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Centred in Motion presents a strategy for adapting the existing suburban development of Pickering, Ontario to accommodate contemporary needs. The cultural and geographical conditions that generated Pickering, along with similar suburbs in the Toronto area and across North America, are vastly different from current conditions. An adaptive response addressing these suburbs is necessary to foster intelligent future growth in the Greater Toronto Area. The thesis proposes the design of a mixed-use complex that builds on existing infrastructure and adds density in centrally located, underutilized space within Pickering. A key element is an “inhabitable bridge” that connects the Pickering Town Centre mall in downtown Pickering to commuter services at the GO Transit station and lands to the south. The project embeds a variety of residential, commercial, and civic programs within this infrastructure, providing new services to existing residents, and creating expanded living options with a reduced dependency on personal automobiles within Pickering.

Centred in Motion presents a strategy for adapting the existing suburban development of Pickering, Ontario to accommodate contemporary needs. The cultural and geographical conditions that generated Pickering, along with similar suburbs in the Toronto area and across North America, are vastly different from current conditions. An adaptive response addressing these suburbs is necessary to foster intelligent future growth in the Greater Toronto Area. The thesis proposes the design of a mixed-use complex that builds on existing infrastructure and adds density in centrally located, underutilized space within Pickering. A key element is an “inhabitable bridge” that connects the Pickering Town Centre mall in downtown Pickering to commuter services at the GO Transit station and lands to the south. The project embeds a variety of residential, commercial, and civic programs within this infrastructure, providing new services to existing residents, and creating expanded living options with a reduced dependency on personal automobiles within Pickering.

Much research has been carried out in recent years on Pickering emulsions, but understanding of the underlying physics requires considerable strengthening. This thesis seeks to address several fundamental aspects by presenting the results of recent experimental work. This work has focused on a model oil-in-water emulsion system stabilised by fluorescent colloidal silica particles and using a mixture of dodecane and isopropyl myristate as the oil phase. The phase behaviour of the particle dispersions has been altered using sodium chloride and sodium iodide, whilst sodium hydroxide and hydrochloric acid have been used to adjust the pH of samples. Comparisons are also made to emulsions stabilised by commercially available fumed silica. Conventionally, it was assumed that a weakly flocculating particle dispersion is required in order to generate a stable Pickering emulsion. It is shown in this work, however, that in some circumstances a weakly flocculating dispersion leads to the least stable emulsion. It is therefore argued that a more nuanced view of Pickering stabilisation is required, taking into account the factors affecting whether particles will adsorb to the interface during emulsification. Very recently it has begun to be suspected that Pickering emulsions sometimes aggregate due to the sharing of particles between two droplets, an effect known as bridging. In this thesis it is also shown that particle bridges can form in Pickering emulsions at high shear, and that they can subsequently be broken by low shear or by modifying the particle wettability. For the first time, electron microscopy has been used to provide direct evidence of droplets sharing particles. A simple theoretical model is developed, based on collisions between partially coated droplets, which captures the trends observed experimentally. It is argued that particle bridging may have been overlooked in the literature, and that the shear history of emulsions is a crucial determinant of subsequent behaviour. The deaggregation of bridged emulsions has been studied using a novel method where two different colours of particles are used. By starting with two emulsions which are bridged, each stabilised by a different colour of particle, and then using confocal microscopy to study them as they are mixed together and deaggregate, the processes involved in deaggregation can be elucidated. These experiments have also shown, for the first time, the dynamic nature of particles in Pickering emulsions; particles transfer readily between droplets when the samples are placed on a roller bank. It is found that a period of unbridging and rebridging takes place prior to deaggregation of the emulsions, and the timescale of deaggregation can be tuned by varying the particle wettability. The two-colour method has also been applied to the study of Pickering emulsions which are repeatedly sheared. It is found that limited coalescence is not reestablished simply by re-applying the shear rate which was used in the initial emulsification. This behaviour is attributed to the presence of an elastic shell of particles at the interface, which inhibits droplet breakup, and is in contrast to that of surfactant-stabilised emulsions, where increasing the stabiliser concentration makes droplets more liable to deform and breakup. Finally, a short study has been carried out attempting to increase the scale of the experiments presented in this thesis to sample volumes of approximately one litre. This study has demonstrated the relevance of particle bridging to industrial emulsification processes. Overall, experiments with carefully controlled model Pickering emulsions, including those using two colours of particles, have revealed the fundamental workings of these arrested systems.

