Thesis (Ph. D.)--University of Delaware, 2006. / Principal faculty advisor: Brian J. Bahnson, Dept. of Chemistry & Biochemistry. Includes bibliographical references.

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A novel oligomer was synthesized for the purpose of investigating the effects of ultraviolet, thermal, and microwave polymerization. The synthesis involved an anionic ring-opening equilibration reaction to produce poly(dimethylsiloxane) which was then endcapped with an acid chloride to result in a material which was linear, flexible, had a functionality of four, and a strong dipole moment. Acrylamide terminated poly(dimethylsiloxane) was the end product and was cured with ultraviolet radiation, thermal energy, and microwaves. Characterization of the cured materials demonstrated interesting findings. Microwave cured materials resulted in higher degrees of cure than thermal or ultraviolet cured samples, despite using the best match for the heating rate-sample temperature profiles for each cure process. Several characterization techniques were employed and the procedures and results may be useful for others interested in finding the most efficient cure mode for their material. / Master of Science

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / This study comprises the synthesis, functionalization, and characterization of 1-butene oligomers, as well as the synthesis of oligobutene-based macro-RAFT agent. The directed oligomerization of 1-butene was carried out with a Cp2ZrCl2 as a catalyst, activated with MAO as a co-catalyst (10% in toluene), in the ratio Al/Zr =1000/1. Oligomers possessing vinylidene double bonds, with low molecular weight (Mw), ranging between 800 and 2000 g.mol-1 as confirmed by gel permeation chromatography, were obtained. The oligomers were successfully functionalized by adding hydroxyl functionality to the vinylidene double bond using oxymercuration-demercuration reaction, and as a result hydroxy-terminated oligobutenes were obtained. Characterization techniques such as 1H NMR, 13C NMR, GC-MS and FTIR confirmed the successful synthesis and functionalization of 1-butene oligomers. The hydroxy-terminated oligobutenes were used to prepare an oligobutene-based macro-RAFT agent. The synthesis of the macro-RAFT agent was carried out with an esterification reaction between the hydroxy-terminated oligobutenes and an acid functionalized RAFT agent. The successful synthesis of the macro-RAFT agent was confirmed by 1H NMR, 13C NMR, FTIR, and UV spectroscopy. The chain transfer ability of the macro-RAFT agent to induce living characteristics in free radical styrene polymerization was investigated with respect to molecular weight control and kinetic behaviour. The macro-RAFT agent was identified as suitable RAFT agent, yielding polystyrene-b-oligobutnes with low polydispersities and molecular weight ranging from 3000 to 40000 g/mol.

Using two different model systems, this thesis considers the old, but fascinating question: how do atoms or particles possessing a particular set of individual characteristics combine to form assemblies with quite distinct, ensemble characteristics, and how do those characteristics evolve as a function of the size of the assembly? For the last thirty years, numerous experiments studying the emergence of collective material properties have focused on a class of semiconducting, colloidal nanocrystals commonly known as quantum dots, which are notable for the size-dependence of their optical properties. Despite years of effort, even the most uniform quantum dot samples possess some heterogeneity in size, shape, and composition, which has prevented complete structure determination and hindered understanding of structure-property relationships. Chapter 1 of this thesis presents an approach to overcoming this challenge and reports the synthesis of a set of four, new, atomically precise cadmium selenide nanocrystal samples, which we call CdSe(350 nm), CdSe(380 nm), CdSe(408 nm), and CdSe(435 nm) after their lowest energy absorption features. We determine their structures and formulas through a combination of single crystal and powder X-ray diffraction measurements, elemental analysis, and spectroscopy. We also describe the optical properties of these samples and their sensitivity to ligand coverage, compare them to other previously reported cadmium selenide nanomaterials, and discuss ongoing experiments. Because CdSe(350 nm), CdSe(380 nm), CdSe(408 nm), and CdSe(435 nm) are atomically precise, they allow us to correlate specific structural features with material properties, which is the focus Chapter 2. Here we present a series of Raman scattering experiments designed to probe the evolution of vibrational structure with size. We find that the Cd-Se stretching region of the Raman spectra exhibits two peaks, which are assigned to primarily surface-derived and interior-derived atomic motions using density functional theory calculations. By performing variable temperature measurements, we discover that the smallest sample, CdSe(350 nm), exhibits behavior that can be well-described using a model developed for small molecules while the vibrations of the largest measured cluster, CdSe(408 nm), are better described by a model developed for bulk materials. This observation is evidence that the transition to a more bulk-like vibrational structure occurs relatively rapidly when cadmium selenide materials are approximately 2 nm in size. The emergence of collective material properties is also the subject of Chapter 3, but the topic is approached from a different perspective. Instead of focusing on a series of atomically precise clusters that differ in size, Chapter 3 presents a series of molecules composed of atomically precise clusters. We prepare octahedral hexaruthenium carbonyl clusters, [Ru₆C(CO)₁₆]²⁻, and use them as building blocks to assemble oligomers linked by single metal atom bridges. We synthesize and structurally characterize a set of compounds varying in length (from monomer to trimer) and linker atom identity (cadmium and mercury) and study the effect on electronic structure using infrared and UV-Visible absorption spectroscopies and density functional theory calculations. With increasing oligomer length, the UV-Vis absorption profile changes and shifts to lower energy, which we attribute in part to the development of coupling between neighboring clusters. Our calculations show that the infinite polymer composed of [Ru₆C(CO)₁₆]²⁻ linked by Hg²⁺ would be a one-dimensional semiconductor with a 1.5 eV direct band-gap. More detailed abstracts can be found at the beginning of each chapter.

