Klaus, Angelika and Tiddy, Gordon J. T. and Touraud, Didier and Schramm, Anette and Stuehler, Georgine and Kunz, Werner (2010) Phase Behavior of an Extended Surfactant in Water and a Detailed Characterization of the Concentrated Phases. LANGMUIR, 26 (22). pp. 16871-16883. ISSN 0743-7463,
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The formation of microemulsions with triglycerides at ambient conditions can be improved by increasing the surfactant water and surfactant-oil interactions. Therefore, extended surfactants were developed, which contain hydrophilic/lipophilic linkers. They have the ability to stretch further into the oil and water phase and enhance the solubility of oil in water. In this work, the phase behavior of a chosen extended surfactant (C12-14-PO16-EO2-SO4Na.X-AES) in H2O/D2O at high surfactant concentrations (30-100 wt %) and at temperatures between 0 and 90 degrees C is studied for the first time; The lyotropic liquid crystals formed were determined by optical microscopy. small-angle X-ray scattering (SAXS). and H-2 and Na-23 NMR, and a detailed phase diagram of the concentrated area is given. The obtained mesophases are a hexagonal phase (H-1), at low temperatures and small concentrations, a lamellar phase (L-alpha) at high temperatures or concentrations, a bicontinuous cubic phase (V-2) as well as a reverse hexagonal phase (H-2). To our knowledge. this is the first surfactant that forms both H-1 and H-2 phases without the addition of a third compound. From the H-2 NMR quadrupole splitting of D2O. we have examined water binding in the L-a and the H-2 phases. There is no marked difference in the hound water between the two phases. Where sufficient water is present, the number of bound water molecules per X-AES is estimated to be ca. 18 with only small changes at different temperatures. Similar results were obtained from the Na-23 NMR data, which again showed little difference in the ion binding between the L-alpha and the H-2 phases. The X-ray diffraction data show that X-AES has a much smaller average length in the L-alpha phase compared to the all-trans length than in the case for conventional surfactants. At very high surfactant concentrations an inverse isotropic solution (L-2), containing a small fraction of solid particles, is formed. This isotropic solution is clearly identified and the size of the reversed micelles was determined using H-1 NMR measurements. Furthermore, the solid particles within the L-2 phase and the neat surfactant were analyzed. The observed results were compared to common conventional surfactants (e.g., sodium dodecyl sulfate, sodium lauryl ether sulfate, and sodium dodecyl-p-benzene sulfonate). and the influence of the hydrophilic/lipophilic linkers on the phase behavior was discussed.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | NUCLEAR-MAGNETIC-RESONANCE; LYOTROPIC LIQUID-CRYSTALS; SODIUM DODECYL-SULFATE; X-RAY-DIFFRACTION; LAMELLAR PHASES; IMPROVING SOLUBILIZATION; QUADRUPOLE SPLITTINGS; OPTICAL MICROSCOPY; MICELLE FORMATION; LIPID SYSTEMS; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry VI - Physical Chemistry (Solution Chemistry) > Prof. Dr. Werner Kunz Chemistry and Pharmacy > Central Analytical Services |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 06 Jul 2020 11:00 |
| Last Modified: | 06 Jul 2020 11:00 |
| URI: | https://pred.uni-regensburg.de/id/eprint/23873 |
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