Le comportement de différents systèmes ternaires eau/huile/surfactif dans des puces microfluidiques de configuration « flow focusing » a été étudié sur la base du concept de "formulation optimale". L’influence des variables de formulation (nature du surfactif, polarité de l'huile (caractérisée par son "Equivalent Alkane Carbon Number" ou EACN), salinité de la phase aqueuse, température) et des variables de procédé (débit des phases aqueuses et huileuses, diamètre et mouillabilité des micro-canaux) sur le comportement de flux des systèmes biphasiques eau/huile en présence de surfactifs non ioniques (e.g. alcools gras polyéthoxylés), anioniques (e.g. dodécylsulfate de sodium) et cationiques (sels d'alkylammonium) a été examiné. La prédominance du comportement « jet flow » à l’approche de la « formulation optimale » permet la comparaison des tensioactifs, comme la méthode des balayages de formulation mais en nécessitant moins de réactif et moins de temps. Des émulsions Tween 80-Span 20/esters/eau, pour des applications en cosmétique, ont ainsi été formulées et caractérisées. Par ailleurs, les avantages de la technologie des microréacteurs ont été démontrés par le développement d’un réacteur à flux continu pour l’oxydation catalytique par le peroxyde d'hydrogène en émulsions de Pickering exemptes de solvant et stabilisées par des complexes à base de cyclodextrines. La comparaison des résultats obtenus à ceux des réactions menées en réacteur classique a mis en évidence un accroissement considérable de la vitesse de réaction. / The behavior of various ternary surfactant/oil/water systems in microfluidic chips with flow focusing configuration has been studied based on the concept of "optimal formulation." The influence of formulation variables (nature of the surfactant, polarity of oil (characterized by its "Equivalent Carbon Number Alkane" or EACN) salinity of the aqueous phase, temperature) and process variables (flow rate of the aqueous and oil phases, diameter and wettability of the micro-channels) on the flow behavior of water/oil biphasic systems in the presence of nonionic surfactants (e.g. polyoxyethylene fatty alcohols), anionic (e.g. sodium dodecyl sulfate) and cationic (alkylammonium salts) was examined. The predominance of the "jet flow" behavior in the vincinity of the so called “optimal formulation” allows the comparison of surfactants, similarly to scans formulation consuming less products and requaring a shorter time. Emulsions Tween 80-Span 20/esters/water for applications in cosmetics, have been prepared and characterized. Furthermore, the benefits of the microreactors technology were demonstrated by the development of a continuous flow reactor for the catalytic oxidation with hydrogen peroxide in free solvent Pickering emulsion stabilized by complexes with cyclodextrins. Comparison of the results performed in batch reactor showed a significant improvement in the reaction rate.

