Micellar growth in the presence of quaternary ammonium salts A SANS study
- 1 January 1998
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions
- Vol. 94 (6) , 761-764
- https://doi.org/10.1039/a707590a
Abstract
The effect of the addition of quaternary ammonium bromides, R4NBr (R=H, CH3 or C4H9) on the growth of sodium dodecyl sulfate (SDS) micelles has been studied by small-angle neutron scattering (SANS) measurements at 30°C. SDS forms ellipsoidal micelles at 0.3 M concentration with an average aggregation number ns=110. The effect of adding 0.1 M R4NBr to 0.3 M SDS has been studied and compared with the effect of adding NaBr. The values of ns are in the order: no salt3)4NBr4Br<(n-C4H9)4NBr which shows that the effectiveness of the cation (counterion) in increasing ns is in the order of decreasing hydrated radii. The unusual behaviour of (n-C4H9)4N+ is discussed in terms of its possible intercalation in the micelle. At higher [R4NBr], micellar growth is substantial in the case of (n-C4H9)4NBr which is explained in the light of an increase in the Mitchell–Ninham parameter of the surfactant monomer.Keywords
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