Effect of Salts on the Phase Behavior and the Stability of Nano-Emulsions with Rapeseed Oil and an Extended Surfactant

Abstract

For many decades, the solubilization of long-chain triglycerides in water has been a challenge. A new class of amphiphiles has been created to overcome this solubilization problem. The so-called "extended" surfactants contain a hydrophilic-lipophilic linker to reduce the contrast between the surfactant-water and surfactant-oil interfaces. In the present contribution, the effects of different anions and cations on the phase behavior of a mixture containing an extended surfactant (X-AES), a hydrotrope (sodium xylene sulfonate, SXS), water, and rapeseed oil were determined as a function of temperature. Nanoemulsions were obtained and characterized by conductivity measurements, light scattering, and optical microscopy. All salting-out salts show a transition from a clear region (O/W nanoemulsion), to a lamellar liquid crystalline phase region, a clear phase (bicontinuous L(3)), and again to a lamellar liquid crystalline phase region with increasing temperature. For the phase diagrams with NaSCN and Na(2)SO(4), only one clear region (O/W nanoemulsion) was observed, which turns into a lamellar phase region at elevated temperatures. Furthermore, the stability of the nanoemulsions was investigated by time-dependent measurements: the visual observation of phase separation, droplet size by dynamic light scattering (DLS), and optical microscopy. The mechanism of the different phase transitions is also discussed.

Extended Surfactants Including an Alkoxylated Central Part Intermediate Producing a Gradual Polarity Transition—A Review of the Properties Used in Applications Such as Enhanced Oil Recovery and Polar Oil Solubilization in Microemulsions

“…Other university and industry groups carried out fundamental studies to make these surfactants (Cox and Weerasooriya, ; Weerasooriya, ) and to improve the solubilization of polar soils without alcohol cosurfactants, particularly in the Institute for Applied Surfactant Research in Norman, OK, USA (Arpornpong et al, ; Attaphong et al, ; Attaphong and Sabatini, ; Budhathoki et al, ; Charoensaeng et al, ; Do et al, ; Naksuk et al, ; Phan et al, , ; Phaodee et al, ; Witthayapanyanon et al, , , b, ), as well as other independent research and development groups (Abdel‐Azim et al, ; Acosta et al, ; Adkins et al, ; Aoudia et al, ; Barnes et al, ; Dong et al, ; Flaaten et al, ; Hadji et al, ; Hammond and Acosta, ; He et al, ; Hirasaki et al, ; Hornof and Hombek, ; Huang et al, ; Jakobs et al, , ; Johannessen and Spildo, ; Khristov et al, ; Klaus et al, , , ; Liyanage et al, ; Lu et al, ; Lu et al, ; Puerto et al, ; Sarkar and Alexandridis, ; Shusharina et al, , ; Smith et al, ; Solairaj et al, ; Wu et al, ; Yang et al, ).…”

Preparation of nanoemulsions by phase inversion temperature (PIT)

“…The droplet size and the PDI of nanoemulsions decrease as a function of the number and temperature cycles up to stabilize a steady state 54 . Klaus et al 55 reported that more than one cycle of heating and cooling in PIT method confers increased stability of Rapeseed oil nanoemulsions 55 . However, the effect of temperature cycling treatment is directly linked to the non-ionic surfactant amount in the system: the lower the surfactant amount, the higher the number of cycles required for stabilizing the nanoemulsions 54 .…”

A Normalized HLD (HLDN) Tool for Optimal Salt-Concentration Prediction of Microemulsions

“…Influenced by oxygen molecules, the EO group acts as the hydrophilic part, while the PO (C 3 H 6 O) acts as the lipophilic part by extending further into the oil phase [11,13]. Regarding the intermediate structure, extended surfactants can expand the thickness of the interfacial region, which helps to reach ultralow interfacial tension (< 0.01 mN/m) and increase surfactant-oil or surfactant-water interactions [13,14,[16][17][18]. Relative to conventional surfactants, extended surfactants also show a good solubility of oil and water.…”