Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
The Second CMC of an Aqueous Solution of Sodium Dodecyl Sulfate. IV. Fluorescence Depolarization
Yukio KubotaMichiko KodamaMasaji Miura
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1973 Volume 46 Issue 1 Pages 100-103


The depolarization of the fluorescence emitted from a dye solubilized in the micelle was measured over a wide concentration range of sodium dodecyl sulfate (SDS). The polarization of the fluorescence showed an abrupt increase at the 1st CMC and at about 70 mM of SDS; the latter agrees very closely with the 2nd CMC revealed by conductivity and viscosity measurements. This phenomenon implies that there is a certain change in the micelle structure at the 2nd CMC. The micellar size was calculated from the fluorescence depolarization data using Perrin’s equation. The results showed that: (1) the micellar volume below the 2nd CMC is in good agreement with that determined by light-scattering, (2) the micellar volume gradually increases with an increase in the concentration of SDS, and (3) the micellar volume increases abruptly at the 2nd CMC.

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