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

Abstract

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.

Effect of selenium‐position on the redox responsivity of isomeric selenium‐containing anionic surfactants

“…Thus, the water solubility of surfactant C m SeC n SO 4 Na was determined in advance. The Krafft temperature (K T , C) can be used to characterize the solubility of ionic surfactants in water (Fan et al, 2020). The K T of three surfactants of C m SeC n SO 4 Na were less than 29 C (Zhang et al, 2018) S1 and S2).…”

“…The Krafft temperature (K T , C) was measured by the visual observation (Fan et al, 2020). The surface tension (γ, mN m À1 ) and interfacial tension (σ, mN m À1 ) at the liquid paraffin-water interface were measured at 30 AE 0.1 C with a Krüss K100 tensiometer and a SVT20N spinning drop interfacial tensiometer (rotational velocity was 5000 rpm), respectively.…”

Renewable dissymmetric sulfonate gemini surfactants from addition of sodium hydrogensulfite to alkyl linoleate

“…The Krafft points or Krafft temperatures (T K ) of the synthesized sulfonate gemini surfactants were determined at concentration of 1.0 wt% by visual inspection method. 35,36 Each sample was heated in a water bath, and the temperature at which the solid dissolved or precipitated out (upon cooling) was recorded following published procedures. 37 All such measurements were carried out at least three times for reproducibility, and average values were calculated.…”

Organoselenium chemistry-based polymer synthesis

“…Beside these studies, there were sporadic reports on the redox chemistry of selenium, such as reversibletuning Krafft temperature and the reversible sol-gel transition. 179,180…”