Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2004. / Clifford L. Henderson, Committee Chair ; Peter Ludovice, Committee Member ; Laren Tolbert, Committee Member ; Dennis Hess, Committee Member ; W. Brent Carter, Committee Member. Includes bibliographical references (leaves 119-128).

Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Lyon, Louis; Committee Member: Breedveld, Victor; Committee Member: Bunz, Uwe; Committee Member: Collard, David; Committee Member: Srinivasarao, Mohan. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.S.)--Middle East Technical University, 2003. / Keywords: Ethyl methacrylate, atom transfer radical polymerization, gamma irradiation, free radical polymerization, viscosity.

The inverse scattering problem is based on the scattering theory in physics, where measured data such as radiation from an object is used to determine the unique structure of the object in question. This approach has been widely successful in fields ranging from geophysics and medical imaging, to quantum field theory. In 1996 Henrik Flyvbjerg suggested that a similar approach could be used to study a reaction far from equilibrium of the self-assembly of a nucleation dependent biopolymer and, under certain conditions, uniquely determine the kinetics of the assembly. Here we use this approach to elucidate the unique structure of human islet amyloid polypeptide, also known as amylin, in-vitro. We use a systematic phenomenological analysis of the amount of monomer in fibril, of amylin, for various initial concentrations from an unstructured monomer pool. Using the assumption that nucleation is the rate-limiting step in fibril formation, we invoke mass action to develop our model. We find that the fibrillogenesis of amylin is well described by a nucleation dependent polymerization event that is characteristic of the sigmoidal shape of the reaction profile generated by our data. Furthermore, we find a second nucleation event is needed to accurately match model predictions to the observed data for the kinetic profiles of fibril formation, and the experimental length distributions of mature fibrils from in-vitro assays. This analysis allows for the theoretical determination of each step of assembly in the nucleation process. Specifically, we find the number of steps to nucleation, the size of each oligomer formed in the nucleation process, the nucleus size, and the elongation kinetics of fibrils. The secondary nucleation process is found to be a fibril dependent surface mediated nucleation event and is similar in reaction order to the primary nucleation step. Model predictions are found to be congruent with experimental assay results of oligomer populations and monomer concentration. We demonstrate that, a persistent oligomer formation is a natural and necessary consequence of nucleated fibril formation, given certain qualitative features of the kinetic profile of fibril formation. Furthermore, the modeling assumptions about monomer and fibril mass are in agreement with experiment.

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Free radical polymerization is the most common polymerization technique that is used for the manufacturing of polymers, due to the ease of the polymerization initiation, wide latitude of the material design for a large variety of monomers, and the excellent process robustness for commercial production. In the 1990’s, research activities for the precise control of radical polymerization process resulted in the discovery of ‘Living Radical Polymerization’. The discoveries opened the door for the next generation of radical polymerizations. Extensive research has been conducted to understand the mechanisms and kinetics for numerous practical applications, particularly for polymerization in bulk and solution systems. However, despite the interest of industry, the mechanistic understanding in aqueous dispersed systems such as emulsion and miniemulsion polymerization is far behind the aforementioned two systems. There are still major challenges from the production viewpoint. One reason for the poor understanding is the complexity of the heterogeneous system, which includes multiple　reaction phases that are accompanied by the segregation and transfer of the reaction species among different phases. The purpose of this research was to investigate living radical polymerization or “Stable Free Radical Polymerization” (SFRP) in aqueous dispersed systems to obtain better mechanistic understanding of how the heterogeneous nature of the system interacts with the novel living radical chemistry. The theoretical and experimental feasibility of the SFRP emulsion process were studied in this research, in particular, focusing on the compartmentalization effect. Particle size influence on the polymerization kinetics and the polymer livingness was experimentally confirmed, and compared to bulk polymerization. In addition, a comprehensive mathematical model including all major chemical and physical events was developed to further our mechanistic understanding. Based on the results from the experimental and modeling studies, it was shown that rate reduction in the smaller particles is the primary cause of difficulty in implementing a conventional emulsion process (i.e. ab initio emulsion polymerization). Finally, for overcoming this difficulty, a new approach using a combination of TEMPO with highly hydrophobic 4-stearoyl TEMPO was proposed for a coagulum free ab initio emulsion process. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2010-02-18 09:49:52.336

