Calorimetric Observations of the Sphere-rod Transition of Sodium Dodecyl Sulfate
Effects of electrolytes and nonelectrolytes at 25 °C
Incremental calorimetric titrations of small amounts of alcohols into solutions containing 3.5% (w/w) sodium dodecyl sulfate and added electrolytes reveal a sharp break in the partial molar enthalpy of the alcohol. The end of this break corresponds to the micellar sphere-rod transition, as observed by light scattering and other techniques. Unlike other techniques, however, calorimetric measurements show a well-defined beginning and end of the transition in some solutions. This technique has been used to determine the effects of various electrolytes and nonelectrolytes on the transition at 25°C. The effect of electrolytes and nonelectrolytes is generally complementary, but p-dioxane and urea retard the transition while benzyl alcohol and 2-pentanol have little effect. The effects of electrolytes are determined primarily by the cations, decreasing in the series K+ > NH4+ > Na+ > Li+. The effect of alcohols increases with chain length and decreases with branching. © 1992 American Chemical Society.
D. Nguyen and G. L. Bertrand, "Calorimetric Observations of the Sphere-rod Transition of Sodium Dodecyl Sulfate," Journal of Physical Chemistry, American Chemical Society (ACS), Jan 1992.
The definitive version is available at https://doi.org/10.1021/j100183a084
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© 1992 American Chemical Society (ACS), All rights reserved.