Two-step droplet formation in monodisperse nanodroplet generation in quenched hydrothermal solution as revealed by spontaneous transformation of nanodroplets to swollen micelles in octane‑in‑water nanoemulsions
| Autor: | Naoya Sagawa, Shigeru Deguchi, Yu Nagai Kanasaki |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Ostwald ripening
Coalescence (physics) Materials science Micelle Supercritical fluid Surfaces Coatings and Films Electronic Optical and Magnetic Materials Biomaterials symbols.namesake chemistry.chemical_compound Colloid and Surface Chemistry Dynamic light scattering chemistry Chemical engineering Oil droplet symbols Microemulsion Octane |
| Zdroj: | Journal of colloid and interface science. 604 |
| ISSN: | 1095-7103 |
| Popis: | Hypothesis Monodisperse nanodroplet generation in quenched hydrothermal solution (MAGIQ) is a newly developed bottom-up process for preparing nanoemulsions. In this process, homogeneous solutions of oil in supercritical water are quenched by adding cold water containing a surfactant to induce rapid phase-separation, during which oil molecules self-assemble to form nano-sized oil droplets. The droplet size in MAGIQ is known to be influenced by the interplay of the phase‐separation dynamics, coalescence kinetics of the droplets, and adsorption kinetics of the surfactant on the droplet surface; however, the primary stages of the droplet formation are still elusive. Experiments Octane‑in‑water nanoemulsions containing 0.5, 1, and 3 vol% octane were prepared by the MAGIQ method. Their ripening was studied by dynamic light scattering, and the phase diagram was established. Findings The nanoemulsions containing 0.5 and 1 vol% octane transformed to thermodynamically stable microemulsions containing swollen micelles, whereas the nanoemulsion containing 3 vol% octane underwent Ostwald ripening. The initial formation of the nano-sized droplets in the former was ascribed to a unique mechanism of droplet formation in MAGIQ—the droplets are first formed by the phase separation of homogeneous binary solutions of oil in supercritical water and then stabilized upon surfactant adsorption. |
| Databáze: | OpenAIRE |
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