Using cryo-SEM and EDS to investigate the stabilisation of oil-water interfaces in mixed aqueous-and-oil foams.

For multi-phase soft matter systems, optical microscopy is frequently employed to distinguish the different phases. Unfortunately, optical microscopy does not succeed in all cases. Consequently, researchers sometimes require more advanced imaging techniques with superior resolution or sample penetration capabilities. One such complex system is a mixed aqueous-and-oil foam stabilised by colloidal particles, which is composed of two immiscible foams organised as the dispersed and continuous phases of an emulsion. While its morphology has been extensively studied using fluorescence confocal microscopy, not all questions have been answered. While the aqueous phase bubble interfaces are stabilised by silica particles and the oil phase bubble interfaces are stabilised by fluorinated particles, it remains to be seen how the aqueous-oil interfaces are stabilised. Hence, to gain insights into the role of the different particles at the interfaces, we employ cryogenic scanning electron microscopy (Cryo-SEM) and energy-dispersive X-ray spectroscopy (EDS). We find that the hydrophobic silica particles reside at both the aqueous-air and aqueous-oil interfaces. In contrast, the fluorinated particles, which exhibit hydrophobic and oleophobic properties simultaneously, are exclusively found at the oil-air interfaces.

Mixed aqueous-and-oil foams in bulk.

HYPOTHESIS: Because particle-stabilised foams are extremely stable and have a yield stress, a particle-stabilised aqueous foam and a particle-stabilised oil foam can be mixed together to give a stable composite foam which brings together two immiscible liquids. EXPERIMENTS: We have developed a mixed foam system comprised of an olive oil foam with bubbles stabilised using partially fluorinated particles and an aqueous foam with bubbles stabilised using hydrophobic silica particles. The aqueous phase is a mixture of water and propylene glycol. We have studied this system using bulk observations, confocal microscopy and rheology as we vary the proportions of the two foams, the silica particles and the propylene glycol, and the sample age. FINDINGS: The composite foam resembles an emulsion of one foam within another and is stable for a week or more. The structure and flow properties depend on the proportions of the two phases and the quantities of both silica particles and propylene glycol. Inversion between water-in-oil and oil-in-water is observed, where both phases are foams, driven both by silica wettability and by adding increasing quantities of the dispersed foam. Composites formed at the inversion point are the least stable, showing significant phase separation in less than one week.

Mixed Aqueous-and-Oil Foams via the Spinning Together of Separate Particle-Stabilized Aqueous and Oil Foams.

We describe an experimental technique for the production of foams comprised of bubbles in a continuous phase of balanced quantities of aqueous and oil phases. Initially, two highly stable foams are fabricated: one typically made from olive oil with bubbles stabilized using partially fluorinated particles and the other made from a mixture of water and propylene glycol with bubbles stabilized using partially hydrophobic particles. After a rough mixture is prepared, the final mixed foam is fabricated via spinning the components together; the spinning leads to the final foam being well-mixed and dry. Here the final mixed foams are presented in thin-film form. We show the locations and roles of the various components.

Multifocal eosinophilic granuloma of the jaws with long-term follow-up: a case report.

Eosinophilic granuloma, a rare disease, has various clinical manifestations and no specific X-rays features and is thus easily misdiagnosed. This paper reports a case of multifocal eosinophilic granuloma of jaw with long-term follow-up. The patient initially presented with periodontal tissue destruction.The diagnosis, treatment and prognosis of multifocal eosinophilic granuloma of jaw were discussed in combination with the literature to alert this disease in clinical practice.

Lateral diffusion of single poly(ethylene oxide) chains on the surfaces of glassy and molten polymer films.

Fluorescence correlation spectroscopy was used to show that the temperature-dependent diffusion coefficient of poly(ethylene oxide) (PEO) adsorbed on polystyrene and different poly(alkyl methacrylate) (PAMA) films in aqueous solution exhibited a maximum close to (but below) the surface glass transition temperature, Tgs, of the film. This elevated diffusion was observed over a small range of temperatures below Tgs for these surfaces, and at other temperatures, the diffusion was similar to that on silicon, although the diffusion coefficient for PEO on polystyrene at temperatures above Tgs did not completely decrease to that on silicon, in contrast to the PAMA surfaces. It is concluded that the enhanced surface mobility of the films near the surface glass transition temperature induces conformational changes in the adsorbed PEO. The origin of this narrow and dramatic increase in diffusion coefficient is not clear, but it is proposed that it is caused by a coupling of a dominant capillary mode in the liquid surface layer with the polymer. Friction force microscopy experiments also demonstrate an unexpected increase in friction at the same temperature as the increase in diffusion coefficient.