Hypothesis: Due to its huge polar headgroup, octaoxyethylene octyl ether carboxylic acid (CECHCOOH = Akypo LF2™) is supposed not to be able to change its curvature sufficiently to form bicontinuous microemulsions. Instead, upon adding an oil to the binary water - surfactant system, excess oil could be squeezed out or a biliquid foam could form.

Experiments: An auto-dilution setup was used to record small-angle X-ray scattering data along six dilution lines in the newly established phase diagram of the ternary system 2-ethylhexanol - CECHCOOH - water.

Results: Evaluation of the data in combination with the recorded phase diagram revealed that the ternary microemulsions with a slightly amphiphilic oil indeed do not show a classical structural inversion via a bicontinuous structure with increasing oil content, but instead the sequence: O/W micelles - O/W biliquid nanofoam - molecular co-solubilization in the oil phase. The biliquid nanofoam structure with 10-10 oil molecules enclosed by locally flat layers of interdigitated hydrated headgroups exists in the middle of the phase diagram. We may speculate that this phase can be used as a multitude of nanocontainers, e.g., for chemical reactions in an aqueous environment, but with negligible water chemical potential. In the vicinity of the critical point, spontaneous formation of stable mesoscale droplets (an "Onuki-like" structure, as known with antagonistic salts) is detected in a region showing a pronounced Tyndall effect.

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jcis.2025.01.090DOI Listing

Publication Analysis

Top Keywords

phase diagram
12
biliquid nanofoam
8
oil
6
phase
5
biliquid
4
biliquid oil-in-water
4
oil-in-water nanofoams
4
nanofoams spontaneous
4
spontaneous emulsification
4
emulsification surfactant
4

Similar Publications

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!