Enthalpies of Dilution of Dodecyl- and Tetradecyl- Trimethylammonium Bromides in Aqueous Solutions of Sodium Bromide at Elevated Temperatures: Topical Report

摘要

Enthalpies of dilution of dodecyl- and tetradecyl- trimethylammonium bromides in aqueous sodium bromide solutions have been measured from 323 to 448 K and from 373 to 448 K, respectively. Similar to results with no added electrolytes, the onset of micellization can only be characterized by a critical micelle concentration (CMC0 region of finite size and not by a single CMC. The addition of sodium bromide electrolyte shifts the CMC region to a smaller surfactant molality and reduces its diffuseness. For a given temperature, the midpoint of a CMC region and the total electrolyte molality follow a linear relationship on a log-log scale. The change in critical micelle concentration region with respect to added NaBr concentration was used to calcualte midellar ''counter-ion binding fractions.'' 23 refs., 5 figs., 6 tabs. (ERA citation 13:029300)