Redox-Controllable Interfacial Properties of Zwitterionic Surfactant Featuring Selenium Atoms

Abstract

Control of interfacial properties (foaming and emulsification) plays an important role in industry. Here we developed a novel redox-responsive surfactant, 3-(11-benzylselanyl-undecyl)-dimethylammonium acetate (BSeUCB), using selenium atoms as an environmentally sensitive group. In a reduced state, BSeUCB aqueous solution showed good foaming and emulsification abilities as well as conventional betaine surfactants. After oxidization, BSeUCB transformed into a bola-type structure because of the presence of a new hydrophilic group (selenoxide), and thus the critical micellar concentration, equilibrium surface/interfacial tension, and molecular area at the interface correspondingly increase from 0.32 mM, 46.43 mN·m(-1), 5.30 mN·m(-1), and 0.61 nm(2) to 4.98 mM, 59.15 mN·m(-1), 18.29 mN·m(-1), and 1.22 nm(2), respectively, resulting in a greater amount of energy input required to produce foam or emulsion, and a less dense adsorption layer, i.e., poor foaming and emulsification ability. Such a conversion was reversibly controlled by simply adding a trace amount (<0.06 wt % of the dispersion) of oxidant (H2O2) and reductant (Na2SO3). The products of the redox reaction did not interfere in the switchability except at the first cycle. The oxidization was generally time-consuming, whereas the reduction was very fast.

Reversibly Redox‐Switchable Anionic Surfactant Contains Two Selenium Atoms

“…b) revealed that the peaks of the two divalent selenide centers shifted from δ = 147.5 and 245.3 ppm to δ = 864.5 and 878.5 ppm after oxidation with H 2 O 2 , and then returned to δ = 147.5 and 245.3 ppm upon reduction with Na 2 SO 3 . This also confirmed the presence of selenoxide groups in SBSe 2 S‐Ox (Kong et al, ; Xu et al, ; Zhang, Kong, et al, ; Zhang, Yang, et al, ), which could be further reduced with Na 2 SO 3 . UV–vis spectra (Fig.…”

“…, γ and σ for SBSe 2 S‐Ox are higher than those for SBSe 2 S at all concentrations; only slight changes in γ (Δ γ < 5 mN m −1 ) and σ (Δ σ < 8 mN m −1 ) of SBSe 2 S‐Ox over a wide concentration range were observed. These Δ γ and Δ σ values of SBSe 2 S‐Ox are smaller than those of its counterparts with a single selenium atom (Kong et al, ; Zhang, Kong, et al, ; Zhang, Yang, et al, ). These results preliminarily confirmed that γ and σ of SBSe 2 S could be switched off by oxidation to a greater extent than its counterparts (Kong et al, ; Zhang, Kong, et al, ; Zhang, Yang, et al, ).…”

“…The transient foam of SBSe 2 S‐Ox collapsed completely within 5 s after shaking. It is reasonable to conclude that γ of SBSe 2 S‐Ox is too large to produce a stable foam (Kong et al, ). The obtained results, on the other hand, confirmed that the interfacial activities of SBSe 2 S could be switched off to a greater degree than those of its counterparts (Kong et al, ; Zhang, Kong, et al, ; Zhang, Yang, et al, ).…”

“…a). In addition, the distribution of the five aryl protons changes from 4:1 to 3:2 upon oxidation, which reveals that the benzene ring in SBSe 2 S‐Ox is located in a more polar environment (Kong et al, ; Xu et al, ; Zhang, Kong, et al, ; Zhang, Yang, et al, ). After the reduction with Na 2 SO 3 , all of these downfield‐shifted and split signals in the 1 H NMR spectrum of SBSe 2 S‐Ox were restored to those of SBSe 2 S (Fig.…”

“…The first example of a seleniumcontaining surfactant, phenylselenide-1-undecyl triethylammonium bromide, a cationic system, was reported by Han et al (2010). Considering the great importance of seleniumbased compounds in bio-applications and selenium's redox sensitivity, we recently synthesized novel redox-switchable selenium-containing surfactants of zwitterionic betaines (Kong, Guo, Wu, Liu, & Zhang, 2016;Zhang, Kong, et al, 2015) and an anionic sulfate (Zhang, Yang, Guo, Chen, & Liu, 2016). A common feature of these surfactants is a phenylselenide or benzylselenide group at the terminal position of the hydrophobic tail (Han et al, 2010;Kong et al, 2016;Zhang, Kong, et al, 2015;Zhang, Yang, et al, 2016).…”