” chemistry, and antimicrobial testing of the QAC-functionalized TPUs reveal that Q8-SH is most effective against various bacteria. A prototype catheter is extruded and functionalized (post-fabrication) with Q8-SH, and biofilm formation tests demonstrate its ability to inhibit biofilm accumulation. Ionomers for Tunable Softening of Thermoplastic Polyurethane: Plasticizer migration and leaching leads to changes in material properties over time and produces environmental concerns. Thermoplastic polyurethane (TPU) sulfonate ionomers with quaternary ammonium counterions are synthesized to achieve soft TPUs without the use of low molecular weight plasticizers. The incorporation of a functional sulfonate monomer containing bulky ammonium counterions along the polymer backbone reduces the durometer h (open full item for complete abstract)

Committee: Matthew Becker (Advisor); Ali Dhinojwala (Committee Chair); Bryan Vogt (Committee Member); Hazel Barton (Committee Member); Li Jia (Committee Member) Subjects: Polymer Chemistry; Polymers

Master of Science, University of Akron, 2017, Polymer Science

The objective of the research was to study the effects on surface segregation in binary polymer blends of both chain end functionalization of linear chains, and changes in architecture. An important question for the formation and application of a polymer thin film is the degree to which end group functionalization can influence the segregation of a chain to the air/polymer and polymer/substrate interfaces. For the first part of this study, well-defined polystyrene and hydroxyethylated functionalized polystyrene of exactly the same molecular weight (Mn = 6000 g/mol) were synthesized using anionic polymerization in order to minimize the impact of factors other than end group functionalization in the study of the segregation driven by the functionalization. Thin (90 nm) films of blends of these two chains spun cast on silicon substrates were investigated. Key to the study was use of a new method called Surface Layer Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (SL-MALDI-TOF-MS) which determines the composition at the surface (< 2 nm depth) of entire polymer chains, rather than the segment or chain end composition measured with other techniques. This technique requires no isotopic labeling. The most striking finding is that the surface region is not only depleted in the high energy chain end functionality, but, in fact, depleted in chains containing the functional group. Thus, for the first time, depletion of the entire chain, driven by only a single functionalized end group, was observed directly. The depletion of the surface in functionalized chains varies with composition and is more pronounced for blends of near-symmetric composition. For the study of the effect of architecture on surface segregation, star-branched polymers with two different architectures were synthesized. Well-defined 5.5k 4-arm star was successfully synthesized using a combination of anionic polymerization and silane linking chemistry. The structure (open full item for complete abstract)

Committee: Mark Foster (Advisor); Li Jia (Committee Member) Subjects: Physics; Polymer Chemistry; Polymers

Master of Science, The Ohio State University, 2017, Environment and Natural Resources

This study utilized atomic force microscopy (AFM) to study single-molecule interactions between hematite-binding peptides and a hematite-coated surface. The goal of this study was to investigate the relationship between amino acid sequence and peptide affinity for hematite (α-Fe2O3), with a focus on the influence of serine versus threonine residues in a peptide sequence. Data from these single molecule binding experiments suggest that substituting serine with threonine in a hematite-binding peptide increases peptide affinity for a hematite surface. Molecular dynamics (MD) simulations, carried out by our collaborators, were done in parallel with the single molecule binding experiments to model how two serine to threonine substitutions would alter how peptides bound to a hematite matrix. The results of these MD simulations agree with the trends from our single molecule experiments and support the conclusion that replacing serine residues with threonine residues increases peptide affinity for hematite. These findings could be utilized to improve existing biotechnology, including biological fuel cells, biosensing, solar energy production, and medical treatment in humans.

Committee: Brian Lower PhD (Advisor); Steven Lower PhD (Committee Member); Michael Wilkins PhD (Committee Member); Deric Learman PhD (Committee Member) Subjects: Biophysics

