Domain and droplet sizes in emulsions stabilized by colloidal particles

Particle-stabilized emulsions are commonly used in various industrial applications. These emulsions can present in different forms, such as Pickering emulsions or bijels, which can be distinguished by their different topologies and rheology. We numerically investigate the effect of the volume fraction and the uniform wettability of the stabilizing spherical particles in mixtures of two fluids. For this, we use the well-established three-dimensional lattice Boltzmann method, extended to allow for the added colloidal particles with non-neutral wetting properties. We obtain data on the domain sizes in the emulsions by using both structure functions and the Hoshen-Kopelman (HK) algorithm, and demonstrate that both methods have their own (dis-)advantages. We confirm an inverse dependence between the concentration of particles and the average radius of the stabilized droplets. Furthermore, we demonstrate the effect of particles detaching from interfaces on the emulsion properties and domain size measurements.Comment: 9 pages, 9 figure

Timescales of emulsion formation caused by anisotropic particles

Particle stabilized emulsions have received an enormous interest in the recent past, but our understanding of the dynamics of emulsion formation is still limited. For simple spherical particles, the time dependent growth of fluid domains is dominated by the formation of droplets, particle adsorption and coalescence of droplets (Ostwald ripening), which eventually can be almost fully blocked due to the presence of the particles. Ellipsoidal particles are known to be more efficient stabilizers of fluid interfaces than spherical particles and their anisotropic shape and the related additional rotational degrees of freedom have an impact on the dynamics of emulsion formation. In this paper, we investigate this point by means of simple model systems consisting of a single ellipsoidal particle or a particle ensemble at a flat interface as well as a particle ensemble at a spherical interface. By applying combined multicomponent lattice Boltzmann and molecular dynamics simulations we demonstrate that the anisotropic shape of ellipsoidal particles causes two additional timescales to be of relevance in the dynamics of emulsion formation: a relatively short timescale can be attributed to the adsorption of single particles and the involved rotation of particles towards the interface. As soon as the interface is jammed, however, capillary interactions between the particles cause a local reordering on very long timescales leading to a continuous change in the interface configuration and increase of interfacial area. This effect can be utilized to counteract the thermodynamic instability of particle stabilized emulsions and thus offers the possibility to produce emulsions with exceptional stability.Comment: 14 pages, 14 figure

Tunable Dipolar Capillary Deformations for Magnetic Janus Particles at Fluid-Fluid Interfaces

Janus particles have attracted significant interest as building blocks for complex materials in recent years. Furthermore, capillary interactions have been identified as a promising tool for directed self-assembly of particles at fluid-fluid interfaces. In this paper, we develop theoretical models describing the behaviour of magnetic Janus particles adsorbed at fluid-fluid interfaces interacting with an external magnetic field. Using numerical simulations, we test the models predictions and show that the magnetic Janus particles deform the interface in a dipolar manner. We suggest how to utilise the resulting dipolar capillary interactions to assemble particles at a fluid-fluid interface, and further demonstrate that the strength of these interactions can be tuned by altering the external field strength, opening up the possibility to create novel, reconfigurable materials.Comment: 9 pages, 7 figure

Additive Manufacturing of Casting Tools Using Powder-Binder- Jetting Technology

This chapter presents the use of the additive manufacturing (AM) method powder-binder-jetting (PBJ) for the generation of molds and cores for casting applications. Theoretical information on process steps and the binding of particles is given. For the based chemistry, examples are presented and the transfer from conventional production processes to powder-binder-jetting is explained. For sand as a material for metal casting, methods to determine key properties for the casting are in focus. The figures found by our research activities reach up to that of conventional production and indicate the readiness of the technology. These cavities produced by powder-binder-jetting can even be used for cold casting materials such as concrete. Several demonstrators show the impact of this application. A polymer process for the investment casting process is topic of an additional section. To understand this process, theoretical information and figures determined by measurements are presented

Transferring Innovation From Corporate Incubators To Its Parent Company: Derivation Of Requirements For The Interfaces

The transfer of innovations into the parent company is one of the major challenges that separate innovation paths, such as corporate incubators, are facing these days. So far there is no specific design model for the transfer of innovation from corporate incubators. This research paper therefore focusses on the development of requirements for the configuration of the interfaces between these two entities. Based on an intensive literature study as well as interviews within a German automotive supplier, requirements for the transfer process between corporate incubator and its parent company are derived and discussed

Equilibrium orientation and adsorption of an ellipsoidal Janus particle at a fluid-fluid interface

We investigate the equilibrium orientation and adsorption process of a single, ellipsoidal Janus particle at a fluid-fluid interface. The particle surface comprises equally sized parts that are hydrophobic or hydrophilic. We present free energy models to predict the equilibrium orientation and compare the theoretical predictions with lattice Boltzmann simulations. We find that the deformation of the fluid interface strongly influences the equilibrium orientation of the Janus ellipsoid. The adsorption process of the Janus ellipsoid can lead to different final orientations determined by the interplay of particle aspect ratio and particle wettablity contrast.Comment: 23 pages, 7 figure