Les travaux de cette thèse portent sur la formation et la polymérisation d'émulsions de Pickering stabilisées par des nanocristaux de cellulose (NCC). Tout d’abord, les NCC sont fonctionnalisés en surface de façon à modifier d'une part, leur balance hydrophile/hydrophobe et d'autre part, apporter des fonctions promoteurs de la polymérisation par ATRP de la phase interne ou externe. A l'aide de ces NCC, des émulsions directes, inverses et doubles de styrène et de monomères acryliques ont été stabilisées puis polymérisées. L'impact, de la fonctionnalisation des NCC, de la nature du monomère et de l’amorceur, de la présence ou pas de sel sur, la taille, la stabilité, la couverture des gouttes et la morphologie des objets obtenus, a été étudiée. Les latex issus de la polymérisation radicalaire d’émulsions directes de Pickering ont permis la préparation de composites aux propriétés mécaniques améliorées par rapport à celles de la matrice sans charge. Les émulsions stabilisées par des NCC réactifs ont conduit à la synthèse de capsules ou de billes pleines en fonctions de la nature du monomère polymérisé. Des matériaux poreux ont été obtenus par polymérisation des émulsions inverses de Pickering. Enfin, la polymérisation des émulsions doubles a permis l’obtention d’objets à morphologie tout à fait inédite avec l’encapsulation de capsules de polystyrène dans des capsules plus volumineuses de ce même polymère. / Pickering emulsions are based on amphiphilic particle stabilizers, which adsorb irreversibly at the liquid-liquid interface and form a rigid structure around the droplets. Amongst these particles, biosourced and biorenewable cellulose nanocrystals (CNCs) have demonstrated good performances as Pickering stabilizers for oil in water emulsions. In this thesis, a wide range of emulsions of monomers were stabilized by amphiphilic modified CNCs. These Pickering emulsions subsequently serve as vessel to perform radical polymerization. In a first step, the CNCs are modified to tailor the hydrophobic/hydrophilic balance and are used to efficiently stabilize direct (O/W), inverted (W/O) or double W/O/W Pickering emulsions of monomers. The different emulsions obtained were subsequently polymerized, by thermal radical polymerization or by SI-ATRP. The polymerization of the direct emulsions allowed producing either capsules or filled beads, depending on the monomer used, which we assigned to differences in monomer reactivity. Hence, the method offers the opportunity to tune the morphology of the polymerized spheres (empty or filled), by simply controlling the monomer conversion. The polymerization of the inverted emulsion on the other end, led to the formation of a porous material. The polymerization of the double W/O/W emulsions was also envisaged, leading original morphology such as small empty beads encapsulated into larger capsules.

The primary purposes of the study are to explain the essentials of citizen participation and see how the community has reacted to an actual example of citizen participation, the North Pickering Public Participation Program. Citizen participation emerges as a consequence of both the planners' and the people's consciousness. It means different things to different people, but few cases represent true participation. In the study, an implicit comparison is made between an officially initiated public participation process and a community-preferred one. Urbanization and suburbanization have brought about intense growth in the existing urban centres and tremendous loss of agricultural land in Southern Ontario. The choice of North Pickering as the site for a new town is claimed to be an answer to the growth objective of decentralization and deconcentration. Its planning process has proceeded with a large-scale citizen participation program. "Information and consultation" are the official strategies from which "decision-making is to be a shared one". Most people are not happy with the participation process for they have not been truly consulted and their opinions have not been considered, although official sources say the final plan for North Pickering reflects public inputs. The community prefers a process in which they are given some power over the bargaining process.It is suggested that the North Pickering Participation Process represents some degree of tokenism. The officials have the intent, but not the proper way, of involving the people. Thus frustrations arise on both sides. This probably explains why a similar process will not go with the planning of Townsend, another new town to be built in Southen1 Ontario. Though not satisfactory, citizen participation in North Pickering is a worthwhile experience. It should be a start rather than an end in itself. / Thesis / Bachelor of Arts (BA)

Dans ce travail, nous nous sommes intéressés à la génération d’oxygène singulet (1O2), un oxydant sélectif permettant d'accéder à de nombreux intermédiaires oxygénés d’intérêt pour la chimie fine, par les polyoxométallates (POMs). Le criblage d’une série de POMs a permis de mettre en évidence pour la première fois, grâce à la détection spécifique de la luminescence infrarouge à 1270 nm, la formation de 1O2 par décomposition du peroxyde d'hydrogène catalysée par des POMs. Plus particulièrement, les polyoxoniobates se sont révélés très performants et ont fait l’objet d’une étude approfondie. Afin de pouvoir appliquer ces systèmes à l’oxydation de substrats hydrophobes, des sels d'alkylammonium ont été préparés, leur conférant ainsi des propriétés amphiphiles permettant d’envisager une catalyse interfaciale. Ainsi, nous avons montré que