Friesen, Sergej and Buchecker, Thomas and Cognigni, Alice and Bica, Katharina and Buchner, Richard (2017) Hydration and Counterion Binding of [C12MIM] Micelles. LANGMUIR, 33 (38). pp. 9844-9856. ISSN 0743-7463,
Full text not available from this repository. (Request a copy)Abstract
Surface-active ionic liquids based on imidazoRum cations are promising targets for micellar catalysis in aqueous solution, yielding enhanced rate constants compared to surfactants based on n-alkyltrimethylammonium cations and exhibiting a pronounced counterion dependence (Bica et al. Chem. Commun. 2012, 48, 5013-5015; Cognigni et al. Phys. Chem. Chem. Phys. 2016, 18, 13375-13384). Probably most relevant to these effects is the interplay between headgroup hydration and counterion binding. To obtain more detailed information on these effects, aqueous solutions of 1-dodecy1-3methylimidazolium ([C12MIM]) bromide, iodide, and triflate (TfO-) were investigated at 45 degrees C using broadband dielectric spectroscopy, viscosity measurements, and small-angle X-ray scattering experiments. Effective hydration numbers were determined, and information on the locations and mobilities of the condensed counterions, X-, was derived. It was found that [C12MIM] halide micelles were less hydrated than the corresponding n-dodecyltrimethylammonium ([C(12)TA]X) aggregates. Together with their somewhat weaker counterion condensation, this difference probably explains their higher catalytic activity. Whereas [C12MIM]Br micelles remained roughly spherical in the studied concentration range, rodlike aggregates were formed at high concentrations of the iodide and, in particular, the triflate surfactants. It appears that the much lower mobility of condensed TfO- counterions is the reason for the very low catalytic activity of [C12MIM]TfO micelles.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | IMIDAZOLIUM IONIC LIQUIDS; AQUEOUS-SOLUTION; DIELECTRIC-RELAXATION; CATIONIC MICELLES; AGGREGATION BEHAVIOR; SOLVENT RELAXATION; MOLECULAR-DYNAMICS; TRIFLATE MICELLES; WATER; SURFACTANTS; |
| 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) 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: | 14 Dec 2018 13:20 |
| Last Modified: | 20 Feb 2019 10:54 |
| URI: | https://pred.uni-regensburg.de/id/eprint/2162 |
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