Theoretical Studies of Structural and Electronic Properties of Donor-Acceptor Polymers

The development of new electronic devices requires the design of novel materials since the existing technologies are not suitable for all applications. In recent years, semiconducting polymers (SCPs) have evolved as fundamental components for the next generation of costumer electronics. They provide interesting features, especially flexibility, light weight, optical transparency and low-cost processability from solution. The research presented in this thesis was devoted to theoretical studies of donor-acceptor (DA) copolymers formed by electron-deficient 3,6-(dithiophene-2-yl)-diketopyrrolo[3,4-c]pyrrole (TDPP) and different electron-rich thiophene compounds. This novel type of SCPs has received a lot of attention due to experimental reports on very good electronic properties which yielded record values for organic field-effect transistor applications. In order to get a deeper understanding of the structural and electronic properties, the main objective of this work was to study this material type on the atomic scale by means of electronic structure methods. For this, density functional theory (DFT) methods were used as they are efficient tools to consider the complex molecular structure. This work comprises three main parts: a comparative study of the structural and the electronic properties of TDPP based DA polymers obtained by means of different theory levels, the calculation of the intermolecular charge transfer between pi-pi stacked DA polymer chains based on the Marcus transfer theory and investigations of molecular p-doping of TDPP based DA polymers. For the first, DFT using different functionals was compared to the density functional based tight binding (DFTB) method, which is computationally very efficient. Although differences in structural properties were observed, the DFTB method was found to be the best choice to study DA polymers in the crystalline phase. For the second, correlations between the molecular structure and the reorganization energy are found. Moreover, the dependency of the electronic coupling element on the spatial shape of the frontier orbitals is shown. Furthermore, a Boltzmann-type statistical approach is introduced in order to enable a qualitative comparison of different isomers and chemical structures. For the last part, the p-doping properties of small, multi-polar dopant molecules with local dipole provided by cyano groups were investigated theoretically and compared with experimental observations. The one with the strongest p-doping properties was studied in this work for the first time on a theoretical basis. Comparing these different p-dopants, rich evidence was found supporting the experimentally observed doping strength

Untersuchung zur immunmodulierenden Wirkung von Milchsaft aus Euphorbia mauritanica L. auf humane Hautzellen

Die vorliegende Arbeit dient der Untersuchung zur immunmodulierenden Wirkung von Milchsaft aus Euphorbia mauritanica L. auf humane Hautzellen. Milchsäfte der Pflanzenfamilie Euphorbiaceae gehören zu den am stärksten entzündungsauslösenden Pflanzensäften im gesamten Pflanzenreich. Entzündliche Haut- und Augenreaktionen nach dem Kontakt mit Milchsäften einiger Euphorbiaceae, wie z.B. dem von Hippomane mancinella L., sind ein massives Problem für Menschen, die in unmittelbarer Nähe zu diesen Pflanzen leben und mit ihnen in Kontakt kommen. Neben Proteinen wie Proteasen, Lysozym und Chitinasen beinhalten die Milchsäfte der Euphorbiaceae auch sekundäre Pflanzeninhaltsstoffe wie Diterpene, Zucker, Alkaloide oder Polyterpene. Da die Ursachen der Immunreaktionen auf die Milchsäfte bisher nicht geklärt ist, sollte in der vorliegenden Arbeit der Milchsaft von Euphorbia mauritanica L. (Euphorbiaceae) auf seine immunmodulierende Wirkung an humanen Hautzellen untersucht werden. Neben den G-Protein-gekoppelten Protease-aktivierten Rezeptor 2 (PAR2) ist auch die Aktivierung der PKC durch Diterpene geeignet, Entzündungsreaktionen auslösen zu können. Mögliche synergistische Einflüsse sollten dahingehend untersucht werden. Dazu wurde zunächst ein humanes Hautmodell entwickelt, um Informationen über die immunmodulierende Wirkung des verdünnten Milchsaftes von E. mauritanica zu erhalten. Desweiteren wurde an HaCaT-Keratinozyten und primären humanen dermalen Fibroblasten untersucht, ob es einen gemeinsamen Effekt in der Entzündungsmediation zwischen der in E. mauritanica stark exprimierten Protease Mauritanicain und dem Diterpen Phorbol-12-myristat-13-acetat gibt. Dazu wurde die relative Freisetzung von IL-8 Parameter zur Entzündungsauslösung gemessen und mit dem positiven PAR2 Agonisten 2-Furoyl-LIGRLO-Amid verglichen. In der vorliegenden Dissertation konnte zusätzlich die Aminosäuresequenz von der Subtilisin-like Protease Mauritanicain aufgeklärt werden

Klimaethik – Klimapolitik – Klimasoziologie

What is meant by the social climate catastrophe? What changes does climate change bring in relation to people and their livelihoods? In this volume, Florian Günther discusses the consequences of climate change and how they relate to social circumstances, deficiencies in development and international climate policy