Doctor of Philosophy (Ph.D.), Bowling Green State University, 2020, Photochemical Sciences

We present the study of Fe(III)-carboxylate photochemistry of natural polyuronates in aqueous solutions and in soft hydrogel materials with near UV and violet light. Described in this dissertation are the use of Fe(III)-carboxylate photochemistry for sustainable material applications such as surface modifications and controlled plant nutrient delivery. Quantitative photochemistry of the Fe(III)-alginate system in aqueous solutions was studied using near UV light, and the effect of factors such as alginate composition and solution pH was studied. Degradation of alginate chain with the photochemical reaction was observed by the changes in the solution viscosity. The photochemical reaction seemed to proceed through a radical species and the generation of carbon dioxide anion radical (CO2.-) was identified using Electron Paramagnetic Resonance (EPR) spectroscopy. We present all polysaccharide hydrogels prepared with agarose and carboxylate group containing pectin which showed photoresponsive behavior. Upon Fe(III) coordination and irradiation with 405 nm LED for various time intervals, these gels changed their pH, mechanical properties, porous structure and swelling properties. Based on the radical generation phenomenon, studies on polymerization of selected acrylic monomers using this Fe(III)-carboxylate photochemical system was studied. Other than polyuronate based hydrogels, fabrics with introduced carboxylate functionality showed their ability to polymerize acrylic monomers on their surface, and change their physical and mechanical properties with the use of light. Hydrogel beads prepared with alginate or alginate and other polysaccharide mixtures with Fe(III) showed their ability to absorb phosphate ions from model waste solutions. The solution phosphate concentration dependent phosphate uptake showed a maximum phosphate uptake around 1.5 mgg-1. Phosphate uptake above 1 mgg-1 was seen for a wide pH range of 4.8 - 11.5 due to the strong binding betwe (open full item for complete abstract)

Committee: Alexis Ostrowski PhD (Advisor); Pavel Anzenbacher PhD (Committee Member); George Bullerjahn PhD (Committee Member); Lewis Fulcher PhD (Other) Subjects: Agriculture; Biogeochemistry; Chemistry; Environmental Science; Geochemistry; Inorganic Chemistry; Materials Science; Polymers

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

Carbon nanotubes (CNTs) are considered to be one of the most promising materials to be used in thermally conductive polymer composites, since CNTs couple extremely high thermal conductivity with high aspect ratios, thus enduing CNTs with the ability to form percolated networks at very low loadings. [1] The addition of a small amount of CNTs is expected to increase thermal conductivity dramatically, however, thermal conductivity measurements of CNT-polymer nanocomposites present unclear results. This is primarily attributed to: (1) CNTs are easy to aggregate into bundles when blended with polymers due to the strong Van der Waals interactions, causing poor dispersion in the matrix. [1] (2) CNT-polymer interfacial resistance that comes from the large interfacial resistance between CNT and polymer matrix, hindering the phonon conducting heat in polymers and CNTs, [1] which is found to be the dominant reason. [2] While it is very important to study CNT-polymer interfacial resistance in order to produce CNT-polymer composites with higher thermal conductivity, controlling the dispersion of CNTs is extremely challenging. In this work, 3-D CNT foams have been synthesized and used as the templates to fabricate CNT- polyvinyl alcohol (PVA) composites, because in foams the dispersion of CNTs is perfectly controlled. CNT foams have been modified using water plasma modification and metal coating in the hope of forming hydrogen bonding and metal complexation between CNTs and PVA matrix.

Committee: Ali Dhinojwala (Advisor); Yu Zhu (Committee Member) Subjects: Nanoscience; Physical Chemistry; Polymers

Doctor of Philosophy (PhD), Wright State University, 2005, Engineering PhD

Pulikollu, Rajasekhar Venkata. Ph.D., Department of Mechanical and Materials Engineering, Wright State University, 2005. Nano-coatings on Carbon Structures for Interfacial Modification. Surface modification of materials is a rapidly growing field as structures become smaller, more integrated and complex. It opens up the possibility of combining the optimum bulk properties of a material with optimized surface properties such as enhanced bonding, corrosion resistance, reactivity, stress transfer, and thermal, optical or electrical behavior. Therefore, surface functionalization or modification can be an enabling step in a wide variety of modern applications. In this dissertation several surface modification approaches on carbon foam and carbon nano-fibers will be discussed. These are recently developed sp 2 graphitic carbon based structures that have significant potential in aerospace, automotive and thermal applications. Influence of surface modification on composite formation and properties have also been investigated. Two types of property changes have been investigated: one for enhancing the surface reactivity and another for surface inertness. Characterization techniques such as X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), Contact Angle Measurement, Scanning Electron Microscope (SEM), Transmission Electron Microscope(TEM), and mechanical testing are used in this study to find out the influence of these coatings on surface composition, chemistry, and morphology. Mechanical testing has been performed on composites and stand-alone foam to study the influence of surface modification on physical and mechanical properties of the composite materials. The effectiveness of these coatings on metallic/graphite interface has also been investigated for metal-matrix composite related applications. Additionally, the influence of plasmacoatings on nucleation and growth of nanotubes on larger carbon structures (to produce multiscale, multifunctional mater (open full item for complete abstract)

Committee: Sharmila Mukhopadhyay (Advisor) Subjects: Engineering, Materials Science