Micelle size and shape of sodium dodecyl sulfate in concentrated sodium chloride solutions

TLDR: In this article, light scattering from aqueous solutions of sodium dodecyl sulfate has been measured in the presence of NaCl of different concentrations at different temperatures, and the angular dependence indicates formation of a rodlike micelle having a length of 597 angstroms.

Abstract: Light scattering from aqueous solutions of sodium dodecyl sulfate has been measured in the presence of NaCl of different concentrations at different temperatures. In NaCl solutions more concentrated than 0.45 M, surfactant micelles formed at the critical micelle concentration further associate into large micelles with increasing surfactant concentration. In 0.60 and 0.80 m NaCl at 25 C, light scattering exhibits anomalous dissymmetry attributable to the formation of trace amounts of microgel particles. In 0.80 M NaCl at 35 C, light scattering is normal and gives the micelle aggregation number as high as 1410 at 1.10 x 10/sup -2/ g cm/sup -3/. The angular dependence indicates formation of a rodlike micelle having a length of 597 angstroms. It is concluded that sodium dodecyl sulfate forms spherical micelles at low NaCl concentrations (< 0.45 M), but it associates into rodlike micelles at high NaCl concentrations when its micelle concentration is high. 41 references.