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Three solution models: ideal, regular, and quasi- regular, were used to predict the melting point of eutectic mixtures containing Polyethylene Glycol (PEG) 400 and PEG 4000 with nine poorly water- soluble drugs: 1-naphthoic acid, estrone, griseofulvin, indomethacin, phenobarbital, paracetamol, salicylic acid, salicylamide and naproxen. PEG 400 was physically mixed with drug at different weight percentages to determine the melting points of the pure drugs and the melting point depression using Differential Scanning Calorimetry (DSC). The PEG 4000 eutectic mixtures were processed by the solvent evaporation method. In both the PEG 400 and PEG 4000 study, the quasi-regular solution model accounted for the most realistic conditions of entropy and enthalpy of the mixtures compared to ideal and regular solution models.

Depuis leur découverte, les nanotubes de carbone (CNT) ont connu de nombreux succès en raison de leurs performances mécaniques, électriques et thermiques exceptionnelles. L'exploitation de ces propriétés requiert néanmoins de pouvoir isoler les CNT, de les manipuler et de les localiser au sein d'un matériau d'architecture plus ou moins complexe. Pour cela, il est souvent nécessaire de disperser les CNT en raison de leur très grande insolubilité dans tout solvant. De nombreuses stratégies de dispersion reposent sur la stabilisation des CNT par des tensioactifs. Cependant, très peu d'études visent à déterminer les forces colloïdales mises en jeu, un des paramètres clés de la dispersion. Ainsi, la dispersion des CNT reste souvent un art plutôt qu'un processus bien contrôlé et maîtrisé. Dans cette étude, le mécanisme d'adsorption en milieu aqueux de quatre tensioactifs usuels a été clarifié, en particulier grâce à la détermination de leur isotherme d'adsorption. En se basant sur les résultats d'adsorption, des dispersions concentrées et sans agrégats de CNT ont été préparées et ensuite utilisées pour la formulation des nanocomposites polymériques. Une seconde méthode de dispersion est basée sur l'encapsulation des CNT par une écorce polymérique. Alors que la majorité de telles méthodes requiert la modification covalente des CNT, ce qui entraîne la détérioration des propriétés des CNT, nous présentons une méthode de dispersion et d'encapsulation des CNT qui ne nécessite pas de modification covalente de leur surface. Cette méthode se base sur l'adsorption physique des polymères préparés par polymérisation par transfert de chaîne de type addition et fragmentation, appelée polymérisation RAFT. Cette procédure d'encapsulation est versatile et permet la formation d'une couche polymérique homogène et continue sur la surface des CNT. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : nanotubes de carbone (CNT), dispersion, isotherme d'adsorption, encapsulation, polymérisation RAFT.