suivant la nature du solvant, en présence d’eau, des systèmes de microémulsions et d’émulsions de Pickering peuvent être obtenus. Leur intérêt en catalyse d’oxydation a été démontré, illustrant ainsi un nouvel exemple du concept "Pickering Interfacial Catalysis" (PIC) en émulsion. Par ailleurs, nous reportons également, pour la première fois, un nouveau surfactif catalytique équilibré (concept BCS) à base de POMs conduisant à la formation spontanée de systèmes de microémulsion triphasique en présence d'eau et d'huile. Enfin, les émulsions de Pickering catalytiques à base de cyclodextrines (CDs), développées précédemment au laboratoire, ont été reconsidérées sous l'angle de la catalyse interfaciale, ce qui nous a menés à proposer un nouveau concept de nanoparticules hybrides auto-assemblées cœur-écorce (CD@POM). / In this work, we focused on the catalytic generation of singlet oxygen (1O2), a selective oxidant allowing access to many oxygenated intermediates of interest for fine chemistry, by polyoxometalate (POMs). The screening of a series of POMs allowed us to evidence, through the specific detection of the infrared luminescence at 1270 nm, the formation of 1O2 from the decomposition of hydrogen peroxide catalyzed by POMs. More specifically, polyoxoniobates have been proved to be more active, and have been the subject of extensive studies. In order to use these systems for the oxidation of hydrophobic substrates, alkylammonium salts have been prepared, giving them amphiphilic properties to carry out interfacial catalysis. Thus, we have shown that depending on the nature of the solvent, in the presence of water, microemulsion systems and Pickering emulsions can be obtained. Their interest in oxidation catalysis has been demonstrated, illustrating a new example of the "Pickering Interfacial Catalysis" (PIC) concept in emulsion. In addition, we also report, for the first time, a new balanced catalytic surfactant (BCS concept) based on POMs leading to the spontaneous formation of triphasic microemulsion systems in presence of oil and water. Finally, catalytic Pickering emulsions based on cyclodextrins (CDs), previously developed in the laboratory, were reconsidered from the perspective of interfacial catalysis, which led us to propose a new concept of hybrid self-assembled core-shell nanoparticles (CD@POM).

Des nanoparticules amphiphiles catalytiques ont été préparées et caractérisées en recourant à diverses techniques telles que la microscopie électronique à transmission et à force atomique et la diffusion dynamique de la lumière et des rayons X aux petits angles. Celles-ci résultent de l’association électrostatique entre une entité amphiphile de type ammonium quaternaire et un catalyseur d’oxydation de type polyoxométallate (POM), e.g. le dodécatungstophosphate de tri(dodécyltriméthylammonium), [C12]3[PW12O40]. Elles sont obtenues spontanément par échange d’ions et présentent une sphéricité relativement monodisperse variant entre 30 et 65 nm selon la nature du POM. En présence d’eau et un solvant aromatique, ces nanoparticules amphiphiles stabilisent des émulsions de Pickering dont la taille des gouttelettes est d’environ 20 µm. En présence d’eau oxygénée, ces nouveaux milieux réactionnels se sont révélés très efficaces pour la conversion d’oléfines en époxydes. De plus, ils permettent une séparation aisée des produits (dans la phase organique) et du catalyseur (solide) par simple centrifugation. Par ailleurs, un criblage d’une vingtaine de solvants « verts », stables dans des conditions d’oxydation, a mis en évidence une activité remarquable de ces nanoparticules en système solvant en comparaison aux formes sodiques et acides classiquement utilisées. Le méthoxycyclopentane et le 2-méthyltétrahydrofurane se sont révélés parmi les meilleurs solvants pour l’époxydation d’oléfines. L’obtention de dispersions stables permet une récupération facile du catalyseur par centrifugation et sa recyclabilité a été démontrée. / Amphiphilic nanoparticles with catalytic properties were prepared and characterized using various techniques such as transmission electron microscopy and dynamic light scattering to determine their size, small angles X-ray scattering to their internal structure and atomic force microscopy for their contact angle. These nanoparticles result from the electrostatic association between an amphiphilic quaternary alkylammonium and an oxidation catalyst as polyoxometalate (POM), e.g. tri(dodecyltrimethylammonium) dodecatungstophosphate, [C12]3[PW12O40]. They are obtained spontaneously by simple exchange of ions and are monodisperse sphere between 30 and 65 nm depending on the nature of the POM. In presence of water and aromatic solvent, such amphiphilic nanoparticles stabilize Pickering emulsions whose droplet size is about 20 µm. In presence of hydrogen peroxide, the new reaction media are very efficient especially for the conversion of olefins to epoxides. In addition, they allow easy separation of the products (in the organic phase) and the catalyst (solid phase) by simple centrifugation. Furthermore, screening of around twenty "green" solvents, stable under oxidizing conditions, showed remarkable activity of these nanoparticles in the solvent system compared to sodium and acid forms of POMs conventionally used. The cyclopenthyl methyl ether and 2-methyltetrahydrofuran were found among the best solvents for the epoxidation of various olefins (e.g. cyclooctene, cyclohexene, 1-octene, terpenes...). The stable dispersions obtained allow an easy recovery of the catalyst by centrifugation and its recyclability has been demonstrated.

