Structures And Properties Of Responsive And Functional Colloidal Aggregates Based On Surfactants

Self-assembly is an interesting phenomenon in nature.As regard to surfactants,conventional aggregates have been investigated by researchers for decades.And responsive amphiphiles/surfactants gradually attract people's attention for their excellent responsivity and functionality.The outline of this dissertation is as follows:In Chapter ?,Introduction.Chapter I mainly covers the basic concepts in self-assembly and responsive surfactants.The species of the responsive surfactants,conventional colloidal aggregates and new kinds of colloidal assemblies were concluded.In Chapter ?:A multi-stimuli-responsive hydrogel consisting of a cationic surfactant CTABr and an azobenzene derivative(AzoNa4)with four carboxylic acid groups(COOH)was fabricated.The achiral azobenzene molecule(AzoNa4)could act as an excellent gelator and generates supramolecular chirality in the presence of H+ The gelation and morphological variation of supramolecular gels induced by acid were investigated by cryo-TEM,circular dichroism(CD)and so on.A chiroptical switch in response to pH and light stimuli is constructed.It proposes a new way to construct multi-responsive supramolecular switches for future functional materials.In Chapter ?:A chiral gel containing vesicles and disc-like micelles constructed from achiral molecules was reported.The supramolecular chirality was acquired by regulating pH in this special colloidal system,and a sol-gel-sol transition is also reported.A gelator(AzoNa4)and a zwitterionic surfactant(C14DMAO)were employed.The chirality related intimately with the state of aggregation,that is,only the gels exhibit chiral sense and sols not.The coexistence of disc-like micelles and vesicles was for the first time captured in supramolecular chiral hydrogels.In Chapter ?,colloidal chirality was regulated by the redox and host-guest interaction in wormlike micellar systems.The role of secondary assembly of fiber-like aggregates(wormlike micelles)in chirality generation was discussed in this chapter.The wormlike micelles were designed by combining a redox-responsive surfactant(FTMA)and AzoNa4.Both the chirality and viscosity of the wormlike micelle gels could be switched reversibly by chemical redox.Besides,?-CD successfully regulated the wormlike micelles via the host-guest interaction with FTMA and tuned the hydrophobic interaction and H-bond between FTMA and AzoH4.This system provides a new route to switch the colloidal supramolecular chirality.In Chapter ?:A new fabrication of wormlike micelles was reported to manipulate the ferromagnetic property of molecular magnets in magnetic-ionic-liquid(mag-IL)complexes(CTAFe and AzoNa4(or AzoH4)).In the mag-IL complexes,the ferromagnetism was elavated and enhanced 4 times via forming wormlike micelles,inspiring a new thought of the essence of molecular magnetism generation.The ferromagnetism elevation was explained from the view of the molecular/ionic distribution.CTAFe has ability of magnetizing AzoNa4(or AzoH4)by an interplay of the magnetic hydrophobic ions[FeCl3Br]-both in the Stern layer and in the wormlike micelle cores.In Chapter ?:A nontoxic artificial carrier by polyoxometalate(POM)and a double-tailed magnetic surfactant(mag-surfactant)(Ci6H33)2(CH3)2N+[FeCl3Br]-was developed for the capture,transport and delivery of biomolecules.Herein,the double-tailed magnetic surfactant(C16H33)2(CH3)2N+[FeCl3Br]-was for the first time synthesized.Virus-shaped hybrid assemblies were fabricated at a time-dependent dynamic interface by POM {Mo72Fe3o}/mag-surfactant.The hybrid assemblies have hollow shell structures and can serve as a robust high-surface-area vehicle manipulated in magnetic fields.The virus-shaped self-assemblies can be utilized for binding,anchoring and delivery of DNA,having a 95%absorption capacity in 24 hrs.In Chapter ?,for POM-surfactant hybrid systems,the modification of negative counter-ions(from Cl-to[FeCl4]-)of the amphiphilic compounds is for the first time exploited.Herein,we reported the hybrid-assembly(hierarchical magnetic aggregate)of a double-tailed magnetic surfactant((C18)2C2N+[FeCl4]-)and polyoxometalate-{Mo72Fe30} at a time-dependent interface.Both of these two components are used as magnetic source in this magnetic design and thus their magnetism is strengthened via the facile combination.Interestingly,the hybrid magnetic design was introduced to serve as magnetic vehicles in transporting protein molecule(Mb).