The current thrust towards the compaction of electrical power equipment, resulting in increased insulation electrical stress levels, necessitates new electrical insulating materials. In the last few decades, polymeric materials that exhibit light weight, excellent mechanical properties, low cost, and some with unique non-wetting surface characteristics, have surpassed the use of the conventional porcelain and glass insulating materials. Despite these advantages, polymeric materials are incapable of withstanding the high heat from surface arcing that is instigated by the synergism of pollution, moisture, and voltage. Surface arcing results in material loss due to heat ablation and/or the electrical tracking of polymeric materials. To overcome such issues, inorganic fillers are added to the base polymers to enhance their resistance to surface discharge activities and other performances. Since their addition can significantly reduce material costs, their use is compelling. Micron-sized fillers, here after defined as microfillers, have been used to acquire these desirable properties, but due to limitations in material processability, the further application of such fillers is limited. Consequently, nano-sized fillers, here after defined as nanofillers, have been viewed as replacements or assistant combinations to microfillers. Nanofillers are characterized by large surface areas, resulting in increased bond strengths that yield significant improvements in the various properties at fill levels well below that of microfillers. However, the primary problem of using nanofillers is their characteristic property of agglomeration due to their physical size and the forces between the fillers. Conventional mechanical mixing of nanofillers does not adequately separate the nanofillers, leading to behaviour similarly to that of microfillers. Therefore, the implementation of nanofillers is not completely effective. In chemical dispersion techniques, for example, the use of surfactants, are normally very elaborate and complicated. Due to the negative impact of agglomeration, the successful dispersion of nanofillers is pivotal in the further development of nanodielectrics for various insulation applications. In this thesis, electrospinning is proposed and realized as a new dispersal method for nanofillers in polymeric materials. This novel technique facilitates polymeric nanocomposites with improved properties due to the uniform distribution of fillers. Scanning electron microscopy (SEM) images and energy dispersive X-ray analysis (EDX) clearly indicate that electrospun nanocomposites demonstrate a better filler distribution than nanocomposites, produced by conventional mechanical mixing. Also electrospinning introduces the possibility of separating different nanofillers in different base polymers. The mechanical properties: tensile strength and hardness; the electrical properties: permittivity, tracking, and erosion resistance; and the thermal properties: thermal conductivity, thermal degradation, and heat erosion resistance of electrospun nanocomposites are compared to those of conventional nanocomposites for silicone rubber and cycloaliphatic epoxy-based polymers. All the experimental studies in this thesis confirm that electrospun nanocomposites exhibit better thermal performances than the conventional composites which are attributed to the improved distribution of the nanofillers by the newly developed electrospinning process. Also in this investigation, a two-dimensional thermal model is developed in COMSOL MultiphysicsTM by using the finite element method (FEM) to theoretically address the benefits of using nanofillers and the effects of filler dispersion. The model confirms that electrospun nanocomposites have much more uniform temperature distribution than conventional nanocomposites. This thesis presents the possible mechanisms by which nanofillers improve the heat and erosion resistance of silicone rubber nanocomposites, and also addresses the possible mechanism by which electrospinning improves nanofiller dispersion.

The bio-renewable monomer γ-methyl-α-methylene-γ-butyrolactone (MeMBL) has been thoroughly investigated in this thesis. MeMBL is a relatively unstudied monomer that had received little attention since the early 1980’s but has become a subject of renewed interest since a process to produce it from biomass derivatives was developed in 2004. The principle interest with this monomer aside from the “green” potential associated with bio-renewables results from its structure being cyclically analogous to methyl methacrylate (MMA) as well as improved solvent resistance and a high (215oC+) glass transition temperature (Tg) compared to most petroleum sourced acrylics. There are three major areas of focus in this work, examining polymerization kinetics, synthesis and polymer characterization. The polymerization kinetics of MeMBL were investigated with a variety of petroleum sourced monomers. MeMBL is in all cases preferentially incorporated into copolymers, presenting challenges for composition control. Preliminary investigations of aqueous phase polymerizations of MeMBL were problematic and led to investigations of organic phase polymerizations. The dispersion polymerization method was used to produce copolymers of MeMBL and MMA; during the study we obtained new insight into the mechanisms of particle nucleation and growth. With the acquired knowledge of MeMBL polymerization kinetics, the dispersion technique was used to produce MeMBL/MMA copolymers of controlled composition by semibatch for characterization studies. The addition of MeMBL raises polymer Tg and lowers molecular weight, but due to unexpected difficulties in processing MeMBL copolymers, mechanical properties could not be investigated in this study. Future work may need to revisit other polymerization techniques in order to produce processable polymers to test whether or not MeMBL might be a suitable alternative to petroleum sourced monomers that is capable of extending the range and utility of acrylics. / Thesis (Master, Chemical Engineering) -- Queen's University, 2011-04-25 09:39:19.959

High-speed particle dispersion research is motivated by the energy release enhancement of explosives containing solid particles. In the initial explosive dispersal, a dense gas-solid flow can exist where the physics of phase interactions are not well understood. A dense particle flow is generated by the interaction of a shock wave with an initially stationary packed granular bed. The initial packed granular bed is produced by compressing loose aluminum oxide powder into a 6.35 mm thick wafer with a particle volume fraction of 0.48. The wafer is positioned inside the shock tube, uniformly filling the entire cross-section. This results in a clean experiment where no flow obstructing support structures are present. Through high-speed shadowgraph imaging and pressure measurements along the length of the channel, detailed information about the particle-shock interaction was obtained. Due to the limited strength of the Mach 2 incident shock wave, no transmitted shock wave is produced. The initial “solid-like” response of the particle wafer acceleration forms a series of compression waves that coalesce to form a shock wave. Breakup is initiated along the periphery of the wafer as the result of shear that forms due to the fixed boundary condition. Particle break-up starts at local failure sites that result in the formation of particle jets that extend ahead of the accelerating, largely intact, wafer core. In a circular tube the failure sites are uniformly distributed along the wafer circumference. In a square channel, the failure sites, and the subsequent particle jets, initially form at the corners due to the enhanced shear. The wafer breakup subsequently spreads to the edges forming a highly non-uniform particle cloud. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-09-25 14:15:37.615

