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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Understanding of charge effects in pickering emulsions and design of double pickering emulsion templated composite microcapsules

Wang, Hongzhi 12 January 2015 (has links)
Particle stabilized emulsions, also known as Pickering emulsions, have been widely used in many industry applications. While the breadth of potential applications for Pickering emulsions keeps growing, our fundamental understanding of Pickering emulsions is still poor. My thesis work addresses both fundamentals and applications of particle stabilized emulsions. In the fundamental part of this thesis work, we investigated the effects of particle charge on particle adsorption and the particle contact angle, and to investigate their ensuing consequences for the stability of Pickering emulsions. We provided the first experimental hint that the widely overlooked image charge repulsion can hinder the adsorption of particle to the oil-water interface and prevent the formation of Pickering emulsions. Consistently with the experimental suggestion, our theoretical model also confirmed that the image charge repulsion has the right order of magnitude, relative to the other forces acting on the particle, to impede particle adsorption and Pickering emulsification. For the conditions in which particle adsorption to the liquid interface does occur, the particle contact angle will play an important role in influencing the stability and type of Pickering emulsions. Our experimental work showed that the equilibrium contact angle of particles at interfaces and the type of emulsions preferentially stabilized by these particles can be strongly affected by the particles' charging state, which we attribute to a free energy contribution from the electric field set up by the charged particle and its asymmetric counterion cloud. A very simplistic calculation considering only the dipole field as the leading contribution and treating the water phase as a perfect conductor, found that the energy stored in the field is indeed strong enough and shows sufficient variation with the particle position to shift the equilibrium position significantly from where it would be based on interfacial tension alone. In a separate, more application oriented part of this thesis work, we have fabricated microcapsules from double Pickering emulsions and demonstrated that the combined use of hard silica particles and pH-responsive dissoluble polymer particles at the emulsion interface imparts a combination of pH-responsiveness (stimulated pore opening) and structural integrity to resulting capsules. We have further demonstrated the first double Pickering emulsion templated capsules in which interfacial polymerization was carried out at both emulsion interfaces, yielding a capsule with two composite shells, composed of polyurethane and silica particles, and characterized the transport of a model cargo through the capsules walls as well as the capsules' mechanical properties.

Electrostatic enhancement of lipase catalysed hydrolysis in a spray reactor

Jones, Elizabeth January 1997 (has links)
No description available.

Interactions between an air bubble and emulsified oil droplets

Seoud, Hicham F. January 1974 (has links)
No description available.

Formulation and characterisation of nanoparticles from biocompatible microemulsions

