Abstract
Herein, we present the direct observation and quantification of a water-in-oil (w/o) emulsion, its destabilization, and the effect of additives on such processes at the nanoscale. This is achieved via liquid phase transmission electron microscopy (LPTEM), wherein a small volume of emulsion is encapsulated against vacuum in its liquid state to allow observation of its initial morphology and its evolution over time at excellent spatial and temporal resolution. Emulsions of this class are useful for delivering payloads of materials insoluble in their delivery medium and are currently widely used across food science, pharmaceuticals, and environmental applications. However, their utility is inherently limited by their thermodynamic tendency to demulsify, eventually leading to bulk phase separation. This occurs via several degradation mechanisms, operating at times collectively, and which are difficult to differentiate via traditional ensemble methods (e.g., light scattering), obscuring mechanistic nuances. LPTEM as a characterization technique has the potential to augment our understanding of emulsion behavior and improve performance and formulations. In this work, we also emphasize the importance of the included videographic Supporting Information data in demonstrating the behavior of the studied materials.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 7783-7793 |
| Number of pages | 11 |
| Journal | ACS nano |
| Volume | 16 |
| Issue number | 5 |
| DOIs | |
| State | Published - May 24 2022 |
Funding
We acknowledge support of this work through government funding awarded through the Army Research Office (Grants W911NF-17-1-0326, W911NF-18-1-0359, and MURI W911NF-15-1-0568) and the National Science Foundation (Grant CHE-MSN 1905270). This work made use of the EPIC facility within Northwestern University\u2019s NUANCE facility, which receives support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (Grant NSF ECCS-202563), the International Institute for Nanomaterials (Grant NIH-S10OD026871), and the Materials Research Science and Engineering Centers (Grant NSF DMR-1720139). Research reported in this publication was supported in part by instrumentation provided by the Office of The Director of the National Institutes of Health under Award No. S10OD026871. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. M.A.V. is grateful for the support of the National Science Foundation through their Graduate Research Fellowship (Grant DGE-1842165) and of Northwestern University via the Dr. John N. Nicholson Fellowship. Proctor & Gamble also generously contributed to this study via a gift to Northwestern University. We are grateful to Karthikeyan Gnanasekaran for fruitful discussions.
Keywords
- droplet dynamics
- emulsions
- liquid phase TEM
- phase separation
- surfactants
ASJC Scopus subject areas
- General Materials Science
- General Engineering
- General Physics and Astronomy