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Nanosecond pulse electroporation of biological cells is gaining significant interest due to its ability to influence intracellular structures. In nanosecond pulse electroporation of biological cells nanosecond duration pulses with high frequency spectral content are applied to the cell. In this research we show that accurate modeling of the nanosecond pulse electroporation process requires considering the effect of the membrane dielectric relaxation on the electric potential across the membrane. We describe the dielectric relaxation of the membrane as dispersion in the time-domain and incorporate it into the nonlinear asymptotic model of electroporation. Our nonlinear dispersive model of a biological cell is solved using finite element method in 3-D space enabling arbitrary cell structures and internal organelles to be modeled. The simulation results demonstrate two essential differences between dispersive and non-dispersive membrane models: the process of electroporation occurs faster when the membrane dispersion is considered, and the minimum required electric field to electroporate the cell is significantly reduced for the dispersive model.

This work presents the design, theory, and measurement of a phase-reconfigurable reflectarray (RA) element for beamforming applications enabled by fluidic networks and colloidal dispersions. The element is a linearly polarized microstrip patch antenna loaded with a Coaxial Stub Microfluidic Impedance Transformer (COSMIX). Specifically, adjusting the concentration of highly dielectric particulate in the dispersion provides localized permittivity manipulation within the COSMIX. This results in variable impedance load on the patch and ultimately continuous, low-loss phase control of a signal reflected from the patch. Different aspects of design, modeling, and measurement are discussed for a proof-of-concept prototype and three further iterations. Initial measurements with manual injections of materials into a fabricated proof-of-concept demonstrate up to 200 degrees of phase shift and a return loss of less than 1.2 dB at the operating frequency of 3 GHz. The next design iteration addresses fabrication challenges as well the general cumbersomeness of the proof-of-concept by replacing the static material delivery system with a dynamic closed-loop fluidic network. It also makes use of a design procedure to maximize the phase sensitivity. Measurements demonstrate progressive phase shifts through dilution of the system reservoir; however, the initial measurements with this system are not in line with simulated predictions. Investigations suggest the primary culprit to be inaccurate material data. The dielectric constant of the particulate (colloidal BSTO) was overrated and the loss tangent of the fluid medium (a silicone-based oil) was underrated. After accounting for these issues the measurement a second measurement with the system demonstrates 270 degrees of phase shift with return loss of 9 dB. The next design iteration examines a trade-off between phase sensitivity and reduced losses. The design also features modifications to the fluidic system to allow for layered fabrication in the GND plane as well integration with a 2-port coaxial measurement cell. Attempted measurements discover the fluidic system cannot flow the higher concentrations of nanoparticles necessary for phase shifting. A final design iteration addresses this challenge by expanding and repositioning inlets to the fluidic system. Free space reflection measurements with this element initially demonstrate phase shifting until a buildup of nanoparticles form within the COSMIX.

Nanosecond pulse electroporation of biological cells is gaining significant interest due to its ability to influence intracellular structures. In nanosecond pulse electroporation of biological cells nanosecond duration pulses with high frequency spectral content are applied to the cell. In this research we show that accurate modeling of the nanosecond pulse electroporation process requires considering the effect of the membrane dielectric relaxation on the electric potential across the membrane. We describe the dielectric relaxation of the membrane as dispersion in the time-domain and incorporate it into the nonlinear asymptotic model of electroporation. Our nonlinear dispersive model of a biological cell is solved using finite element method in 3-D space enabling arbitrary cell structures and internal organelles to be modeled. The simulation results demonstrate two essential differences between dispersive and non-dispersive membrane models: the process of electroporation occurs faster when the membrane dispersion is considered, and the minimum required electric field to electroporate the cell is significantly reduced for the dispersive model.