Synthesis Of Ionic Surfactants And Reversible Tuning Of The Krafft Temperature

Surfactants can be adsorbed on the interface and self-assemble in solution to form micelles,which can effectively reduce the surface or interfacial tension,emulsify,foam and solubilize etc.The performance of ionic surfactant that widly and the largest amount of use,is closely related to their Krafft temperature?K_T?.Too high K_T means poor water solubility of ISAA,which will greatly restrict the performance of them in aqueous system.Many strategies have been established for tuning the K_T,such as tailoring the molecular structure,adding chemicals,and mixing different surfactants.Among these methods,mixing different surfactants can reversibly tuning the K_T of ISAA,but it needs to be adding surfactant to the system continuously,and other methods can only change K_T monotonously.There are few reports on tuning the K_T of ISAA easily,effectively and reversibly.In this paper,based on the strategy of the switchable surfactant,two switchable methods of CO₂/N₂ and Redox were used to tuning the K_T of ISAA reversibly.Furthermore,CO₂/N₂-Redox dual switchable have been tuning the K_T of selenium-containing sodium sulfonate.Within the scope of this article,the main research contents and conclusions are summarized as follows:?1?Synthesis and characterization of ionic surfactantSynthesis of sodium tetradecyl sulfonate(C₁₄SS),sodium 3-decyl selenide-1-propyl sulfonate(C₁₀SeC₃SS),sodium 3-dodecyl selenide-1-propyl sulfonate(C₁₂SeC₃SS),sodium3-tetradecylselen-1-propylsulfonate(C₁₄SeC₃SS),sodium 3-tetradecylselen-1-propanesulfate(C₁₄SeC₃AS)and 3-tetradecylselen-1-propanesulfonate betaine(C₁₄SeC₃SB).The molecular structure of the synthesized product was verified by some methods such as ¹H NMR,⁷⁷Se NMR and ESI-MS,then the purity of C₁₄SS,C₁₀SeC₃SS,C₁₂SeC₃SS,C₁₄SeC₃SS and C₁₄SeC₃AS were determined by two-phase titration and C₁₄SeC₃SB by reverse phase HPLC method.?2?CO₂/N₂ method to tuning K_T of sodium alkyl sulfonateThe tertiary amine has good CO₂/N₂ switchable performance.In the aqueous solution of C_n SS?n=12,14,16?contain TMEDA or TEOA,blowing CO₂ can decrease the K_T of C_nSS effectively and then blowing N₂ can increase the K_T of C_nSS effectively.Alternating blowing CO₂ and N₂ can tuning the K_T of C_nSS at least 10 times effectively.When TMEDA/C_nSS molar ratio is 2.5,blowing CO₂ the K_T of C₁₂SS was reduced from 36.7±0.2 ^oC to 18.0±0.2 ^oC,the K_T decreased 18.7 ^oC.Then,blowing N₂ the K_T rise to 30.0±1.5 ^oC,and amplitude of K_T is 12.0 ^oC;the K_T reduce of C₁₄SS and C₁₆SS by CO₂ were 16.2 ^oC and 12.3 ^oC,amplitudes were 8.9 ^oC and 8.5 ^oC.When the TEOA/C_n SS molar ratio is 5,blowing CO₂ the K_T of C₁₂SS,C₁₄SS and C₁₆SS were reduced 15.0 ^oC,12.0 ^oC and11.9 ^oC,respectively.When alternating blowing CO₂ and N₂,the K_T of C₁₂SS,C₁₄SS and C₁₆SS amplitudes were 10.0 ^oC,8.8 ^oC and 8.5 ^oC,respectively.In contrast,the bicarbonate of TMEDA reduced the K_T of C₁₂SS,C₁₄SS and C₁₆SS more effectively than the bicarbonate of TEOA.In addition,as the length of the carbon chain increases,the bicarbonate of TMEDA or TEOA reduces the effectiveness,and the amplitude of K_T becomes smaller by alternating blowing CO₂ and N₂.?3?Redox method to tuning K_T of selenium-containing surfactantIn the aqueous solution of C₁₄SeC₃SS,C₁₄SeC₃AS and C₁₄SeC₃SB,the addition of H₂O₂ can reduced the K_T from 54.2±0.4 ^oC,38.6±0.2 ^oC and>90 ^oC to 1.4±0.2 ^oC,1.3±0.3 ^oC and 0.5±0.3 ^oC,respectively.The amplitude up to 90 ^oC.Then add Na₂SO₃ to the C₁₄SeC₃SS and C₁₄SeC₃AS aqueous solution to increase its K_T to 57.7±0.3 ^oC and 41.1±0.2 ^oC.Alternating add H₂O₂ and Na₂SO₃ cantuning the K_T of C₁₄SeC₃SS and C₁₄SeC₃AS reversibly up to 10 times;and add Vc to the C₁₄SeC₃SB aqueous solution can to increase its K_T to>90 ^oC.Alternately add H₂O₂ and Vc can tuning the K_T of C₁₄SeC₃SB reversibly at least 5 times.The molecular structure of C₁₄SeC₃SS,C₁₄SeC₃AS,and C₁₄SeC₃SB by redox were studied by means of ¹H NMR,⁷⁷Se NMR,and ESI-MS.The results showed that Se changes between-Se-and-Se?=O?-alternately.The C₁₄SeC₃SS,C₁₄SeC₃AS and C₁₄SeC₃SB before and after Redox are surfactants.?4?CO₂/N₂-Redox method double tuning K_T of alkyl selenium-propane sulfonateThese two methods amplitude are difference,CO₂/N₂-Redox dual switchable used to tuning the K_T of C_nSeC₃SS?n=10,12,14?.The C_nSeC₃SS aqueous solution?TMEDA/C_n SeC₃SS molar ratio is 1:1?.Blowing CO₂,the K_T of C_nSeC₃SS were reduced from 23.4±0.2 ^oC,42.5±0.3 ^oC and52.2±0.2 ^oC to 9.0±0.2 ^oC,18.6±0.2 ^oC and 18.0±0.2 ^oC,respectively;then H₂O₂ were added and the K_T was further reduced to 0.5±0.2 ^oC,0.3±0.1 ^oC and 0.9±0.1 ^oC,respectively;then Na₂SO₃were added and the K_T rises to 23.3±0.1 ^oC,33.7±0.1 ^oC and 43.3±0.2 ^oC;then blowing N₂ while the K_T rise to 31.3±0.1 ^oC,45.7±0.3 ^oC and 51.8±0.1 ^oC,respectively.