Reversible-Tuning Krafft Temperature of Selenium-Containing Ionic Surfactants by Redox Chemistry

An easy, effective, and reversible strategy for tuning the Krafft temperature (K-T) of selenium-containing ionic surfactants, with head groups ranging in nature from anionic to amphoteric, has been achieved for the first time via the redox chemistry of selenium. After oxidation with H2O2, the selenide group was converted to a more hydrophilic selenoxide group. This made the oxidized forms of the surfactants more water-soluble, which results in a marked reduction in the K-T. In contrast, the hydrophilic selenoxide was restored to its reduced form of selenide via reduction reaction, which allowed the K-T value to return to its initial value. By alternating the oxidization and reduction treatments, the K-T of the selenium-containing surfactants in this work could be reversibly switched over 5-10 cycles without causing obvious adverse distortions.