Protein aggregation, oligomer and fibril formation is one of the dominant characteristics in the pathogenesis of a number of neurodegenerative diseases, such as Alzheimer’s disease (AD). Inhibition of toxic oligomer and fibril formation is one of the approaches to find potential drug candidates for AD. Additionally, early diagnosis of these amyloid species can provide mechanistic understanding of protein aggregation and thus can pave the way for preventing the onset of AD. The aim of this dissertation was 1) to explore the effects of charged cholesterol derivatives on the aggregation kinetic behavior of Amyloid-β40 (Aβ40), 2) to probe Aβ40 oligomer and amyloid formation in vitro using gold nanoparticles (AuNPs), and 3) to monitor the kinetic effect of various natural product molecules on Aβ40 aggregation in vitro. In the first chapter, a general introduction about AD as an amyloidogenic disease, amyloid cascade hypothesis, and the manipulation of Aβ peptides aggregation kinetics using different approaches was presented. In the second chapter, we studied the effects of oppositely charged cholesterol derivatives on the aggregation kinetics of Aβ. In the third chapter, we developed a gold nanoparticles (AuNPs) assay to probe Aβ40 oligomers and amyloid formation. In chapter IV, we monitored the effects of various small molecules on the aggregation kinetics of Aβ40. In chapter V, we discussed the methods and experimental details. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

The following dissertation discusses the role of Aβ42 dependent hyperactivation of AMPK mediating synaptic loss through coordinated Mff-dependent mitochondrial fission and Ulk2-dpendent mitophagy in dendrites of PNs. In Chapter 1, I provide a brief background on Alzheimer’s disease and the cellular and molecular mechanisms that have been relevant to the pathogenesis of the disease including disruption on mitochondrial homeostasis and autophagy. In Chapter 2, I discuss the findings of my main project describing the role of Aβ42 induced mitochondrial remodeling leading to synapse loss in vitro and in vivo in part by hyperactivation of CAMKKII-AMPK. Chapter 3 covers a review article that I participated in in examining the role of mitochondria in various ND. In Chapter 4, I discuss about a project I was involved in in examining the mechanism behind maintaining mitochondrial morphology in axon versus dendrite and its functional consequence. In Chapter 5, I end the dissertation by highlighting key findings, potential future studies, and concluding remarks.

by Wong Tak Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 74-77). / Contents --- p.i / Acknowledgments --- p.iii / Abstract --- p.iv / Abbreviations --- p.v / Chapter Chapter 1. --- Introduction / Chapter 1.1. --- General background on conducting polymers and oligomers --- p.1 / Chapter 1.2. --- Conjugated oligomers and polymers --- p.3 / Chapter 1.2.1 --- Theory of conducting polymers / Chapter 1.2.2 --- Oligo- and poly-(p-phenylene)s / Chapter 1.2.3 --- Oligo and poly(phenylenevinylene)s / Chapter 1.2.4 --- Oligo and poly(phenylenethynylene)s / Chapter 1.3. --- Synthesis and solubilization of structurally rigid conjugated oligomers by dendritication --- p.19 / Chapter 1.4. --- Introduction of dendrimer chemistry --- p.20 / Chapter Chapter 2. --- Results and discussion / Chapter 2.1. --- An accelerated approach to the synthesis of oligo(phenylenevinylene)s -preparation of the propagating dimeric unit72 --- p.25 / Chapter 2.2. --- Synthesis of the polyether dendritic fragments --- p.29 / Chapter 2.3. --- Attempted coupling reactions between the polyether dendrimer and the propagating unit72 --- p.32 / Chapter 2.4. --- Synthesis and characterization of dendritic-solubilized oligo-(phenylenethynylene)s (OPE) --- p.34 / Chapter 2.4.1 --- Synthesis of conjugated propagating units / Chapter 2.4.2 --- Characterization of conjugated propagating units / Chapter 2.5. --- Synthesis and characterization of dendritic-solubilized oligo-(phenylenethynylene) fragments dendrimerized at one end --- p.39 / Chapter 2.5.1 --- Synthesis / Chapter 2.5.2 --- Characterization / Chapter 2.6. --- Synthesis and characterization of oligo(phenylenethynylene)s dendrimerized at both ends --- p.43 / Chapter 2.6.1 --- Synthesis / Chapter 2.6.2 --- Purification and characterization / Chapter 2.6.3 --- Solubility and physical appearance / Chapter Chapter 3. --- Summary --- p.49 / Chapter Chapter 4. --- Experimental section --- p.50 / References --- p.74 / List of spectra --- p.78

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