Master of Science, University of Akron, 2016, Polymer Science

Osteoarthritis (OA) is the most common articular disease and the most prevalent condition resulting in disability among the United States adult population. According to the U.S. Department of Health and Human Services, from 2010-2012, 52.5 million (22.7%) of adults aged > 18 years had self-reported doctor-diagnosed arthritis, and 22.7 million (9.8%) reported arthritis-attributable activity limitation, which indicates not only an ethical, but also economic importance of this disease. OA is characterized by progressive loss of articular cartilage and leads to chronic pain and functional restrictions in the affected joint. Although current treatments are successful in some aspects to provide short-term pain relief and recovered joint mobility, their long term benefits remain elusive and there is still no cure for the disease. The limited capacity for treatment is mainly due to the cartilage`s inability to repair itself. Regenerative medicine using tissue-engineered cartilage has the potential to address this issue, but a remaining challenge is the development of a feasible large scale cell expansion process, since during the expansion in monolayer cultures, chondrocytes undergo the process of dedifferentiation. Several surface-engineering approaches with bioactive factors and surface chemistry have been previously studied to look at increasing the interfacial interaction between the materials and cells. This project aimed to study the effects of various concentrations of surface functional groups on chondrocyte behavior. The cell proliferation and phenotype maintenance within continuously variable one-dimensional concentration gradients were examined. This method included fabrication of functionalized gradients by a vapor deposition technique that provided a fast, efficient, and reliable strategy by incorporating a series of concentrations in single substrates. Finally, human primary chondrocytes density and cellular survival were studied as response of amine and hydro (open full item for complete abstract)

Committee: Matthew Becker Dr. (Advisor); Abraham Joy Dr. (Committee Member) Subjects: Biomedical Research; Polymers

Master of Science, University of Toledo, 2014, Chemical Engineering

Water is essential for the survival of life on Earth, but pollutants in water can cause dangerous diseases and fatalities. The need for purified water has been increasing with increasing world population; however,, natural sources of water such as rivers, lakes and streams, are progressively falling shorter and shorter of meeting water needs. The provision of clean, drinkable water to people is a key factor for the development of novel and alternative water purification technologies, such as membrane separations. Nanofiltration (NF) is a membrane separations technology that purifies water from lower quality sources, such as brackish water, seawater and wastewater. During the filtration of such sources, materials that are rejected by the membrane may accumulate on the surface of the membrane to foul it. Such materials include organic and inorganic matter, colloids, salts and microorganisms. The former four can often be controlled via pretreatment; however, the accumulation of microorganisms is more problematic to membranes. Biofouling is the accumulation and growth of microorganisms on the surface of membranes and on feed spacers. After attachment, microorganisms excrete extracellular polymeric substances (EPS), which form a matrix around the organism's outer surface as biofilm. These biofilms are detrimental and result in irreversible membrane fouling. Copper and silver ions inactivate the bacterial cells and prevent the DNA replication in microbial cells. Previous studies using copper-charged feed spacers have shown the ability of copper to control biofouling without a significant amount of copper leaching from copper-charged polypropylene (PP) feed spacers during crossflow filtration. Also, filtration using unmodified speed facers experienced almost 70% flux decline, while filtration using copper-charged feed spacers displayed only 25% flux decline. These intriguing results led to the hypothesis that the polymer chemistry could be extrapolated to produce membranes (open full item for complete abstract)

Committee: Isabel Escobar (Committee Chair); Maria Coleman (Committee Member); Cyndee Gruden (Committee Member) Subjects: Chemical Engineering; Environmental Engineering

Doctor of Philosophy, University of Akron, 2014, Polymer Engineering

Effective energy storage is a key challenge of the 21st century that has fueled research in the area of energy storage devices. In this dissertation, structure-property relationships have been evaluated for polymers that might be suitable for storing energy in high-energy density, high-temperature capacitors. Firstly, hydroxyl-modified polypropylenes (PPOH) were synthesized by copolymerization of the propylene and undecenyloxytrimethylsilane monomers. The presence of H-bonding in PPOH copolymers increased their glass-transition temperature. Steric hindrance by the comonomer reduced the PP crystal growth rate and crystal size, resulting in a melting point depression. The comonomer was restricted outside the crystalline domains leaving the α-monoclinic crystal structure of PP unaffected, but increasing the fold-surface free energy. Crystallization was slower for PPOH copolymers than PP, but exhibited a skewed bell curve as a function of hydroxyl concentration. H-bonding persisted even at melt temperatures up to 250°C resulting in a higher elasticity and viscosity for PPOH copolymers. Secondly, sulfonated poly(ether ether ketone) (HSPEEK) was synthesized by sulfonating PEEK with sulfuric acid, and further neutralized with Zn to obtain ZnSPEEK. The thermal and dielectric properties of SPEEK were compared with PEEK. The glass-transition increased and melting point were high enough to enable the use of polymer at 180°C. The incorporation of sulfonic groups in PEEK increased the dielectric constant. HSPEEK had a higher dielectric constant than ZnSPEEK due to higher dipolar mobility, but the dielectric loss was also higher for HSPEEK due to electrode polarization and DC conduction. These results were consistent with our observations from sulfonated polystyrene (HSPS), which was used as a 〉model&lang' polymer. Lastly, commercial poly(4-methyl-1-pentene) (P4MP) was characterized to check its viability as a high-temperature polymer dielectric. Thermal stability up to (open full item for complete abstract)

