Phase Inversion and Interfacial Layer Microstructure in Emulsions Stabilized by Glycosurfactant Mixtures

Abstract

Identification of strategies to prolong emulsion kinetic stability is a fundamental challenge for many scientists and technologists. We investigated the relationship between the emulsion stability and the surfactant supramolecular organization at the oil–water interface. The pseudo-phase diagrams of emulsions formed by water and, alternatively, a linear or a branched oil, stabilized by mixtures of two sugar-based surfactants, Span80 and Tween80, are presented. The surfactant ordering and dynamics were analyzed by electron paramagnetic resonance (EPR) spectroscopy. In Oil-in-Water (O/W) emulsions, which are stable for more than four days, disordered surfactant tails formed a compact and viscous layer. In Water-in-Oil (W/O) emulsions, whose stability is much lower, surfactants formed an ordered layer of extended tails pointing toward the continuous apolar medium. If linear oil was used, a narrow range of surfactant mixture composition existed, in which emulsions did not demix in the whole range of water/oil ratio, thus making it possible to study the phase inversion from O/W to W/O structures. While conductometry showed an abrupt inversion occurring at a well-defined water/oil ratio, the surfactant layer microstructure changed gradually between the two limiting situations. Overall, our results demonstrate the interconnection between the emulsion stability and the surfactant layer microstructuring, thus indicating directions for their rational design.

Model Emulsions Stabilized with Nonionic Surfactants: Structure and Rheology Across Catastrophic Phase Inversion

“…Interestingly, the O/W gel emulsions are formed before the emulsion phase inversion at almost any HLB values, while the generation of O/W gel emulsions was only found at a few HLB values for the emulsion with the same surfactant. 12 , 31 , 32 This indicates that the regulation of HLB values of a mixed surfactant is vital to the performance of O/W gel emulsions.…”

Mechanisms of lipid oxidation in water‐in‐oil emulsions and oxidomics‐guided discovery of targeted protective approaches

“…As a consequence, the use of multiple physical markers could be necessary for providing a more comprehensive understanding of lipid oxidation and help to confirm or refine conclusions drawn from a single marker. There are many well‐established techniques to evaluate the physical stability of W/O emulsions, such as analyzing the lipid layer structure by EPR spectroscopy (Caianiello et al., 2020 ) and characterizing the droplet size and distribution by dynamic light scattering (Esposito et al., 2021 ) and transmission electron microscopy (Nguyen et al., 2015 ). In a very recent study, the application of mass spectrometric imaging accomplished the localization of emulsifiers on the surface of water droplets and structural determination of crystal network in W/O emulsions (Shiota, Shimomura, et al., 2018 ).…”

Pengaruh Surfaktan terhadap Pemisahan Logam Transisi Periode Pertama Menggunakan Metode Emulsion Liquid Membrane

“…Nilai hydrophilic-lipophilic balance (HLB) dari Span-80 sebesar 4,3 sehingga cenderung lebih larut dalam minyak [33]. Molekul Span 80 terdiri dari ion oleat pada bagian kepala yang bersifat polar sehingga akan menempel pada lapisan air, sedangkan pada bagian ekornya berupa alkil yang bersifat non-polar sehingga akan menempel pada lapisan minyak [34]. Struktur molekul Span 80 dapat dilihat pada Gambar 2.…”