Bicontinuous Pickering emulsions (or bijels) are a relatively new class of novel soft material with many potential industrial applications, including microfluidics, tissue engineering and catalysis. They are typically formed by initiating the spinodal decomposition of a binary liquid mixture in the presence of neutrally-wetting colloidal particles. The particles attach at the liquid-liquid interface and arrest the phase separation by jamming when the concentration of particles approaches the 2D close-packing limit. Predicted by simulations in 2005 and realized in the laboratory in 2007, many aspects of the bijels complex behaviour and properties have remained unexplored. This thesis expands the knowledge of the bijels structural and dynamical properties, while focusing specifically on the role of particle size. The bijels porosity (average interfacial separation L) according to simulations can be controlled by varying the size r and volume fraction ϕ of particles in the system (L ∝ r/ϕ). The inverse scaling of L with ϕ has been verified for one size of particle, but to access smaller values of L (to allow the structure to be used for a wider range of industrial applications) the scaling with r must be tested. Chapter 3 presents the first systematic study of reducing particle size in bijels made with the liquid pair water/lutidine (W/L).We find that a five-fold reduction in r only requires moderate modification to preparation methods (concentrations of reactants during particle synthesis and increased particle sonication time) and in principle allows L values of between 1 & 10 μm to be accessed in the W/L system, where previously 10 μm was the limit. We demonstrate that this reduced lower bound of L can be translated into a lower bound for polymerized bijels also. Unfortunately, reducing particle size even further (in the same way) reveals a law of diminishing returns, as the uptake fraction of particles to the interface also reduces as we reduce particle size. Hence, to reduce lengthscale even further, a new bijel fabrication paradigm is required. Unexpectedly, we find that the temperature quench rate becomes less important for smaller particles (which constitutes a direct material synthesis advantage) and develop a new theoretical framework to take account of this observation. Large particles promote domain pinch-off during the coarsening (due to a larger driving force towards spontaneous curvature) resulting in bijel failure when slow rates are used because the time required to jam is greater than the time required for depercolation. To further probe the bijels structure as a function of particle size and quench rate, and to account for the success/failure scenarios which seem not to depend on L, in Chapter 4 we quantitatively characterize the morphology by measuring distributions of interfacial curvatures. By computing area-averaged quantities to make valid comparisons, we find that smaller particles and faster quench rates produce bijels with greater hyperbolic `open' character, aligning with our understanding of bijel formation gained from Chapter 3. We compare to simulated bijel data and an estimate of the hyperbolicity of the bare liquids undergoing spinodal decomposition, validating the results. In addition, we uncover a time-dependent `mutation' of the curvature distributions when large particles are used, but not when smaller particles or a different liquid pair is used. The mutation appears to correlate with the propensity of the interfacial particles to form a 'monogel', whereby the interfacial particles develop permanent bonds and remain as a 3D percolating network after the interface is removed, although the precise mechanism of the mutation is still to be verified. Following the results from Chapters 3 & 4 it is clear that there are potentially microscopic phenomena in the bijel which result in macroscopic aging and/or a determination of macroscopic structural properties. To investigate further, we use diffusing-wave spectroscopy (a form of light scattering) to probe the microscopic dynamics of the interfacial particles and/or the particle-laden liquid-liquid (L-L) interface. We find that bijel dynamics show two-step (fast/slow) decay behaviour, with the dynamics slowing as the system ages. The two-step decay is very similar to that observed in colloidal gels formed by diffusion-limited cluster aggregation (DLCA), with the initial (fast) decay due to