Committee: Robert Weiss Dr. (Advisor); Mukerrem Cakmak Dr. (Committee Member); Alamgir Karim Dr. (Committee Member); Ali Dhinojwala Dr. (Committee Member); Shing-Chung Wong Dr. (Committee Member) Subjects: Energy; Engineering; Materials Science; Morphology; Plastics; Polymer Chemistry; Polymers

PhD, University of Cincinnati, 2013, Engineering and Applied Science: Materials Science

With the advancement of nanotechnology, cancer therapy requires that the carrier at nanoscale integrates cell targeting, imaging, drug storage and controlled drug release simultaneously. Extensive efforts have been devoted to isotropic sphere nanoparticle based carrier systems for their uniform surface properties. However, multifunctionality also leads to a challenge issue: different moieties may interfere with each other in bioconjugation process due to the similar conjugation chemistry applied to the same surface. As a result, Janus nanoparticles which are anisotropic in shape, composition or surface chemistry have attracted increasing attention. Asymmetric composition could achieve multifunctionality simultaneously. More importantly, surfaces could be selectively loaded with targeting ligands, imaging probes or drugs, which made the Janus nanoparticles “truly multifunctional entities”. A variety of fabrication methods have been studied to synthesize Janus nanoparticles for applications such as surfactants, magnetic-fluorescent display or imaging, and catalysts, etc. In contrast, exploration in the biomedical application field is rather limited. Based on our previous work on iron oxides@polystyrene matrix multifunctional nanoparticles and yolk-shell nanocomposites, we designed the polystyrene/Fe3O4@SiO2 superparamagnetic Janus nanocomposites (SJNCs). The SJNCs (~300 nm) are composed of a polystyrene (PS) core and a silica half shell embedded with iron oxide nanoparticles. We demonstrated the innovative dual functionalities on independent surfaces were obtained simultaneously during one-pot facile synthesis, which is much more convenient than the previous report on generating the similar structure through selectively coating. PS surfaces were decorated with carboxyl groups and silanol groups on silica surfaces provided enormous opportunities for further functionalization. To achieve cell targeting and controlled drug release, we conjugated folic acid (FA) to the (open full item for complete abstract)

Committee: Donglu Shi Ph.D. (Committee Chair); Vikram Kuppa Ph.D. (Committee Member); Giovanni Pauletti Ph.D. (Committee Member); Vesselin Shanov Ph.D. (Committee Member) Subjects: Materials Science

Master of Science in Chemical Engineering, University of Toledo, 2012, Chemical Engineering

Forward osmosis is the movement of water across a selectively permeable membrane. The driving force for water permeation through the membrane is the difference in osmotic pressure between the feed and draw solutions. Polybenzimidazole (PBI) is a material with excellent chemical resistance and high mechanical and thermal stability that is a promising material for forward osmosis separations. Drawbacks associated with the use of PBI as a membrane material include low hydrophilicity and surface charge neutrality at neutral pH values. These properties effect membrane wettability and solute rejection. In this study, PBI membranes were cast using the phase-inversion technique in the form of asymmetric flat sheets, and membrane surfaces were functionalized using different modifying agents with the goal of increasing hydrophilicity, increasing surface charge, and reducing membrane pore sizes. A charge increase of the membrane surface was expected to yield an increased rejection of ions and of charged species in the feed solution. An increase in hydrophilicity was expected to reduce fouling propensity and enhance wettability of the membrane surface. Lastly, a reduction in pore size was expected to allow for greater steric effects. In order to modify the membranes, the surfaces of the membranes were first activated with 4-(chloromethyl) benzoic acid (CMBA). The modifying agents selected for membrane functionalization included: taurine, para-phenylene diamine, ethylene diamine, and poly(acrylamide-co-acrylic acid). Membranes were characterized using Fourier transform infrared spectroscopy in attenuated reflectance mode (FTIR-ATR), zeta potential, environmental scanning electron microscopy (ESEM), contact angle measurements, and total organic carbon (TOC). Functionalization, surface charge, increased hydrophilicity, and reduced pore size were all verified. Pure water permeability and monovalent salt rejection were tested in a pressure driven mode for comparison between both vir (open full item for complete abstract)

