Chemically Tuning Attractive and Repulsive Interactions between Solubilizing Oil Droplets.

Micellar solubilization is a transport process occurring in surfactant-stabilized emulsions that can lead to Marangoni flow and droplet motility. Active droplets exhibit self-propulsion and pairwise repulsion due to solubilization processes and/or solubilization products raising the droplet's interfacial tension. Here, we report emulsions with the opposite behavior, wherein solubilization decreases the interfacial tension and causes droplets to attract.

Interfacially-adsorbed particles enhance the self-propulsion of oil droplets in aqueous surfactant.

Understanding the chemo-mechanical mechanisms that direct the motion of self-propulsive colloids is important for the development of active materials and exploration of dynamic, collective phenomena. Here, we demonstrate that the adsorption of solid particles on the surface of solubilizing oil droplets can significantly enhance the droplets' self-propulsion speeds. We investigate the relationship between the self-propulsion of bromodecane oil droplets containing silica particles of varying concentration in Triton X-100 surfactant, noting up to order of magnitude increases in propulsion speeds.

Particle Stabilization of Oil-Fluorocarbon Interfaces and Effects on Multiphase Oil-in-Water Complex Emulsion Morphology and Reconfigurability.

Stabilization of oil-oil interfaces is important for nonaqueous emulsions as well as for multiphase oil-in-water emulsions, with relevance to a variety of fields ranging from emulsion polymerization to sensors and optics. Here, we focus on examining the ability of functionalized silica particles to stabilize interfaces between fluorinated oils and other immiscible oils (such as hydrocarbons and silicones) in nonaqueous emulsions and also on the particles' ability to affect the morphology and reconfigurability of complex, biphasic oil-in-water emulsions. We compare the effectiveness of fluorophilic, lipophilic, and bifunctional fluorophilic-lipophilic coated nanoparticles to stabilize these oil-oil interfaces.

Colouration by total internal reflection and interference at microscale concave interfaces.

Many physical phenomena create colour: spectrally selective light absorption by pigments and dyes, material-specific optical dispersion and light interference in micrometre-scale and nanometre-scale periodic structures. In addition, scattering, diffraction and interference mechanisms are inherent to spherical droplets, which contribute to atmospheric phenomena such as glories, coronas and rainbows. Here we describe a previously unrecognized mechanism for creating iridescent structural colour with large angular spectral separation.

Electrophilic Cyclization of Phenylalkynediols to Naphthyl(aryl)iodonium Triflates with Chelating Hydroxyls: Preparation and X-ray Analyses.

Alkynediols containing one propargylic alcohol as well as a second alcohol, which is propargylic or homopropargylic, react with PhICNOTf (Stang's reagent) or 3,5-(CF)CHICNOTf to afford naphthyl(aryl)iodonium triflates. The reaction occurs at room temperature over the course of 6-12 h and provides 36-82% yields of microcrystalline solids. Slow diffusion of EtO into CHCN solutions of the salts afforded X-ray quality crystals of five compounds with hydroxyl groups forming five- and six-membered chelation complexes with the iodine atom.