Physical Sciences and Mathematics Commons^™

Design, Synthesis, Characterization, And Applications Of Matrix Free Polymer Nanocomposites, Yucheng Huang

Theses and Dissertations

This dissertation focuses on the design, synthesis, characterization and application of matrix free polymer nanocomposites. Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize block copolymers and polymer grafted silica nanoparticles with precise control over architectures.

In the first chapter, thermoplastic elastomer (TPE) grafted nanoparticles were prepared by grafting block copolymer poly(styrene-block-(n-butyl acrylate)) onto silica nanoparticles (NPs) (~15nm) via surface initiated RAFT polymerization. The effects of polymer chain length and graft density on the mechanical properties were investigated using films made solely from the grafted NPs. The ultimate tensile stress and elastic modulus increased with the increase of PS …

Synthesis And Characterization Of Polydiene-Grafted Nanoparticles, Zaid Mohammed Abbas Alajeeli

Theses and Dissertations

This dissertation presents the design, synthesis, and characterization of polydiene grafted nanoparticles as a way to tailor nanocomposite interfaces and properties via interface design. The polymerization of dienes was done via reversible addition fragmentation chain transfer (RAFT) polymerization. The grafting of polymer chains on the surface of silica nanoparticles can be controlled through the molecular design of the RAFT agents attached to the nanoparticles surface. The properties of the nanocomposites largely depended on the interface between the particles and the polymer matrix. In the first part of this work, the polymerization of diene monomers was done on 15 nm diameter …

Characterization Of Sufs And Sufe Of Suf Pathway For Fe-S Cluster Assembly In Escherichia Coli, Guangchao Dong

Theses and Dissertations

Fe-S clusters are one major type of the sulfur-containing cofactors, which conduct essential functions in organisms. The Suf pathway is one of the three main pathways for the biosynthesis of Fe-S clusters. In E. coli, the Suf pathway is utilized under iron limitation and oxidative stress. This ability is important for pathogens to survive. Also, the Suf pathway is found to be exclusive in bacteria, so it is a good target for novel antibiotic design. SufS is a cysteine desulfurase in the Suf pathway to extract sulfur from L-cysteine. It needs the enhancement of SufE. To better understand the catalytic …

Characterization Of The Suf Fe-S Pathway In Escherichia Coli, Naimah Bolaji

Theses and Dissertations

Iron is an essential transition metal required by almost all organisms for use as a cofactor in many metabolic processes such as respiration and photosynthesis. Iron can be combined with elemental sulfur to form an iron-sulfur (Fe-S) cluster. In bacterial pathogens, Fe-S cluster cofactors carry out critical functions and the Fe-S cluster biogenesis pathway is essential for their survival. In E. coli, the Suf pathway assembles Fe-S clusters under conditions of iron starvation and oxidative stress. While some mechanistic details of the Fe-S cluster biogenesis have been well-characterized, the process of in vivo iron donation remains unclear. Iron storage proteins …

Materials Discovery Of Reduced Early Transition Metal Compounds: Crystal Growth And Characterization, Dileka Abeysinghe

Theses and Dissertations

Materials discovery via crystal growth is an active area of research that has led to the preparation of many novel materials along with the determination of their crystal structures. One sub-category in this diverse field of materials is the preparation of early transition metal reduced oxides. These reduced oxides often exhibit unusual electronic and magnetic properties. Due to the synthetic challenges associated with early transition metal reduction, new and facile methods to prepare reduced oxides is of great interest. These limitations can be overcome by using a carefully selected redox neutral flux, a vacuum sealed fused silica tube, and metal …

Characterization Of 1-Deoxy-D-Xylulose 5-Phosphate Reductoisomerase (Dxr) From Vibrio Vulnificus, Nikita K. Ussin

Theses and Dissertations

Vibrio vulnificus, a gram-negative bacterium, is the leading cause of seafood-borne illnesses and mortality in the United States. Previous studies of bacterial pathogens have identified a metabolite essential to V. vulnificus growth and function. 1-deoxy-D-xylulose 5-phosphate reductoisomerase (Dxr) is an essential enzyme in the viability of many bacteria and catalyzes the rearrangement of 1-deoxy-D-xylulose 5-phosphate (Dxp) to 2-C-methylerythritol 4-phosphate (MEP) within the MEP pathway found in plants and bacteria. Previous studies have been conducted to characterize Dxr homologs from other pathogens including E. coli, M. tuberculosis, and P. falciparum. Information on the structural and enzymatic characteristics of Dxr from Vibrio …

Crystal Growth And Characterization Of Reduced Early Transition Metal Compounds Grown Via Hydrothermal And Molten Flux Methods, Anthony J. Cortese

Theses and Dissertations

Interest in new and facile ways to prepare early transition metal reduced oxides has recently been increasing. In the past difficult flux techniques involving vacuum furnaces, expensive metal tubing, complicated electrolytic reduction apparatuses, were used to achieve in situ reduction of fully oxidized transition metal precursors. Often times these techniques were coupled with use of a difficult flux, such as boric acid, which is hard to remove due to its insolubility in water at room temperature. These limitations can be circumvented in multiple ways, including carefully choosing a redox neutral flux, using evacuated fused silica tubes for reaction vessels, and …