Study Of Properties On Multi-response Smart Worm-like Micelle Systems

Smart responsive wormlike micelles are a series of self-assembled aggregates constructed by adding special additives of responds to external environmental stimuli in an aqueous surfactant solution.Its viscoelasticity has the advantages of reversibility,controllability and recyclability and has attracted widespread attention of many researchers.In this paper,we use a cationic surfactant R₁₆HTAB（3-hexadecyloxy-2-hydroxyl propyltrimethyl-ammonium bromide）as the research object and combine with a series of aromatic compounds to construct the multiple response smart micellar systems.Their viscoelastic properties were mensured by rheological method,and performance characterization and mechanism discussion of different systems combined with UV spectrophotometer,nuclear magnetic resonance（¹H NMR）spectroscopy,fourier transform infrared（FTIR）spectroscopy and cryogenic-transmission electron microscopy（cryo-TEM）.This work not only enriches the types of multi-response intelligent wormlike micelles but also provides theoretical basis and technical support for their application in different fields,so it has great research significance.The main research work of this paper is as follows:1.Multi-responsive wormlike micellar system formed by the mixture of cationic surfactant and azobenzene-4-benzoic acid（Azo COOH）.The mixed micellar solution of R₁₆HTAB and Azo COOH was constructed,the structural changes of this system under different conditions such as p H,temperature and UV irradiation time and other conditions was investigated by rheology,UV-visible spectroscopy,nuclear magnetic spectroscopy,and cryo-electron microscopy.The results showed that the wormlike micelles can be formed in mixed solution of R₁₆HTAB/Azo COOH with a certain ratio.The microstructure switched between spherical,wormlike and rod shaped by adjusting p H in solution.The influence of temperature on viscoelasticity of the system was investigated,and the results showed that the temperature response characteristic of mixed solution,that is,the maximum viscosity value of the micelle solution appeared with the change of temperature within the range of temperature studied.The viscoelasticity of the R₁₆HTAB/Azo COOH mixed system can be reversibly regulated under UV-Vis irradiation due to the cis-trans isomerization properties of azobenzen-4-benzoic acid.2.Multi-responsive wormlike micellar system composed of cationic surfactants and cinnamic acid（CA）compounds with different substituents.A series of worm-like micellar systems were constructed by introducing cinnamic acid（CA）derivatives with different substituents（O-methoxy sodium cinnamate,Na OMCA,O-hydroxy sodium cinnamate,Na OHCA）in the surfactant solution.The influences of additives with different substituents on constructing the system of multiple response worm-like micelles rheological behavior were inspected,and the interaction mechanism of surfactant and aromatic small molecules were discussed.Both the R₁₆HTAB/Na OMCA and the R₁₆HTAB/Na OHCA systems can not only form wormlike micelles and show p H response characteristics,but also have good reversibility.The viscosity of R₁₆HTAB/Na OMCA system showed obvious temperature response characteristics and its value increased first and then decreased with the temperature increasing at the range of 20-70^oC.Nevertheless,the temperature change of R₁₆HTAB/Na OHCA system conformed to Arrhenius Law.Whatever acidic and alkaline conditions,the R₁₆HTAB/Na OMCA mixed system exhibited the photo-responsive characteristics,but the viscosity of dilute micellar solution irradiated by UV light then by visible light only returned to 1/2 of the initial state.Under strong acidic conditions R₁₆HTAB/Na OHCA system did not have photosensitivity after UV irradiation.Viscosity of the solution was irregularly under UV light and weak acidic conditions,while the viscosity decreased under alkaline conditions and had no reversibility.3.Dual responsive micellar system constructed by cationic surfactant and sodium phthalate.A dual stimulus response（p H-and thermo-responsive）wormlike micellar system was constructed by mixing sodium hydroxide solution of phthalic acid and R₁₆HTAB.The rheological characteristics of the mixed solution of phthalic acid and R₁₆HTAB were measured by steady-state and oscillating shear experiments under different conditions at25^oC.The results indicated that the p H-sensitive flow behavior was induced due to the transformation of microstructure between wormlike micelles and short cylindrical micelles.Combined with NMR,it was proved that the p H response performance of viscoelastic fluid was attributed to the different binding ability of additives and surfactant as p H varied.The temperature measurement results showed that the viscosity value of the system first increases with the temperature increase and then decreases after reaching the maximum value.It shows that the mixed solution has good temperature-sensitive properties.