Study On Stimuli-responsive Wormlike Micelles Systems

Surfactants can self-assemble into various types of aggregates in solvent.Among them,wormlike micelles have received great attention due to their unique microstructure and rheological behavior.It has been used in many fields such as petroleum industry,drug delivery,biosensors,and nanomaterial synthesis.In recent years,stimuli-responsive or“smart”wormlike micelles have received attention.Stimuli-responsive wormlike micelles can regulate the viscoelastic properties through environmental changes?such as pH,temperature,light,redox,etc.?.Compared with traditional wormlike micelles,the rheological properties and the viscosity of the“smart”wormlike micelles can be controlled more flexibly and accurately.Therefore,organic salt which containing environmentally responsive groups?such as disulfide bonds,tertiary amine groups,carboxyl groups,styrene groups?is introduced into the system,and self-assembling with surfactant into stimuli-responsive wormlike micelles.The viscoelastic properties,microscopic morphology and response mechanism of wormlike micelles system were studied by rheometer,cryo-TEM,¹H NMR and DLS.The main results are summarized as follows:?1?Synthesis and properties of disulfide Gemini surfactants:Gemini surfactant?dithiobis-2,1-ethanediyl?-bis?N-dodecyl-N,N-dimethylammonium bromide?(C₁₂SSC₁₂)containing a disulfide group in the spacer chain and a series of conventional Gemini surfactants C₁₂-n-C₁₂?n=6,5,4,2?were synthesized.The disulfide bond is more lipophilic than-CH₂-CH₂-,so C₁₂SSC₁₂ has lower cmc and?_cmc than C₁₂-6-C₁₂with the same spacer length.The disulfide bond can be broken into sulfhydryl group?-SH?by redox reaction.Thus,C₁₂SSC₁₂ forms monomeric surfactant C₁₂SH in the presence of a reducing agent.And the surface tension results show that C₁₂SSC₁₂ has ultra-low cmc compared to monomer C₁₂SH.In addition,C₁₂SSC₁₂ can form an emulsion at a concentration higher than 0.6 mM.In addition,the formation and demulsification of the emulsion and can be controled by the redox reaction.?2?CTAB-NaSal-C₁₂SSC₁₂ redox responsive wormlike micelles:The conventional Gemini surfactant C₁₂-n-C₁₂?n=6,5,4,2?and disulfide Gemini surfactant C₁₂SSC₁₂ was added to the binary conventional wormlike micelles system of cetyltrimethylammonium bromide?CTAB?and sodium salicylate?NaSal?respectively.The results show that when the concentration of C₁₂-n-C₁₂ and C₁₂SSC₁₂ increases,the zero shear viscosity??₀?decreases rapidly.The longer the spacer chain,the faster?₀ decreases.In addition,a redox-responsive wormlike micelles system was successfully constructed.The CTAB-NaSal-C₁₂SSC₁₂?70/40/15 mM?solution was reversibly transformed between wormlike micelles and rod micelles by redox reaction.?3?pH-redox dual-responsive wormlike micelles system constructed by N,N,N',N'-tetramethylcystamine?TMCDD?and a conventional anionic surfactant sodium dodecyl sulfate?SDS?:A pH-redox responsive wormlike micelles system was constructed with N,N,N',N'-tetramethylcystamine?TMCDD?and conventional anionic surfactant?SDS?.The destruction and recombination of the wormlike micelles can be achieved by adjusting the pH of the solution owing to disulfide bond and tertiary amine groups in the structure of TMCDD.In addition,the wormlike micelles system was destroyed after the addition of the reducing agent,and the viscosity rapidly decreased.But the wormlike micelles could not be reformed after the addition of the oxidizing agent.?4?Redox-pH-temperature multi-response wormlike micelles system constructed by sodium 2,2'-dithiodibenzoate?DTSA?and conventional cationic surfactant CTAB:The DTSA-CTAB wormlike micelles system was constructed with DTSA and conventional surfactant?CTAB?.The viscoelasticity of DTSA-CTAB system can be controlled by changing the pH.In addition,the destruction and recombination of the DTSA-CTAB wormlike micelles can be achieved by redox reaction.DTSA-CTAB?50/180mM?wormlike micelles also have sensitive temperature responsiveness.The zero shear viscosity of the system decreases exponentially with increasing temperature.?5?pH-light dual stimuli-responsive wormlike micelles system constructed by trans-2-hydroxycinnamate?trans-NaOCA?and CTAB:A pH-light stimuli-responsive wormlike micelles system was prepared by trans-NaOCA and CTAB.The self-assembled structure of trans-NaOCA-CTAB solution can be adjusted by pH to make it reversible between wormlike micelles and spherical micelles.By UV irradiation,the styrene group in the trans-NaOCA can be cis-trans isomerized,resulting in destruction of the wormlike micelles into rod micelles.