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Catanionics from biosurfactants and regular surfactants: miscibility and structure
Janine Birnbach1,2,3, Niki Baccile3, Tanya K Todorova4
1Henkel AG & Co. KGaA, Henkelstraße 67, 40589 Düsseldorf, Germany. peter.schmiedel@henkel.com.
Soft Matter
|July 2, 2026
Summary
Cationic and anionic biosurfactants form unusual micelles, not precipitates, due to carbohydrate interactions. These findings reveal novel self-assembly behaviors for biosurfactant mixtures.
Area of Science:
- Supramolecular Chemistry
- Colloid and Surface Science
- Biophysical Chemistry
Background:
- Cationic and anionic surfactant mixtures (catanionics) exhibit synergistic properties like reduced surface tension.
- Typically, catanionics precipitate near equimolar ratios and form vesicles.
- Biosurfactants, such as rhamnolipid and sophorolipid, present unique structural and interaction characteristics.
Purpose of the Study:
- To investigate the self-assembly behavior of catanionic mixtures composed of anionic biosurfactants.
- To explore the formation of micelles instead of precipitates or vesicles in these specific systems.
- To understand the role of carbohydrate-carbohydrate interactions in driving nanoscopic phase separation and heterogeneous structures.
Main Methods:
- Pulsed field-gradient spin-echo NMR spectroscopy
- Molecular dynamics simulations
- Small-angle X-ray scattering (SAXS)
- Contrast variation by small-angle neutron scattering (SANS)
Main Results:
- Catanionics of rhamnolipid or sophorolipid form micelles, deviating from typical catanionic behavior.
- Evidence suggests specific carbohydrate-carbohydrate interactions overcome electrostatic repulsion.
- Nanoscopic phase separation leads to heterogeneous internal micellar structures.
Conclusions:
- The unique properties of biosurfactant catanionics stem from their complex, asymmetric, and hydrophilic nature.
- Strong hydrogen-bonding interactions play a crucial role in the observed self-assembly.
- These findings offer insights into novel self-assembly mechanisms driven by biosurfactant-specific interactions.
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