Preparation And Properties Of Two-selenium-containing Surfactants

The surface activity of stimuli-responsive surfactants can be modulated by the switch,drawing wide attention.Redox stimuli-responsive surfactants are unique in stimulating methods due to their mild reaction conditions and fast response,selenium has been found to have unique redox properties,leading to its introduction into common surfactant structures as a new kind of stimuli-responsive redox surfactants that is surfactant containing selenium,the properties of foam,emulsions,and wormlike micelles can be reversibly regulated.The reported surfactants containing selenium are mostly single-selenium surfactants,however,a few of reports have been devoted to poly-selenium-containing surfactant.Therefore,we designed and prepared two two-selenium-containing surfactants,that are sodium 3-?3-?benzylselany?-propylselenide?-propylsulfate?SBSe₂S?andlauricacid3-?3-?benzylselensulfoxide?-propylselensulfoxide?-propyl ester?BSe₂DC-Ox?.Besides,the switch-response behavior of the SBSe₂S and BSe₂DC-Ox on the interfacial activityies of the oxidation-reduction was investigated.In the context of this test,the main experimental results and conclusions are summarized as follows:?1?SBSe₂S was synthesized by a five-step reaction;the molecular structure and molecular structure before and after oxidation were confirmed by FT-IR,¹H NMR,⁷⁷Se NMR and ESI-MS.At 25 ^oC,the cmc and surface tension(?_cmc)of SBSe₂S were 1.15×10^-2 mol·L^-1and?_cmc=50.61 mN·m^-1,respectively.Compared with sodium dodecyl sulfate with similar structure,the interface activity of SBSe₂S is weaker.The results of ¹H NMR,⁷⁷Se NMR and ESI MS indicated that under the oxidation of tiny H₂O₂,two groups of hydrophobic divalent selenide?C-Se-C?in SBSe₂S were converted into two groups of hydrophilic selenoxide?Se=O?,and then the initial hydrophobic tail of SBSe₂S was separated into three segments by two hydrophilic groups of selenoxide,The size of each C-H segment does not exceed five CH₂ groups by which SBSe₂S-Ox is not a bola-type structure.The?of SBSe₂S-Ox is 70.32mN·m^-1,the surface tension difference of SBSe₂S and SBSe₂S-Ox at cmc is 19.7 mN·m^-1,which is larger than the surface tension difference??of single-selenium-containing surfactant.The?value of SBSe₂S-Ox in a wide range of concentration is larger than the?of a surfactant containing single-selenium anion and is closer to the?value of water(71.8 mN·m^-1),it can be seen that SBSe₂S-Ox has no interface activity Therefore the interfacial activities of SBSe₂S aqueous solution could be therefore switched off in a greater degree than its single-selenium-containing counterparts.After reduction by Na₂SO₃,two groups of selenoxide in SBSe₂S-Ox were reduced to the initial selenide,which restored the SBSe₂S-Ox to the initial state of SBSe₂S.The interfacial activities?foam,emulsification,wettability?of SBSe₂S could be switched reversibly under the alternating effect of H₂O₂-Na₂SO₃ without obvious significant deterioration in the degree of reversible cycling over five to ten cycles.?2?BSe₂DC-Ox was synthesized by a six-step reaction;the molecular structure was confirmed by FT-IR,¹H NMR,⁷⁷Se NMR and ESI-MS;At 25 ^oC,the solubility of BSe₂DC-Ox was 1.5×10^-5 mol·L^-1 in water.Therefore,the capability of the solution of BSe₂DC-Ox to reduce the surface tension of water was relatively weak,?_min is 46.35 mN·m^-1,but due to the presence of BSe₂DC-Ox solids synergistically enhance the role of the interface activity,suspension of BSe₂DC-Ox displays good emulsifying ability.BSe₂DC-Ox can be reduced by N₂H₄·H₂O and becomes BSe₂DC,the interface activity disappears.As the results of ¹H NMR,⁷⁷Se NMR presented,under the oxidation of tert-butyl hydroperoxide??CH₃?₃COOH?,two groups of hydrophobic divalent selenide?C-Se-C?in BSe₂DC were converted into two groups of hydrophilic selenoxide?Se=O?,which becomes the corresponding hydrophilic head groups of the oxidation BSe₂DC-Ox,making BSe₂DC-Ox have interface activity.After reduction by N₂H₄·H₂O,two groups of hydrophilic selenoxide in BSe₂DC-Ox was reduced to the selenide so that BSe₂DC-Ox was restored to BSe₂DC.Moreover,in view of the reduction of tert-butyl alcohol,the influences of byproduct tert-butanol on emulsion were studied.With the increase of tert-butyl alcohol,the particle size of emulsion became smaller,and the stability of the emulsion increased.When the tert-butanol concentration reached eight times the concentration of BSe₂DC-Ox,the stability and particle size of emulsion were the best,and when the concentration continued to increase,the stability deteriorates and the particle size gradually increased.Emulsification and demulsification of the BSe₂DC/petroleum ether system can be circulated reversibly at least five times under the alternating effect of tert-butyl peroxide-N₂H₄·H₂O.