Committee: Isabel Escobar PhD (Committee Chair); Maria Coleman PhD (Committee Member); Saleh Jabarin PhD (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, University of Akron, 2009, Polymer Science

Synthesis of the inimer (initiator-monomer) 4-(1,2-oxirane-isopropyl)styrene (EPOIM) and copolymerization of this inimer with isobutylene (IB) to form arborescent polyisobutylene (arb_PIB) was carried out using TiCl4 coinitiator. The effect of reaction conditions was investigated. Size exclusion chromatography (SEC) was used to show incorporation of EPOIM across the molecular weight distribution. The average number of branches was measured by selective link destruction. Polymer architecture analysis was carried out using branching parameters based on the radii of gyration (Rg) and hydrodynamic radii (Rh) determined by multidetector SEC. In situ FTIR was utilized to monitor the polymerization of EPOIM. Block copolymers were synthesized by the blocking of arb_PIB with p-methylstyrene to form novel 4th generation SIBS materials, arb_poly[isobutylene(OH)-b-(isobutylene-co-pmethylstyrene] [arb_IB(OH)-MS]. Proof of the presence of hydroxyl groups in the polymer was obtained using 1H-NMR spectroscopy and by silylation with chlorotrimethylsilane. The reinforcement and surface functionalization of thermoplastic elastomers (TPEs) for soft tissue replacement was investigated. The materials investigated were soft TPE based PIBs, with surfaces more hydrophilic than poly(styrene-b-isobutylene-b-styrene) (SIBS) and silicone rubber. The material reinforced with carbon black (CB) [arb_IB(OH)-MS_CB] had an interpenetrating network structure, in which the Tg of the dispersed phase increased to 126 °C, making the material steam-sterilizable. It also had the lowest water contact angle at 82°, and superior mechanical properties in comparison with silicone rubber. After 180 days implantation into rabbits arb_IB(OH)-MS_CB displayed the thinnest capsule around the implant in comparison to arb_IB(OH)-MS and silicone. A new method of surface functionalization to increase the hydrophilicity of arb_IB(OH)-MS was developed. Using a low molecular weight thymine-functionalized polyisobutylene (open full item for complete abstract)

Committee: Judit Puskas PhD (Advisor) Subjects: Polymers

Master of Science, University of Akron, 2013, Polymer Science

Tissue loss and end-stage organ failure has been a significant health challenge for millions of Americans, with the total national health cost exceeding $400 billion per year. Tissue engineering aims to address this challenge. During the process of tissue engineering, scaffolds and matrices are needed as supporting structures for cells to grow. Meanwhile, the roughness and stiffness of the scaffold material can largely influence cell growth and differentiation. The macro- and meso- structures of the scaffold, along with the functional groups or growth factors present on the surface plays an important role in cell function. Poly(ester urea) (PEU) is regarded as a promising biodegradable scaffold material for tissue engineering. In this study, physical and mechanical properties including Young's modulus, storage modulus, water uptake profile, and degradation rate for PEUs of different structures were tested. Two different amino acids, phenylalanine and leucine, and various diol lengths were used in the synthesis of these PEUs. In this study, the data show that changing the amino acid from leucine (LEU) to phenylalanine (PHE) can result in a 20 degree increase in Tg, and a 30% increase in storage modulus. Tuning the length of the diols reduces the stiffness of the polymer backbone affording multiple opportunities to tune the property of the polymer. A structure-property relationship profile for PEUs can therefore be established. The effect of macro structure of poly(L-lactic acid) (PLLA) and poly(e-caprolactone) (PCL) scaffold was also explored. Electrospinning was used to fabricate fibrous scaffold of non-woven mats. 4-dibenzocyclooctynol (DIBO) terminated PCL was electrospun into nanofibers. The existence of DIBO groups on the surface was characterized by attaching an azide functionalized florescent dye. DIBO-PLLA was electrospun into fiber mats and functionalized by YIGSR peptide via metal-free click reaction on the DIBO group. Both random and uniaxial aligne (open full item for complete abstract)

Committee: Matthew Becker Dr. (Advisor); Abraham Joy Dr. (Committee Member) Subjects: Materials Science; Nanoscience; Neurosciences; Polymer Chemistry; Polymers