Amidine-based switchable surfactants can be used as stabilizers during emulsion polymerization and the resulting latexes can then be destabilized by the removal of CO2. High Tg polymers have been successfully redispersed, as shown by recovery of primary particle size (measured by light scattering methods), but an input of energy was required. Sonication was the first method used, but lower-energy methods such as rotor-stators and a blender have also been successful in redispersing aggregated latexes. Colloidal stability was found to be reversible for at least three aggregation/redispersion cycles, and redispersibility was retained after the removal of water and addition of fresh water. Stimuli-responsive polymer colloids with reversible colloidal stability may have many uses. The shipping of latexes, for example, would be easier and less energy intensive if the latex particles could be aggregated and the bulk of the water removed. The latexes would then have to be redispersed prior to use. Switchable surfactants have also been used for the semi-continuous copolymerization of butyl acrylate and methyl methacrylate to form a high solids content (42 wt%), low-Tg latex. The latex can be destabilized with air and heat but cannot undergo redispersion because the low Tg polymer particles fuse upon aggregation. The copolymer, when dried at room temperature, formed a continuous film. Latexes with high solids content and low Tg’s are representative of latex paint formulations. Because the switchable surfactants have been shown to be successful in preparing these latexes, it is possible that they may be useful in the latex paint industry, for example as fast setting paints. / Thesis (Master, Chemistry) -- Queen's University, 2011-09-26 13:18:33.905

A novel dual-plasma process for the synthesis of organic layer-coated metal nanoparticles is presented. Metal nanoparticles are synthesized by the low-pressure pulsed arc evaporation of a metal cathode surface, followed by the in-flight deposition of a thin organic layer by capacitively-coupled radio-frequency (CCRF) plasma polymerization from a gaseous hydrocarbon monomer. The system is simple to operate and can be designed for high throughput. The combination of the synthesis and surface treatment of metal nanoparticles in the whole system avoids newly produced metal nanoparticles from being contaminated by surrounding environment. / A home-made self-oscillatory pulsed power supply has been designed and built for the arc evaporation of metal sources. The stability of the pulsed arc system and the cathode erosion rate are discussed. The inductor present in the discharge loop is shown to have a stabilizing effect on the train of pulsed arcs. It was shown that the erosion rate was strongly dependent on peak arc currents due to the increased emission of macroparticles with peak arc currents, and the yield of metal nanoparticles was found to be slightly influenced by the peak arc current. / The produced coated copper nanoparticles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). It was revealed that the coated copper nanoparticles have a metal core of size ranging from a few to 50 nm, and that the thickness of the organic layer ranges from 3 to 10 nm. The smallest copper nanoparticles are crystalline, while the organic coating has a macromolecular structure and shows a hydrophobic behavior. The XPS results showed that the plasma polymer film is chemically adsorbed onto the surface of the copper nanoparticle. / The effects of operating conditions such as reactor pressure and inert gas flow rate on the average size of the produced bare copper nanoparticles were studied. It was demonstrated that the metal nanoparticle size tends to decrease with decreasing reactor pressure, while inert gas flow rate has little influence on the mean nanoparticle size. / The morphology of the plasma polymer coating was revealed to be strongly dependent on the RF plasma power, reactor pressure, and inert gas flow rate. Two kinds of organic films were produced: a smooth, uniform and dense polymer film and a liquid polymer film. Based on a series of experiments, a "characteristic map" for the in-flight plasma polymerization from the C2H 6 monomer generating an organic layer onto the Cu nanoparticles was developed. A simplified free-radical mechanism was proposed for the plasma polymerization from ethane. / Other metal sources such as iron and aluminum were used as cathodes in the arc evaporation reactor. Transmission electron microscopy confirmed the production of coated nanoparticles similar in morphology to the ones obtained with the copper cathode. Lastly, ethylene glycol vapor were introduced as an alternative monomer into the plasma polymerization region. A non-uniform coating was observed on the metal nanoparticle surface.

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