Stabilization of Pickering Emulsions with Oppositely Charged Latex Particles: Influence of Various Parameters and Particle Arrangement around Droplets

© 2015 American Chemical Society. In this study we explore the fundamental aspects of Pickering emulsions stabilized by oppositely charged particles. Using oppositely charged latex particles as a model system, Pickering emulsions with good long-term stability can be obtained without the need for any electrolyte. The effects of parameters like oil to water ratio, mixed particle composition, and pH on emulsion type and stability are explored and linked to the behavior of the aqueous particle dispersion prior to emulsification. The particle composition is found to affect the formation of emulsions, viz., stable emulsions were obtained close to a particle number ratio of 1:1, and no emulsion was formed with either positively or negatively charged particles alone. The emulsions in particle mixtures exhibited phase inversion from oil-in-water to water-in-oil beyond an oil volume fraction of 0.8. Morphological features of emulsion droplets in terms of particle arrangement on the droplets are discussed

Стратегічні пріоритети подолання демографічної кризи в Україні

We report a computational study on the spontaneous self-assembly of spherical particles into twodimensional crystals. The experimental observation of such structures stabilized by spherical objects appeared paradoxical so far.We implement patchy interactions with the patches point-symmetrically (icosahedral and cubic) arranged on the surface of the particle. In these conditions, preference for self-assembly into sheet-like structures is observed. We explain our findings in terms of the inherent symmetry of the patches and the competition between binding energy and vibrational entropy. The simulation results explain why hollow spherical shells observed in some Keplerate-type polyoxometalates (POM) appear. Our results also provide an explanation for the experimentally observed layer-by-layer growth of apoferritin - a quasi-spherical protein

Phase separation of rotor mixtures without domain coarsening driven by two-dimensional turbulence

Understanding the precise role of hydrodynamic interactions in the self-organization of circle-swimming active matter is an exciting avenue. Here, in a mixture of counter-rotating disks, the authors show that phase separation formed the largest size structure directly, without domain coarsening, and is driven by the inverse cascade phenomena characteristic of 2D turbulence

Staggered Linear Assembly of Spherical-Cap Colloids

Linear assembly of colloidal particles is of fundamental interest in visualizing polymer dynamics and living organisms. We have developed a fluid–fluid interface-based method to synthesize spherical-cap polymeric latex particles. These particles are shown to spontaneously self-assemble in zigzag arrangement. The linear assembly is induced due to the shape anisotropy (one side is curved and the other side is nearly flat) and heterogeneous charge distribution on the particle surfaces. The necessities of these conditions are justified within the framework of DLVO theory. Spherical-cap particles of various size and aspect ratio reproduced the observed linear assembly, thus demonstrating the robustness of the self-assembly mechanism. While these types of assemblies are observed in spherical particles using microfluidic devices or electric field, the proposed approach is rather facile and does not require any external field. These novel assemblies could be potentially useful to understand kinetics of nucleation and growth of amyloidogenic proteins and to prepare artificial swimming microorganisms