Medos, Ziga and Friesen, Sergej and Buchner, Richard and Bester-Rogac, Marija (2020) Interplay between aggregation number, micelle charge and hydration of catanionic surfactants. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 22 (18). pp. 9998-10009. ISSN 1463-9076, 1463-9084
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Catanionic mixtures are commonly used in applications due to synergetic properties of both cationic and anionic surfactants. To better understand the mechanism of the micellization process of salt-free catanionic surfactants, alkyltrimethylammonium alkanecarboxylates, [CxMe3N](+)[C-y](-), with medium to long alkyl chains on both cation and anion (x,y = 6-10), were investigated in aqueous solution by density and zeta potential measurements, isothermal titration calorimetry (ITC), and dielectric relaxation spectroscopy (DRS). The obtained ITC data was analysed with the help of a two-step model equation, yielding the thermodynamic parameters, micelle charge and aggregation numbers. Comparison with the "parent" decyltrimethylammonium chloride and sodium decanoate reveals that combined dehydration of both alkyl chains increases entropy upon micellization. In the first step neutral smaller micelles with partly dehydrated alkyl chains are formed, while in the second step larger charged micelles with fully dehydrated alkyl chains are equally favourable. At low temperature both formations are thermodynamically equivalent, while with increasing temperature neutral micelles become more entropically favourable and charged micelles more enthalpically favourable. The resulting average micelle charge and average aggregation number are decreasing with temperature. From the DRS spectra, effective hydration numbers of the free monomers and micelles were deduced and are comparable to the "parent" cationic surfactant micelles.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | DIELECTRIC-RELAXATION SPECTROSCOPY; ACTIVE IONIC LIQUIDS; PHASE-BEHAVIOR; ALKYLTRIMETHYLAMMONIUM CHLORIDES; CATIONIC SURFACTANTS; AQUEOUS-SOLUTIONS; LOW-FREQUENCY; SALT; MICELLIZATION; THERMODYNAMICS; |
| 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) > PD Dr. Richard Buchner |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 24 Mar 2021 10:11 |
| Last Modified: | 24 Mar 2021 10:11 |
| URI: | https://pred.uni-regensburg.de/id/eprint/44567 |
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