abstract: A comprehensive and systematic investigation on the diffusion and phase behaviors of nanoparticles and macromolecules in two component liquid-liquid systems via Molecule Dynamic (MD) simulations is presented in this dissertation. The interface of biphasic liquid systems has attracted great attention because it offers a simple, flexible, and highly reproducible template for the assembly of a variety of nanoscale objects. However, certain important fundamental issues at the interface have not been fully explored, especially when the size of the object is comparable with the liquid molecules. In the first MD simulation system, the diffusion and self-assembly of nanoparticles with different size, shape and surface composition were studied in an oil/water system. It has been found that a highly symmetrical nanoparticle with uniform surface (e.g. buckyball) can lead to a better-defined solvation shell which makes the “effective radius” of the nanoparticle larger than its own radius, and thus, lead to slower transport (diffusion) of the nanoparticles across the oil-water interface. Poly(N-isopropylacrylamide) (PNIPAM) is a thermoresponsive polymer with a Lower Critical Solution Temperature (LCST) of 32°C in pure water. It is one of the most widely studied stimulus-responsive polymers which can be fabricated into various forms of smart materials. However, current understanding about the diffusive and phase behaviors of PNIPAM in ionic liquids/water system is very limited. Therefore, two biphasic water-ionic liquids (ILs) systems were created to investigate the interfacial behavior of PNIPAM in such unique liquid-liquid interface. It was found the phase preference of PNIPAM below/above its LCST is dependent on the nature of ionic liquids. This potentially allows us to manipulate the interfacial behavior of macromolecules by tuning the properties of ionic liquids and minimizing the need for expensive polymer functionalization. In addition, to seek a more comprehensive understanding of the effects of ionic liquids on the phase behavior of PNIPAM, PNIPAM was studied in two miscible ionic liquids/water systems. The thermodynamic origin causes the reduction of LCST of PNIPAM in imidazolium based ionic liquids/water system was found. Energy analysis, hydrogen boding calculation and detailed structural quantification were presented in this study to support the conclusions. / Dissertation/Thesis / Doctoral Dissertation Chemical Engineering 2017

No / This paper presents a comparison of experimental results and numerical predictions of drop formation from a single submerged nozzle for a liquid-liquid system. The theoretical model is a modification of previous models used for a two-stage drop formation mechanism. The model has been tested against experimental data for kerosene drop formation in distilled water using a range of different nozzle diameters. In addition, our liquid-liquid model has been compared with both experimental and predicted results from published literature. These comparisons demonstrate that for liquid-liquid systems, the present predictions of drop diameter versus dispersed phase nozzle velocity are in overall agreement with both the present and previous experimental results. In addition, the present model predictions are more accurate than those of previous models for liquid-liquid systems.

La récupération assistée du pétrole implique la progression dans unmilieu poreux d'une phase aqueuse qui pousse une phase organique. Al'échelle du pore, les forces visqueuses et la gravité sontnégligeables, et la capillarité joue un rôle prépondérant : ledéplacement des fluides est gouverné par leur affinité avec lessurfaces et par les hétérogénéités de canaux. Les films liquidesexistent dans les pores d'une roche. Trois systèmes microfluidiquessont mis en place pour étudier le rôle des films microscopiques (demouillage) ou des films macroscopiques (de coins). Le premier consisteen un capillaire de section circulaire dans lequel on suit lemouvement d'un ménisque dans des conditions de mouillage variées. Enparticulier, en mouillage pseudo-partiel, un hystérésis d'angle decontact est observé, mais les films de mouillage présents dans cesystème conduisent à un accrochage de ligne de contact beaucoup plusfaible qu'en absence de film. Les deuxième et troisième systèmesmettent en évidence l’influence des films de coins dans un canalrectangulaire sur l'avancée du ménisque. Le couplage de l'écoulemententre la phase du coin et la phase du milieu entraîne le drainage del’huile piégée. Les propriétés de ce nouveau mécanisme sontcaractérisées par des expériences et s’accordent avec le modèleconstruit. / Enhanced oil recovery involves the displacement of an organic fluid byan aqueous one in the pores of the rocks. At the pores scale. Thedisplacement of fluids is governed by wetting condition of the system.The viscous and gravity forces are negligible and the capillarityplays a dominant role heterogeneities of channel sizes. Threemicrofluidic systems are designed to study experimentally the role ofmicroscopic liquid films (wetting) or macroscopic ones (corners) inthe pores level. The first one consists of the displacement of ameniscus in a circular capillary with various wetting conditions. Inparticular, for pseudo-partial wetting systems, a contact anglehysteresis is observed but with a weak pinning as compared to partialwetting systems where there are non wetting films. The second andthird ones show the influences of liquid films in the corners of asquare channel. The coupling between the corner flows and the mainflow involves the drainage of the trapped oil cluster. The propertiesof this new mechanism are consistent with the theoretical model, andalso characterized by experiments.