Krauel, Karen, n/a January 2005 (has links)
The aims of this study were to prepare poly (ethylcyanoacrylate) (PECA) nanoparticles on the basis of different types of microemulsions, to investigate the entrapment within and release of a bioactive from these particles and to establish a set of delivery systems with varying entrapment and release characteristics, thereby giving the formulator the opportunity of a more tailor-made approach in the development of a delivery system. Furthermore the scale up of particle preparation and the possible enhancement of the immunogenic properties of PECA particles by incorporation of the adjuvant Quil A was investigated. Methods: Four phase triangles were established and microemulsion samples, used as a template to prepare nanoparticles, were characterised by viscosity and conductivity measurements, polarising light microscopy, freeze fracture transmission electron microscopy (TEM), cryo field emission electron microscopy (cryo FESEM) and self-diffusion NMR to determine their microemulsion type (droplet, bicontinuous, solution type). PECA nanoparticles were prepared from different types of microemulsions by interfacial polymerisation. Particle size, polydispersity index (PI) and [zeta]-potential were measured by photon correlation spectroscopy and electrophoretic mobility respectively. Normal scanning electron microscopy (SEM) and cryo FESEM were used to visualise particles. Fluorescently labelled ovalbumin (FITC-OVA) was used as a model protein/antigen and entrapment within and release from nanoparticles was investigated. To scale up nanoparticle preparation an instrumental set-up with reactor, peristaltic pump and stirrer was used. A 2⁷ fractional factorial study was designed to observe possible factors or their interactions that could influence particle formation under scale up conditions. For an immunological study freeze dried formulations of PECA nanoparticles, having FITC-OVA and Quil A entrapped, were prepared, and activation and uptake of formulations by murine bone marrow derived dendritic cells (DCs) and T cells in vitro were monitored. Results: Results obtained from the measurements described above, for formulations from the four different phase triangles, indicated that microemulsions of w/o droplet, bicontinuous or solution type could be formed. It was possible to prepare PECA nanoparticles from all of the different types of microemulsions. Particles had an average size of 265 nm � 24, with an average PI of 0.18 � 0.05 and an average negative [zeta]-potential of -17 mV � -5. Particle size, PI and [zeta]-potential were not influenced by the type of microemulsion that was used as a polymerisation template. Entrapment and release were however influenced by the type of microemulsion and although entrapment of FITC-OVA was generally high for PECA particles, it was highest for particles prepared from a droplet type microemulsion. Entrapment could also be increased by increasing amounts of monomer. The rate of release was dependent on the amount of monomer used for polymerisation and the type of microemulsion used for particle preparation, with nanoparticles prepared from a w/o droplet type microemulsion showing the slowest release. Furthermore it was shown that particle preparation could be scaled-up with the instrumental set-up used in this study, but conditions need to be refined as the average particle size and polydispersity index were considerably larger (441 nm � 101, 0.68 � 0.14) when compared to particles prepared by the beaker-pipette method (see above). The adjuvant Quil A could efficiently be entrapped into PECA nanoparticles together with FITC-OVA. Incubation of DCs and T cells with the various formulations did, however, not result in increased uptake or activation. Conclusions: PECA nanoparticles with high entrapment efficiency of antigen and adjuvant can be prepared from different types of microemulsions. Particles show different rates of entrapment and release depending on the type of microemulsion used as a polymerisation template, possibly because two different types of nanoparticles form. Nanocapsules are believed to form on the basis of droplet type microemulsions and nanospheres form on the basis of bicontinuous and solution type microemulsions. Freeze dried formulations of PECA nanoparticles, containing Quil A and FITC-OVA, were not able to induce an immune response, which might be due to charge repulsion effects between the negatively charged PECA nanoparticles and the negatively charged surface of dendritic cells. Moreover, no adjuvant effect of Quil A was apparent, perhaps caused by total encapsulation of the compound into the particle matrix with no active groups extending out displaying adjuvanticity.

Investigation into optimal Rh(III) dopant placement in silver bromide emulsions /

Telep, David A. January 1993 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 1993. / Typescript. Includes bibliographical references.

Preparation of surfactant-free oil-in-water emulsions by ultrasonication for inductively coupled plasma-mass spectrometry measurement

Chan, Tsz-kwan, January 2008 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references. Also available in print.

Structure and phase behavior in microemulsions /

Billman, John Frederick, January 1990 (has links)
Thesis (Ph. D.)--University of Washington, 1990. / Vita. Includes bibliographical references (leaves [163]-175).

Un modèle pour la séparation d'une émulsion huile-eau /

Dallaire, Antonin, January 1997 (has links)
Mémoire (M.Eng.)--Université du Québec à Chicoutimi, 1997. / Document électronique également accessible en format PDF. CaQCU

Stability of water-in-diluted bitumen emulsion droplets

Gao, Song. January 2010 (has links)
Thesis (Ph. D.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on April 1, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemical Engineering, Department of Chemical and Materials Engineering, University of Alberta. Includes bibliographical references.

Perfluorooctyl bromide emulsions as In Vivo carriers for laser polarized 129Xe for Magnetic Resonance imaging : the effect of phosphatidylcholine chain-leghth and oxygenation of the emulsion on longitudinal relaxation time (T1) and line-with /

McPhee, Daniel P. January 1900 (has links)
Thesis (M. Sc.)--Carleton University, 2001. / Includes bibliographical references (p. 77-81). Also available in electronic format on the Internet.

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