thermally-activated modes of the gel network, and the later (slow) decay due to the relaxation of internal stresses induced by gel syneresis. For a bijel, the internal stresses could be due to syneresis, but could also be due to the jamming transition and/or the monogelation process and/or the forces acting on the L-L interface by the particle layer. In terms of the aging, if the system does not form a monogel, the correlation functions can be (almost) rescaled on to a master curve, indicating the property of universal aging. If the system does monogel, the functions cannot be superimposed, implicating the monogelation process as a potential cause for a different kind of aging in this system. Due to the interesting differences found when changing the size of the stabilizing particles in a bijel, in Chapter 6 we combine large and small particles (making `bimodal' bijels) and look for evidence of particle segregation by size, quantitatively estimate the ratio of particle uptake fractions and measure kinetics. Larger particles are found to adsorb to the interface in twice the quantity as smaller particles, and we find evidence to suggest the preference of larger particles for interfaces curved in only one direction, corroborating results from previous Chapters. Bimodal bijels take longer to jam than an equivalent monomodal (standard) bijel, which is backed up by simulations and highlights the increased ability of the bimodal particles to reorganise at the interface before arriving at the jammed metastable state. Finally, we also observe that the lengthscale of a bimodal bijel can heavily depend on the quench rate used during the preparation, suggesting that quench rate could be used (as well as particle size, volume fraction and contact angle) as a lengthscale control parameter. This thesis adds to the bijel literature, building on previous experimental studies and verifying/contradicting simulations. Particle size is shown to be a pivotal parameter for bijel formation in the W/L system, with particles of size r = 63 nm proving more versatile (markedly less sensitive to quench rate) than particles of size r ≈ 300 nm. However, even-smaller particles (of the same type) do not provide any additional advantage. We also show how the particle size can not only control bijel porosity (according to L ∝ r/ϕ as predicted by simulations) but can control bijel topology (smaller particles result in structures with greater hyperbolic character). By monitoring the bijel structure over time (topology and dynamics) we have shown that the bijel (in some cases) continues to age for at least c. 1 hr (topology) and in all cases c. 1 day (dynamics). For the first time experimentally, we have used a bimodal dispersion of particles to stabilize a W/L bijel and have uncovered a potentially useful new way to produce samples with different porosities from the same starting mixture, by changing the quench rate. The knowledge of the interplay between particle size and quench rate along with the effect on bijel topology will both assist in the scaling up of processes for industrial-level production and inform future strategies for tailoring the structure for specific applications. Future research should focus on several remaining open questions. The volume fraction of r = 63 nm particles in the W/L system should be increased towards 10% and sonication procedures improved to allow good redispersion to test the lower bound of L, which we expect to be around 1 μm. Also, a new W/L fabrication paradigm should be devised which uses sterically-stabilized particles, to continue the reduction of r towards the value used in simulations (5 nm) in order to test the fundamental physics of bijel formation, specifically what value of interfacial attachment energy is needed for long-term stability. Bijel dynamics can be further probed by using a technique which allows a variation in the probe lengthscale (e.g. / differential dynamic microscopy, DDM), as well as developing a better theoretical model for (multiple) light scattering in a bijel system to arrive at the mechanisms responsible for the anomalous aging, and compare to the predictions of monogelation. Finally, higher magnification/resolution microscopy should be used to look for particle segregation on the liquid-liquid interface (as seen in simulations) and to identify in real-space the locations of the changes in Gaussian curvature over time as measured in Chapter 4.