Lima, Filipe S. and Cuccovia, Iolanda M. and Buchner, Richard and Antunes, Filipe E. and Lindman, Bjorn and Miguel, Maria G. and Horinek, Dominik and Chaimovich, Hernan (2015) Sodium Triflate Decreases Interaggregate Repulsion and Induces Phase Separation in Cationic Micelles. LANGMUIR, 31 (9). pp. 2609-2614. ISSN 0743-7463,
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Dodecyltrimethylammonium triflate (DTATf) micelles possess lower degree of counterion dissociation (a), lower hydration, and higher packing of monomers than other micelles of similar structure. Addition of sodium triflate ([NaTf] > 0.05 M) to DTATf solutions promotes phase separation. This phenomenon is commonly observed in oppositely charged surfactant mixtures, but it is rare for ionic surfactants and relatively simple counterions. While the properties of DTATf have already been reported, the driving forces for the observed phase separation with added salt remain unclear. Thus, we propose an interpretation for the observed phase separation in cationic surfactant solutions. Addition of up to 0.03 M NaTf to micellar DTATf solutions led to a limited increase of the aggregation number, to interface dehydration, and to a progressive decrease in a. The viscosity of DTATf solutions of higher concentration ([DTATf] = 0.06 M) reached a maximum with increasing [NaTf], though the aggregation number slightly increased, and no shape change occurred. We hypothesize that this maximum results from a decrease in interaggregate repulsion, as a consequence of increased ion binding. This reduction in micellar repulsion without simultaneous infinite micellar growth is, probably, the major driving force for phase separation at higher [NaTf].
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | MOLECULAR-DYNAMICS SIMULATIONS; CETYLTRIMETHYLAMMONIUM BROMIDE; SURFACTANT SOLUTIONS; WORMLIKE MICELLES; AQUEOUS-SOLUTIONS; FORCE-FIELD; AROMATIC COUNTERIONS; AIR/WATER INTERFACE; ROD TRANSITION; HYDRATION; |
| 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. Dominik Horinek |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 24 Jul 2019 07:06 |
| Last Modified: | 24 Jul 2019 07:06 |
| URI: | https://pred.uni-regensburg.de/id/eprint/5796 |
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